JP2013061454A - Light beam scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light beam scanner that can suppress distortion in a beam shape of a deflected light beam output from an electro-optical device to output a light beam with good intensity distribution.SOLUTION: In a light beam scanner, a pump light source 4 for entering a pump light b with a wavelength shorter than a wavelength of a scan beam a output from a laser beam source 3 into an electro-optical crystal substrate 8, and when the scan beam a is output from the laser beam source 3, the pump light b output from the pump light source 4 enters into an area where the scan beam a in the electro-optical crystal substrate 8 propagates.

Description

  The present invention relates to a light beam scanning apparatus using an electro-optic element having an electro-optic effect as a light beam deflection element (hereinafter referred to as “light deflection element”).

  For example, a light beam scanning device used in a laser printer, a laser processing apparatus, or the like includes a laser light source such as a semiconductor laser and a light deflection element that deflects the traveling direction of the laser light from the laser light source. Conventionally known light deflection elements that perform optical scanning by controlling the reflection angle of a light beam, such as a rotating polygon mirror, a galvano mirror, and a MEMS mirror, are known.

  Incidentally, in recent years, as a technique capable of scanning a light beam at a higher speed, an electro-optical element using a change in refractive index of an optical material due to an electro-optical effect (Electro-Optical: EO effect) is known (for example, , See Patent Document 1).

  Patent Document 1 discloses an electro-optic element in which electrodes are arranged on both sides of a ferroelectric substrate provided with a domain-inverted domain formed in a triangle or the like, and the domain-inverted domain is applied by applying a voltage between the electrodes. Causes a change in refractive index, thereby deflecting the light beam passing therethrough.

  The operation principle of the electro-optic element having the electro-optic effect will be described with reference to FIGS. FIGS. 13A and 13B are electro-optic elements having triangular electrodes, and FIGS. 14A and 14B are triangular prism-shaped electro-optic crystal substrates made of an electro-optic material. An electro-optical element having a domain-inverted region.

  13 and 14, the X-axis direction is the laser beam deflection direction, the Y-axis direction is the voltage application direction to the electro-optic element, and the Z-axis direction is the laser beam propagation direction.

  In the electro-optic element shown in FIGS. 13A and 13B, electrodes 101a and 101b are respectively disposed on both surfaces of an electro-optic crystal substrate 100 made of an electro-optic material. The electrodes 101a and 101b have a continuous triangular portion 101c.

  When a voltage is applied from the voltage source 102 to the electrodes 101a and 101b, an electric field parallel to the polarization axis (symbol A in FIG. 13A) of the electro-optic crystal substrate 100 is formed. Symbol A indicates the direction of the polarization axis. The refractive index of the region where the electric field is formed on the electro-optic crystal substrate 100 changes due to the electro-optic effect. When the refractive index change due to the Pockels effect is used, the refractive index change amount Δn of the electro-optic crystal substrate 100 is expressed by the following formula (1).

In formula (1), n is the refractive index of the electro-optic crystal substrate 100 (electro-optic material), r _ij is the electro-optic constant (Pockels constant), V is the applied voltage, and d is the thickness (crystal thickness) of the electro-optic crystal substrate 100. ).

  Then, the laser light a is input to the incident end face of the electro-optic crystal substrate 100, and the voltage is applied between the electrodes 101a and 101b from the voltage source 102, so that the refractive index change region also has a triangular shape. Function as a prism part. In other words, the light beam is given a deflection angle as it propagates through the refractive index changing region.

  The deflection angle θ of the laser light (light beam) a output from the emission surface of the electro-optic crystal substrate 100 is proportional to the refractive index change amount of the electro-optic crystal substrate 100 (electro-optic material), and the following equation ( 2).

  In Expression (2), L is the length of the entire prism portion (the entire triangular portion 101c) (see FIG. 13A), and D is the width of the prism portion (the triangular portion 101c) (see FIG. 13A). It is.

  Therefore, the laser light a can be output at an arbitrary deflection angle θ by controlling the voltage applied to the electro-optic element.

  In general, the polarization axis of an electro-optic crystal substrate made of an electro-optic material can be controlled. Accordingly, as shown in FIGS. 14A and 14B, a polarization inversion region 100a in which a plurality of triangular prism portions are arranged is provided on an electro-optic crystal substrate 100 made of an electro-optic material. Then, a voltage is applied to the electro-optic crystal substrate 100 through the electrode layers 101a and 101b disposed on both surfaces of the electro-optic crystal substrate 100 so as to cover the entire domain-inverted region 100a. It is possible to create a refractive index changing region having a shape.

  Therefore, since the refractive index change direction is different between the refractive index change region (the polarization inversion region 100a) of the electro-optic crystal substrate 100 and other regions, a structure having a plurality of triangular prism portions inside the electro-optic crystal substrate 100. Is obtained. In FIG. 14A, symbols A1 and A2 indicate the directions of the polarization axes.

  Then, laser light a is input to the incident end face of the electro-optic crystal substrate 100, and a voltage is applied between the electrodes 101a and 101b from the voltage source 102, thereby propagating through the triangular refractive index change region of the electro-optic crystal substrate 100. As the light beam propagates, the propagating light beam is given a deflection angle. Then, the laser beam a deflected from the emission end face of the electro-optic crystal substrate 100 is output.

  Thus, the reversal of the refractive index change direction due to the polarization reversal in the polarization reversal region 100a causes the refractive index change amount to be the configuration of the electro-optic element having the triangular electrode shown in FIGS. 13 (a) and 13 (b). Twice as much. Therefore, the deflection angle θ of the laser beam (optical boom) a output from the emission end face of the electro-optic crystal substrate 100 is expressed by the following formula (3).

