JP2003318474A - Semiconductor laser unit - Google Patents

Abstract

(57) [Problem] To provide a semiconductor laser unit which mounts a polarization hologram element and realizes improvement of light receiving efficiency in a light receiving element. SOLUTION: A semiconductor laser light source 11 for irradiating laser light to pits formed on an optical information recording medium, a light receiving element 12 for photoelectrically converting reflected light from the optical information recording medium, and a light emitted from the semiconductor laser light source. A polarization hologram element 13 for separating the laser light and the reflected light by polarization, a cover glass 14 for preventing dust and the like from entering the inside, an adhesive 15 for fixing the polarization hologram element 13 to a cap 17, a semiconductor laser light source, and Stem 16 for holding and fixing the light receiving element
And the semiconductor laser light source 1 formed integrally with the stem 16.
1 and a cap 17 for protecting the light receiving element 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser unit, and more particularly to a semiconductor laser unit in which a diffraction grating, a light emitting element and a light receiving element are integrated.

[0002]

2. Description of the Related Art In recent years, with the development of personal computers and IT, the capacity of storage media has increased, and it has become difficult for conventional magnetic storage media to handle this. Therefore, an optical information recording medium having a storage capacity of an order of magnitude has come into general use. Therefore, an optical pickup device corresponding to various optical information recording media has been researched and developed, and one of them is a CD using a laser beam having a wavelength of 780 nm.
A DVD (Digital Video Disc) which is a (Compact Disc) type optical pickup for reading and writing, and another one using a laser wavelength of about 660 nm.
It is an optical pickup device for reading and writing of the system. In addition, as a high-density optical disc in the future, an optical disc pickup using a blue laser beam is also attracting attention. These optical pickup devices have their own technical problems, but they are common problems for downsizing and cost reduction of the pickup part, and researches to solve the problems are actively conducted. Has been. Then, as an effective configuration for downsizing and cost reduction of the optical pickup, an optical system using a polarization hologram element as a polarization separation element is adopted. This is an element for separating the forward and backward paths of the laser light. Conventionally, since a polarization beam splitter or the like was used, the optical system was upsized. The polarization hologram element not only solves this problem, but also has a great merit that the optical path can be easily designed and the number of parts can be reduced because the signal detection element can be arranged on the same surface as the laser emission. In addition, writing of multiple types of recording media with different recording densities
Even when one optical pickup is used for reading, it is considered to be an effective optical system because the optical path can be shared.

As such a polarization hologram element,
For example, Japanese Unexamined Patent Publication No. 2000-221325 discloses a technique for manufacturing a polarization separation element in which a periodic grating is formed with good yield by pattern-exposing ultraviolet rays to a polydiacetylene alignment film formed on an optically isotropic substrate. ing. According to this, when manufacturing the polarization separation element,
When the polydiacetylene alignment film as the birefringent material layer is pattern-exposed with ultraviolet rays, the pattern direction is aligned with the alignment direction of the polydiacetylene alignment film to form a periodic lattice parallel to the alignment direction. This allows
When the periodic grating is aligned with the above-mentioned orientation direction, the diffraction efficiency can be increased and the variation in the diffraction efficiency can be suppressed. Further, Japanese Patent Application Laid-Open No. 2000-75130 discloses a low-cost polarization separation element that does not take a long time to produce and can be easily produced without complicated steps. According to this, in order to separate two orthogonal polarization components, a birefringent film having a different refractive index with respect to the polarization plane of different incident light is loaded on the transparent substrate as a periodic uneven grating,
Further, an isotropic overcoat layer is coated or loaded on it, which is a polarization separation element for separating orthogonal polarization of incident light into 0th order light and diffracted light, and the birefringent film is a polymer birefringent film. (For example, a stretched organic polymer film). In addition, as an example of a laser unit light source using a polarization hologram element, Japanese Patent Laid-Open No. 9-63 is known.
In Japanese Patent Laid-Open No. 111, a light emitting element and a light receiving element for signal detection are mounted on the same cap, and in order to realize the configuration, a polarization hologram element is used, a part of which is used as output monitor light of the light emitting element. The technology used is disclosed.

