JPH08202247A - Semiconductor laser device and production of hologram plate used for it - Google Patents

Abstract

PURPOSE: To provide a light source suitable for light spacial transmission with a relative short distance reducing spacial coherency of a semiconductor laser and dissolving a sanitary problem for the eyes. CONSTITUTION: An optical member for reducing the spacial coherency is provided in the radiative optical path of the semiconductor laser, and light reducing the spacial coherency is radiated out of a case of a semiconductor laser device through the optical member. As the optical member, a silicon member 3 having a scattered reflection surface formed by etching, etc., and converting to optional coherent light or a hologram plate formed so as to generate the optional coherent light is used. Further, basic laser light with high coherency is sealed so as to be not leaked out the case. Thus, the light source with the low spacial coherency dissolving the sanitary problem for the eyes is dealt with as a single device.

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, and more particularly to a semiconductor laser device having means for reducing the spatial coherency of laser light.

[0002]

2. Description of the Related Art A conventional semiconductor laser device will be described with reference to FIGS.

First, as shown in FIG. 5, the structure of a conventional semiconductor laser device 120 is such that a semiconductor laser element 1 is fixed to a mounting base 2 by contacting one side of an electrode, and the mounting base 2 is mounted on a case base 5 and a semiconductor. The laser element 1 is fixed so as to be located at a substantially central portion of the case. The electrodes 8A and 8B are respectively inserted into the case base 5 via the insulator 9 to supply electricity to the semiconductor laser device 1 via the lead wires 10A and 10B. Further, the cap 6 is the semiconductor laser device 1.
It is fixed to the case base 5 in order to enclose the like. A transparent sealing member 7 is provided at the center of the cap 6 as an emission window for the laser beam L2.

By applying a voltage to the lead wires 10A and 10B of the semiconductor laser device 120 described above, laser light L2 having high spatial coherency is emitted from the end face of the active layer of the semiconductor laser device 1.

Next, the spatial coherency of the laser according to the present invention will be described with reference to FIGS. 6 and 7. Spatial coherency is also called coherence, and is defined as the amount of light that has a certain phase relationship and indicates the degree to which interference fringes appear due to superposition of lights. This amount is related to the directivity of light, that is, the spread and condensing property of emitted light when a lens is used.

First, the directivity of light and the spatial coherency will be described with reference to FIG. FIG. 6A shows a light source having a spread other than the laser. When the size of the light source is d and the focal length of the lens 40 is f, the light beam emitted from the lens 40 has a geometrical half angle of Θg = d. It becomes / f, and has the spread shown by Θg. For example, d
= 1 mm and f = 10 mm, Θg = 0.1 rad
Becomes In addition to this, since the lens aperture is finite, there is a spread due to the diffraction effect, but this amount is generally an extremely small value compared to Θg. Therefore, in order to improve the directivity of the light source having the spread shown in FIG. 6A, it is necessary to reduce d, and when d is large, only a light beam having poor focusing properties can be obtained.

Further, FIG. 6B shows a case where the light source is laser light, and the spread of the emitted light is Θ _L = d / f = ω, where the spot size is ω ₀ and the oscillation wavelength is λ. ₀ /
From f, for example, when ω ₀ = 10 μm and f = 10 mm, Θ _L
= About 10 ^-3 rad. In an actual laser, this value is larger than this value by an order of magnitude, but its divergence angle is extremely smaller than that of the general light source described above. That is, it can be said that the spatial coherency of laser light is extremely higher than that of general light sources.

Next, the light converging property and the spatial coherency will be described with reference to FIG. FIG. 7A shows a case of a light source having a spread other than the laser. When the light source is placed at the point P1 and an image is formed at the point Q1 by the lens 40, the image also becomes large with a spread. At this time, the wavefront of light propagating in space is composed of spherical waves with various curvatures,
From this point as well, it can be said that the spatial coherency of a light source having a spread is low.

Further, FIG. 7B shows a case where the light source is a laser beam, and light is emitted at a high output from a minute point P1. When this light is focused on the point Q1 by the lens 40, the size of the image is small and the light power density is an extremely high light spot. At this time, the wavefront of the light propagating in the space is composed of substantially the same spherical waves, and it can be said that the spatial coherency of the laser light is high, contrary to the light source having the spread.

