WO2014148541A1

WO2014148541A1 - Laser light source device

Info

Publication number: WO2014148541A1
Application number: PCT/JP2014/057504
Authority: WO
Inventors: 吉田　和弘; 彩五十嵐
Original assignee: ウシオ電機株式会社
Priority date: 2013-03-22
Filing date: 2014-03-19
Publication date: 2014-09-25
Also published as: JP2014187138A

Abstract

The present invention achieves a laser light source device in which extraction efficiency is improved by effectively utilizing fundamental light emitted from a plurality of light-emitting parts mounted on a semiconductor element to extract laser light. The laser light source device (1) is provided with: a semiconductor element (11) provided with a plurality of light-emitting parts (2) that emit fundamental light; a wavelength selection element (3) that selects a prescribed wavelength band of the fundamental light, and extracts a first light; and a wavelength conversion element (95) that converts the wavelength of a portion of the first light, and extracts a second light. The wavelength selection element (3) has a configuration in which a prescribed wavelength band, which can be selected in a first selection region through which fundamental light emitted from a first light-emitting part among the plurality of light-emitting parts passes, becomes shorter in wavelength than the prescribed wavelength band, which can be selected in a second selection region through which fundamental light emitted from a second light-emitting part, wherein a rise in temperature caused by heat produced when light is emitted from other light-emitting parts is higher than the first light-emitting part, passes.

Description

Laser light source device

The present invention relates to an external resonance type laser light source device. More particularly, the present invention relates to an external resonance type semiconductor laser light source device using a nonlinear optical crystal.

2. Description of the Related Art Conventionally, there has been known a wavelength conversion type laser light source device in which an external resonator is provided in a surface emitting semiconductor laser, and a wavelength conversion element formed of a nonlinear optical crystal is disposed between the semiconductor laser and the external resonator. Yes. A wavelength-selective reflecting mirror is used as the external resonator, and a technique using an optical crystal such as a polarization inversion type lithium niobate (PPLN) is known as the wavelength conversion element (the following patent document) 1). In addition, a technique using a volume Bragg grating (VBG) instead of a reflector used for an external resonator is also known (see Patent Document 2 below).

Special table 2003-526930 gazette JP 2012-098495 A

In forming the laser light source device, the light emitting part is designed so that the target wavelength component is in the vicinity of the peak value, and further, the narrow wavelength band including this peak value is selected, and thus the emitted light showing a narrow wavelength distribution Is generated as a laser beam. In addition, if necessary, wavelength conversion is performed on light of a selected narrow wavelength band to generate radiated light having a desired wavelength as laser light.

That is, in a laser light source device, a wavelength selection element efficiently selects a desired wavelength from light having a wavelength distribution (hereinafter, referred to as “fundamental light” as appropriate) emitted from each light emitting unit. Is important.

The present inventor has found a problem that the light emitted from the light emitting unit cannot be used completely effectively by the configuration of the conventional laser light source device through intensive research. Hereinafter, this content will be clarified while explaining the configuration of the conventional laser light source device.

FIG. 1 schematically shows a configuration of a conventional laser light source device disclosed in Patent Document 2. As shown in FIG. A conventional laser light source device 90 includes a semiconductor element 11 having a light emitting portion, a volume Bragg grating (VBG) 93 as a wavelength selection element, and a periodically poled lithium niobate (PPLN) 95 as a wavelength conversion element.

As shown in FIG. 2, a plurality of light emitting sections 2 are arranged in an array on the semiconductor element 11. FIG. 2 shows a configuration in which a plurality of light emitting units 2 are arranged in a row on the semiconductor element 11. In this figure, an example in which 24 light emitting units 2 are arranged is illustrated. Basic light is emitted from these light emitting units 2. The semiconductor element 11 is in contact with a heat sink 17 for radiating heat generated from the light emitting unit 2.

The basic light emitted from each light emitting unit 2 is light having a predetermined wavelength distribution. The VBG 93 is provided for selecting a specific wavelength band from this light. In addition, the PPLN 95 has a function of performing wavelength conversion on a part of light in a specific wavelength band out of incident light and emitting the light.

Each light emitting unit 2 mounted on the semiconductor element 11 emits basic light. This basic light is not light having only a component in a specific wavelength band but light having a certain wavelength distribution. When this basic light passes through the VBG 93, only light in a predetermined wavelength band is selectively reflected. Hereinafter, the light selected by the VBG 93 as the wavelength selection element is referred to as “first light”. The VBG 93 has a function of transmitting light in the second light wavelength band described later.

The first light reflected from the VBG 93 passes through the PPLN 95. As described above, the PPLN 95 is configured to perform wavelength conversion on a part of light in a specific wavelength band and emit the light. Here, the PPLN 95 converts the wavelength of part of the light of the wavelength component included in the first light, and generates light of another different wavelength. Hereinafter, the light having the converted wavelength converted by the PPLN 95 is referred to as “second light”.

Even when the wavelength band of the first light is within the wavelength band that can be converted by the PPLN 95, not all of the incident first light is converted into the second light at one time. Passes through the PPLN 95 without being converted. For this reason, the second light generated by the PPLN 95 and the first light that has not been wavelength-converted by the PPLN 95 are emitted from the PPLN 95 toward the semiconductor element 11.

Reflective members

25 and 27 are provided between the PPLN 95 and the semiconductor element 11. These reflecting

members

25 and 27 are configured to reflect light in the wavelength band of the second light and transmit at least light in the wavelength band of the first light. For this reason, the second light emitted from the PPLN 95 toward the semiconductor element 11 is reflected by the reflecting

members

25 and 27 to change the direction of the light, and is then emitted to the outside of the device 90 (first 2 light 40).

On the other hand, the first light that has passed through the PPLN 95 without being wavelength-converted passes through the reflecting member 25 and enters the semiconductor element 11. The semiconductor element 11 is provided with a reflecting member (internal mirror) (not shown), and the incident first light is reflected toward the PPLN 95.

As described above, when the first light incident from the semiconductor element 11 side passes through the PPLN 95, a part of the first light is converted into the second light. This second light reaches VBG93. As described above, since the VBG 93 transmits light in the wavelength band of the second light, the incident second light is transmitted as it is and emitted to the outside of the device 90 (second light 50). . On the other hand, the first light that has not been wavelength-converted is reflected again by the VBG 93 and travels toward the PPLN 95.