[0004]

However, the polarization hologram elements as disclosed in the above publications theoretically have a maximum diffraction efficiency of about 40%, and it is impossible to further improve the diffraction efficiency. In addition, when used in optical pickups, etc., the laser light once passes through the element, and the laser light reflected on the disk surface is diffracted by the polarization hologram element and then enters the light receiving element, so that substantial diffraction occurs. Efficiency will be further reduced. In addition, there are variations in the characteristics of the polarization hologram element to be manufactured, and the efficiency decreases due to errors during mounting. Improvement is desired. In view of the above problems, it is an object of the present invention to provide a semiconductor laser unit that is equipped with a polarization hologram element and realizes an improvement in the light receiving efficiency of the light receiving element.

[0005]

In order to solve the above problems, the present invention provides a semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light.
A light receiving element for photoelectrically converting the reflected light from the optical information recording medium, a diffraction grating for polarization separating the laser light emitted from the semiconductor laser light source and the reflected light, the semiconductor laser light source, and holding and fixing the light receiving element And a cap that protects the semiconductor laser light source and the light receiving element,
And mounting the semiconductor laser light source and the light receiving element in parallel in the cap, the opening of the cap is provided at a position to be a beam emission port of the semiconductor laser light source,
The opening surface of the opening is formed to be perpendicular to the optical axis of the beam, and the diffraction grating is fixed to the opening so as to be inclined at a predetermined angle with respect to the opening surface. There is a relationship between the incident angle of light on the polarization hologram element and the diffraction efficiency that the diffraction efficiency increases when the incident angle is inclined at a predetermined angle. Therefore, in order to arrange the polarization hologram element at a predetermined angle with respect to the laser optical axis, when the polarization hologram element is fixed to the opening of the cap, the polarization hologram element is inclined and fixed at a predetermined angle. In this method, when fixing the polarization hologram element with an adhesive, the adhesive may be adhered by bending the getter so as to have a predetermined angle, or the adhesive may be solidified while maintaining the predetermined angle. According to this invention,
By arranging the polarization hologram element at a predetermined angle with respect to the laser optical axis, the diffraction efficiency can be improved and the light receiving efficiency of the semiconductor laser unit can be improved.

According to a second aspect of the present invention, a semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light, a light receiving element for photoelectrically converting reflected light from the optical information recording medium, and the semiconductor laser light source. A diffraction grating for polarization-separating the laser light and the reflected light emitted from the semiconductor laser light source, and a stem for holding and fixing the light receiving element, the semiconductor laser light source, and a cap for protecting the light receiving element, The semiconductor laser light source and the light receiving element are mounted in parallel in the cap, an opening portion of the cap is provided at a position that serves as a beam emission port of the semiconductor laser light source, and an opening surface of the opening portion is formed by the light beam of the beam. The diffraction grating is formed so as to be perpendicular to an axis, a surface on which the beam is incident is formed parallel to the opening surface, and a surface from which the beam is emitted is the opening surface. Characterized in that it is formed by a predetermined angle slanted against. There are various methods of inclining the diffraction grating, but there are a method of inclining the planar diffraction grating by some means and a method of inclining the surface of the diffraction grating itself at the time of production. In the former case, it is necessary to adjust the tilt angle when the device is installed at an angle, but in the latter case, the adjustment is not necessary because the product is manufactured with a predetermined accuracy at the time of manufacturing. According to this invention, since the surface of the beam exit of the diffraction grating is manufactured at a predetermined angle at the time of manufacturing, high angle accuracy can be ensured, and since the adjustment is not necessary, the manufacturing process can be simplified. it can.