  In Expression (3), L is the length of the entire prism portion (the entire domain-inverted region 100a) (see FIG. 14A), and D is the width of the prism unit (the domain-inverted region 100a) (see FIG. 14A). It is.

  By the way, as a problem generally known with respect to the electro-optic material forming the electro-optic crystal substrate of the electro-optic element, there is a photorefraction (light damage). This is a phenomenon in which when the material is irradiated with high energy light, the beam shape of the light beam is greatly disturbed. Photo refraction is caused by the fact that free electrons generated inside the material due to light energy excitation drift and a random internal electric field is formed in the material. It is thought to cause irregular refractive index changes.

  Attempts have been made to optimize the composition of the material in order to solve the photorefractive problem described above. For example, there is lithium niobate as a general electro-optic material and nonlinear optical material, but this material has low photorefractive resistance, and magnesium is used as a wavelength conversion element to cope with a short-wavelength laser beam output such as a green laser. Etc. are doped with metals. It is believed that increasing the electrical conductivity of the material by doping the optimum amount of magnesium increases the drift velocity of the electrons excited by the light and creates a uniform distribution of electrons in the material.

  Therefore, even when an electro-optic element (electro-optic light deflection element) is used as a light deflection element in the light beam scanning device, an electro-optic material having excellent photorefractive resistance is used according to the light intensity of the laser beam to be scanned. It is effective.

  Here, the relationship between the voltage (electric field strength) applied to the electro-optic crystal substrate (electro-optic material) of the electro-optic element as shown in FIGS. 14A and 14B and the deflection angle at that time is evaluated. did.

Assuming a lithium niobate crystal as an electro-optic crystal substrate (electro-optic material), a refractive index n = 2.2 and an electro-optic constant r _ij = 30.8 pm / V.

  When the thickness d of the electro-optic crystal substrate (electro-optic material) is set to 300 μm, the width D of the prism portion is 1 mm, and the total length L of the prism portion is 20 mm, the above formula (1) is used. When the relationship between the applied voltage V and the deflection angle θ is calculated from the equation (2), when the voltage of 1.6 kVpp is applied, the deflection angle (scanning angle) of the output light beam is 1 degree, and the voltage of 8.0 kVpp is When applied, the deflection angle (scanning angle) of the output light beam is 5 degrees. The electric field strengths formed inside the electro-optic crystal substrate (electro-optic material) are 2.7 kV / mm and 3.3 kV / mm, respectively, and an extremely large electric field is formed inside the crystal.

  By the way, in an optical phase modulator and an optical intensity modulator that have been put to practical use as an application of the electro-optic effect, such a large electric field is not necessary. For example, the electric field intensity formed inside the crystal in the optical intensity modulator is About 0.1 kV / mm.

  Therefore, it is peculiar to the electro-optic element used in the light beam scanning device to operate the electro-optic material by forming an extremely high electric field. The inventor of the present application has found the following problems peculiar to the formation of a high electric field by actually manufacturing and evaluating a light beam scanning device including an electro-optic element.

  In other words, in electro-optic elements using magnesium-doped lithium niobate as an electro-optic material in order to increase photorefractive resistance, the problem that the light beam profile propagating inside the element is greatly disturbed when a voltage is applied has been confirmed. It was done.

  As a cause of the occurrence of the above-mentioned problem, when an electric field is formed in the electro-optic element, an excessive free charge is generated inside the electro-optic crystal substrate (electro-optic material) and a random electric field is formed by drifting, It is conceivable that the refractive index of the material has a non-uniform distribution. There are two possible causes for this free charge.

  One is that electric charges are injected into the electro-optic crystal substrate (electro-optic material) through the electrode from the outside by applying a voltage. Electrons or holes injected from outside move inside the crystal as free charges and disturb the electric field distribution formed inside the crystal.

  Another possibility is that charges trapped in defect levels such as donor sites, acceptor sites, and impurity levels existing in the material are excited by voltage application and behave as free electrons. In any case, a local electric field is generated inside the electro-optic crystal substrate (electro-optic material) due to free charges generated by voltage application, and the electric field distribution originally formed in the material is disturbed.

  For the above reason, in the light beam scanning apparatus using the electro-optic element, there is a problem that the beam shape of the light beam output from the electro-optic element is distorted. Even when an electro-optic element having electrodes arranged on both sides of a ferroelectric substrate provided with a domain-inverted domain formed in a triangle or the like as described in Patent Document 1 is output. The distortion of the beam shape of the light beam could not be suppressed.

  Further, this beam shape distortion appears prominently during a DC operation that maintains a predetermined deflection angle for a certain time or more. This is because voltage application always continues with the same polarity. When using random access, which is a feature of an electro-optic element (optical deflecting element) that utilizes the electro-optic effect, it is assumed that no beam distortion occurs during DC operation. However, due to the above-mentioned beam distortion, there is a problem that the beam distortion when using random access cannot be eliminated, and the scanning performance of the light beam scanning apparatus is significantly reduced.

  Accordingly, the present invention provides a light beam scanning device capable of suppressing a distortion of the beam shape of a deflected light beam output from an electro-optic element and outputting a light beam having a good intensity distribution. With the goal.

  In order to achieve the above object, a light beam scanning apparatus according to the present invention includes a light beam light source that emits a light beam having a predetermined wavelength, and an electro-optic element in which electrodes are disposed on both sides of an electro-optic crystal substrate made of an electro-optic material And changing the refractive index of the refractive index modulation region formed in the electro-optic crystal substrate in accordance with the voltage applied between the electrodes, from the light beam light source to the electro-optic crystal substrate. In a light beam scanning device that makes a light beam incident, gives a desired deflection angle to the light beam propagating in the electro-optic crystal substrate, and outputs the light beam to the outside from the emission end face, the light beam has a wavelength shorter than the wavelength of the light beam. A pump light source that allows pump light to enter the electro-optic crystal substrate is provided, and the light beam in the electro-optic crystal substrate propagates through the pump light emitted from the pump light source. It is characterized in that is incident on that area.

