JPH11110785A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device, which can simplify and miniaturize the device configuration in the case of using the plural laser beams of different wavelengths. SOLUTION: The output laser beam of a semiconductor laser element 1 is transmitted through a diffraction grating 3 as it is and advanced along with an optical axis Ma. On the other hand, the output laser beam of a semiconductor laser element 2 is first advanced along with an optical axis Mb and made incident to the diffraction grating 3. The 1st-order laser beam diffracted by the diffraction grating 3 is advanced along with the optical axis Ma. On the assumption that this 1st-order diffracted light is the transmitted light of the diffraction grating 3, it can be regarded from the design condition of the diffraction grating 3 its light emitting point 2A is located on the optical axis Ma of the semiconductor laser element 1, and light emitting points 1a and 2a of the semiconductor laser elements 1 and 2 apparently exist on the same optical axis Ma. Therefore, an optical system can be constituted commonly for the respective wavelengths of the semiconductor laser elements 1, and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device for outputting laser beams of a plurality of different wavelengths, and for example, relates to an improvement of a semiconductor laser device suitable for an optical pickup for CD and DVD.

[0002]

Background Art and Problems to be Solved by the Invention CD and DV
As a light source of an optical pickup in a disc player such as D, a semiconductor laser element is generally used. Here, the emission wavelength of the laser element is different for CD and DVD, 780 nm for CD-R and 65 for DVD.
It is 0 nm. In the first-generation DVD player, since only a laser element having an emission wavelength of 650 nm was incorporated, it was impossible to reproduce a CD-R. But,
It is convenient if one player can reproduce various discs such as CD, CD-R and DVD. Therefore, in order to enable reproduction of those discs, 650
An optical pickup incorporating a two-wavelength light source of nm / 780 nm has been studied.

FIG. 4 shows the background art of such a two-wavelength laser device. First, the one shown in FIG.
D and DVD are configured separately.
For VD900, a laser element 902 emitting light at a wavelength of 650 nm and an optical system 904 for DVD are provided.
Laser element 9 emitting 780 nm wavelength for D910
12, a CD optical system 914 is provided. In this method, the optical path from the laser element to the disk is DVD, C
D is independent.

In FIG. 4B, a laser element 902 for DVD and a laser element 912 for CD are provided in separate packages, and their output laser beams are separated by a wavelength filter (dichroic mirror) 920. Has been synthesized. Such a method is described in Sadao Mizuno et al.
Optical head '' (National Technical Report Vol.43 No.3
Jun. P. 275 (1997)). in this way,
An optical system 922 from the wavelength filter 920 to the disks 900 and 910 is shared by CD and DVD.

However, in such background art,
There are the following disadvantages. (1) In the method of FIG.
The pickups for D and CD are simply provided in parallel, and it is not possible to reduce the size and the number of parts. (2) In the method of FIG. 4 (B), although the number of common parts increases as compared with (A), a new wavelength filter is required,
This is not always satisfactory, for example, the number of parts increases and the device configuration becomes complicated.

The present invention has been made in view of the above points, and provides a semiconductor laser device capable of simplifying the device configuration when using a plurality of laser beams having different wavelengths and reducing the size thereof. Is the purpose.

[0007]

In order to achieve the above object, the present invention provides two semiconductor laser elements having different oscillation wavelengths, a diffraction grating or a hologram element incorporated in a housing, and two semiconductor lasers in the housing. The diffraction grating and the hologram element are designed such that the apparent light emitting points of the elements are on the same optical axis or the same point.

[0008] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. First, referring to FIG. 1 and FIG.
Form will be described. FIG. 1 shows a partially cutaway side view, and FIG. 2 shows a partially cutaway perspective view. In these figures, a first semiconductor laser device 1 having a unique oscillation wavelength and a second semiconductor laser device 2 having a unique oscillation wavelength different from the laser device are housed in a housing 4. The diffraction grating 3 is provided on the upper surface of the housing 4.