According to a third aspect of the present invention, there is provided a semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light, a light receiving element for photoelectrically converting reflected light from the optical information recording medium, and the semiconductor laser light source. A diffraction grating for polarization-separating the laser light and the reflected light emitted from the semiconductor laser light source, and a stem for holding and fixing the light receiving element, the semiconductor laser light source, and a cap for protecting the light receiving element, The semiconductor laser light source and the light receiving element are mounted in parallel in the cap, an opening portion of the cap is provided at a position that serves as a beam emission port of the semiconductor laser light source, and an opening surface of the opening portion is formed by the light beam of the beam. The diffraction grating is tilted at a predetermined angle with respect to the axis, and the diffraction grating is fixed to the opening. As another method of inclining the diffraction grating, there is a method of providing a predetermined angle on the cap opening surface of the portion where the diffraction grating is fixed. This is because the cap is generally formed by a mold, and therefore the opening surface of the opening is designed in advance at that angle when the mold is manufactured. According to this invention, since the predetermined angle is provided on the opening surface of the cap for fixing the diffraction grating, the inclination angle is determined by the mold of the cap, and the manufacturing cost can be realized at low cost. According to a fourth aspect of the present invention, a plurality of the semiconductor laser light sources are provided, and a plurality of wavelengths corresponding to the optical information recording medium can be emitted. There are roughly two types of optical pickups. They are a CD-based optical pickup that uses a laser beam with a wavelength of 780 nm and a DVD-based optical pickup that uses a laser beam with a wavelength of 660 nm. Two types of laser light sources having different wavelengths are necessary to read information on the recording medium having these two types of wavelengths. Further, it is necessary to put this light source in one cap in order to reduce the size and cost of the device. According to this invention, since the two types of laser light sources having different wavelengths are provided in the cap, the semiconductor laser unit can be downsized and the cost can be reduced.

A fifth aspect of the present invention is characterized in that the diffraction grating is a diffraction grating in which diffracted light of a plurality of wavelengths for acquiring a signal is condensed at the same position of the light receiving element. If the reflected lights from the two light sources are condensed at different positions, a plurality of light receiving elements are required, the light receiving element becomes large, and the cost also increases accordingly. In order to prevent this, it is preferable to make the light collecting area as small as possible. According to this invention, by using the diffraction grating that focuses light at the same position of the light receiving element, the element can be downsized and the cost can be reduced. According to a sixth aspect of the present invention, the direction in which the diffraction grating is inclined at a predetermined angle with respect to the opening surface is opposite to the side of the light receiving elements mounted in parallel in the cap. The direction in which the diffraction grating is tilted must be oriented so that the area for receiving the reflected light from the recording medium is the largest with respect to the light receiving element. For that purpose, it is necessary to mount the semiconductor laser and the light receiving element in parallel on a plane and incline to the side opposite to the light receiving element side. According to this invention, the diffraction efficiency is improved by arranging the diffraction grating so as to be inclined to the side opposite to the light receiving element side, and the light receiving efficiency of the semiconductor laser unit can be further improved. Claim 7
The diffraction grating is a polarizing diffraction grating. The light emitted from the laser light source is first converted into circularly polarized light by the diffraction grating as the outward path and reflected by the recording medium. Then, as a return path, the reflected light is converted into linearly polarized light by the diffraction grating. By this operation, it is possible to separate the outward path and the return path of light using the same diffraction grating. That is, it is necessary for the diffraction grating to have polarizability. According to this invention, since the diffraction grating has a polarization property, it is possible to separate light with the same diffraction grating.