  According to the light beam scanning device of the present invention, the pump light emitted from the pump light source is incident on the region where the light beam in the electro-optic crystal substrate propagates, so that the light beam in the electro-optic crystal substrate is changed. The beam shape distortion of the light beam output from the electro-optic element can be suppressed without disturbing the electric field distribution in the propagating region. Therefore, good light beam scanning can be performed with a light beam having no beam shape distortion.

(A) is a schematic side view showing the configuration of the light beam scanning device according to the first embodiment of the present invention, (b) is a schematic plan view showing the configuration of the light beam scanning device, and a schematic cross-sectional view showing a lens barrel . (A) is a diagram schematically showing the shapes of a scanning beam and pump light propagating in the electro-optic element of the light beam scanning apparatus according to the first embodiment, and (b) is an electro-optic of the light beam scanning apparatus. The schematic side view which shows a part of element. The figure which showed the relationship between the light intensity of pump light and a scanning beam. The schematic side view which shows the structure of the light beam scanning apparatus which concerns on Embodiment 2 of this invention. (A) is a schematic side view which shows the principal part structure of the light beam scanning apparatus which concerns on Embodiment 3 of this invention, (b) is a schematic plan view which shows the principal part structure of this light beam scanning apparatus. The schematic side view which shows the principal part structure of the light beam scanning apparatus which concerns on Embodiment 4 of this invention. FIG. 9 is a schematic side view showing a main configuration of a light beam scanning apparatus according to Embodiment 5 of the present invention. (A) is a schematic side view which shows the structure of the light beam scanning apparatus which concerns on Embodiment 6 of this invention, (b) is a schematic plan view which shows the structure of this light beam scanning apparatus. FIG. 9 is a schematic plan view showing a configuration of a light beam scanning apparatus according to a seventh embodiment of the present invention. (A) is a figure which shows the scanning beam entrance plane side of the electro-optic element of the light beam scanning apparatus which concerns on Embodiment 8 of this invention, (b) is the electro-optic element of the light beam scanning apparatus which concerns on this embodiment. The schematic side view which shows a part. (A) is a schematic side view which shows the structure of the light beam scanning apparatus which concerns on Embodiment 9 of this invention, (b) is a schematic plan view which shows the structure of this light beam scanning apparatus. (A), (b) is a schematic plan view which shows the structure of the light beam scanning apparatus which concerns on the modification of Embodiment 9, respectively. The figure which shows the operation principle of the electro-optic element which has an electro-optic effect. The figure which shows the operation principle of the electro-optic element which has an electro-optic effect.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<Embodiment 1>
FIG. 1A is a schematic side view showing the configuration of the light beam scanning apparatus according to Embodiment 1 of the present invention, and FIG. 1B is a schematic plan view showing the configuration of the light beam scanning apparatus.

  As shown in FIGS. 1A and 1B, the light beam scanning apparatus 1 according to the present embodiment includes a laser light source 3 that generates laser light and a pump light that generates pump light in a housing 2. A generation source 4, an electro-optic element 5 as an optical deflection element, an optical combiner 6, and an optical separation element 7 are provided as main constituent members. In the present embodiment, the light emitted from the laser light output from the laser light source 3 as a parallel beam is referred to as a scanning beam a.

  In FIGS. 1A and 1B, the X-axis direction is the deflection direction of the scanning beam a, the Y-axis direction is the voltage application direction to the electro-optic element 5, and the Z-axis direction is the light propagation direction of the scanning beam a. is there. The same applies to the following drawings.

  The laser light source 3 is composed of a semiconductor laser, a collimation lens, and the like, and outputs laser light (scanning beam a) having a predetermined wavelength. The pump light generation source 4 includes a semiconductor laser and a collimation lens, and outputs pump light b having a predetermined wavelength in a direction orthogonal to the emission direction of the scanning beam a.

  The electro-optical element 5 has a well-known configuration in which the electrodes 9a and 9b are disposed on both surfaces of an electro-optical crystal substrate 8 made of an electro-optical material so as to face each other. The electro-optic crystal substrate 8 has a polarization inversion region 8a as a refractive index change region in which a plurality of triangular prisms are arranged, and the electro-optic crystal substrate 8 covers the entire polarization inversion region 8a. Electrodes 9a and 9b are arranged on both sides. Then, by applying a voltage from the voltage source 10 between the electrodes 9a and 9b, the refractive index of the domain-inverted region 8a (refractive index changing region) of the electro-optic crystal substrate 8 can be changed by the electro-optic effect.

  In the present embodiment, lithium niobate doped with magnesium (hereinafter referred to as “Mg-LN”) is used as the electro-optic material constituting the electro-optic crystal substrate 8.

  The optical combiner 6 has a function of combining the scanning beam a emitted from the laser light generation source 3 and the pump light b emitted from the pump light generation source 4 and inputting them to the electro-optic crystal substrate 8 of the electro-optic element 5. Have. As the optical combiner 6, for example, a dichroic prism or the like can be used.

  The light separation element 7 is formed of a wavelength selection filter element having a function of separating the scanning beam a and the pump light b output from the emission surface of the electro-optic element 5 and transmitting only the scanning beam a.

  In this light beam scanning apparatus 1, when the pump b is not emitted from the pump light generation source 4, the laser light output from the laser light generation source 3 becomes a parallel beam and passes through the optical combiner 6 as the scanning beam a. 5 is input to the electro-optic crystal substrate 8. Note that a voltage is applied to the electro-optic element 5 via the electrodes 9a and 9b on both sides to which a voltage is applied.

