JP2014211528A - Optical switch element and laser oscillation device - Google Patents

Abstract

A Q-switching element according to the prior art must apply a switching voltage with a high voltage of several hundreds or more and a fast falling or rising time in order to rotate the polarization by 90 ?. In the waveguide type optical Q switch, high-speed switching is possible at several V, but in the lithium niobate waveguide manufactured by the titanium diffusion method, optical damage occurs. In order to avoid optical damage, the upper limit of operable input optical power remains at most about 200 mW. A switching element according to the present invention includes an optical waveguide having a channel-type waveguide structure including a core and a lower cladding, and first and second electrodes provided on the upper surface of the core and the upper surface of the lower cladding, respectively. And a Q switch driving device that applies a voltage between the first and second electrodes so as to be turned on and off. It is manufactured by joining a core material and a clad material having different refractive indexes by a direct joining method. [Selection] Figure 1

Description

  The present invention relates to an optical waveguide switch element using an electro-optic effect, and a Q-switch laser apparatus using the switch element.

  Laser oscillators are used not only in optical communication but also in various industrial fields such as medical technology and laser processing. The operation of a laser oscillator is roughly classified into continuous oscillation (CW) and pulse oscillation. As an example of the pulse oscillation operation, an oscillator based on the Q switch method is known as will be described later, and is used for micro machining, drilling, marking, etc. on precision parts such as electronic parts and semiconductor parts.

  As an example of a Q switch element used in an oscillator based on the Q switch method of the prior art, a Q switch element using an electro-optic crystal having a Pockels cell effect has been proposed (for example, see Patent Document 1). . A Q switch element using an electro-optic crystal is configured in a resonator by combining a polarization separation splitter and a polarizer such as a thin film polarizer. The Pockels cell is operated so as to obtain a Q switch pulse by electrically controlling the direction of polarization of the Pockels cell to change the ratio of the transmission component to the reflection component of the polarizer and changing the Q value in the resonator.

  Further, as another Q switch element used in a conventional oscillator using the Q switch method, an optical waveguide type Q switch element using a saturable absorber as an optical waveguide material has been proposed (for example, non-patent). Reference 1). The saturable absorber in the optical waveguide type Q switch element disclosed in Non-Patent Document 1 is a substance that gradually becomes transparent when absorbing light. When the saturable absorber is inserted into the resonator, the saturable absorber becomes a loss at the start of excitation. However, when excitation is started, it becomes gradually transparent while suppressing the laser oscillation, and when the gain becomes larger than the loss over time, the laser oscillation is rapidly started to operate so as to obtain the Q switch pulse.

  Patent Document 2 discloses an example of a conventional Q-switch laser device. A laser device disclosed in Patent Document 2 includes a resonator including an output mirror and a total reflection mirror, a laser light source (laser rod, polarizer, and Pockels cell) disposed in the resonator, and a laser rod. And a Pockels cell driving circuit that changes the voltage applied to the Pockels cell. This Q-switched laser device operates to obtain a giant pulse by controlling the polarization direction in the resonator by applying a voltage to the Pockels cell and changing the Q value in the resonator by combining with a polarizer. To do.

JP-A-9-64448 Japanese Patent Laid-Open No. 61-168979

J. et al. I. Mackenzie “End-pumped, passively Q-Switched Yb: YAG double-clad waveguide laser” OPTICS LETTERS / Vol. 27, NO. 24 / December 15, 2002

  However, the conventional Q-switch element and the Q-switch laser apparatus using the same have various problems as described below. Both the Q switch element disclosed in Patent Document 1 and the Q switch laser device disclosed in Patent Document 2 have a high voltage of several hundreds to several kV and a high speed in order to rotate the polarization by 90 °. A switching voltage having a proper fall or rise time must be applied to the Q switch element. Such a switching circuit capable of driving a high-voltage / high-speed control voltage becomes a large-scale one, and there is a problem that the number of parts of the entire laser device increases.

  Further, when a material such as Nd: YAG is used for the laser medium, depolarization loss (depolarization loss) due to thermal birefringence occurs, the voltage to be applied to the Q switch element increases, and the efficiency in the drive circuit increases. There was a problem of lowering.