That is, in the laser light source device 90, an external resonator is formed between the internal mirror formed in the semiconductor element 11 and the VBG 93, and the first light is repeatedly reflected between the two. And while this reflection is repeated, the wavelength of the first light that has passed through the PPLN 95 is successively converted into the second light, and is extracted from the VBG 93 or the reflection member 27 to the outside of the device 90.

That is, the laser light source device 90 selects the first light having the first wavelength band selected by the VBG 93 from the basic light emitted from the plurality of light emitting units 2, and converts the wavelength from the first light by the PPLN 95. Thus, the second light having the second wavelength band is generated, and the second light is emitted to the outside as the target laser light. As an example, the first light can be infrared light having a peak wavelength of about 1065 nm, and the second light can be green visible light having a peak wavelength of about 532.5 nm.

FIG. 3 shows a wavelength distribution 41 of basic light, a wavelength distribution 42 that can be selected by the VBG 93 (hereinafter referred to as “selected wavelength distribution”), and a wavelength distribution 43 that can be converted by the PPLN 95 (hereinafter, “converted wavelength distribution”). ")."

According to FIG. 3, the basic light shows a wide wavelength distribution with a peak wavelength of about 1065 nm. As described above, in order to generate desired laser light from this basic light, it is necessary to first select light in a predetermined wavelength band by the VBG 93. The selection wavelength distribution 42 of the VBG 93 draws a steep curve as shown in FIG. In the selection wavelength distribution 42 shown in FIG. 3, the peak of the selectable wavelength band is about 1065 nm. Therefore, the VBG 93 can select the first light having a wavelength of about 1065 nm from the basic light.

Furthermore, it is necessary to convert the first light selected by the VBG 93 into the second light having a desired wavelength by the PPLN 95. FIG. 3 shows a converted wavelength distribution 43 when a broadband PPLN 95 is used. In the converted wavelength distribution 43 shown in FIG. 3, the peak of the wavelength band that can be converted is about 1065 nm. Therefore, the PPLN 95 performs wavelength conversion on the first light having a peak wavelength of about 1065 nm.

That is, in order to generate laser light having a desired wavelength from the basic light emitted from the light emitting unit 2, the wavelength distribution 41 of the basic light, the selection wavelength distribution 42, and the conversion wavelength distribution 43 need to overlap each other. The larger the overlapping area, the more efficiently laser light can be generated from the basic light. Actually, the laser light can be extracted most efficiently by aligning the positions of the peak wavelengths of the wavelength distribution 41, the selection wavelength distribution 42, and the conversion wavelength distribution 43 of the basic light.

By the way, it has been experimentally recognized that the wavelength of light (basic light) emitted from the light emitting unit 2 shifts to the longer wavelength side as the temperature of the light emitting unit 2 increases. FIG. 4 is a graph showing the wavelength distribution of the basic light emitted when the temperature of a certain light emitting unit 2 is changed. It is recognized that the peak wavelength and the wavelength band are shifted to the longer wavelength side as the temperature of the light emitting unit 2 is increased to 25 ° C, 30 ° C, 35 ° C, and 40 ° C.

FIG. 5 is a graph showing the relationship between the peak wavelength of light emitted from each light emitting section 2 and the temperature of each light emitting section 2 in FIG. From the graph of FIG. 5, it can be seen more clearly that the peak wavelength of light shifts to the longer wavelength side as the temperature of the light emitting unit 2 increases. In addition, according to FIG. 5, it turns out that the temperature of the light emission part 2 and the peak wavelength of the light radiated | emitted from the light emission part 2 have a substantially linear relationship.

Each light emitting unit 2 generates heat due to energization during light emission. In the semiconductor element 11 in which the plurality of light emitting units 2 are arranged as shown in FIG. 2, the heat generated from the self light emitting unit 2 and the heat generated from the adjacent or surrounding light emitting units 2 raise the temperature of each light emitting unit 2. Let The inventor paid attention to the difference in the degree of temperature rise caused by the heat generated from the surrounding light emitting units 2 depending on the arrangement position of each light emitting unit 2.

FIG. 6 is a graph showing the temperature distribution of the plurality of light emitting units 2 while the semiconductor laser device 90 is being driven. In order to make the temperature conditions the same, the temperature of each light emitting unit 2 was measured when the bottom surface of the heat sink 17 was cooled to a uniform temperature. FIG. 3 is a graph in which the distance from the position of the light emitting unit 2a in FIG.

According to FIG. 6, in each light emitting unit 2 arranged in an array, the temperature of the

light emitting units

2a, 2b, 2w, and 2x near the outer edge of the array is lower than the other light emitting units near the center. It is recognized that

Since the light emitting section 2 arranged at a position close to the center of the array has many other light emitting sections 2 around it, heat generated by these light emitting sections is easily transmitted and the temperature is likely to rise. is there. On the other hand, the number of light emitting units 2 existing around the light emitting units (2a, 2b, 2w, 2x, etc.) arranged near the outer edge of the array is larger than that of the light emitting units arranged near the center. (Density) is low. Therefore, it is considered that the degree of temperature rise is lower than that of the light emitting unit 2 arranged at a position close to the central portion.

The inventor has inferred from the results of FIGS. 4 and 6 that the basic light emitted from the plurality of light emitting units 2 mounted on the semiconductor element 11 may vary in wavelength distribution depending on the position. .

FIG. 7 is a graph showing the peak wavelength values of the basic light emitted from the light emitting units 2. As in FIG. 6, the distance from the position of the light emitting unit 2a is plotted on the horizontal axis, and the peak wavelength value is plotted on the vertical axis. According to FIG. 7, it is confirmed that the wavelength of the basic light varies according to the position, as inferred by the inventor. More specifically, in each light emitting unit 2 arranged in an array, the

light emitting units

2a, 2b, 2w, and 2x near the outer edge of the array are shifted to the shorter wavelength side than the other light emitting units near the center. It is recognized that

As described above with reference to FIG. 3, in order to efficiently extract laser light having a desired wavelength from the basic light emitted from the light emitting unit 2, the wavelength distribution 41 of the basic light, the selection wavelength distribution 42, and the conversion It is necessary to make the overlapping area of the wavelength distributions 43 as wide as possible.