  The input scanning beam a is output from the exit surface after being given a predetermined deflection angle by the polarization inversion region 8a (refractive index change region) as the electro-optic element 5 propagates in the electro-optic crystal substrate 8. The light is output to the outside of the housing 2 through the transparent element 11 that is transmitted through the separation element 7 and provided in the housing 2. The scanning beam a can be output at an arbitrary deflection angle (scanning angle) by controlling the voltage applied to the electro-optical element 5.

  By the way, in this embodiment, Mg-LN is used as an electro-optic material constituting the electro-optic crystal substrate 8 of the electro-optic element 5. Mg-LN is known as a nonlinear optical material excellent in photorefractive resistance, and is widely used as a wavelength conversion material in addition to an optical modulator, a switch, and a deflector.

  Mg-LN has a higher material conductivity than normal non-magnesium-doped lithium niobate and has a higher drift rate of free charge generated by photoexcitation when irradiated with high-intensity light. It is believed that the charge is evenly distributed within the material and distortion of the beam shape is suppressed.

  However, when Mg-LN was used as an electro-optic material for the purpose of application to an electro-optic element having high optical damage resistance, the problem that the output light beam from the electro-optic element was distorted was revealed. . From the inventor's consideration, it was concluded that the cause of this beam distortion occurs on the following principle.

  That is, when a high voltage is applied between the electrodes 9a and 9b of the electro-optic element 5, excessive free charges are generated inside the Mg-LN material and drift. This free charge forms a local electric field inside the material, and the refractive index of the material has a non-uniform distribution, which is a cause of beam distortion.

  Furthermore, there are two possible causes for the generation of this free charge. One is considered that electric charge is injected into the electro-optic material from the outside through an electrode by applying a voltage. Electrons or holes injected from outside move inside the crystal as free charges and disturb the electric field distribution formed inside the crystal. Another possibility is that charges trapped in defect levels such as donor sites, acceptor sites, and impurity levels existing in the material are excited by voltage application and behave as free electrons.

  On the other hand, if the excessive free electrons generated by applying the voltage are guided outside the propagation region of the scanning beam a, the beam shape distortion of the scanning beam can be suppressed, and the free electron has a higher energy than the scanning beam a. It has been confirmed that it is effective to irradiate the light as the pump light b. As specific pump light b, light intensity of about 400 mW or more with a wavelength of 400 nm to 550 nm was suitable. It was also found that this effect has temperature dependence, and that the induction speed increases as the temperature of the electro-optic element 5 increases.

  Therefore, in the present embodiment, when the scanning beam a is output from the laser light generation source 3 in the light beam scanning apparatus 1 of FIG. 1, the pump light b is output from the pump light generation source 4 at the same time. As a result, the scanning beam a and the pump light b are input to and combined with the optical combiner 6, and the combined scanning beam a and the pump light b are input to the electro-optic element 5. At this time, the pump light b has a wavelength of 400 nm to 550 nm and a light intensity of about 100 mW or more. On the other hand, the scanning beam a is set to have a wavelength longer than that of the pump light b and lower energy than the pump light b.

  Further, in the present embodiment, the heating device 20 is disposed below the electro-optical element 5 in the housing 2, and the electro-optical element 5 can be heated to a predetermined temperature by the heating device 20. By heating the electro-optic element 5, it becomes possible to effectively induce excess free electrons generated by voltage application outside the propagation region of the scanning beam a.

  When the electro-optic material (Mg-LN) constituting the electro-optic crystal substrate 8 of the electro-optic element 5 is irradiated with high-energy pump light b, the free charge generated by the voltage application is drift-moved in a certain direction, and the pump It can be unevenly distributed at the boundary of the irradiation region of the light b (hereinafter, this phenomenon is referred to as “optical screening effect”).

  By utilizing the optical screening effect by irradiation with the pump light b, free electrons are not generated in a random distribution in the light propagation region of the scanning beam a, and a local internal electric field is not formed. Accordingly, in the propagation region of the scanning beam a, the electric field formed for the purpose of original beam scanning is not disturbed, and the beam shape distortion of the scanning beam a is suppressed.

  Note that the scanning beam a and the pump light b are output from the emission end face of the electro-optic element 5, but only the scanning beam a is transmitted through the light separation element 7 disposed on the downstream side of the emission face of the electro-optic element 5. , And output to the outside of the housing 2 through the window material 11. On the other hand, the pump light b is totally reflected by the light separating element 7 and is not output outside the housing 2. The pump light b totally reflected by the light separation element 7 is absorbed by the inner peripheral surface of the housing 2 or the like.

  2A schematically shows the shapes of the scanning beam and pump light propagating in the electro-optic element of the light beam scanning apparatus according to this embodiment, and FIG. 2B shows this embodiment. It is a schematic side view which shows a part of electro-optical element of the light beam scanning apparatus which concerns on a form.

  The scanning beam a input to the electro-optic element 5 passes through the polarization inversion region 8a (refractive index change region) of the electro-optic crystal substrate 8 and thereby has a predetermined deflection angle as it propagates through the element. Given. On the other hand, the pump light b input to the electro-optic element 5 induces free electrons at the boundary of the beam profile.

  Therefore, as shown in FIG. 2A, it is desirable that the irradiation region of the pump light b completely includes the beam profile of the scanning beam a. That is, the irradiation sectional area of the pump light b is set to be larger than the beam diameter of the scanning beam a. Further, the width H of the irradiation region of the pump light b is made larger than the width h of the electrodes 9a and 9b of the electro-optic element 5.

  FIG. 3 shows the relationship between the pump light and the light intensity of the scanning beam. In FIG. 3, C1 is the light intensity distribution of the pump light b, and C2 is the light intensity distribution of the scanning beam a. In FIG. 3, h is the width of the electrodes 9a and 9b (see FIG. 2A).