  Furthermore, the optical waveguide type Q switch element disclosed in Non-Patent Document 1 has a problem that the efficiency is lowered due to the residual loss of the saturable absorber. In order to increase the peak power of the oscillator, the optical density (Optical Density) of the saturable absorber needs to be increased. At this time, since the residual loss of the saturable absorber increases in proportion to the optical density, the pulse width widens, the peak power decreases, and the efficiency decreases greatly. Further, when a saturable absorber is used, it is difficult to accurately control the oscillation timing of the pulse, and there is a problem that the oscillation timing varies greatly due to variations in the intensity of the excitation light.

  From the background described above, a waveguide-type optical switch using an optical material having a Pockels effect that can reduce the driving voltage in the Pockels cell in the Q-switched laser device is desired.

  Currently, as a waveguide type optical switch, a lithium niobate waveguide by a titanium diffusion method is often used from the viewpoint of high speed and low driving voltage. In this method, by diffusing Ti in the LN substrate, the refractive index of the diffused portion is increased compared to the surroundings, thereby realizing a waveguide structure. As the drive voltage, the half-wave drive voltage Vπ is several volts, and high-speed switching is possible.

  However, in the lithium niobate waveguide fabricated by the titanium diffusion method described above, the refractive index changes when a large optical power is incident due to the photorefractive effect caused by defects caused by the diffusion of Ti. So-called photodamage occurs. In order to avoid this optical damage, the upper limit of operable input optical power remains at most about 200 mW. The lithium niobate waveguide produced by the titanium diffusion method could not be applied to a laser device that handles W-class light as required for a Q-switch laser device.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to realize an optical waveguide switch element that realizes a high extinction ratio, ultra-small size, and low driving voltage. . Another object of the present invention is to realize a small, highly efficient and accurate timing control in a Q-switched laser device using an optical waveguide type switching element while suppressing the number of parts while ensuring a high light output.

  In order to achieve the above object, the present invention provides a high refractive index electro-optic material for propagating light in a switch element that changes the light intensity using the electro-optic effect. An optical waveguide bonded to the electro-optic material and having a dielectric material having a refractive index lower than that of the electro-optic material, and the electro-optic material has a channel structure that forms a core ridge; and the optical waveguide A first electrode formed on the top surface of the core ridge and applied with a driving voltage for changing a dielectric constant of the electro-optic material; and formed on the dielectric material and applied with the driving voltage. And a second electrode having a second electrode. The electro-optic material and the dielectric material are preferably joined directly to form a core ridge.

  The invention according to claim 2 is the waveguide type switch element according to claim 1, wherein at least one of the first electrode and the core ridge, or the second electrode and the dielectric material. Further, an amorphous material thin film is provided.

The invention according to claim 3 is the waveguide type switch element according to claim 1 or 2, wherein the electro-optic material is a LiNbO ₃ (LN) crystal to which ZnO is added, and MgO is added to a low refractive index material. It is characterized by being one of LN crystal, LiTaO ₃ (LT) crystal, quartz crystal or amorphous material.

A fourth aspect of the present invention is the waveguide switch element according to the first to third aspects, wherein the amorphous material thin film is made of SiO ₂ .

  A fifth aspect of the present invention is the waveguide switch element according to the first to fourth aspects, wherein the channel structure of the optical waveguide is manufactured by a dry etching method.

  The present invention can also be realized as a laser oscillation device, and includes the above-described waveguide switch element, a drive device that supplies a drive voltage to the first electrode and the second electrode, and the waveguide switch. A polarizer for selecting the polarization of light to the element, a laser medium on which light passing through the core ridge of the waveguide switch element is incident, and both ends of an optical path that passes through the laser medium and the waveguide switch element It is possible to realize a Q-switched laser oscillation device including two arranged reflection devices and a collimation device placed between the laser medium and the polarizer.

  As described above, according to the present invention, it is possible to drive at a low voltage due to light polarization due to an electro-optic effect in an optical waveguide manufactured by a direct bonding method or a change in refractive index in the optical waveguide, and a high extinction ratio. Thus, it is possible to realize a miniaturized optical waveguide switch element having high optical power resistance by controlling light.

