JPWO2005015701A1 - Light source using multi-beam laser - Google Patents

Abstract

The wedge-shaped transparent dielectric plates 9 and 9A facing the multi-beam laser 1 are opposed to each other. Part of the laser beam from the multi-beam laser 1 passes through both transparent dielectric plates. The remaining laser beam does not pass through both transparent dielectric plates. Between the laser beam that does not pass through both transparent dielectric plates and the laser beam that passes through, and between the laser beams that pass through both transparent dielectric plates, each laser beam has a plane perpendicular to the total laser beam. A difference occurs in the optical path length between the intersection and each light emitting point. If the transparent dielectric plate 9 is moved in parallel to the opposing surfaces, the optical path length difference can be changed between the laser beam that does not pass through the transparent dielectric plate 9 and the laser beam that passes through it.

Description

  The present invention relates to a light source using a multi-beam semiconductor laser that emits a plurality of laser beams, and more particularly to a light source used for recording and / or reproducing an optical recording signal.

For some time, attempts have been made to perform data recording and reproduction in parallel using multiple beams by using a multiple beam semiconductor laser in order to increase the data transfer speed of the optical disc apparatus. This type of technology is disclosed in, for example, Japanese Patent Laid-Open Nos. 1-204235 and 3-088153. In these apparatuses, usually, multiple beams are collected by one optical system, and a signal is recorded on an adjacent track, or an optical recording signal is reproduced from an adjacent track.
Here, the multi-beam semiconductor laser refers to a semiconductor laser (hereinafter simply referred to as “laser”) that outputs laser beams having the same or different wavelengths that can be controlled independently. There are two types, a monolithic multi-beam laser and a hybrid multi-beam laser. A monolithic multi-beam laser refers to a laser obtained by forming a plurality of active layers on one substrate by crystal growth and then performing main electrode processes and element isolation processes. A hybrid multi-beam laser is a laser element that outputs a single beam by crystal growth on separate substrates, and then an electrode process and an element separation process are performed for each, and then the laser elements are combined. It is designed to output multiple beams. A multi-beam laser having two or more beams having different oscillation wavelengths is particularly called a multi-wavelength laser.
In the above-described multi-beam laser according to the prior art, the emission points of all laser beams are formed in the same plane in front of the laser, and their positions in the optical axis direction are the same. However, the interval between the light emitting points is generally much wider than the interval between the recording marks recorded on the optical disc surface by a plurality of laser beams. Therefore, when a plurality of laser beams emitted from a multi-beam laser are condensed on the disk surface of the optical disk by one optical system, there is a problem that not all the beams are necessarily focused on the disk surface of the disk. It was.
Further, there is a land / groove recording / reproducing system in which information recording marks are written in both the concave and convex portions of the groove of the optical disk and information is read from the recording marks in order to increase the recording density. Due to the difference in groove depth that minimizes crosstalk between land recording / reproduction and groove recording / reproduction, in this method, when irradiating a beam simultaneously to each of the land and the groove, the land and the groove are optimal. Since the focal positions are different, it is necessary to shift the focal positions in the optical axis direction between the beam for recording / reproducing the land and the beam for recording / reproducing the groove. In addition, since the optimum focal position deviation amount varies depending on the track pitch and groove depth of the optical disc, it is desirable that the focal amount deviation amount can be changed for each individual optical disc.
In recent years, as a next-generation high-density optical disk apparatus, an apparatus using a nitride compound semiconductor laser (hereinafter referred to as “GaN blue-violet laser”) having an oscillation wavelength of about 405 nm is expected. However, even in such a next-generation optical disk device, a conventional DVD (Digital Versatile Disc) device using a red laser with an oscillation wavelength of 650 nm as a light source, or a CD-R (Compact Disc Recordable) using a laser with an oscillation wavelength of 780 nm as a light source. In order to maintain compatibility with the apparatus, it is desirable to mount not only a laser having an oscillation wavelength of 405 nm but also a laser having a wavelength of 650 nm or 780 nm. In this case, if a multi-wavelength laser formed monolithically is mounted, it is very advantageous in terms of cost and the like. However, in the apparatus using this multi-wavelength laser, the same problem as the multi-beam laser having the same wavelength as described above becomes more obvious. This is because the focal length of the lens differs depending on the oscillation wavelength of the laser because the refractive index of the material of the lens of the optical system has wavelength dependency.