  As the light intensity of the pump light b increases, the influence of the light screening effect increases, and the time until the beam distortion is eliminated when a high voltage is applied between the electrodes 9a and 9b of the electro-optical element 5 is shortened. Therefore, as shown in FIG. 3, the light intensity peak of the pump light b is set to be larger than the light intensity peak of the scanning beam a.

  As described above, according to the light beam scanning apparatus 1 of the present embodiment, the irradiation sectional area of the pump light b is set to be larger than the beam diameter of the scanning beam a, and the light intensity peak of the pump light b is further increased. It is set to be larger than the light intensity peak of the scanning beam a.

  Therefore, even when Mg-LN is used as the electro-optic material constituting the electro-optic crystal substrate 8 of the electro-optic element 5 so as to have high optical damage resistance, the electric field distribution in the region where the scanning beam a propagates is disturbed. Without this, the beam shape distortion of the scanning beam a output from the electro-optical element 5 can be suppressed. Therefore, good light beam scanning can be performed by the scanning beam a having no beam shape distortion.

<Embodiment 2>
FIG. 4 is a schematic side view showing the configuration of the light beam scanning apparatus according to the second embodiment of the present invention. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 4, the light beam scanning device 1a of the present embodiment is configured such that the polarization directions of the scanning beam a and the pump light b are orthogonal to each other. In addition, a deflection separation element having a deflection filter function as the light separation element 7 a is disposed on the emission surface side of the electro-optic element 5. Other configurations are the same as those of the light beam scanning apparatus according to the first embodiment. In FIG. 4, symbol p1 indicates the polarization direction of the scanning beam a, and symbol p2 indicates the polarization direction of the pump light b.

  As shown in the formula (1), the deflection angle when a voltage is applied between the electrodes of the electro-optic element is proportional to the electro-optic constant. Therefore, in order to obtain a large deflection angle at a low voltage, it is desirable to form an electric field in a crystal orientation with a large electro-optic constant.

For example, when the electro-optic material is lithium niobate, if an electric field parallel to the c-axis of the crystal is formed, the amount of change in the refractive index is determined by the Pockels coefficient r _ij , and the deflection is larger than when an electric field is formed in other directions. A corner is obtained. In FIG. 4, the c-axis of the electro-optic element 5 is in the Y-axis direction, and thus the electric field is formed in the Y-axis direction. Further, the polarization direction of the scanning beam a at that time is also determined. In this case, it is necessary to have an electric field component in the Y-axis direction.

  On the other hand, the polarization direction of the pump light b does not need to be limited to the Y-axis direction, and the optical screening effect is not hindered even if it is orthogonal to the scanning beam a as shown in FIG. In the configuration in which the polarization directions of the scanning beam a and the pump light b are orthogonal to each other, the scanning beam a and the pump light b output from the emission surface of the electro-optic element 5 have a deflection filter function as the light separation element 7a. It is separated by a deflection separation element having.

  Then, the light separating element 7a (deflection separating element) transmits only the scanning beam a and outputs it to the outside of the housing 2 through the window member 11. On the other hand, the pump light b is totally reflected by the light separation element 7 a (deflection separation element) and is not output outside the housing 2. The pump light b totally reflected by the light separation element 7a is absorbed by the inner peripheral surface of the housing 2 or the like.

  Thus, according to the light beam scanning apparatus 1a of the present embodiment, the electro-optic element 5 can be used even when the wavelengths of the scanning beam a and the pump light b are relatively close or the wavelength band of the pump light b is wide. The beam shape distortion of the scanning beam a output from the emission surface can be satisfactorily suppressed.

<Embodiment 3>
FIG. 5A is a schematic side view showing the main part configuration of the light beam scanning apparatus according to Embodiment 3 of the present invention, and FIG. 5B is a schematic plan view showing the main part structure of the light beam scanning apparatus. It is. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIGS. 5A and 5B, the light beam scanning apparatus 1b of the present embodiment replaces the light separating element 7b having a concave reflecting surface 7b ′ on the electro-optic element 5 side with the electro-optic light deflecting element 5. It is the structure arrange | positioned at the output surface side. Other configurations are the same as those of the light beam scanning apparatus according to the first embodiment.

  The light separation element 7b of the present embodiment separates the scanning beam a and the pump light b output from the emission surface of the electro-optic element 5 in the same manner as the light separation element 7 of the first embodiment, so that only the scanning beam a is obtained. It has a function as a wavelength selective filter element to transmit. Further, the light separating element 7 b is configured to totally reflect the pump light b having a different wavelength by the reflecting surface 7 b ′ and condense it toward the emission end face of the electro-optic element 5. The light separating element 7b may have a configuration in which a concave reflecting surface is provided similarly to the deflecting / separating element having the deflection filter function as the light separating element 7a of the second embodiment.

  The pump light b reflected by the reflecting surface 7 b ′ is collected and incident from the emission end face side of the electro-optic element 5.

  As described above, the higher the light intensity of the pump light b, the faster the induction of free space charge by the screening effect, which is preferable for suppressing the beam shape distortion of the scanning beam a. Therefore, as in the present embodiment, the pump light b reflected by the reflecting surface 7 b ′ is collected and incident from the emission end face side of the electro-optical element 5, thereby efficiently pumping the pump light b of the electro-optical element 5. The electro-optic crystal substrate 8 can be recombined with the electro-optic material.

  As a result, the effective light intensity of the pump light b can be increased, so that the beam shape distortion of the scanning beam a output from the emission end face of the electro-optic element 5 can be satisfactorily suppressed.