FIG. 1 is a perspective view showing a configuration of an optical waveguide switch element according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view including the AA ′ line in FIG. 1 showing the configuration of the optical waveguide switch according to the first embodiment of the present invention. FIG. 3 is a diagram showing a configuration of a Q-switch laser oscillation apparatus including the optical switch element of the present invention. FIG. 4 is a diagram showing an electric field distribution in the optical waveguide element generated by applying a voltage between the electrodes in the optical waveguide type switching element (cladding is MgLN crystal) of Example 1. FIG. 5 is a graph showing the response characteristics of the transmittance of the optical waveguide switch device according to the first embodiment. FIG. 6 is a diagram showing an electric field distribution in the optical waveguide device generated by applying a voltage between the electrodes in the optical waveguide switch device of Example 2 (cladding is an LT crystal). FIG. 7 is a graph showing the response characteristics of the transmittance of the optical waveguide switch device according to the second embodiment. FIG. 8 is a diagram showing an electric field distribution in the optical waveguide device generated by applying a voltage between the electrodes in the optical waveguide switch device of Example 3 (the clad is a SiO ₂ substrate). FIG. 9 is a graph showing the response characteristics of the transmittance of the optical waveguide switch device according to the third embodiment.

  The switch element of the present invention includes an optical waveguide having a channel-type waveguide structure composed of a core and a lower clad, and first and second electrodes provided on the upper surface of the core and the lower clad, respectively. And a Q switch driving device for applying a voltage between the two electrodes in an on / off manner. The clad is provided on the lower surface side of the core in order to confine light in the core. The first electrode and the second electrode described above are made of a material having high electrical conductivity, and are formed on the core ridge and the lower cladding surface, respectively.

  In the switch element of the present invention, an optical buffer means is provided between the first electrode and the core ridge or between the second electrode and the lower clad to prevent light from being attenuated by the electrode material. Has the structure. The core is made of an electro-optic crystal, and is made of a material whose refractive index changes due to an electro-optic effect when an electric field is applied between the electrodes on both end faces.

  The optical waveguide in the switch element of the present invention is manufactured by joining the core material and the clad material having different refractive indexes by the direct joining method without using the titanium diffusion method as in the prior art. Hereinafter, the configuration and manufacturing method of the switch element of the present invention will be described in more detail. Each of the following examples is shown for illustration, and as long as the technical idea of the present invention is included, these implementations are not necessarily performed. Needless to say, the examples are not limited.

  FIG. 1 is a perspective view showing a configuration of an optical waveguide switch element according to Embodiment 1 of the present invention. In FIG. 1, in addition to the optical waveguide switch element 10, a part of a laser device including a Q switch driving device 7 and a polarizer 8 is also drawn.

  FIG. 2 is a cross-sectional view of the surface including the AA ′ line in FIG. 1 of the optical waveguide switch according to the first embodiment of the present invention. First, referring to FIG. 2, the optical waveguide switch 10 is composed of a channel optical waveguide 10. The optical waveguide 10 includes a core ridge 3, a lower clad 4 below the core ridge 3, and an optical buffer layer 5 that covers the entire surface of the core ridge 3 and the clad 4. The first electrode 1 is formed on the upper surface of the core ridge 3, and the second electrodes 2 a and 2 b are formed on the upper surface of the cladding 4 via the optical buffer layer 5.

  That is, the optical switch element of the present invention is a switch element that changes the light intensity using the electro-optic effect, and is joined to the electro-optic material having a high refractive index that propagates light, and the electro-optic material. A dielectric material having a refractive index lower than that of the optical material, and the electro-optic material is formed on the uppermost surface of the core ridge of the optical waveguide, the optical waveguide having a channel-type structure constituting the core ridge, A first electrode to which a driving voltage for changing a dielectric constant of the electro-optic material is applied; and a second electrode that is formed on the dielectric material and to which the driving voltage is applied.