Accordingly, an object of the present invention is a light source using a multi-beam laser, and an optical path length difference is given between each beam within the light source so that each laser beam is focused at a predetermined position. Alternatively, an object is to provide a light source capable of changing the optical path length difference.
Other objects of the present invention which are not specified here will become apparent from the following description and the accompanying drawings.
The tree invention is a light source using a multi-beam laser, and gives an optical path length difference between each beam inside the light source so that each laser beam is focused at a predetermined position. The main feature is to change.

FIG. 1 is a perspective view of a light source according to Embodiment 1 of the present invention,
FIG. 2 is a perspective view of a light source according to Example 2 of the present invention,
FIG. 3 is a perspective view of a light source according to a modification of the second embodiment of the present invention.
FIG. 4 is a perspective view of a light source according to Embodiment 3 of the present invention.
FIG. 5 is a perspective view of a light source according to Embodiment 4 of the present invention.
FIG. 6 is a perspective view of a light source according to Example 5 of the present invention.
FIG. 7 is a perspective view of a light source according to Embodiment 6 of the present invention, and
FIG. 8 is a perspective view of a light source according to Embodiment 7 of the present invention.

The resistance heating element according to the present invention will be described below.
A mirror is arranged at a different position from the light emitting surface for each laser beam so as to face the light emitting surface of a multi-beam semiconductor laser that emits a plurality of laser beams, or a transparent region having a different thickness for each laser beam. A dielectric is disposed.
With the above configuration, a difference occurs in the optical path length between the intersection where the plurality of laser beams intersect with a plane orthogonal to the laser beams after being output from the light source, and the emission point of the laser beams.
Alternatively, a transparent dielectric is arranged so as to face a light emitting surface of a multi-beam semiconductor laser that emits a plurality of laser beams so that a part of the plurality of laser beams is transmitted, and the transparent dielectric of the laser beams is transmitted. Make the distance variable. The remaining laser beam does not pass through the transparent dielectric.
With the above configuration, between the laser beam that passes through the transparent dielectric and the laser beam that does not pass, the laser beam intersects with a plane orthogonal to the laser beam after output from the light source, and the laser The difference in optical path length from the light emitting point of the beam becomes variable.
Hereinafter, preferred embodiments of a resistance heating element according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a light source according to Embodiment 1 of the present invention. A multi-beam laser 1 that emits four laser beams is mounted on a recess 3 formed on one main surface of a substrate 2. The multi-beam laser 1 is a monolithic GaN-based blue-violet multi-beam laser that emits a blue-violet multi-beam (four beams in this embodiment). All four emission points of the multi-beam laser 1 are formed in the same plane in front of the laser.
Planar mirrors 4 to 7 are formed at different distances from the respective light emitting points on the inner wall surface facing the light emitting surface of the multi-beam laser 1 among the inner wall surfaces defining the recess 3. Each laser beam emitted from the multi-beam laser 1 is reflected by a corresponding mirror. Each of the plane mirrors 4 to 7 is formed to be inclined with respect to the main surface of the substrate 2 so that the plane thereof is parallel to the direction in which the four laser beams emitted from the multi-beam laser 1 are arranged. . Each of these planes is preferably formed such that the perpendicular to each plane forms 45 ° with each laser beam, that is, each laser beam is deflected by 90 °. With such an arrangement, it is possible to prevent the cross section from expanding when each laser beam is reflected by the respective plane mirrors 4 to 7.
As is clear from the above description, the light source of the present embodiment is such that each of the plane mirrors 4 to 7 is formed at a different distance from each light emitting point. There is an effect that a difference occurs in the optical path length between the intersection of each reflected laser beam with the plane orthogonal to the entire laser beam and each light emitting point. And it is possible to fix these optical path length differences to arbitrary magnitude | sizes by the distance of each plane mirror 4-7 and each light emission point. Therefore, by setting these optical path length differences to an appropriate size, when the light source of this embodiment is incorporated in the optical disc apparatus, each laser beam is focused at a predetermined position with respect to the recording medium. In each case, the optical recording signal can be recorded and / or reproduced in an optimum state. Further, the light source of the present embodiment is such that the laser beam is mounted on the concave portion of one substrate in which the inner wall surface of the concave portion forms a mirror, and thus the above effect can be obtained with a compact configuration. Have
In the above description, a GaN blue-violet multibeam laser is used as the multibeam laser 1. The GaN-based blue-violet multi-beam laser is a multi-beam laser using a semiconductor represented by the general formula [InxAlyGa1-xyN] (0 ≦ x <1, 0 ≦ y <1, 0 ≦ x + y <1). is there. Such semiconductors have a wider forbidden band than general compound semiconductors such as InP and GaAs. Therefore, a laser using such a semiconductor emits light of a short wavelength (from green to ultraviolet region). , Enabling high-density recording on an optical recording medium. However, the multi-beam laser used for the light source of the present embodiment is not limited to the GaN blue-violet multi-beam laser, and may be a multi-beam laser using InP or GaAs. The multi-beam laser used for the light source of this embodiment may be a multi-wavelength laser in which at least the two laser beams have different wavelengths. Furthermore, the multi-beam laser used for the light source of this embodiment is not limited to a monolithic multi-beam laser, and may be a hybrid multi-beam laser. As shown in FIG. 1, the substrate 2 has a mirror surface such that the inner wall surface of the recess facing the light emitting surface of the multi-beam laser 1 is parallel to the direction in which a plurality of laser beams emitted from the multi-beam laser 1 are arranged. Any material can be used as long as it can form the film. Also, all the mirrors do not always have to be at different distances from each light emitting point, and at least two mirrors may only be at different distances. Needless to say, the number of laser beams emitted from the multi-beam laser is not limited to four, and may be any number as long as it is plural.