The semiconductor laser elements 1 and 2 are arranged in a housing 4 so that laser light enters from the same side of the diffraction grating 3. The light emitting point of the semiconductor laser device 1 is denoted by 1a, the output optical axis is denoted by Ma, and the light flux is denoted by MA. The light emitting point of the semiconductor laser device 2 is indicated by 2a, the output optical axis is indicated by Mb, and the light flux is indicated by MB. The diffraction grating 3 is designed to transmit the output laser light of the semiconductor laser element 1 as it is and output it, diffract the output laser light of the semiconductor laser element 2 and output the primary light in the direction of the optical axis Ma. Have been. That is, it is designed such that an apparent light emitting point 2A can be present on the optical axis Ma of the semiconductor laser element 1 assuming that the first-order diffracted light of the semiconductor laser element 2 is the zero-order transmitted light.

Next, the operation of the embodiment will be described. Focusing on the semiconductor laser element 1, the output laser light passes through the diffraction grating 3 as it is and travels along the optical axis Ma. On the other hand, the output laser light of the semiconductor laser element 2 first travels along the optical axis Mb and enters the diffraction grating 3. The primary laser light diffracted by the diffraction grating 3 travels along the optical axis Ma as described above. Here, assuming that this first-order diffracted light is transmitted light of the diffraction grating 3, it can be considered that the light emitting point 2 A is on the optical axis Ma of the semiconductor laser device 1 from the design conditions of the diffraction grating 3. it can.

Therefore, the light emitting points 1a and 2a of the semiconductor laser elements 1 and 2 are apparently present on the same optical axis Ma. As a result, the optical system from the diffraction grating 3 to the disk can be configured in common for each wavelength, and the configuration can be simplified to reduce the size and cost.

Next, another embodiment will be described with reference to FIG. In this embodiment, a hologram element is used instead of the diffraction grating. In the figure, a first semiconductor laser element 5 having a unique oscillation wavelength and a second semiconductor laser element 6 having a unique oscillation wavelength different from the laser element are housed in a housing 8. The hologram element 7 is provided on the upper surface of the housing 8.

The semiconductor laser elements 5 and 6 are arranged in a housing 8 so that a laser beam enters from the same side of the hologram element 7. The light emitting point of the semiconductor laser element 5 is denoted by 5a, the output optical axis is denoted by Na, and the light flux is denoted by NA. The light emitting point of the semiconductor laser element 6 is 6a, and the output optical axis is N.
b, the luminous flux is indicated by NB. The hologram element 7 is designed so as to transmit the output laser light of the semiconductor laser element 5 as it is and output it, diffract the output laser light of the semiconductor laser element 6, and output the primary light in the direction of the optical axis Na. Have been. That is, it is designed such that an apparent light emitting point when the first-order diffracted light of the semiconductor laser element 6 is assumed to be transmitted light can exist on the optical axis Na of the semiconductor laser element 5.

Next, the operation of the present embodiment will be described. First, it is assumed that the hologram element 7 is designed so that the light emitting point of the semiconductor laser element 6 can be apparently present at a point 6A1 on the optical axis Na of the semiconductor laser element 5. Focusing on the semiconductor laser element 5, the output laser light passes through the hologram element 7 as it is and travels along the optical axis Na. On the other hand, the output laser light of the semiconductor laser element 6 first travels along the optical axis Nb,
Incident on. The primary laser light diffracted by the hologram element 7 travels along the optical axis Na as described above. The light flux is as indicated by NB1.

Here, assuming that this first-order diffracted light is transmitted light of the hologram element 7, the light emitting point 6A1 is considered to be on the optical axis Na of the semiconductor laser element 6 from the design conditions of the hologram element 7. Can be Therefore, the light emitting points 5a and 6a of the semiconductor laser elements 5 and 6 are apparently on the same optical axis Na. As a result, the optical system from the hologram element 7 to the disk can be configured in common for each wavelength, and the configuration can be simplified to reduce the size and cost. The above operation is almost the same as that of the embodiment shown in FIG.