According to an eighth aspect of the present invention, the diffraction grating is formed by filling the diffraction grating with an optically transparent substrate, a birefringent film formed by stretching a polyester organic material, and a material having a controlled refractive index. The polarizing diffraction grating described above, an overcoat layer formed so as to fill the diffraction grating, and a λ / 4 plate that converts the phase of the laser beam are sequentially laminated. Λ / integrated with the polarization hologram
The laser light is converted into circularly polarized light by the effect of the four plates. Further, the laser light emitted from the unit passes through an optical element such as a collimator lens and is applied to the optical disc. The laser light applied to the optical disc carries signal information, enters the unit again, and passes through the λ / 4 plate again, thereby becoming linearly polarized light rotated by 90 degrees with respect to the outgoing light and diffracted by the polarization hologram element. receive. The diffracted laser light is guided to the light receiving element, and the signal of the optical disk can be read. According to this invention, since the λ / 4 plate integrated with the polarization hologram has a laminated structure, the optical system that achieves the polarization function can be made compact. According to a ninth aspect, the predetermined angle for fixing the diffraction grating is in the range of 2 ° to 6 °. The characteristics of the diffraction grating change up and down when the diffraction efficiency of the + 1st-order diffraction light and the -1st-order diffraction light is changed to ± with reference to the light incident angle of 0 °. At this time, the diffraction efficiency is highest in the range of 2 ° to 6 °. According to such a technical means, the diffraction efficiency can be maximized by setting the predetermined angle for fixing the diffraction grating within the range of 2 ° to 6 °.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, the constituent elements, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely explanatory examples, not the gist of limiting the scope of the present invention thereto, unless specifically stated. . FIG. 1 is a configuration diagram of a semiconductor laser unit according to a first embodiment of the present invention. With this structure, a semiconductor laser light source 11 that irradiates a pit formed on the optical information recording medium with laser light, a light receiving element 12 that photoelectrically converts reflected light from the optical information recording medium, and a semiconductor laser light source emits light. The polarization hologram element 13 for polarization-separating the laser light and the reflected light, the cover glass 14 arranged in the opening of the cap 17 to prevent dust and the like from entering the inside, and the polarization hologram element 13 are fixed to the cap 17. Adhesive 15
A stem 16 for holding and fixing the semiconductor laser light source and the light receiving element; a cap 17 mounted on the stem 16 for protecting the semiconductor laser light source 11 and the light receiving element 12;
Composed of. Then, the semiconductor laser light source 11 and the light receiving element 12 are mounted in parallel in the cap 17, and the cap 17 is placed at a position to be a beam emission port of the semiconductor laser light source 11.
Is provided, and the opening surface of this opening is set to the optical axis 1 of the beam.
8 and the polarization hologram element 13
Was fixed to the opening so as to be inclined at a predetermined angle (about 2 °) with respect to the opening surface. Here, the semiconductor laser 11 has a wavelength of 66
The LD is 0 nm, and the light receiving element 12 uses a Si photodiode.

The structure of the polarization hologram element 13 used in this embodiment is shown in FIG. BK7 here
The rectangular diffraction grating 4 is formed on a substrate 41 on which an organic birefringent film 42 formed by stretching a polyester organic material is formed on a substrate 41 via an adhesive layer made of an acrylic ultraviolet curing adhesive.
8, 49 and 50 are formed, and an overcoat layer 43 made of an epoxy-based ultraviolet curable resin is formed on the upper part thereof so as to fill the lattice, and a λ / 4 plate is formed on the upper layer as an optically transparent isotropic substrate. BK7 substrate 4 with 44 formed in advance
6 are stacked. Further, here, an antireflection layer for the wavelength used is provided at the interface of the BK7 substrate with air. The rectangular diffraction grating 49 portion is a portion for detecting the signal of the optical disc, and is a polarization hologram element for detecting the Tr signal and the Fo signal. The rectangular diffraction grating 50 portion is a polarization hologram element for reflecting a part of the output of the semiconductor laser light source directly on the light receiving element and monitoring the output, and a reflection film 45 made of Al is provided on the upper portion thereof. Further, the rectangular diffraction grating 48 is a polarization hologram element for detecting the tilt of the optical disc, and in combination with the diffraction grating 47 made of glass therebelow, the tilt is detected by using a part of the output of the semiconductor laser. It is a part. Here, the diffraction gratings of the diffraction gratings 48, 49, and 50 have a pitch of about 2 μm and a depth of about 4.0 μm, and a diffraction efficiency of about 40% is obtained.