  Referring again to FIG. 1, the first electrode 1 and the second electrodes 2 a and 2 b of the optical waveguide switch element 10 are connected to the Q switch driving device 7. Only linearly polarized light 6 having an angle of 45 degrees with respect to the x-axis passing through the polarizer 8 is incident on one end of the core ridge 3 of the optical waveguide switch element 10. Propagating in the z-direction through the core ridge 3, polarized light 9 is emitted as outgoing light 9 from the other end. The optical buffer layer 5 is provided in order to prevent a part of the guided light from being absorbed in the electrode 1 and increase in propagation loss. That is, the optical switch element of the present invention is characterized in that an amorphous material thin film is provided between at least one of the first electrode and the core ridge or between the second electrode and the dielectric material.

  FIG. 3 is a diagram showing a configuration of a Q-switch laser oscillation apparatus including the optical switch element of the present invention. The Q-switch laser oscillation device 100 includes a laser medium 12 and the optical switch element 10 of the present invention placed between two reflection devices 16 and 17. In an optical path between the optical switch element 10 and the laser medium 12, a polarizer 8 and a first collimator device 11 are provided. Further, the second collimating device 13 is also provided between the reflecting device 14 for extracting the output light 17 and the laser medium 12, and the third collimating device 13 is provided between the optical switch element 10 and the reflecting device 16. Is provided.

Examples of the laser medium 12 include Nd: YAG, CO ₂ , and a dye laser. In this embodiment, the oscillation wavelength is 1.06 μm. In each of the collimator devices 11, 13, and 15, when the laser beam reciprocates in the resonator, the diameter of the laser beam is widened, so that light does not efficiently enter the waveguide mode of the laser medium or the waveguide type element. To prevent that. Specifically, an optical lens system is used as each collimator, and input / output is performed with a beam diameter optimum for the laser medium 12 and the waveguide mode. However, the beam diameter can be optimized by this optical lens system by making the shapes of the reflectors (mirrors) 14 and 16 for the resonator concave. Therefore, the second collimating device 13 and the third collimating device 15 adjacent to the reflecting devices 14 and 17 can be omitted.

Returning to FIG. 2 again, in the optical switch element of this example, a Z-cut LN crystal substrate (ZnLN) added with ZnO as a core material and a Z-cut LN crystal substrate added with MgO as a cladding material are used. It was. These two substrates are joined by direct joining. Thereafter, the core ridge 3 was formed by dry etching, and an SiO ₂ film was further formed by sputtering as the optical buffer layer 5. After producing the optical waveguide, a gold electrode was formed by vapor deposition, and the first electrode 1 on the core ridge and the second electrodes 2a and 2b on the clad were produced by a wet etch process. Next, the operation of the optical switch according to the first embodiment of the present invention shown in FIGS. 1 and 2 will be described.

  FIG. 4 is an explanatory diagram showing an electric field distribution in the optical waveguide device generated by applying a voltage between the electrodes in the optical waveguide switch device of the first embodiment. FIG. 4A is a cross-sectional view showing a location where the electric field distribution of the optical waveguide device is calculated, and shows only the right half region of the device in consideration of symmetry. FIG. 4B shows an electric field distribution when a unit voltage (1 V) is applied between the electrodes in a region substantially corresponding to the rectangular region surrounded by the broken line in FIG. The positions of 0 and 60 on the horizontal axis in FIG. 4B correspond to both ends of the rectangular area in FIG. The position 20 on the vertical axis in FIG. 4B corresponds to the upper end of the rectangular area in FIG. 4A, and the position 0 on the vertical axis corresponds to the boundary between the core ridge 3 and the clad 4 in FIG. The unit of each axis in FIG. 4B is μm.

  The small area of each triangle in FIG. 4B is an analysis unit in the finite element method. The core ridge thickness, core width (upper side of the core 3 in FIG. 2), and electrode interval (gap in the x-axis direction between the electrode 1 and the electrode 2a or 2b) of the optical waveguide type Q switch element of this example are as follows: They are 7 μm, 9 μm, and 5 μm, respectively. As can be seen from the electric field distribution in FIG. 4B, the vertical y-direction electric field mainly dominates at the center of the core 3, and the horizontal x-direction electric field is almost negligible.