In the conventional laser light source device 90, a VBG 93 designed in advance for each wavelength to be selected has been used. For example, when it is desired to select light having a wavelength of 1065 nm from the basic light emitted from each light emitting unit 2, each light emitting unit 2 is designed so that the peak wavelength of the basic light has a wavelength distribution of 1065 nm, and 1065 nm. VBG93 designed so that the selectivity of the light of a wavelength becomes high is used.

However, as described above, when the wavelength distribution of the basic light varies depending on the position of each light emitting unit 2, the basic light whose peak wavelength is shifted from 1065 nm is generated depending on the position of the light emitting unit 2. It will be.

For example, according to the result of FIG. 7, in the case where 24 light emitting units 2 are provided on the semiconductor element 11, the basic light from the light emitting unit 2 arranged in the center and the outer edge of the array are arranged. The fundamental light from the light emitting part 2 has a peak wavelength shift of about 1 nm. Considering this result together with FIG. 3, the wavelength distribution of the basic light emitted from the light emitting units (2a, 2b, 2w, 2x, etc.) arranged at a position close to the outer edge of the array is the wavelength shown in FIG. The distribution 41 is shifted to the short wavelength side by about 1 nm.

As a result, the area of the overlapping area with the selected wavelength distribution 42 is reduced. That is, the intensity of the first light selected from the basic light emitted from the light emitting unit 2 in this region is the first light selected from the basic light emitted from the light emitting unit 2 disposed near the center of the array. Less than. This suggests that the emitted light from the light emitting section 2 located at the outer edge of the array cannot be converted into laser light with high efficiency.

In the above example, the case where 24 light emitting units 2 are arranged in a row is considered. However, as this number increases, the wavelength distribution of the basic light emitted from each light emitting unit 2 according to the arrangement position is increased. It can be seen that there is a difference. This means that the area of the overlapping region of the fundamental light wavelength distribution 41 and the selection wavelength distribution 42 is further reduced, that is, the efficiency of extracting the first light from the fundamental light is further reduced. .

Here, when there is a variation in the peak wavelength value of the wavelength distribution 41 of the basic light emitted from the light emitting unit 2 according to the position, the wavelength distribution 41 of the basic light emitted from each light emitting unit 2 and the selected wavelength distribution 42. Considering only increasing the overlapping area, a method using a wavelength selection element that provides a selection wavelength distribution 42 showing a wide band is also conceivable. However, in the first place, the feature of the wavelength selection element is that the laser light is light in a narrow wavelength band, and that the first light of the narrow band wavelength is selected from the basic light emitted from the light emitting unit 2. Exists. That is, it is not practical to deal with the above problem by widening the selection wavelength distribution 42 of the wavelength selection element (here, VBG93).

As described above, in the case of the conventional laser light source device, the inventor effectively uses the basic light emitted from some of the light emitting units 2 even when the plurality of light emitting units 2 are arranged in the semiconductor element 11. I found that I did not use it.

In view of the above-described problems, the present invention provides a laser light source device that enhances extraction efficiency by efficiently using basic light emitted from a plurality of light emitting units mounted on a semiconductor element to extract laser light. It aims to be realized.

The laser light source device of the present invention comprises:
A semiconductor element comprising a plurality of light emitting portions that emit basic light;
A wavelength selection element for selecting the predetermined wavelength band of the basic light and extracting the first light;
A wavelength conversion element for converting the wavelength of a part of the first light and extracting the second light;
The wavelength selection element is configured such that the predetermined wavelength band that can be selected in a first selection region through which the basic light emitted from the first light emitting unit of the plurality of light emitting units passes is, of the plurality of light emitting units, The predetermined wavelength band that can be selected in a second selection region through which the basic light emitted from the second light emitting unit, which has a temperature rise due to heat generated when the other light emitting units emit light, is higher than that of the first light emitting unit. It is the structure which becomes a shorter wavelength than this.

The wavelength selection element provided in the laser light source device has a configuration in which wavelength bands that can be selected in different regions are different. That is, light emitted from a light emitting unit (the “second light emitting unit”) disposed at a location where the temperature is likely to rise due to the influence of heat generated from the other light emitting units among the plurality of light emitting units passes. In the region (the “second selection region”), light having a relatively long wavelength is selected. On the contrary, the light emitting part (the above “first light emitting part”) that is not affected as much as the second light emitting part and is less likely to rise in temperature than the second light emitting part. In the region through which the light emitted from the light passes (the “first selection region”), light having a wavelength shorter than that of the second selection region is selected.

The basic light emitted from the light emitting part (second light emitting part) arranged at a location where the temperature is likely to rise due to the influence of heat generated from other light emitting parts is emitted as the basic light indicating the wavelength distribution of the long wavelength. The On the other hand, compared to the second light emitting unit, the basic light emitted from the light emitting unit (first light emitting unit) that is less affected by heat generation from the other light emitting units and is difficult to rise in temperature is Basic light having a wavelength distribution shorter than that of the second light emitting unit is emitted.

In the wavelength selection element described above, in the region through which the basic light having a long wavelength distribution (the “second selection region”) passes, the selectable wavelength band is a long wavelength, and the basic wavelength distribution has a short wavelength distribution. In a region through which light passes (the “first selection region”), a selectable wavelength band has a short wavelength. Therefore, both the basic light emitted from the first light emitting unit and the basic light emitted from the second light emitting unit can be efficiently selected by the wavelength selection element.

The wavelength selection element provided in the conventional laser light source device has a configuration that selects light in one wavelength band from the wavelength distribution of incident basic light. That is, it is not taken into account that the wavelength distribution of the basic light radiated from each light emitting unit varies depending on the position due to the temperature distribution occurring in each light emitting unit due to the heat generation of the light emitting unit. It was. Therefore, the light emitting unit and the wavelength selection element are designed so as to select the wavelength band in which the wavelength distributions of the basic light emitted from each light emitting unit overlap most. As a result, with respect to the light emitting part that emits basic light having a wavelength distribution that is not selected by the wavelength selection element, the light emitted from the light emission part is not selected by the wavelength selection element, and the light is effectively utilized. I could not say.