As described above, the semiconductor laser used for optical space transmission has a very small light emitting area and a high spatial coherency, so that it is essentially necessary as a light source for long-distance optical transmission such as outdoors. It has various elements. However, on the other hand, because of its high coherency, the power density per unit area of the laser is determined from the effect on the human body, that is, hygiene to the eyes,
Especially in the visible light band, due to the high transparency and absorption of the eyeball,
Its value is limited to a very small value.

On the other hand, in indoor optical space transmission with a relatively short distance, a light emitting diode having a large light emitting area has been widely used instead of a laser due to the property required of a light source.
However, the light emitting diode has a problem that a large output and a high speed response are not compatible due to its characteristics. For example, in high-definition image transmission, the amount of transmitted information increases,
Since the modulation frequency also becomes high, it is difficult to transmit by the light emitting diode.

That is, under the present circumstances, it does not have a light-collecting property that causes an adverse effect on the eye, but it has a high spatial coherency which is sufficient for spatial transmission over a relatively short distance. Since there is no light source having ultra-high speed modulation characteristics, the selection range of the light source used for optical space transmission was extremely limited.

[0013]

Therefore, the present invention has the ultra-high speed modulation characteristic of a semiconductor laser and does not have a converging property enough to adversely affect the eye, but has a sufficiently high spatial coherency. However, the present invention aims to provide a light source that is optimal for use in space transmission with a relatively short distance, high speed, and large capacity.

[0014]

The present invention has been devised in order to solve these problems, and an optical member for reducing the spatial coherency of laser light in the case of delivering a semiconductor laser device. Is provided and the laser light is reflected or transmitted through this optical member to generate light having a spatial coherency of a low value arbitrarily designed, and solves the problem.

An optical member for generating the light having low spatial coherency by reflection is formed by forming a scattering reflection surface on a silicon substrate.

An optical member for generating the light with low spatial coherency by transmission is constructed by using a hologram.

Further, the semiconductor laser device and an optical member for lowering the spatial coherency of the laser light are integrally provided in the case and sealed so that the basic laser light with high spatial coherency does not radiate to the outside. One device configuration.

[0018]

[Function] Due to the interaction between the laser light and the optical member that lowers the spatial coherency of the laser light, it has an ultra-high-speed modulation characteristic, and on the other hand, it does not have a converging property enough to adversely affect the eyes, Emits light with high spatial coherency.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor laser device for generating light with reduced spatial coherency according to the present invention will be described with reference to FIGS.

First Embodiment A semiconductor laser device 100 of the first embodiment according to the present invention will be described with reference to FIG. The semiconductor laser device 1 is fixed to the mounting base 2 with one surface of the electrode in contact with the light emitting end face sideways, and the mounting base 2 is fixed to the case base 5. The electrodes 8A and 8B are respectively inserted into the case base 5 via the insulator 9 to supply electricity to the semiconductor laser device 1 via the lead wires 10A and 10B.

The silicon member 3 is fixed to the case base 5 so as to face the semiconductor laser device 1, and the surface of the silicon member 3 facing the semiconductor laser device 1 forms a slope having an arbitrary inclination angle. The inclined surface is an arbitrary scattering reflection surface described later and reflects the laser light from the semiconductor laser device 1 upward. Further, a cap 6 is fixed to the case base 5 to enclose the semiconductor laser element 1 and the like, and a transparent sealing member 7 is provided at the center of the cap 6 as an emission window for the emitted light L1.

By applying a voltage to the lead wires 10A and 10B of the semiconductor laser device 100 described above, laser light with high spatial coherency is emitted from the end surface of the active layer of the semiconductor laser device 1.

Next, a method of reducing the spatial coherency of laser light by reflection, which is a feature of the present invention, will be described. The inclined surface of the silicon member 3 facing the semiconductor laser device 1 is provided with an etching surface 4 for generating light whose spatial coherency is reduced by an arbitrary amount by scattering reflection by a technique such as etching. The structure of the light scattering state of the etching surface 4, that is, the surface state that determines the degree to which the spatial coherency is lowered is as follows. One point on the P plane and one point on the Q plane with respect to the optical axis vector of light passing therethrough are defined. It suffices to calculate the tilt and the position that associate the optical axis vector of the light passing therethrough and realize it on the silicon surface.