Next, it is assumed that the hologram element 7 is designed so that the light emitting point of the semiconductor laser element 6 can be apparently present at the same 6A2 point as the light emitting point 5a of the semiconductor laser element 5. In this case, the semiconductor laser element 6
The primary laser light travels along the optical axis Na by the hologram element 7, and its light flux becomes as indicated by NB2. Assuming that this first-order diffracted light is transmitted light of the hologram element 7, the light emitting point 6A2 can be regarded as the same as the light emitting point 5a of the semiconductor laser element 5 from the design conditions of the hologram element 7. In this case, the same effect can be obtained.

A comparison between the case where the apparent light emitting point of the semiconductor laser element 6 is 6A1 and the case where the apparent light emitting point is 6A2 indicates that when the light emitting point is the same 6A2, the spread of the luminous flux of the semiconductor laser elements 5 and 6 is almost the same. Become. Therefore, the same optical path design can be made for two different wavelengths of laser light. On the other hand, in a compatible playback system for DVD and CD, a method (so-called finite length correction method) has been proposed in which aberration caused by a difference in disk thickness is canceled by intentionally shifting the position of a light emitting point in the optical axis direction. When this method is adopted, it is more advantageous to set the apparent light emitting point of the semiconductor laser element 6 to 6A1.

The present invention has many embodiments, and various modifications can be made based on the above disclosure.
For example, the present invention is one of the preferable application examples of compatible reproduction of DVD, CD, and CD-R, but is generally applicable if a plurality of laser lights having different wavelengths are obtained.

[0020]

As described above, according to the present invention,
While incorporating a plurality of semiconductor laser elements with different oscillation wavelengths and a diffraction grating or hologram element in the housing,
The diffraction grating and the hologram element are designed so that the apparent light emitting points of the semiconductor laser elements in the housing are on the same optical axis or the same point, so that the configuration of the optical system is simplified and simplified. In addition, it is possible to reduce the size and cost of the player and the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor laser device using a diffraction grating according to one embodiment of the present invention.

FIG. 2 is a schematic perspective view showing the appearance of the semiconductor laser device of the embodiment shown in FIG.

FIG. 3 is a schematic configuration diagram of a semiconductor laser device using a hologram element according to another embodiment of the present invention.

FIG. 4 is a diagram showing a background art.

[Explanation of symbols]

 1, 2, 5, 6 ... semiconductor laser elements 1a, 2a, 5a, 5b ... light emitting points 2A, 6A1, 6A2 ... apparent light emitting points 3 ... diffraction grating 4, 8 ... housing 7 ... hologram elements Ma, Mb , Na, Nb: Optical axis MA, MB, NA, NB1, NB2: Light flux

Claims (3)

[Claims] 1. A first semiconductor laser device for outputting a laser beam of a first wavelength; a second semiconductor laser device for outputting a laser beam of a different second wavelength; these first and second semiconductor laser devices And a housing provided with a diffraction grating on their laser light output side; and a light emitting point of the first semiconductor laser element and the second semiconductor laser element formed by the diffraction grating. A semiconductor laser device, wherein the diffraction grating is designed such that an apparent light emitting point of the first-order diffracted light is located on the same optical axis. 2. A first semiconductor laser device for outputting a laser beam of a first wavelength; a second semiconductor laser device for outputting a laser beam of a different second wavelength; these first and second semiconductor laser devices And a housing provided with a hologram element on their laser light output side; and a light emitting point of the first semiconductor laser element and the second semiconductor laser element formed by the hologram element. A semiconductor laser device, wherein the hologram element is designed such that an apparent light emitting point of the first-order diffracted light is located on the same optical axis. 3. A first semiconductor laser device for outputting a laser beam of a first wavelength; a second semiconductor laser device for outputting a laser beam of a different second wavelength; these first and second semiconductor laser devices And a housing provided with a hologram element on their laser light output side; and a light emitting point of the first semiconductor laser element and the second semiconductor laser element formed by the hologram element. A semiconductor laser device, wherein the hologram element is designed such that an apparent light emission point of the first-order diffracted light is the same point.