Therefore, when the voltage V is applied between the electrodes, the refractive index of the core changes in the x direction and the y direction as follows due to the primary electro-optic effect.
Δnx = −0.5 × nx ³ × r ₁₃ × a × V Formula (1)
Δny = −0.5 × ny ³ × r ₃₃ × a × V Formula (2)
In Expressions (1) and (2), a is a coefficient representing how much of the applied voltage contributes to the y-direction electric field at the core center. In the waveguide size and electrode arrangement, a is approximately 0.055 × 10 ⁶ . nx and ny indicate refractive indexes in a direction parallel to and perpendicular to the substrate of the core material, respectively. r ₁₃ and r ₃₃ indicate refraction in a direction parallel to and perpendicular to the substrate of the core material, respectively. The rate electro-optic constant is shown. Further, the birefringence change Δn is expressed by the following equation.
Δn = 0.5 (ny ³ r ₃₃ −nx ³ r ₁₃ )
Here, when the electrode length is L, the guided light passes through the electrode, and then a phase difference φ between intrinsic polarizations expressed by the following equation, that is, retardation is generated.
φ = 2πλ ⁻¹ ΔnL

In the laser resonator, only the linearly polarized light 6 having an angle of 45 degrees with respect to the x axis is incident on the core 3 of the optical waveguide switch element by the polarizer 8 and reflected by the mirror of the resonator not shown in FIG. The The reflected light again passes through the core 3 of the optical waveguide element, so that the amount of retardation is doubled and the following phase difference is generated as a whole.
φ _total = 2 × φ
If Φ _total is π, the light is reflected by the reflector of the oscillator and transmitted through the switch element 1, and after passing through the 45 ° polarizer 8, it becomes linearly polarized light again orthogonal to the transmission axis of the polarizer 8. . For this reason, light can be blocked and the Q value of the laser resonator can be controlled.

  Therefore, the present invention can be applied to a Q-switch laser oscillation device, and includes the above-described waveguide switch element, a drive device that supplies a drive voltage to the first electrode and the second electrode, and the waveguide A polarizer that selects the polarization of light to the waveguide switch element, a laser medium on which light passing through the core ridge of the waveguide switch element is incident, and an optical path that passes through the laser medium and the waveguide switch element It is possible to realize a Q-switched laser oscillation device comprising two reflecting devices arranged at both ends of the laser beam and a collimating device placed between the laser medium and the polarizer.

  As is well known, the Q-switched laser oscillation device can reduce the Q value by blocking light and obtain a large inversion distribution so as not to oscillate. Then, the light is transmitted in accordance with the time when the inversion distribution is maximized, and the Q value is rapidly increased, so that the oscillation rapidly occurs and a short optical pulse is obtained. In the switch element of this example, the electrode length was 40 mm, and the switch voltage was about 2.4V.

  FIG. 5 is a diagram showing the response characteristics of the transmittance of the optical waveguide switch element of the present embodiment. A sine wave oscillator for evaluation was connected between the electrodes of the optical waveguide switch element 1, and a drive voltage was applied. The left vertical axis represents the sine wave of the drive voltage applied between the electrode 1 and the electrodes 2a and 2b, and the right vertical axis represents the light transmittance at that time. The drive voltage (pp) is about 2.4 V, and a high extinction ratio modulation characteristic is obtained. If the extinction ratio is expressed in decibels of minimum transmittance value / maximum transmittance value, an extinction ratio of 13 dB is obtained. Moreover, the response with respect to the input signal of frequency 1GHz was shown, and it has confirmed that the waveguide type switch element laser of this invention had sufficient zone | band to use as a Q switch.

  It should be noted that in the switching element 1 of the present invention shown in FIG. 1, the scale in the z direction and the scale in the x-axis and y-axis directions are not drawn in exact proportion. That is, the electrode length in the z-axis direction is appropriately adjusted according to other necessary conditions, and is not limited to the relationship in dimensions between the switch elements depicted in FIG.