  Note that the deflection angle (scanning angle) of the scanning beam a output from the emission end face of the electro-optic element 5 is as small as about 10 degrees, and even if the concave curvature radius of the reflecting surface 7b ′ of the light separating element 7b is large, the light beam The size of the separation element 7b does not increase. For example, when the deflection angle of the scanning beam a output from the emission end face of the electro-optic element 5 is 10 degrees in all angles and the radius of curvature of the light separation element 7b (reflection surface 7b ′) is 10 mm, the amount of beam displacement in the X-axis direction Is 1.7 mm, and the width of the light separating element 7b in the X-axis direction may be about 2 mm or more.

<Embodiment 4>
FIG. 6 is a schematic side view showing a main configuration of a light beam scanning apparatus according to Embodiment 4 of the present invention. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 6, the light beam scanning device 1 c of the present embodiment has a configuration in which a prism element is disposed as the light separation element 7 c on the emission end face side of the electro-optic element 5. In addition, the light absorber 12 is disposed at the passage position of the pump light b on the emission end face side of the light separation element 7c. Other configurations are the same as those of the light beam scanning apparatus according to the first embodiment.

  In the first to third embodiments, only the scanning beam a is transmitted by the light separation element and the pump light b is reflected by the light separation element so as not to be output outside the housing. However, the Z of the scanning beam a and the pump light b is not used. The propagation angle with respect to the axial direction may be made different from each other so that only the scanning beam a is output to the outside of the housing.

  That is, since the wavelengths of the scanning beam a and the pump light b are different, as in this embodiment, a prism element is used as the light separation element 7c to separate the two lights (the scanning beam a and the pump light b). . Only the scanning beam a separated by the light separation element 7 c is output to the outside of the housing 2 through the window member 11. On the other hand, the pump light b separated by the light separation element 7 c is absorbed by the light absorber 12 and is not output outside the housing 2.

<Embodiment 5>
In the fourth embodiment, a prism element is used as the light separating element 7c to separate two lights (scanning beam a and pump light b). However, as shown in FIG. 7, the light beam scanning according to the present embodiment is performed. The apparatus 1d has a configuration in which a diffractive optical element is disposed as the light separating element 7d on the emission end face side of the electro-optical element 5. Other configurations are the same as those of the light beam scanning apparatus according to the fourth embodiment.

  Since the scanning beam a and the pump light b have different wavelengths and the diffraction angle of the diffracted light differs depending on the different wavelengths, two light beams (scanning beam a and scanning beam a) are used as the light separating element 7d as in the present embodiment. The pump light b) was separated. Only the scanning beam a separated by the light separation element 7 c is output to the outside of the housing 2 through the window member 11. On the other hand, the pump light b separated by the light separation element 7 c is absorbed by the light absorber 12 and is not output outside the housing 2.

  As described above, also in the light beam scanning devices 1c and 1d of the fourth and fifth embodiments, similarly, the beam shape distortion of the scanning beam a output from the emission end face of the electro-optic element 5 can be satisfactorily suppressed.

<Embodiment 6>
FIG. 8A is a schematic side view showing the configuration of the light beam scanning apparatus according to Embodiment 6 of the present invention, and FIG. 8B is a schematic plan view showing the configuration of the light beam scanning apparatus. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In each of the above-described embodiments, the pump light b is input to the incident end face of the electro-optical element 5 from the same direction (Z-axis direction) as the scanning beam a. However, the scanning beam a input to the electro-optical element 5 is used. Even if the propagation directions of the pump light b are different from each other, the light screening effect by the irradiation of the pump light L2 does not change.

  Therefore, as shown in FIGS. 8A and 8B, the light beam scanning apparatus 1e of the present embodiment places the pump light generation source 4 above the electro-optic element 5 in the housing 2 (FIG. 8A). The pump light b is irradiated from above the electro-optical element 5 through the lens 13. The scanning beam a is input from the laser light source 3 to the electro-optic element 5 along the Z-axis direction as in the above embodiments. Therefore, the scanning beam a and the pump light b propagate in directions orthogonal to the electro-optic element 5.

  Further, the pump light “b” irradiated to the electro-optical element 5 substantially covers the entire area along the longitudinal direction (Z-axis direction) of the electro-optical element 5 (electro-optical crystal substrate 8), as shown in FIG. 8B. The irradiation range is set to be covered. The pump light b irradiated to the electro-optical element 5 is emitted from the electro-optical element 5 (electro-optical crystal substrate 8), and then the vicinity of the inner peripheral surface of the housing 2 on the side opposite to the pump light generation source 4 or the like. Absorbed in. Therefore, in this embodiment, it is not necessary to provide a light separation element between the electro-optic element 5 and the window material 11.

  The scanning beam a input to the electro-optic element 5 is given a predetermined deflection angle as the electro-optic element 5 propagates in the electro-optic crystal substrate 8 and is output from the emission end face. It is output to the outside of the housing 2 through the transparent window material 11.

  As described above, similarly in the light beam scanning apparatus 1e of the present embodiment, the beam shape distortion of the scanning beam a output from the emission end face of the electro-optic element 5 can be satisfactorily suppressed.

<Embodiment 7>
FIG. 9 is a schematic plan view showing the configuration of the light beam scanning apparatus according to the seventh embodiment of the present invention. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 9, the light beam scanning device 1 f of the present embodiment arranges the pump light generation source 4 on the electrode 9 b side (upper side in FIG. 9) of the electro-optic element 5 in the housing 2 to provide pump light. b was irradiated from the electrode 9b side of the electro-optic element 5. The scanning beam a is output from the laser light generation source 3 to the electro-optic element 5 along the Z-axis direction as in the above-described embodiments. Therefore, the scanning beam a and the pump light b propagate in directions orthogonal to the electro-optic element 5.