Next, the operation of the present embodiment will be described with reference to FIGS. 1 and 4 when it is used for an optical pickup. The laser light emitted from the semiconductor laser 11 is generated by the cover glass 14 and the polarization hologram element 49.
And is emitted from the unit. At that time, the laser light is converted into circularly polarized light by the effect of the λ / 4 plate 44 integrated with the polarization hologram. Further, the laser light emitted from the unit passes through an optical element such as a collimator lens (not shown) and is applied to the optical disc. The laser light applied to the optical disc carries signal information,
By entering the unit again and passing through the λ / 4 plate 44 again, the outgoing light becomes a linearly polarized light rotated by 90 ° and is diffracted by the polarization hologram element 49. The diffracted laser light is guided to the light receiving element 12, and the signal of the optical disc can be read. The laser light that has passed through the polarization hologram element 50 is used as light for monitoring the output of the semiconductor laser. In the operation, the laser light incident on the polarization hologram element 50 is reflected by the reflection film 45 and guided to the light receiving element 12. Here, the laser light reflected by the reflection film 45 by passing through the λ / 4 plate 44 twice is diffracted by the polarization hologram element 50 and guided to the light receiving element 12. The output of the semiconductor laser is controlled by the received light. Also,
The laser light that has passed through the diffraction grating 47 made of glass passes through the polarization hologram element 48 and is irradiated onto the optical disc.
It passes through the polarization hologram element 48 and is guided to the light receiving element 12. This is used as laser light for detecting the tilt of the optical disc. As for the diffraction efficiency of the polarization hologram element, data of the diffraction efficiency with respect to the inclination of incident light is shown in FIG. In this figure, the vertical axis represents the diffraction efficiency (%) and the horizontal axis represents the light incident angle (°). According to this, by tilting +2 degrees, the efficiency of the + 1st order diffracted light can be improved from 40% to 45%. Thus, in the first embodiment, the polarization hologram element 1
3 is tilted from the laser optical axis 18 and its direction is shown in FIG.
When it is arranged as described above and is fixed to the opening portion of the cap 17, the cap 17 is inclined and fixed. Thereby, the diffraction efficiency is improved and the light receiving efficiency of the semiconductor laser unit is improved.
Further, a polarizing diffraction grating is used as the diffraction grating, and the diffraction grating is made of a material in which a birefringent film 42 having the diffraction grating is formed on an optically transparent substrate 41 to control the refractive index. The birefringent film 42 is an organic material, and is a material to which birefringence is added by stretching. As a result, the light receiving efficiency of the semiconductor laser unit is improved and the cost is reduced.

FIG. 2 is a block diagram of a semiconductor laser unit according to the second embodiment of the present invention. Since the same components are designated by the same reference numerals, duplicate description will be omitted. 2 is different from FIG. 1 in that the polarization hologram element 2
3 is that the surface on which the beam is incident is formed parallel to the opening surface, and the surface on which the beam is emitted is formed inclined with respect to the opening surface by a predetermined angle (about 2 °). Here, the semiconductor laser has a wavelength of 660 nm and the light receiving element is S
i photodiode is used. The configuration of the polarization hologram element 23 used in this embodiment is shown in FIG.
Same as the above, but the part to be bonded to the cap part of the unit was inclined about 2 °. As described above, in the second embodiment, since the polarization hologram element 23 is tilted with respect to the laser optical axis 18, the surface from which the beam is emitted is tilted at a predetermined angle (about 2 °) with respect to the opening surface. . Thereby, the diffraction efficiency is improved and the light receiving efficiency of the semiconductor laser unit is improved. In addition, a polarizing diffraction grating is used as the diffraction grating, and the diffraction grating is composed of a birefringent film with a diffraction grating formed on an optically transparent substrate and is diffracted by a material whose refractive index is controlled. It is a polarizing diffraction grating filled with a grating, and its birefringent film is an organic material and is a material to which birefringence is added by stretching. As a result, the light receiving efficiency of the semiconductor laser unit is improved and the cost is reduced.