As in the above configuration, it is assumed that there is a variation in the wavelength distribution of the basic light emitted from the light emitting unit depending on the position, and there is also a distribution in the selectable wavelength band of the wavelength selection element according to this variation. By doing so, the basic light emitted from all the light emitting units can be efficiently selected by the wavelength selection element. Therefore, by extracting the light having the selected wavelength after wavelength conversion by the wavelength conversion element, it is possible to increase the amount of the extracted laser light as compared with the conventional case.

In particular, when a plurality of light emitting units are arranged in an array, there is a difference in the susceptibility to heat generation depending on the position of the light emitting unit. In other words, since the light emitting section arranged near the center of the array has many other light emitting sections around it, the heat generated by these light emitting sections is easily transferred and the temperature is likely to rise. is there. On the other hand, the number of light emitting parts (density) present in the periphery of the light emitting parts arranged near the outer edge of the array is smaller than that of the light emitting parts arranged near the center part. Thereby, compared with the light emission part arrange | positioned in the position close | similar to a center, the raise degree of temperature becomes low.

That is, as a wavelength selection element, a selectable wavelength band is set to a short wavelength in the first selection region through which the basic light emitted from the first light emitting unit arranged near the outer edge of the array passes, and the first light emitting unit In the second selection region through which the basic light emitted from the second light emitting unit arranged closer to the center of the array passes, the selectable wavelength band is set to a long wavelength, so that all the light emitting units The wavelength can be efficiently selected for the emitted fundamental light.

When forming a plurality of light emitting portions on a semiconductor element, generally, a semiconductor element is formed on a wafer and a plurality of light emitting portions are formed thereon. At this time, the semiconductor elements are densely formed so as to form as many semiconductor elements as possible on one wafer. Naturally, the light emitting portions are densely arranged on each semiconductor element. The semiconductor element formed in this way is divided into a predetermined number of light emitting units and mounted on each laser light source device.

Therefore, from the viewpoint of increasing manufacturing efficiency, it is common to arrange a plurality of light emitting portions densely on each semiconductor element. At this time, the light emitting portions are arranged in an array on the semiconductor element. In this case, as described above, there is a difference in the emission wavelength between the light emitting unit near the center of the array and the light emitting unit near the outer edge of the array. That is, according to said structure, when manufacturing a laser light source device, maintaining high manufacturing efficiency, the effect which utilizes effectively the basic light radiated | emitted from each light emission part is acquired.

There are the following methods as specific methods for providing a distribution of wavelengths that can be selected by the wavelength selection element.

One method can be realized by configuring the wavelength selection element with a dielectric multilayer film bandpass filter and forming the film thickness of the first selection region thinner than the film thickness of the second selection region.

Another method can be realized by forming the wavelength selection element with an etalon filter and forming the gap length of the first selection region shorter than the gap length of the second selection region.

Still another method can be realized by forming the wavelength selection element with a volume Bragg grating (VBG) and forming the layer of the first selection region to be thinner than the layer of the second selection region.

In addition to the above-described configuration, the wavelength band that can be converted in the first conversion region through which the first light selected in the first selection region of the wavelength selection element passes is the second wavelength selection element. It is preferable that the wavelength is shorter than the wavelength band that can be converted in the second conversion region through which the first light selected in the selection region passes.

The first light selected by the basic light emitted from the first light emitting unit passing through the first selection region of the wavelength selecting element and the basic light emitted from the second light emitting unit are the second selected by the wavelength selecting element. The first light selected by passing through the region has a difference in wavelength.

If the wavelength conversion element is configured to be able to convert a broadband wavelength, the first light having a difference in peak wavelength depending on the position is converted into the second light even when the first light having a difference in peak wavelength is incident. Is possible. However, when a wavelength conversion element that can convert such a wide-band wavelength is designed, the intensity of the second light obtained after the conversion is relatively low.

Conversely, when a wavelength conversion element having a narrow band of convertible wavelength band is designed, the intensity of the second light obtained after conversion can be increased. However, in this case, since the first light having a different peak wavelength is incident according to the position, if the band of the convertible wavelength band is made too narrow, the wavelength of the first light can be converted according to the position. It is assumed that it is located outside or the conversion efficiency is extremely lowered.

Therefore, similarly to the wavelength selection element, the wavelength conversion element has a distribution in the wavelength band that can be converted according to the position. This makes it possible to convert the first light incident at all locations while narrowing the wavelength band that can be converted at one location to increase the light intensity after conversion. More specifically, the second selection region selects the wavelength band that can be converted in the region through which the first light having a relatively short wavelength passes (the “first conversion region”) selected by the first selection region. In the region through which the first light having a relatively long wavelength passes (the “second conversion region”), the wavelength is shorter than the convertible wavelength band. Thereby, high intensity | strength 2nd light is produced | generated and extraction efficiency improves.

As a specific method for providing a distribution of wavelengths that can be converted by the wavelength conversion element, the wavelength conversion element is composed of periodically poled lithium niobate (PPLN), and the thickness of the first conversion region layer is set to a second value. This can be realized by forming the conversion region to be thinner than the thickness of the layer.

According to the configuration of the present invention, in the laser light source device including a plurality of light emitting units with different degrees of temperature rise caused by heat generation of the light emitting units, the wavelength distribution of the basic light emitted from each light emitting unit varies. However, it is possible to efficiently select light in a predetermined wavelength band from the wavelength distribution indicated by the basic light emitted from each light emitting unit by the wavelength selection element. As a result, the amount of laser light extracted to the outside can be increased, and the extraction efficiency is increased.