FIG. 2 is a perspective view of a light source according to Embodiment 2 of the present invention. In FIG. 2, the same reference numerals are given to the same parts as those in FIG. The light source according to the present embodiment is different from the light source according to the first embodiment shown in FIG. 1 in that each laser beam emitted from the multi-beam laser 1 is not reflected by a mirror, but a transparent dielectric plate 8 is used. It is a point of transmitting. The transparent dielectric plate 8 is made of sapphire, and a plurality of regions having different thicknesses in the traveling direction of the laser beam are formed stepwise corresponding to each light emitting point of the multi-beam laser 1. The stepped surface may face the light emitting surface of the multi-beam laser 1. Further, it is desirable that the surface of the transparent dielectric plate 8 facing the light emitting surface of the multi-beam laser 1 and the opposite surface are all parallel to the light emitting surface of the multi-beam laser 1. In that case, the laser beam incident on the surface of the transparent dielectric plate 8 goes straight as it is and is emitted from the opposite surface of the transparent dielectric plate 8.
Each laser beam emitted from the multi-beam laser 1 passes through a region having a different thickness of the transparent dielectric plate 8 corresponding to the laser beam. Accordingly, each laser beam emitted from the multi-beam laser 1 has a region having a refractive index substantially higher than that of air (refractive index in the a-axis direction of sapphire at a wavelength of 589 nm: 1.760) by different distances. Therefore, a difference occurs in the optical path length between the intersection of each laser beam transmitted through the transparent dielectric plate 8 and the plane perpendicular to the entire laser beam and each light emitting point. Then, by adjusting the thickness of each region of the transparent dielectric plate 8 in the traveling direction of the laser beam, it is possible to fix these optical path length differences to an arbitrary size. Accordingly, as in the first embodiment, by setting these optical path length differences to an appropriate size, when the light source of this embodiment is incorporated in the optical disc apparatus, each laser beam is predetermined with respect to the recording medium. The optical recording signals can be recorded and / or reproduced in an optimum state.
Note that the plurality of regions having different thicknesses of the transparent dielectric plate 8 do not always have to have different thicknesses, and at least two regions may be at different distances. In the above description, all the laser beams are transmitted through the transparent dielectric plate 8. However, there may be a laser beam that does not pass through the transparent dielectric plate 8 and passes only through the air layer. Further, when only one optical path length different from the optical path length of the laser beam passing through the air layer is required, the transparent dielectric plate 8 is formed with a uniform thickness in the traveling direction of the laser beam. Also good. Further, in this embodiment, a transparent dielectric made of sapphire is used as a material for adjusting the optical path length of each laser beam. However, a gas space (air or light source through which the laser beam passes) Any material can be used as long as it is a transparent material having a refractive index different from that of the sealing gas inside. Here, “transparent” does not necessarily mean that the absorption coefficient of the laser beam is 0, and it is sufficient that the absorption coefficient for the laser beam is sufficiently low in practice.
FIG. 3 shows a modification of the light source of this embodiment. 3, parts that are the same as the parts in FIG. 2 are given the same reference numerals, and redundant descriptions will be omitted as appropriate. The light source shown in FIG. 3 is different from the light source shown in FIG. 2 in that each of the laser beams emitted from the multi-beam laser 1 is formed in a plurality of steps having different thicknesses in the traveling direction of the laser beam. Instead of transmitting through the plate region, the transparent dielectric plate transmits through a plurality of regions having different refractive indexes. Since the two laser beams pass through the transparent dielectric regions 131 and 132 having different refractive indexes of the transparent dielectric plate 13, they have different optical path lengths inside the transparent dielectric plate 13. Therefore, it is clear that the light source shown in FIG. 3 has the same effect as the light source shown in FIG.