The laser light of the semiconductor laser device 1 is scattered and reflected on the etching surface 4 determined and formed as described above, converted into light having a reduced spatial coherency, and further reflected upward on the etching surface 4. Then, the emitted light L1 is emitted to the outside of the semiconductor laser device 100 through the transparent sealing member 7.

Second Embodiment Next, a semiconductor laser device 110 of a second embodiment will be described with reference to FIG. In this embodiment, instead of the silicon member 3 for scattering and reflection used in the first embodiment described above, an optical member for generating light with a reduced spatial coherency formed by a hologram is provided on the laser optical path. is there.

The structure of the semiconductor laser device 110 is shown in FIG.
As shown in FIG. 3, the semiconductor laser device 1 is fixed to the mounting base 2 by contacting one side of the electrode, and the mounting base 2 is fixed to the case base 5.
The semiconductor laser device 1 is fixed to the case so as to be located substantially in the center of the case. The electrodes 8A and 8B are respectively inserted into the case base 5 via the insulator 9 to supply electricity to the semiconductor laser device 1 via the lead wires 10A and 10B. Further, a cap 6 is fixed to the case base 5 to enclose the semiconductor laser device 1 and the like. Further, a transparent sealing member 7 is provided at the center of the cap 6 as an emission window for the laser beam L1, and a hologram plate 2 for generating light with reduced spatial coherency is further provided on the transparent sealing member 7.
0 is stuck.

In the semiconductor laser device 110 described above, by applying a voltage to the lead wires 10A and 10B, laser light having high spatial coherency is emitted from the end surface of the active layer of the semiconductor laser element 1. The emitted laser light passes through the hologram plate 20, and at this time, the emitted light L having a low spatial coherency formed on the hologram plate 20.
Will produce 1.

Next, two examples of a method of manufacturing the hologram plate 20 for generating the light with low spatial coherency described above will be described. It is needless to say that a manufacturing method that exhibits the same effect may be used other than these two methods.

FIG. 3 shows a method of manufacturing the hologram plate 20 using a plurality of mirrors having a random inclination. FIG. 3A shows the outline of the manufacturing optical system. First, the laser light L3 is split into a reference wave and an object wave by the half mirror 21, the reference wave is bent by the mirror 22A, is condensed by the lens 23, and a pinhole 25 is formed at the condensing point to remove higher-order light. An open shutter 24 is provided and forms a laser substitute light source 30.
The hologram plate 20 is irradiated with the reference wave thus shaped.

On the other hand, the object wave split by the half mirror 21 is reflected by a plurality of mirrors 22C, 22D and 22E, which are arranged with different inclinations in the optical path, and is further reflected by the mirror 22B. Then, the hologram plate 20 is irradiated. Therefore, the hologram image formed by the reference wave and the object wave is the hologram plate 20.
Will be formed on top.

Therefore, in the semiconductor laser device 110 in which the hologram plate 20 manufactured by the above-mentioned method is fixed to a predetermined position of the case, the hologram plate 20 is irradiated with the laser light of the semiconductor laser element 1 so that a random optical axis is generated. It is possible to obtain light having a low spatial coherency by generating an object wave having.

In this example, a structure of three mirrors is shown as a plurality of mirrors, but it is needless to say that the number of mirrors may be increased, and it may be determined by the degree of reduction in spatial coherency. Further, as shown in FIG. 3B, the mirror must cover the entire laser beam 31 as an object wave and reflect it in an arbitrary direction.

Next, the second step for producing the hologram plate 20
The method will be described with reference to FIG. This method is the same as the above-mentioned first method, but instead of a plurality of mirrors,
The scattering reflecting plate 26 manufactured by the method of manufacturing the scattering reflecting surface of silicon that generates light with low spatial coherency described in the first embodiment of the present invention is used.