  The pump light source 4 is irradiated with incoherent pump light b such as an LED or UV lamp from the electrode 9b side, whereby the longitudinal direction (Z-axis direction) of the electro-optic element 5 (electro-optic crystal substrate 8). An irradiation range that substantially covers the entire area along the line can be obtained. The electrode 9b on the side irradiated with the pump light b is made of a transparent electrode material such as ITO (Indium Tin Oxide) or ZnO (Zinc Oxide) so that the pump light b is input without reflecting on the surface. Is formed. Similarly, the other electrode 9a is formed of a transparent electrode material (ITO, ZnO or the like).

  The pump light b applied to the electro-optic element 5 from the electrode 9b side is emitted from the electro-optic element 5 (electro-optic crystal substrate 8), and then the inner peripheral surface of the housing 2 on the opposite side to the pump light generation source 4. Absorbed in the vicinity. Therefore, in this embodiment, it is not necessary to provide a light separation element between the electro-optic element 5 and the window material 11.

  The scanning beam a incident on the electro-optic element 5 is output from the exit surface with a predetermined deflection angle as it propagates in the electro-optic crystal substrate 8 of the electro-optic element 5, and is provided in the housing 2. It is output to the outside of the housing 2 through the transparent window material 11.

  As described above, in the light beam scanning device 1 f of this embodiment, similarly, the beam shape distortion of the scanning beam a output from the emission surface of the electro-optical element 5 can be satisfactorily suppressed.

<Embodiment 8>
FIG. 10A is a diagram showing the scanning beam incident surface side of the electro-optic element of the light beam scanning apparatus according to the eighth embodiment of the present invention, and FIG. 10B is the light beam scanning apparatus according to the present embodiment. It is a schematic side view which shows a part of electro-optical element. Note that members having the same functions as those of the light beam scanning apparatus according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIGS. 10A and 10B, the electro-optic crystal substrate 8 is disposed between the electro-optic crystal substrate 8 of the electro-optic element 5 and the electrodes 9a and 9b of the light beam scanning apparatus according to this embodiment. The clad layers 14a and 14b made of a material having a refractive index smaller than that of the electro-optic material forming the optical waveguide structure are provided. Other configurations are the same as those of the light beam scanning apparatus according to the first embodiment, for example.

  In general, the amount of change in the refractive index due to the electro-optic effect of the electro-optic element is very small, and a high applied voltage is required when driving the electro-optic element in the light beam scanning apparatus as in the present invention. In order to lower the applied voltage, it is effective to reduce the thickness of the electro-optic material as shown in the above formula (1).

  On the other hand, when the thickness of the electro-optic crystal substrate 8 made of an electro-optic material is reduced, it becomes difficult for the scanning beam a to propagate through the electro-optic crystal substrate 8 in free space. This is because when the beam diameter of the scanning beam a is reduced to match the thickness of the electro-optic crystal substrate 8, the beam spread at the time of spatial propagation increases, and the electro-optic crystal substrate is propagated in the middle of propagation through the electro-optic crystal substrate 8. This is because the boundary surface between the electrode 8 and the electrodes 9a and 9b is reached.

Therefore, when the thickness of the electro-optic crystal substrate 8 of the electro-optic element 5 is reduced, as shown in FIG. 10A, the clad layer 14a, between the electro-optic crystal substrate 8 and the electrodes 9a, 9b, It is effective to provide 14b. The condition of the cladding layers 14a and 14b is that the clad layers 14a and 14b are transparent and have a refractive index smaller than that of the electro-optic material forming the electro-optic crystal substrate 8. Specifically, a glass material such as SiO ₂ having a refractive index of about 1.46 or Ta ₂ O ₅ having a refractive index of about 2.1 is suitable, and a mixed glass of these materials may be used. Moreover, you may comprise a clad with polymer materials, such as PMMA.

  Thus, by providing the clad layers 14a and 14b, it is possible to optically guide using total reflection due to the refractive index difference between the clad layers 14a and 14b and the electro-optic crystal substrate 8, and therefore the electro-optic crystal substrate 8 Even if the thickness is reduced, light can be efficiently transmitted.

<Embodiment 9>
FIG. 11A is a schematic side view showing the configuration of the light beam scanning apparatus according to Embodiment 9 of the present invention, and FIG. 11B is a schematic plan view showing the configuration of the light beam scanning apparatus. In addition, the same code | symbol is attached | subjected to the member which has the same function as the light beam scanning apparatus of Embodiment 1, 8, and the overlapping description is abbreviate | omitted.

  While the electro-optic crystal substrate 8 can be made thin by making the electro-optic element 5 an optical waveguide structure as in the eighth embodiment, the scanning beam a of the electro-optic element 5 is input (incident). ), The allowable error when inputting the scanning beam a and the pump light b from the incident end face is reduced. For this reason, there is a concern that it becomes difficult to input both the scanning beam a and the pump light b having different wavelengths with high efficiency.

  Therefore, as shown in FIGS. 11A and 11B, the light beam scanning apparatus 1g according to the present embodiment has one side surface (cladding layer) on the incident end face side to which the scanning beam a of the electro-optic element 5 is input. 14b), the diffraction grating 15 is provided, and the pump light source 4 is disposed obliquely in front of the diffraction grating 15. Other configurations are the same as those of the light beam scanning apparatus according to the eighth embodiment shown in FIGS.

  In the light beam scanning device 1g, the scanning beam a output from the laser light source 3 is input to the incident end face of the electro-optic element 5 along the Z-axis direction. The inputted scanning beam a is propagated by the optical waveguide structure formed by the electro-optic crystal substrate 8 and the clad layers 14a and 14b of the electro-optic light deflection element 5. As the light propagates through the electro-optic crystal substrate 8, the case 2 is given a predetermined deflection angle, is output from the exit surface, passes through the light separation element 7, and passes through the transparent window member 11 provided in the case 2. Is output outside of.