  In the optical waveguide type switch element of this example, the electrode spacing can be made extremely narrow by adopting a waveguide configuration. For this reason, the driving voltage is significantly reduced as compared with the conventional Q switch element (several hundreds V or more), and a driving voltage of about 2.4 V is sufficient. A Q-switch operation is performed by turning on and off the voltage using a generally easily available signal generator that does not require an additional peripheral circuit, and an optical pulse having a pulse width of 5 ns and a light intensity of 2 W is optically damaged. It was possible to generate stably while suppressing.

The configuration of the optical waveguide switch element of the second embodiment is the same as the configuration shown in FIGS. 1 and 2 of the first embodiment. In this example, a substrate material different from that of Example 1 was used, and a Z-cut ZnLN crystal substrate was used as the core material, and a Z-cut LT crystal substrate was used as the cladding material. These two substrates are joined by direct joining. Then, after forming a core ridge by dry etching, an SiO ₂ film as an optical buffer layer was formed by a CVD method unlike the sputtering in Example 1. After producing the optical waveguide, a gold electrode was formed by vapor deposition, and electrodes were produced on the upper surface of the core ridge and the upper surface of the clad by a wet etch process.

  FIG. 6 is an explanatory diagram showing an electric field distribution in the optical waveguide device generated by applying a voltage between the electrodes in the optical waveguide switch device of the second embodiment. FIG. 6A is a cross-sectional view showing the location where the electric field distribution of the optical waveguide device is calculated, and shows only the right half region of the device in consideration of symmetry. FIG. 4B shows an electric field distribution when a unit voltage (1 V) is applied between the electrodes in a region substantially corresponding to the rectangular region surrounded by the broken line shown in FIG. The relationship between (a) and (b) in FIG. 6 is the same as in FIG. The core ridge thickness, the core width, and the electrode interval of the optical waveguide switch element of this example are 5.2 μm, 6 μm, and 5 μm, respectively. As in the case of the first embodiment, the vertical y-direction electric field is mainly dominant at the core center, and the horizontal x-direction electric field can be almost ignored.

The coefficient a is approximately 0.058 × 10 ⁶ in the material used for the optical waveguide switch element of this embodiment, the waveguide size, and the electrode arrangement. In this example, since the electrode length was 35 mm, the switch voltage was about 2.6V.

  FIG. 7 is a graph showing the response characteristics of the transmittance of the optical waveguide switch element of Example 2. In FIG. The vertical axis on the right shows the sinusoidal drive voltage applied between the electrode 21 and the electrodes 22a and 22b, and the vertical axis on the left shows the transmittance at that time. A high extinction ratio modulation characteristic is obtained when the drive voltage (pp) is about 2.6V. In this example, the response to an input signal having a frequency of 2 GHz is shown, and it was confirmed that the optical waveguide type switch element of this example has a sufficient band for use as a laser Q switch.

  Also in the optical waveguide type switch element of this embodiment, since the distance between the electrodes can be made very narrow by forming the waveguide, the driving voltage is only about 2.6V. A Q signal is operated by turning on and off the voltage using a generally available simple signal generator that does not require an additional peripheral circuit, and an optical pulse with a pulse width of about 3 ns and a light intensity of 3 W is obtained. It was possible to generate stably while suppressing optical damage.

The configuration of the optical waveguide switch element according to the third embodiment is the same as that shown in FIGS. 1 and 2 shown in the first embodiment. In this example, a substrate material different from those in Example 1 and Example 2 was used, and a Z-cut ZnLN crystal substrate was used as the core material, and an SiO ₂ substrate was used as the cladding material. These two substrates are joined by direct joining. Thereafter, a core ridge was formed by dry etching, and then an SiO ₂ film was formed as an optical buffer layer by the CVD method as in Example 2. After producing the optical waveguide, a gold electrode was formed by vapor deposition, and electrodes were produced on the upper surface of the core ridge and the upper surface of the cladding by a wet etch process.