FIG. 3 is a block diagram of a semiconductor laser unit according to the third embodiment of the present invention. FIG. 7A is a configuration diagram when one semiconductor laser is provided, and FIG. 7B is a configuration diagram when two semiconductor lasers are provided. 3A is different from FIG. 1 in that the opening surface of the opening of the cap 27 is tilted at a predetermined angle (about 2 °) with respect to the optical axis of the beam, and the polarization hologram element 2 is placed there.
This is the point where 5 is fixed. 3B is different from FIG. 1 in that the opening surface of the opening of the cap 37 is tilted at a predetermined angle (about 2 °) with respect to the optical axis of the beam, and the polarization hologram element 34 is fixed thereto. A plurality of semiconductor lasers 31,
That is, 32 is used. Here, the semiconductor laser has a wavelength of 6
60 nm LD and 780 nm LD, the light receiving element is Si
I am using a photodiode. Here, the configuration of the polarization hologram element used in the present embodiment is the same as that in FIG. 4, so the description thereof will be omitted, but the rectangular diffraction grating 49 portion is a portion for detecting a signal of the optical disc. ,
A polarization hologram element for detecting a Tr signal and a Fo signal. In this portion, the diffraction grating of each wavelength is divided into strips and patterned so that the laser light of two wavelengths as shown in FIG. 3B can be guided to the light receiving element. The rectangular diffraction grating 50 portion is a polarization hologram element for reflecting a part of the output of the semiconductor laser light source directly on the light receiving element and monitoring the output, and a reflection film made of Al is provided on the upper portion thereof. The rectangular diffraction grating 48 is a polarization hologram element for detecting the tilt of the optical disc, and the diffraction grating 47 made of glass below the polarization hologram element.
This is a part for detecting tilt by using a part of the output of the semiconductor laser in combination with. Here, the diffraction gratings of the diffraction gratings 48, 49 and 50 have a pitch of about 2 μm,
The depth is about 4.0 μm and the diffraction efficiency is 6
Efficiency of about 40% is obtained for a 60 nm LD and about 35% for a 780 nm LD.

Next, the operation of the embodiment shown in FIG. 3B will be described when it is used in an optical pickup. The basic operation is the same as in the first and second embodiments, but the same operation is performed with respect to the laser light of two wavelengths. Further, the laser light to the light receiving element is operated such that laser light of two different wavelengths can be received in the same area, and thus the light can be received without increasing the number or area of the light receiving elements. Here, in the present embodiment, the polarization hologram element 34 is arranged so as to be tilted from the laser optical axis, and the direction thereof is arranged as shown in the figure and tilted and fixed. Thereby, the diffraction efficiency is improved and the light receiving efficiency of the semiconductor laser unit is improved. In addition, a polarizing diffraction grating is used as the diffraction grating, and the diffraction grating is composed of a birefringent film with a diffraction grating formed on an optically transparent substrate and is diffracted by a material whose refractive index is controlled. It is a polarizing diffraction grating filled with a grating, and its birefringent film is an organic material and is a material to which birefringence is added by stretching. As a result, the light receiving efficiency of the semiconductor laser unit is improved and the cost is reduced. In addition, a polarization hologram element is adopted, which has a plurality of semiconductor lasers 31 and 32 having different wavelengths and allows the light receiving element to receive light in the same region. Further, since the diffraction grating has a plurality of functions, the semiconductor laser unit can be made multifunctional. In the first and second embodiments, the case where there is one semiconductor laser has been described, but it is also possible to use two semiconductor lasers having different wavelengths.

[0016]

As described above, according to the invention of claim 1, by arranging the polarization hologram element at a predetermined angle with respect to the laser optical axis, the diffraction efficiency is improved and the light receiving efficiency of the semiconductor laser unit is improved. Can be improved. Further, according to the second aspect, since the surface of the beam exit of the diffraction grating is manufactured at a predetermined angle at the time of manufacturing, high angle accuracy can be ensured, and adjustment is not necessary, so that the manufacturing process can be simplified. it can. Further, according to the third aspect, since the predetermined angle is provided on the cap opening surface of the portion for fixing the diffraction grating, the inclination angle is determined by the mold of the cap, and the manufacturing cost can be realized at low cost. Further, in claim 4,
By providing two types of laser light sources having different wavelengths in the cap, it is possible to realize the size reduction and the cost reduction of the semiconductor laser unit. Further, according to the fifth aspect, by using the diffraction grating that is focused on the same position of the light receiving element, the element can be downsized and the cost can be reduced. Further, in the sixth aspect, the diffraction efficiency is improved by arranging the diffraction grating so as to be inclined to the side opposite to the light receiving element side, and the light receiving efficiency of the semiconductor laser unit can be further improved. Further, in claim 7, since the diffraction grating has a polarization property, it is possible to separate light with the same diffraction grating. Further, in claim 8, λ / which is integrated with the polarization hologram
Since the four plates have a laminated structure, the optical system that achieves the polarization function can be made compact. In the ninth aspect, the diffraction efficiency can be maximized by setting the predetermined angle for fixing the diffraction grating within the range of 2 ° to 6 °.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a semiconductor laser unit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a semiconductor laser unit according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a semiconductor laser unit according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a polarization hologram element of the present invention.