FIG. 4 is a perspective view of a light source according to Embodiment 3 of the present invention. 4, parts that are the same as the parts in FIG. 2 are given the same reference numerals, and redundant descriptions will be omitted as appropriate. The light source according to the present embodiment is different from the light source according to Embodiment 2 shown in FIG. 2 in that the transparent dielectric plate whose thickness changes stepwise is not opposed to the multi-beam laser, but a wedge shape. The transparent dielectric plates 9 are opposed to each other.
The wedge-shaped transparent dielectric plate 9 is disposed so that the surface on the opposite side of the inclined surface faces the light emitting surface of the multi-beam laser 1. The wedge-shaped transparent dielectric plate 9 is movable on the substrate 2 in a direction perpendicular to each laser beam from the multi-beam laser 1 or in a direction parallel to the inclined surface. In the arrangement of FIG. 4, at least one emitted from the multi-beam laser 1 when the transparent dielectric plate 9 is moved to the rightmost side at least in the traveling direction of the laser beam emitted from the multi-beam laser 1. The transparent dielectric plate 9 is disposed so that one laser beam does not pass through the transparent dielectric plate 9 and at least one laser beam passes through the transparent dielectric plate 9. In this case, since the laser beam passing through the transparent dielectric plate 9 is refracted on the slope of the wedge, the laser beam deviates from the perpendicular direction. For example, a single mirror (not shown) is used to It is easy to modify the passing laser beam parallel to the non-passing laser beam. Alternatively, a transparent dielectric plate similar in shape to the transparent dielectric plate 9 may be arranged in the traveling direction of the laser beam that does not pass through the transparent dielectric plate 9. If the wedge-shaped transparent dielectric plate 9 is movable in a direction parallel to the inclined surface, the emission point of the emitted beam may be shifted when the wedge-shaped transparent dielectric plate 9 is moved. Absent.
In such an arrangement, the transparent dielectric through which the laser beam passes between the laser beam that does not pass through the transparent dielectric plate 9 and the laser beam that passes through and between the laser beams that pass through the transparent dielectric plate 9. Since the distance of the body plate 8 (zero for laser beams that do not pass through the transparent dielectric plate 9) is different, it is clear that the light source of this embodiment has the same effect as the light source of Embodiment 2. Further, in the light source of this embodiment, the transparent dielectric plate 9 can be obtained by moving the wedge-shaped transparent dielectric plate 9 in a direction perpendicular to each laser beam from the multi-beam laser 1 or in a direction parallel to the inclined surface. Between the laser beam that does not pass 9 and the laser beam that passes, the difference in optical path length between the intersection of the laser beam with the plane perpendicular to the laser beam and each light emitting point is continuously changed. It is possible.
The wedge-shaped transparent dielectric plate 9 may have its inclined surface facing the multi-beam laser 1. Further, the transparent dielectric plate 9 is not limited to the wedge shape, and the thickness in the direction of travel of the laser beam continuously changes nonlinearly in a direction parallel to the plane of the substrate 2 and perpendicular to the direction of travel of the laser beam. You may have the shape to do. In this case, when the transparent dielectric plate is moved, between the laser beams passing through the transparent dielectric plate, the intersection between the laser beam and the plane perpendicular to the laser beam, and each light emitting point The difference in the optical path length between them changes continuously.