It is the figure which showed typically the structure of the conventional laser light source device. 1 schematically shows a substrate on which semiconductor elements constituting a light emitting section are arranged in an array. The wavelength distribution of the basic light, the selection wavelength distribution, and the conversion wavelength distribution are shown in an overlapping manner. It is a graph which shows the relationship between the wavelength of the light radiated | emitted from a light emission part, and the temperature of a light emission part. It is a graph which shows the relationship between the peak wavelength of the light radiated | emitted from a light emission part, and the temperature of a light emission part. The temperature distribution of each light emission part when light-emitting each light emission part is made into a graph. The wavelength distribution radiated | emitted from each light emission part when light-emitting each light emission part was made into the graph. It is the figure which showed typically the structure of the laser light source apparatus of 1st Embodiment. It is an example of typical cross-sectional structure of TFF. It is a graph which shows the wavelength selection distribution in TFF of FIG. It is the figure which showed typically the structure of the laser light source apparatus of 2nd Embodiment. It is the figure which showed typically the structure of the laser light source apparatus of 3rd Embodiment. It is the figure which showed typically the structure of the laser light source apparatus of 4th Embodiment. The wavelength distribution of the basic light, the selection wavelength distribution, and the conversion wavelength distribution are shown in an overlapping manner. It is the figure which showed typically the structure of the laser light source apparatus of another embodiment.

The laser light source device of the present invention will be described with reference to the drawings. In each figure, the dimensional ratio in the drawing does not necessarily match the actual dimensional ratio.

[First Embodiment]
A first embodiment of the laser light source device will be described.

FIG. 8 is a diagram schematically showing the configuration of the laser light source device in the present embodiment. The laser light source device 1 is different from the conventional laser light source device 90 shown in FIG. 1 in that a TFF (dielectric thin film filter) 3 and an optical member 4 are provided as a wavelength selection element instead of the VBG 93. Since other configurations are the same as those of the laser light source device 90, the description thereof is omitted. In the present embodiment, the TFF 3 corresponds to a “wavelength selection element”.

The TFF 3 has a function of selecting and transmitting the first light of a predetermined wavelength band from the wavelength distribution of the basic light emitted from the plurality of light emitting units 2 mounted on the semiconductor element 11. The optical member 4 is configured to reflect light in the first specific wavelength band and transmit light in the second specific wavelength band. More specifically, it is designed to reflect light (first light) in the wavelength band selected by TFF3 and transmit light (second light) in the wavelength band converted by PPLN95. The optical member 4 is realized, for example, by forming a high reflection (HR) coat for the first specific wavelength band and an anti-reflection (AR) coat for the second specific wavelength band on a glass substrate of TFF3. The

Also in this configuration, the basic principle of the mechanism for extracting the

laser beams

40 and 50 from the light emitting unit 2 is common to the laser light source device 90 of FIG.

That is, the basic light emitted from the plurality of light emitting units 2 mounted on the semiconductor element 11 passes through the TFF 3 as a wavelength selection element, so that only light in a predetermined wavelength band is selectively transmitted. The light selectively transmitted by the TFF 3 corresponds to “first light”. The first light is reflected by the optical member 4 and travels toward the PPLN 95. The PPLN 95 performs wavelength conversion on part of the first light to generate second light, and the second light is extracted to the outside via the reflecting members 25 and 27 (second light 40). ).

Further, the first light that is transmitted as it is without being wavelength-converted by the PPLN 95 passes through the reflecting member 25 and enters the semiconductor element 11, is reflected by the internal mirror, and is sent to the PPLN 95. In the PPLN 95, a part of the first light is wavelength-converted into the second light, which is transmitted through the optical member 4 and extracted outside (second light 50). The first light that has not been wavelength-converted is again reflected by the optical member 4 and sent to the PPLN 95.

That is, in the laser light source device 1, an external resonator is formed between the internal mirror formed in the semiconductor element 11 and the optical member 4 as a reflection element, and the first light is repeatedly reflected between the two. . While this reflection is repeated, the first light that has passed through the PPLN 95 is successively converted into the second light, and is extracted from the optical member 4 or the reflection member 27 to the outside of the device 90.

TFF3 is configured by laminating a plurality of high refractive index materials and low refractive index materials. The wavelength band of the selected light is set by adjusting the refractive index and film thickness of these materials. Note that the wavelength distribution of the selected light (the above-mentioned “selected wavelength distribution”) is a steep curve similar to the curve 42 of the VBG 93 shown in FIG.

Here, the TFF 3 included in the laser light source device 1 has different selectable wavelength bands depending on the position. FIG. 9 is an example of a schematic cross-sectional structure of TFF3. The TFF 3 is designed by making the film thicknesses different in the region 31, the region 32, and the region 33. In FIG. 9, the film is illustrated as if four layers of films are formed on the substrate, but this is schematically shown only to show that the film thickness is different for each region. Actually, the number of layers to be formed may be larger.

As a more specific configuration example, the TFF 3 is formed by alternately laminating SiO ₂ as a low refraction material and Ta ₂ O ₅ as a high refraction material. As the design of TFF3, the most common BPF (bandpass filter) design pattern is a single cavity (configuration having one cavity layer), and the SiO ₂ cavity layer (6qw) is a high refractive index layer / low refractive index. It was set as the structure which pinched | interposed the layer (each 1qw) by 8 pairs. Note that qw indicates a quarter wave, and 6qw indicates a layer having a thickness six times the quarter wavelength. FIG. 10 shows the result of calculating the transmittance at this time using TFCalc known as a membrane design tool. In the region 32, the thickness of each layer in the region 31 was increased by 1.001, and in the region 33, the thickness of each layer in the region 31 was increased by 1.002.

FIG. 10 is illustrated by a drawing method similar to the VBG selection wavelength distribution 42 shown in FIG. The selected wavelength distribution 31a corresponds to a wavelength distribution that can be wavelength-selected in the region 31 in the TFF 3. Similarly, the selected wavelength distribution 32a corresponds to a wavelength distribution in which the wavelength can be selected in the region 32 in the TFF 3, and the selected wavelength distribution 33a corresponds to a wavelength distribution in which the wavelength can be selected in the region 33 in the TFF 3.

According to FIG. 10, when the basic light passes through TFF 3, a wavelength in the vicinity of 1064.04 nm is selected for the basic light that has passed through the region 31, and a wavelength in the vicinity of 1065.10 nm is selected for the basic light that has passed through the region 32. For the basic light that has been selected and passed through the region 33, a wavelength in the vicinity of 1066.16 nm is selected. That is, the wavelength band selected from the basic light can be varied according to the region passing through the TFF 3.