  On the other hand, the pump light b output from the pump light generation source 4 is input into the electro-optical element 5 due to the diffraction effect by the diffraction grating 15. The pump light b input into the electro-optical element 5 due to the diffraction effect by the diffraction grating 15 propagates through the electro-optical crystal substrate 8 and is output from the emission end face of the electro-optical element 5. The pump light b output from the emission surface of the electro-optical element 5 is totally reflected by the light separation element 7 and is not output outside the housing 2. The pump light b totally reflected by the light separation element 7 is absorbed by the inner peripheral surface of the housing 2 or the like.

  As described above, according to the light beam scanning device 1 g of the present embodiment, the pump light b is input from the side surface side of the electro-optic element 5 by the diffraction effect by the diffraction grating 15. With this configuration, since the incident positions of the scanning beam a and the pump light b on the electro-optic element 5 can be made different, even when the electro-optic crystal substrate 8 is made thin by using the electro-optic element 5 as an optical waveguide structure, Both the scanning beam a and the pump light b can be input to the electro-optical element 5 with high efficiency.

  In the present embodiment, the pump light b output from the pump light generation source 4 is configured to be input into the electro-optical element 5 by the diffraction effect of the diffraction grating 15, but the present invention is not limited to this configuration. As shown in (a), the positions of the pump light generation source 4 and the laser light generation source 3 are reversed, and the scanning beam a output from the laser light generation source 3 is converted into an electro-optic element by the diffraction effect of the diffraction grating 15. 5 may be input.

  Further, as shown in FIG. 12B, diffraction gratings 15 are provided on both sides of the electro-optic crystal substrate 8, and the scanning beam “a” output from the laser light source 3 and the pump light source 4 are output. Both pump light b may be input into the electro-optic element 5 by the diffraction effect of each diffraction grating 15.

DESCRIPTION OF SYMBOLS 1, 1a-1g Light beam scanning device 2 Case 3 Laser light generation source 4 Pump light generation source 5 Electro-optic element 6 Optical combiner 7, 7a-7d Light separation element 8 Electro-optic crystal substrate 9a, 9b Electrode 10 Voltage source 14a , 14b Clad layer 15 Diffraction grating

JP-A-9-146128

Claims (10)

A light beam light source that emits a light beam of a predetermined wavelength, and an electro-optic element having electrodes arranged on both sides of an electro-optic crystal substrate made of an electro-optic material,
The light beam is incident on the electro-optic crystal substrate from the light beam light source by changing a refractive index of a refractive index modulation region formed on the electro-optic crystal substrate according to a voltage applied between the electrodes. A light beam scanning device that gives a desired deflection angle to the light beam propagating in the electro-optic crystal substrate and outputs the light beam from the emission end face to the outside.
Providing a pump light source that makes the pump light having a wavelength shorter than the wavelength of the light beam enter the electro-optic crystal substrate;
A light beam scanning apparatus, wherein the pump light emitted from the pump light source is incident on a region of the electro-optic crystal substrate where the light beam propagates. The light beam and the pump light are propagated in the electro-optic crystal substrate from the incident end face to the exit end face side of the electro-optic crystal substrate,
Light separation that separates the light beam and the pump light on the downstream side of the emission end face of the electro-optic crystal substrate, outputs only the light beam to the outside, and prevents the pump light from being output to the outside. 2. The light beam scanning apparatus according to claim 1, further comprising means.   The cross-sectional area of the pump light propagating in the electro-optic crystal substrate is set to be larger than the beam diameter of the light beam propagating in the electro-optic crystal substrate, and the light intensity of the pump light is The light beam scanning apparatus according to claim 1, wherein the light beam scanning apparatus is set to be larger than a light intensity of the light beam.   4. The light beam scanning apparatus according to claim 2, wherein the polarization direction of the light beam and the polarization direction of the pump light are orthogonal to each other. The light separating means has a reflecting surface for reflecting the pump light emitted from the emitting end face of the electro-optic crystal substrate to the emitting end face side,
4. The light beam scanning apparatus according to claim 2, wherein the pump light reflected by the reflecting surface is propagated from the emitting end surface into the electro-optic crystal substrate. The pump light is incident on the electro-optic crystal substrate from a direction orthogonal to the direction in which the light beam is incident on the electro-optic crystal substrate,
A beam width of the pump light incident on the electro-optic crystal substrate is set larger than a total length of the electro-optic crystal substrate along a direction in which the light beam propagates in the electro-optic crystal substrate. The light beam scanning apparatus according to claim 1. Each electrode is formed of a transparent material,
The light beam scanning apparatus according to claim 1, wherein the pump light is transmitted from one electrode side through the electrode and is incident on the electro-optic crystal substrate.   An optical waveguide is formed by providing a clad layer made of a transparent material and a refractive index smaller than that of the electro-optic material between the electro-optic crystal substrate of the electro-optic element and the electrodes. The light beam scanning apparatus according to claim 1, wherein the light beam scanning apparatus is a light beam scanning apparatus. A diffraction grating is disposed on the surface of the electro-optic crystal substrate on the incident end surface side opposite to the emission end surface and the cladding layer is provided, and the pump light source is disposed obliquely forward of the diffraction grating. ,
9. The light beam scanning apparatus according to claim 8, wherein the pump light emitted from the pump light source is incident on the electro-optic crystal substrate by being diffracted by the diffraction grating.   10. The electro-optic material is lithium niobate doped with magnesium, and the refractive index modulation region is a domain-inverted region in which a plurality of triangular prisms are arranged. The light beam scanning apparatus as described in any one of Claims.