FIG. 5 is a diagram showing data of diffraction efficiency with respect to the inclination of incident light according to the present invention.

[Explanation of symbols]

11 semiconductor laser light source, 12 light receiving element, 13 polarization hologram element, 14 cover glass, 15 adhesive, 1
6 stems, 17 caps, 18 optical axes

Claims (9)

[Claims] 1. A semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light, a light receiving element for photoelectrically converting reflected light from the optical information recording medium, and a semiconductor laser light source for emitting light. A semiconductor laser light source and a stem for holding and fixing the semiconductor laser light source and the light receiving element, and a cap for protecting the semiconductor laser light source and the light receiving element. A light source and the light receiving element are mounted in parallel in the cap, an opening portion of the cap is provided at a position to be a beam emission opening of the semiconductor laser light source, and an opening surface of the opening portion is perpendicular to an optical axis of the beam. And the diffraction grating is fixed to the opening so as to be inclined at a predetermined angle with respect to the opening surface. 2. A semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light, a light receiving element for photoelectrically converting reflected light from the optical information recording medium, and a semiconductor laser light source for emitting light. A semiconductor laser light source and a stem for holding and fixing the semiconductor laser light source and the light receiving element, and a cap for protecting the semiconductor laser light source and the light receiving element. A light source and the light receiving element are mounted in parallel in the cap, an opening portion of the cap is provided at a position to be a beam emission opening of the semiconductor laser light source, and an opening surface of the opening portion is perpendicular to an optical axis of the beam. In the diffraction grating, the surface on which the beam enters is formed parallel to the opening surface, and the surface from which the beam exits is located on the opening surface. The semiconductor laser unit, characterized in that it is formed by the angular inclination. 3. A semiconductor laser light source for irradiating a pit formed on an optical information recording medium with laser light, a light receiving element for photoelectrically converting reflected light from the optical information recording medium, and a semiconductor laser light source for emitting light. A semiconductor laser light source and a stem for holding and fixing the semiconductor laser light source and the light receiving element, and a cap for protecting the semiconductor laser light source and the light receiving element. A light source and the light-receiving element are mounted in parallel in the cap, an opening portion of the cap is provided at a position to be a beam emission opening of the semiconductor laser light source, and an opening surface of the opening portion is formed with respect to an optical axis of the beam. And a predetermined angle, and the diffraction grating is fixed to the opening. 4. The semiconductor laser unit according to claim 1, wherein a plurality of the semiconductor laser light sources are provided, and a plurality of wavelengths corresponding to the optical information recording medium can be emitted. 5. The diffraction grating is a diffraction grating in which diffracted light of a plurality of wavelengths for acquiring a signal is condensed at the same position of the light receiving element. The semiconductor laser unit described. 6. The direction in which the diffraction grating is inclined at a predetermined angle with respect to the opening surface is opposite to the side of the light receiving elements mounted in parallel in the cap. 4. The semiconductor laser unit according to any one of 3 to 3. 7. The semiconductor laser unit according to claim 1, wherein the diffraction grating is a polarization diffraction grating. 8. The diffraction grating is formed by filling the diffraction grating with an optically transparent substrate, a birefringent film formed by stretching a polyester-based organic material, and a material having a controlled refractive index. 6. A diffraction grating, an overcoat layer formed so as to embed the diffraction grating, and a λ / 4 plate for converting the phase of a laser beam, which are sequentially laminated. A semiconductor laser unit as described in 1). 9. The predetermined angle for fixing the diffraction grating is 2
The semiconductor laser unit according to any one of claims 1 to 3, wherein the semiconductor laser unit is in the range of 6 ° to 6 °.