That is, by changing the film thickness of the TFF 3 according to the position, the selected wavelength distribution of the TFF 3 can be changed according to the position. More specifically, when the wavelength to be selected is to be on the long wavelength side, the film thickness is formed thicker. On the contrary, when the wavelength to be selected is to be selected on the short wavelength side, the film thickness is thinly formed.

In view of this point, the TFF 3 provided in the laser light source device 1 changes the film thickness according to the position. More specifically, among the plurality of light emitting units 2 mounted on the semiconductor element 1, the light emitting unit 2 (“second light emitting unit”) disposed at a position where the temperature is likely to rise due to heat generated from the surrounding light emitting units 2. In the region through which the basic light emitted from (corresponding to 1) passes (corresponding to the “second selection region”), the film thickness is increased. On the contrary, a region through which the basic light emitted from the light emitting unit 2 (corresponding to the “first light emitting unit”) disposed at a position where it is relatively difficult to be affected by heat generated from the surrounding light emitting units 2 (the “first” With respect to “one selected region”), the film thickness is formed thin.

Thus, even if the peak wavelength of the basic light emitted from each light emitting unit 2 is different depending on the position due to heat generation from the adjacent light emitting unit 2, the TFF 3 as the wavelength selection element is The wavelength selection distribution can be shifted according to the position in accordance with the deviation of the peak wavelength of the basic light. Thereby, the area of the superposition of the wavelength distribution of the basic light from each light emitting unit 2 and the selection wavelength distribution of the TFF 3 as the wavelength selection element can be increased. Therefore, the first light having a high intensity can be selected from the basic light regardless of the position of the light emitting unit 2, and the second light is converted from the first light by the wavelength conversion element (here, PPLN95). By taking out, the light quantity of the laser beam taken out can be increased more than before.

As shown in FIG. 2, when a plurality of light emitting units 2 are mounted on the semiconductor element 11 in an array, basic light emitted from the light emitting units 2 arranged near the center of the array is used. The wavelength tends to be longer than the wavelength of the basic light emitted from the light emitting unit 2 arranged at a position close to the outer edge of the array (see FIG. 7). Therefore, the film thickness of the TFF 3 in the first selection region through which the basic light emitted from the light emitting unit 2 arranged near the outer edge of the array passes is made thin, and conversely, arranged near the center of the array. By increasing the film thickness of the TFF 3 in the second selection region through which the basic light emitted from the light emitting unit 2 passes, the wavelength can be efficiently selected for the basic light emitted from all the light emitting units 2.

It should be noted that various methods can be adopted as a method of varying the film thickness of the TFF 3 depending on the position. As an example, when performing vacuum evaporation during film formation, the film thickness can be changed by changing the distance from the evaporation source by providing a predetermined inclination angle without arranging the substrate perpendicular to the evaporation source. it can. In addition, it is possible to vary the film thickness depending on the position by arranging a mask plate between the substrate and the vapor deposition source and appropriately designing and arranging the mask shape.

[Second Embodiment]
Only a different part from 1st Embodiment is demonstrated about 2nd Embodiment of a laser light source apparatus.

FIG. 11 is a diagram schematically showing the configuration of the laser light source device in the present embodiment. The laser light source device 1a of this embodiment is different from the configuration of the first embodiment shown in FIG. 8 in that an etalon filter 5 is provided as a wavelength selection element instead of TFF3. More specifically, the etalon filter 5 is realized by disposing the optical member 6 so as to face the PPLN 95 with a distance.

The optical member 6 is an optical member that transmits incident light as it is, and is made of, for example, quartz glass. The etalon filter 5 is formed by a gap provided between the first surface 95 a of the PPLN 95 and the first surface 6 a of the optical member 6. The optical member 4 is formed on the second surface 6b side opposite to the first surface 6a of the optical member 6. The optical member 4 is designed to reflect light (first light) in the wavelength band selected by the etalon filter 5 and transmit light (second light) in the wavelength band converted by the PPLN 95.

The laser light source device 1a is the same as the laser light source device 1 of the first embodiment except that an etalon filter 5 is employed as a wavelength selection element instead of the TFF 3, and thus the basic light emitted from the light emitting unit 2 is used. The principle of extracting laser light (second light 40, 50) having a desired wavelength from light is common. Therefore, this description is omitted.

In the present embodiment, the wavelength distribution selected according to the position is different from the etalon filter 5. The wavelength selected for the etalon filter 5 is determined by the distance between the opposing optical surfaces. More specifically, when the gap length d provided between the first surface 95a of the PPLN 95 and the first surface 6a of the optical member 6 is increased, the selected wavelength is shifted to the longer wavelength side, and conversely, the gap length d is decreased. If it is shortened, the selected wavelength is shifted to the short wavelength side. That is, the wavelength distribution selected according to the position can be varied by varying the gap length d according to the position.

More specifically, among the plurality of light emitting units 2 mounted on the semiconductor element 1, the light emitting unit 2 (“second light emitting unit”) disposed at a position where the temperature is likely to rise due to heat generated from the surrounding light emitting units 2. The gap length d of the etalon filter 5 is formed long in the region through which the basic light emitted from (corresponding to 2) passes (corresponding to the “second selection region”). On the contrary, a region through which the basic light emitted from the light emitting unit 2 (corresponding to the “first light emitting unit”) disposed at a position where it is relatively difficult to be affected by heat generated from the surrounding light emitting units 2 (the “first” 1), the gap length d of the etalon filter 5 is formed short. Thereby, the effect similar to the laser light source device 1 of 1st Embodiment is acquired.

That is, even if the peak wavelength of the basic light emitted from each light emitting unit 2 is different depending on the position due to heat generation from the adjacent light emitting units 2, the wavelength of the etalon filter 5 as the wavelength selection element The value of the peak wavelength of the selection distribution can be shifted according to the position. As a result, it is possible to increase the overlapping area of the wavelength distribution of the basic light from each light emitting unit 2 and the selection wavelength distribution of the etalon filter 5 as the wavelength selection element.