FIG. 5 is a perspective view of a light source according to Embodiment 4 of the present invention. In FIG. 5, parts that are the same as the parts in FIG. 4 are given the same reference numerals, and redundant descriptions are omitted as appropriate. The light source according to this embodiment is different from the light source according to the third embodiment shown in FIG. 4 in that the wedge-shaped transparent dielectric plate 9A is opposed to the movable wedge-shaped transparent dielectric plate 9A. Is fixed on the substrate 2. The slopes of the two wedge-shaped transparent dielectric plates 9, 9A face each other in parallel. The slopes of the two wedge-shaped transparent dielectric plates 9 and 9A may be in contact with each other. The opposite surfaces of the slopes of the two wedge-shaped transparent dielectric plates 9 and 9A are parallel to the direction in which the plurality of laser beams are arranged.
As in the case of the third embodiment, the laser beam incident on the transparent dielectric plate 9 is refracted on the slope of the wedge and is emitted out of the orthogonal direction. However, if the laser beam is incident on the slope of the transparent dielectric plate 9A, 2 Since the two inclined surfaces are parallel, they are returned in the orthogonal direction and emitted as they are from the opposite surface of the transparent dielectric plate 9A. Therefore, in the case of the present embodiment, the laser beam that passes through the transparent dielectric plates 9 and 9A is parallel to the laser beam that does not pass, and the extra optical system required in the case of the third embodiment is unnecessary. It has the feature to do.
The wedge-shaped transparent dielectric plate 9 is moved in a direction perpendicular to each laser beam from the multi-beam laser 1 or in a direction parallel to the opposing surfaces of the two transparent dielectric plates 9 and 9A. And the laser beam that does not pass through the transparent dielectric plate 9 and the laser beam that passes through, the difference of the optical path length between the intersection of the laser beam with the plane perpendicular to the laser beam and each light emitting point It is possible to change continuously as in the case of the third embodiment. The transparent dielectric plate 9 may be fixed and the transparent dielectric plate 9A may be movable.