  FIG. 8 is a diagram illustrating an electric field distribution in the optical waveguide device generated by applying a voltage between the electrodes in the optical waveguide switch device of the third embodiment. FIG. 8A is a cross-sectional view showing a location where the electric field distribution of the optical waveguide element is calculated, and shows the right half region of the element in consideration of symmetry. FIG. 8B shows an electric field distribution when a unit voltage (1 V) is applied between the electrodes in a region substantially corresponding to the rectangular region surrounded by the broken line shown in FIG. The relationship between (a) and (b) in FIG. 8 is the same as in FIG. The core ridge thickness, the core width, and the electrode interval of the optical waveguide switch element of this example are 5 μm, 5 μm, and 5 μm, respectively. In the present embodiment as well, as in the case of the first embodiment, the electric field in the y direction in the vertical direction mainly dominates at the center of the core, and the electric field in the x direction in the horizontal direction can be almost ignored.

The coefficient a is approximately 0.026 × 10 ⁶ in the material used for the optical waveguide switch element of the present embodiment, the waveguide size, and the electrode arrangement. In this example, the electrode length was 50 mm, and the switch voltage at this time was about 4.0V.

  FIG. 9 is a diagram showing the response characteristics of the transmittance of the optical waveguide switch element of this example. The right vertical axis represents the sine wave of the drive voltage applied between the electrode 31 and the electrodes 32a and 32b, and the left vertical axis represents the transmittance at that time. A high extinction ratio modulation characteristic is obtained when the drive voltage (pp) is about 4.0V. Also, the response to an input signal having a frequency of 1 GHz is shown, and it was confirmed that the optical waveguide switch element of this example has a sufficient band for use as a laser Q switch.

  Also in the optical waveguide type switch element of this embodiment, since the distance between the electrodes can be made very narrow by forming the waveguide, the drive voltage is only about 4.0V. Q switch operation is performed by turning on and off the voltage using a generally available simple signal generator, and an optical pulse with a pulse width of about 0.02 μs and an optical intensity of 3.5 W is suppressed from optical damage. However, it was able to occur stably.

  As described above in detail, according to the present invention, it is possible to drive at a low voltage by light polarization due to an electro-optic effect in an optical waveguide manufactured by a direct bonding method, or a refractive index change in the optical waveguide, It is possible to realize a miniaturized optical waveguide switch element that controls light with a high extinction ratio and has high optical power resistance.

  The present invention is generally applicable to a laser oscillation device.

1, 2 a, 2 b, 21, 22 a, 22 b, 31, 32 a, 32 b Electrode 3 Core ridge 4 Clad 5 Optical buffer layer 6 Incident light 7 Q switch driving device 8 Polarizer 9 Emission light 10 Channel type optical waveguide 11, 13, 15 Collimator 12 Laser medium 14, 16 Reflector 100 Q-switched laser oscillator

Claims (6)

In a switch element that changes the light intensity using the electro-optic effect,
A high refractive index electro-optic material that propagates light;
An optical waveguide bonded to the electro-optic material, having a dielectric material having a lower refractive index than the electro-optic material, and having a channel-type structure in which the electro-optic material forms a core ridge;
A first electrode formed on an uppermost surface of the core ridge of the optical waveguide and applied with a driving voltage for changing a dielectric constant of the electro-optic material;
A waveguide type switch element, comprising: a second electrode formed on the dielectric material, to which the driving voltage is applied.   The amorphous material thin film is provided between at least one of the first electrode and the core ridge, or between the second electrode and the dielectric material. Waveguide type switch element. The electro-optic material is any one of LiNbO ₃ (LN) crystal added with ZnO, LN crystal added with MgO to a low refractive index material, LiTaO ₃ (LT) crystal, quartz crystal, or amorphous material. The waveguide type switching element according to claim 1 or 2, characterized in that Wherein the amorphous material thin film waveguide type switching element according to any one of claims 1 to 3, characterized in that it is composed of SiO _2.   5. The waveguide type switch element according to claim 1, wherein the channel structure of the optical waveguide is manufactured by a dry etching method. A waveguide switch element according to any one of claims 1 to 5,
A driving device for supplying a driving voltage to the first electrode and the second electrode;
A polarizer that selects the polarization of light to the waveguide switch element;
A laser medium on which light passing through the core ridge of the waveguide switch element is incident;
Two reflecting devices disposed at both ends of an optical path that passes through the laser medium and the waveguide switch element;
A Q-switched laser oscillation device comprising: a collimating device placed between the laser medium and the polarizer.

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