Therefore, the first light having a high intensity can be selected from the basic light regardless of the position of the light emitting unit 2, and the second light is converted from the first light by the wavelength conversion element (here, PPLN95). By taking out, the light quantity of the laser beam taken out can be increased more than before.

As shown in FIG. 2, when a plurality of light emitting units 2 are mounted on the semiconductor element 11 in an array, basic light emitted from the light emitting units 2 disposed near the outer edge of the array. The etalon filter 5 in the second selection region through which the basic light emitted from the light emitting unit 2 disposed near the center of the array passes is reduced by shortening the gap length d of the etalon filter 5 in the first selection region through which the light passes. The gap length d is increased. Thereby, wavelength selection can be performed efficiently for the basic light emitted from all the light emitting units 2.

It should be noted that various methods can be adopted as a method of varying the gap length d of the etalon filter 5 depending on the position. As an example, the first surface 6a of the optical member 6 is a curved surface. More specifically, when the plurality of light emitting units 2 are mounted in an array on the semiconductor element 11, the optical member 6 is arranged such that the center portion is further away from the first surface 95 a of the PPLN 95 than the outer edge portion. This can be realized by forming the first surface 6a into a concave shape. In addition, the 1st surface 95a of PPLN95 may be comprised with a curved surface, and both may be comprised with a curved surface.

[Third Embodiment]
Only a different part from 1st Embodiment is demonstrated about 3rd Embodiment of a laser light source apparatus.

FIG. 12 is a diagram schematically showing the configuration of the laser light source device in the present embodiment. The laser light source device 1b of the present embodiment is different from the configuration of the first embodiment of FIG. 8 in that a VBG 7 is provided instead of TFF 3 as a wavelength selection element. That is, it corresponds to a structure in which the VBG 93 of the conventional laser light source device 90 shown in FIG.

This VBG 7 is different from the conventional VBG 93 in that the selection wavelength distribution is different depending on the position. More specifically, a region through which basic light emitted from the light emitting unit 2 (corresponding to the “second light emitting unit”) disposed at a position where the temperature is likely to rise due to heat generated from the surrounding light emitting units 2 passes (“ For “second selection region”, the selection wavelength distribution is designed to be on the long wavelength side. On the contrary, a region through which the basic light emitted from the light emitting unit 2 (corresponding to the “first light emitting unit”) disposed at a position where it is relatively difficult to be affected by heat generated from the surrounding light emitting units 2 (the “first” For “one selection region”, the selection wavelength distribution is designed to be on the short wavelength side. Thereby, the effect similar to the laser light source apparatus of 1st Embodiment and 2nd Embodiment is acquired.

Various methods can be adopted as a method for differentiating the selection wavelength distribution according to the position with respect to VBG7. The VBG 7 is formed by creating a refractive index distribution of a layer structure in a photosensitive glass material using a technique such as two-beam interference. The wavelength λ of the light reflected by the VBG 7 is expressed as λ = 2n · Δ · cos θ, where Δ is the thickness of the layer and θ is the incident angle of the light incident on the VBG 7. Therefore, the wavelength λ of the light reflected from the VBG 7 can be changed by changing the layer thickness Δ.

Therefore, when a photosensitive glass material is irradiated with light to create a refractive index distribution, a predetermined mask is formed and irradiated with light, so that the position can be determined according to the shape of the mask (for example, using a striped mask). It is possible to change the thickness Δ of the layer according to.

[Fourth Embodiment]
Only a different part from 1st Embodiment is demonstrated about 4th Embodiment of a laser light source apparatus.

FIG. 13 is a diagram schematically showing the configuration of the laser light source device in the present embodiment. The laser light source device 1c of this embodiment is different from the configuration of the first embodiment of FIG. 8 in that a PPLN 8 is provided instead of PPLN 95 as a wavelength conversion element.

This PPLN 8 is different from the PPLN 95 in that the conversion wavelength distribution is different depending on the position.

For this reason, as described above, the basic light emitted from the first light emitting unit is selected by passing through the first selection region of the wavelength selection element, and the basic light emitted from the second light emitting unit. The first light selected by passing through the second selection region of the wavelength selection element has a difference in wavelength.

The laser light source devices of the first to third embodiments described above were configured to include wavelength selection elements (TFF3, etalon filter 5, VBG7) that exhibit different characteristics of the selected wavelength distribution depending on the position. In this configuration, the basic light emitted from the first light emitting unit arranged at a position that is not easily affected by the temperature rise passes through the first selection region of the wavelength selection element, and the temperature The first light selected by the basic light emitted from the second light emitting unit arranged at a position susceptible to the rise passing through the second selection region of the wavelength selection element has a difference in wavelength. Yes. This can be understood from the fact that, for example, in FIG. 10, the peak wavelengths of the light (first light) selected from the basic lights passing through the region 31, the region 32, and the region 33 are different.

However, even in such a state, the wavelength conversion element included in the laser light source device of the first to third embodiments converts a wideband wavelength such as the conversion wavelength distribution 43 of FIG. If possible, even if the first light having a difference in the peak wavelength according to the position is incident, it is possible to convert them into the second light.

However, when a wavelength conversion element that can convert such a wide-band wavelength is designed, the intensity of the second light obtained after the conversion is relatively low.

If the PPLN polarization inversion pitch is accurately manufactured, the conversion efficiency can be increased. However, in this case, the conversion wavelength distribution also becomes a narrow band (see FIG. 14). FIG. 14 shows the wavelength distribution 41 of the basic light, the selection wavelength distribution 42 of the VBG 93, and the conversion wavelength distribution 44 of the PPLN 95 that can be converted with high efficiency in a narrow band, as in FIG.

In the configuration of the first to third embodiments, the case where the PPLN 95 showing the characteristic like the conversion wavelength distribution 44 of FIG. 14 is used will be examined. As described above, the first light selected by the wavelength selection element has a configuration in which the wavelength varies depending on the position. That is, since the first light having a different peak wavelength depending on the position is incident on the PPLN 95, if the band of the wavelength band that can be converted is too narrow, the wavelength of the first light can be converted depending on the position. It is assumed that it is located outside the band or the conversion efficiency is extremely lowered.