FIG. 6 is a perspective view of a light source according to Embodiment 5 of the present invention. In FIG. 6, the same parts as those in FIG. The light source according to this embodiment is different from the light source according to Embodiment 3 shown in FIG. 4 in that the wedge-shaped transparent dielectric plate is not opposed to the multi-beam laser, but a rectangular parallelepiped transparent dielectric plate 11. Is that they face each other. The rectangular parallelepiped transparent dielectric plate 11 is rotatable within the main surface of the substrate 2 around its center.
When the rectangular parallelepiped transparent dielectric plate 11 is rotated around its center, the distance of the laser beam passing through the transparent dielectric plate 11 through the transparent dielectric plate 11 continuously changes. Between the laser beam that does not pass 11 and the laser beam that passes, the difference in optical path length between the intersection of the laser beam with the plane perpendicular to the laser beam and each light emitting point is continuously changed. It is possible.
In this case, since the laser beam transmitted through the transparent dielectric plate 11 is refracted when entering and exiting the transparent dielectric plate 11, the laser beam deviates from the orthogonal direction. For example, a mirror (not shown) having an appropriate curved surface is used. It can be used to be parallel to the laser beam that does not pass through the transparent dielectric plate 11. The rotation of the transparent dielectric plate 11 can be realized using, for example, a micro electro mechanical system (MEMS) technique. Further, the shape of the transparent dielectric plate 11 is not limited to a rectangular parallelepiped, and any shape can be used as long as the distance through which the laser beam passes from the multi-beam laser changes when it is rotated around its center. There may be.

FIG. 7 is a perspective view of a light source according to Embodiment 6 of the present invention. In FIG. 7, the same parts as those in FIG. The light source according to this embodiment is different from the light source according to Embodiment 2 shown in FIG. 2 in that the thickness of the light source is not a transparent dielectric plate in which a plurality of regions having different thicknesses are formed in the traveling direction of the laser beam. Such a transparent dielectric plate 12 faces the multi-beam laser 1. The multi-beam laser 1 is a multi-wavelength laser in which at least two laser beams have different wavelengths.
Since the refractive index of a transparent dielectric such as sapphire generally has chromatic dispersion, when a laser beam having a different wavelength is transmitted from the multi-beam laser 1, the intersection of the laser beam with a plane orthogonal to the entire laser beam A difference occurs in the optical path length between each light emitting point.

FIG. 8 is a perspective view of a light source according to Embodiment 7 of the present invention. In FIG. 8, a multi-beam laser 21 is a monolithic dual wavelength laser composed of a blue-violet laser (oscillation wavelength 405 nm) and a red laser (oscillation wavelength 650 nm) monolithically grown on a GaN substrate. The laser beam emission end face is processed by a RIBE (reactive ion beam etching) method using chlorine gas, which is a kind of dry etching, to form a step.
In this embodiment, since the emission end face of the laser beam is formed so as to form a step, the intersection of the two laser beams emitted from the red laser and the blue-violet laser with the plane orthogonal to the two laser beams, There is an effect that a difference occurs in the optical path length between each light emitting point. For this reason, even when both beams are focused on the disk surface of the optical disk by one optical system, by designing the step of the exit end face to a desired value in advance, both laser beams can be applied to the optical disk. It becomes possible to focus at a predetermined position.
In the above description, a two-wavelength laser is used as the multi-beam laser. However, a laser that emits a multi-beam having three or more wavelengths may be used. Further, although the RIBE method is used to form the step of the emission end face, it may be another dry etching method [for example, reactive ion etching (RIE) method] other than the RIBE method, or a wet etching method. Any method can be used as long as it can form a resonator end face that is smooth and highly perpendicular to the element surface.
In the above embodiments, in Embodiments 3 to 5, only a part of the laser beam is incident and / or emitted without being orthogonal to the incident surface and / or the emission surface when passing through the transparent dielectric plate. Astigmatism associated therewith is added to these laser beams, and the other laser beams do not pass through the transparent dielectric plate, so such astigmatism is not added. For this reason, when the light sources of these embodiments are used as the light source of the optical disk apparatus, there is a difference in astigmatism of individual focused spots on the optical disk surface, although there is no practical problem. On the other hand, in Examples 2 and 6, since all the laser beams are incident and emitted perpendicularly to the incident surface and the emission surface when passing through the transparent dielectric plate, the non-interval between the laser beams is not generated. No difference is added to the point aberration.
In addition, Examples 1-6 may be used combining not only single but multiple things. Further, in Examples 1 to 7, if each laser beam is made variable in wavelength, an objective lens for condensing these laser beams on the optical disk when the light source of these examples is used as the light source of the optical disk apparatus. It is possible to finely adjust the focal length by using the chromatic aberration.
Although the present invention has been described above using some examples, the present invention is not limited to the above-described examples, and can be appropriately changed within the scope of the technical idea of the present invention. Needless to say.