The object wave is incident on the scattering reflection plate 26 at an angle Θ 0, but its reflection is Θ 1 or Θ depending on the portion to be reflected.
It reflects at an angle different from the incident angle, such as 2nd angle, and the mirror 22B
Then, the hologram image is further reflected on the hologram plate 20 to be irradiated, and a hologram image formed by the reference wave and the object wave converted by the scattering reflection plate 26 is formed on the hologram plate 20.

The structure of the other manufacturing apparatus, the method for forming the hologram image, the mounting on the semiconductor laser device 110, and the effect thereof are the same as those described in the first method.
The description is omitted.

[0036]

According to the present invention, light having the ultra-high speed modulation characteristics of a semiconductor laser, but on the other hand, a light having a sufficiently high spatial coherency, although it does not have a light-collecting property that adversely affects the eyes, is generated. It is possible to provide a light source that is suitable for optical space transmission with a relatively short distance, large capacity, and high frequency.

By providing a means for lowering the spatial coherency in the state where the positional relationship with the laser element is determined in the delivery case of the semiconductor laser, it becomes a light source which can be recognized as a single device to the outside, and the method of use is simple. become.

Since the semiconductor laser and the means for lowering the spatial coherency are mounted in the same case with a fixed relative positional relationship, it is possible to prevent laser light having high spatial coherency from being emitted from the case. Even when the semiconductor laser is handled alone, the danger to the eyes can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a semiconductor laser device according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the semiconductor laser device according to the present invention.

3A and 3B are diagrams for explaining a method for manufacturing a hologram plate used in the second embodiment, wherein FIG. 3A is an optical system and FIG. 3B is a diagram showing arrangement of mirrors in the optical system. .

FIG. 4 is a diagram for explaining another method of manufacturing the hologram plate used in the second embodiment.

FIG. 5 is a schematic sectional view showing a conventional semiconductor laser device.

6A and 6B are diagrams for explaining spatial coherency and directivity of a light source, where FIG. 6A shows a light source other than a laser, and FIG. 6B shows a laser light source.

7A and 7B are diagrams for explaining the spatial coherency and light collecting property of a light source, where FIG. 7A shows a light source other than a laser, and FIG. 7B shows a laser light source.

[Description of Reference Signs] 1 semiconductor laser device 2 mounting base 3 silicon member 4 etching surface 5 case base 6 cap 7 sealing member 8A, 8B electrode 9 insulator 10A, 10B lead wire 20 hologram plate 21 half mirror 22A to E mirror 23 lens 24 shutter 26 scattering reflector 31 laser beam

Claims (8)

[Claims] 1. A laser beam of a semiconductor laser having a high spatial coherency is reduced in coherency through an optical member, and the light in which the coherency is reduced is
A semiconductor laser device characterized in that the semiconductor laser is configured to radiate to the outside of a container containing the semiconductor laser. 2. The semiconductor laser device according to claim 1, wherein the laser light having high spatial coherency is reflected by an optical member to reduce coherency. 3. The optical member for reflecting laser light to reduce spatial coherency is formed by etching a scattering surface on a surface of a silicon member for generating reflected light of arbitrary reduced coherency. The semiconductor laser device according to claim 1, which is characterized in that. 4. The semiconductor laser device according to claim 1, wherein the laser beam having high spatial coherency is transmitted through an optical member to reduce coherency. 5. The semiconductor according to claim 1, wherein the optical member that transmits laser light to reduce spatial coherency is formed of a hologram plate that generates light with arbitrary reduced coherency. Laser device. 6. The hologram plate according to claim 5, wherein the reference wave is laser light, and the object wave is branched from the laser light.
A method for manufacturing a hologram plate, characterized in that the hologram plate is formed by a plurality of mirrors each having an individual inclination. 7. The hologram plate according to claim 5, wherein a reference wave is used as a laser beam, an object wave is branched from the laser beam, and the object wave is reflected by an optical member having a scattering / reflecting surface. Method for manufacturing hologram plate. 8. The method of manufacturing a hologram plate according to claim 7, wherein the optical member having the scattering reflection surface is formed by etching the surface of a silicon member.