Therefore, the PPLN 8 of the present embodiment has a characteristic that can be converted with high efficiency in a narrow band like the conversion wavelength distribution 44 and has a distribution in the wavelength band that can be converted according to the position. Yes. More specifically, a wavelength band that can be converted in a region (corresponding to the “first conversion region”) selected by the first selection region through which the first light having a relatively short wavelength passes is selected by the second selection region. In the region through which the first light having a relatively long wavelength passes (corresponding to the “second conversion region”), the wavelength is shorter than the convertible wavelength band. As a result, regardless of the position of the light emitting unit 2, the first light having a high intensity is selected from the basic light, and the first light is converted into the second light having a high intensity. It can be higher than before.

Various methods can be adopted as a method of making the conversion wavelength distribution different depending on the position with respect to the PPLN8. PPLN8 achieves pseudo phase matching for light of a predetermined wavelength by forming a periodic polarization inversion layer inside a bulk crystal such as LiNbO ₃ and changes the period of the polarization inversion layer. Thus, the convertible wavelength band can be adjusted. As an example of the method of forming this domain-inverted layer, slit-like electrodes are formed at a predetermined interval (same as the period of domain-inverted layer) on the upper surface and one side surface of the bulk crystal, and a high voltage is applied to this electrode. Thus, a polarization inversion layer is formed inside the bulk crystal corresponding to the position of the electrode.

Therefore, by changing the interval between the positions of the electrodes formed on the surface of the bulk crystal under a predetermined rule according to the position, it is possible to form different periods of the domain-inverted layers according to the position. As a result, the conversion wavelength distribution can be made different for PPLN 8 depending on the position. In addition, the formation method of this electrode can use the technique similar to semiconductor manufacturing processes, such as sputtering, patterning by photoengraving, and etching.

The laser light source device 1c in FIG. 13 is configured to include the PPLN 8 having the property that the wavelength distribution characteristic differs depending on the position with respect to the laser light source device 1 of the first embodiment. The same applies to the laser light source device 1a and the laser light source device 1b of the third embodiment.

[Another embodiment]
In each of the above embodiments, the wavelength conversion elements (PPLN95, PPLN8) are positioned between the semiconductor element 11 and the wavelength selection element (TFF3, etalon filter 5, VBG7). On the other hand, the positions of the wavelength selection element and the wavelength conversion element may be interchanged.

FIG. 15 schematically shows a laser light source device 1d having a configuration in which the positional relationship between the TFF 3 and the PPLN 95 is reversed in the laser light source device 1 of the first embodiment shown in FIG. In this case, the optical member 4 designed to reflect light in the wavelength band selected by TFF3 (first light) and transmit light in the wavelength band converted by PPLN95 (second light) is TFF3. Is provided at a position facing the PPLN 95 on the opposite surface.

Also in this configuration, the

second lights

40 and 50 are extracted to the outside by the same principle as the laser light source device 1 shown in FIG. In FIG. 15, the laser light source device 1 according to the first embodiment has been described as an example. Similarly, in the second to fourth embodiments, the positions of the wavelength selection element and the wavelength conversion element are interchanged. Is possible.

In the above embodiment, as the wavelength conversion element, PPLN (PPLN95, PPLN8) has been explained the case of using, not limited to this, periodically poled lithium tantalate forming a domain-inverted structure in LiTaO ₃ (PPLT: Other quasi phase matching type wavelength conversion (QPM: Quasi-Phase Matching) elements including Periodically Poled Lithium Tantalate may be used.

1, 1a, 1b, 1c, 1d: Laser light source device 2 (2a, 2b,..., 2w, 2x): Light emitting unit 3: TFF (dielectric thin film filter)
4: Optical member 5: Etalon filter 6: Optical member 6a: First surface of optical member 6b: Second surface of optical member 7: VBG
8: PPLN
11: Semiconductor element 17: Heat sink 25: Reflective member 27:

Reflective member

31, 32, 33: TFF

regions

31a, 32a, 33a: Selected wavelength distribution for each TFF region 40: Second light 41: Wavelength distribution of basic light 42: Selected wavelength distribution 43: Conversion wavelength distribution 44: Narrow band conversion wavelength distribution 50: Second light 90: Conventional laser light source device 93: VBG
95: PPLN
95a: First surface of PPLN d: Gap length of etalon filter

Claims

A semiconductor element comprising a plurality of light emitting portions that emit basic light;
A wavelength selection element for selecting the predetermined wavelength band of the basic light and extracting the first light;
A wavelength conversion element for converting the wavelength of a part of the first light and extracting the second light;
The wavelength selection element is configured such that the predetermined wavelength band that can be selected in a first selection region through which the basic light emitted from the first light emitting unit of the plurality of light emitting units passes is, of the plurality of light emitting units, The predetermined wavelength band that can be selected in a second selection region through which the basic light emitted from the second light emitting unit, which has a temperature rise due to heat generated when the other light emitting units emit light, is higher than that of the first light emitting unit. A laser light source device characterized in that the wavelength becomes shorter than that of the laser light source device.
The plurality of light emitting units are arranged in an array,
2. The laser light source device according to claim 1, wherein the first light emitting unit is disposed at a position closer to an outer edge of the array than the second light emitting unit.
The wavelength selection element is a dielectric multilayer film bandpass filter, and the film thickness of the first selection region is formed thinner than the film thickness of the second selection region. The laser light source device described.
3. The laser light source device according to claim 1, wherein the wavelength selection element is an etalon filter, and the gap length of the first selection region is shorter than the gap length of the second selection region. .
The said wavelength selection element is a volume Bragg grating (VBG), and the thickness of the layer of the said 1st selection area | region is formed thinner than the thickness of the layer of the said 2nd selection area | region. The laser light source device according to 1.
The wavelength conversion element has a wavelength band that can be converted in the first conversion area through which the first light selected in the first selection area of the wavelength selection element passes in the second selection area of the wavelength selection element. 6. The laser light source device according to claim 1, wherein the laser light source device is configured to have a wavelength shorter than a wavelength band that can be converted in the second conversion region through which the selected first light passes. .
The wavelength conversion element is a periodically poled lithium niobate (PPLN), and the thickness of the layer in the first conversion region is thinner than the thickness of the layer in the second conversion region. The laser light source device according to claim 6.