Claims (18)

A light source using a multi-beam semiconductor laser that emits a plurality of laser beams, wherein at least two laser beams intersect with a plane orthogonal to the two laser beams after output from the light sources, and the two A light source having means for causing a difference in the optical path length from the laser beam emission point and changing the optical path length difference. The means for changing the optical path length difference includes a transparent material having a refractive index different from that of a gas space through which at least one of the two laser beams passes, and of the two laser beams. The light source according to claim 1, wherein any one of the transparent materials passes through the transparent substance. The light source according to claim 2, wherein a distance of the laser beam transmitted through the transparent material is variable. The transparent material has an incident surface or reflecting surface orthogonal to the optical axis of the laser beam incident on the transparent material, and an output surface or incident surface inclined with respect to the optical axis of the laser beam incident on the transparent material. The light source according to claim 3, wherein the light source is movable with a moving component in a direction perpendicular to an optical axis of a laser beam incident on the transparent material. A laser beam incident surface parallel to the emission surface of the transparent material and transmitting the transparent material, and a laser beam emission surface transmitting the transparent material parallel to the incident surface of the transparent material, The light source according to claim 4, wherein a transparent material having a refractive index equal to that of the transparent material is disposed to face the transparent material. The light source according to claim 3, wherein the transparent substance is rotatable. A light source using a multi-beam semiconductor laser that emits a plurality of laser beams, wherein at least two laser beams intersect with a plane orthogonal to the two laser beams after output from the light sources, and the two Means for producing a difference in the optical path length between the laser beam and the light emitting point of the laser beam, and the two laser beams are used as beams for recording and / or reproducing an optical recording signal on an optical recording medium. A light source characterized by being designed. A mirror on which each of the plurality of laser beams is incident is formed corresponding to the plurality of laser beams, and the surface of each mirror is parallel to the direction in which the plurality of laser beams are arranged. The light source according to claim 7, wherein each of the laser beams forms a 45 ° angle, and the distance between the two mirrors on which the two laser beams are incident and the emission points of the two laser beams are different. The light source according to claim 7, wherein the two laser beams are transmitted through a transparent material having a different refractive index from a gas space through which the two laser beams pass by a different distance. The light source according to claim 9, wherein the transparent material is formed so as to have a step at a distance through which the two laser beams pass in a region where the two laser beams are incident. The transparent material according to claim 9, wherein the transparent material has an incident surface orthogonal to an optical axis of a laser beam incident on the transparent material, and an output surface inclined with respect to the optical axis of the laser beam incident on the transparent material. light source. The light source according to claim 7, wherein the two laser beams pass through transparent materials having different refractive indexes. The light source according to claim 1, wherein the wavelengths of at least two laser beams are different from each other. A light source using a multi-beam semiconductor laser that emits a plurality of laser beams, wherein at least two of the plurality of laser beams have different wavelengths, and the two laser beams are the two laser beams. A light source that transmits the same distance through a transparent material made of the same material different from the gas space through which the laser beam passes. The light source according to claim 1, wherein light emitting surfaces of the at least two laser beams of the multi-beam semiconductor laser are in the same plane. The light source according to any one of claims 2 to 6 and 9 to 15, wherein the transparent material or a part of the transparent material is sapphire. The light source according to any one of claims 1 to 16, wherein the multi-beam semiconductor laser is a nitride compound semiconductor laser. The light source according to any one of claims 1 to 17, wherein the wavelength of at least one laser beam is variable.

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