JP2008258515A - Semiconductor laser device, laser module, and optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device which can suppress speckles, a laser module and an optical device using the semiconductor laser device. <P>SOLUTION: The semiconductor laser device 1 includes a semiconductor laser array 10 having a plurality of striped ridge portions 13 at the bottom on a heat sink 19. Among the plurality of ridge portions 13, the stripe width of the ridge portion 13 located in a central region G1 is larger than the stripe width of the portion located in an edge region G3. On the other hand, the stripe width of a current injection layer 14 provided on each ridge portion 13 is preferably substantially equal. Spectrum bandwidth of combined light can be expanded to approximately 5 nm and each ridge portion 13 can be driven with uniform current/voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device, a laser module, and an optical device that are preferably used as a light source for a projector device or the like.

  In recent years, with the spread of rear projection televisions and the like, there is an increasing demand for higher image quality for projector devices that project and display images on a screen or the like. In such a projector device, since the image output is displayed by modulating the light output from the light source, it is particularly required to improve the performance of the light source in order to improve the performance of the entire device. For this reason, as a light-emitting device used for a light source, a semiconductor laser capable of realizing a high color gamut and a high brightness is attracting attention.

  However, the light emitted from the semiconductor laser is coherence light having a single wavelength and a uniform phase, and has high color purity (narrow spectrum) characteristics with an oscillation spectrum width of about 1 nm. For this reason, there is a problem that a speckle pattern called speckle is generated on the projection screen, and the image appears to flicker.

As a technique for reducing and removing such speckle, for example, there is a method of converting laser light into light having a spatially different phase by vibrating a screen or an optical element disposed on an optical path ( For example, Patent Document 1). However, such a method is not preferable in terms of cost and reliability because it requires a new drive mechanism for vibrating the screen, optical elements, and the like, resulting in a complicated apparatus configuration. On the other hand, in order to sufficiently suppress the generation of speckles, it is necessary to expand the oscillation spectrum width from about 1 nm to about 5 nm, which is difficult with a single semiconductor laser.
JP-T 9-504920 JP 2004-14793 A JP-T-2004-503923 JP 59-107590 A Journal of Applied Physics, Volume 57 page 5428 (1985)

  Therefore, by arranging a plurality of semiconductor laser elements in an array and combining the light oscillated from the respective semiconductor laser elements, the oscillation spectrum bandwidth can be expanded. This is because the heat dissipation varies depending on the region in the array, and the operating temperature varies from region to region, and the oscillation wavelength shifts. Further, for example, Patent Documents 2 to 4 disclose techniques for expanding the spectral bandwidth of the entire device by actively changing the oscillation wavelength of each semiconductor laser element.

  However, it is difficult to secure an oscillation spectrum bandwidth to such an extent that speckle generation can be suppressed only by the configuration of the above-mentioned patent document or the configuration of simply combining the lights of a plurality of semiconductor laser elements. is there.

  The present invention has been made in view of such problems, and an object thereof is to provide a semiconductor laser device capable of suppressing the generation of speckles, a laser module using the same, and an optical device.

  The semiconductor laser device of the present invention is a semiconductor laser device including a plurality of semiconductor laser elements, and the semiconductor laser element includes a ridge portion and a current injection layer for injecting a current into the ridge portion. The semiconductor laser element includes at least two types of semiconductor laser elements having different ridge widths.

  An optical device of the present invention includes a semiconductor laser device and an optical system that collects light output from the semiconductor laser device. The semiconductor laser device includes a plurality of semiconductor laser elements, and the semiconductor laser element includes a ridge portion. And a current injection layer for injecting current into the ridge portion, and the plurality of semiconductor laser elements include at least two types of semiconductor laser elements having different ridge widths.

  The laser module of the present invention includes a plurality of semiconductor laser devices connected in parallel, and each semiconductor laser device includes a plurality of semiconductor laser elements, and the semiconductor laser element injects a current into the ridge portion. A plurality of semiconductor laser devices including at least two types of semiconductor laser devices having different ridge widths, and the plurality of semiconductor laser devices having different spectral bands of oscillation wavelengths It is.

  Note that “the spectrum bands of the oscillation wavelengths are different from each other” is not limited to the case where the spectrum bands do not overlap at all, but includes the case where some of the spectrum bands overlap.

  The semiconductor laser device and the optical device according to the present invention include at least two types of semiconductor laser elements having different ridge widths, so that in the semiconductor laser element having a relatively large ridge width, the volume of the ridge portion is increased. Increases and heat tends to accumulate inside, so that the heat dissipation is reduced. On the other hand, in a semiconductor laser device having a relatively small width of the ridge portion, the volume of the ridge portion is reduced and heat is less likely to be accumulated therein, so that the heat dissipation is enhanced. As a result, the operating temperature becomes high in the semiconductor laser element having a large ridge portion and lowered in the semiconductor laser element having a small ridge portion. At this time, the wavelength of the output light shifts to the long wavelength side when the temperature increases, and conversely shifts to the short wavelength side when the temperature decreases. Therefore, the spectral bandwidth of the oscillation wavelength is expanded as a whole semiconductor laser device.

  In particular, the width of the current injection layer is preferably substantially uniform in at least two types of semiconductor laser elements having different ridge widths. That is, it is preferable that the width of the current injection layer provided on each ridge portion is substantially equal regardless of the width of the ridge portion. As a result, the current applied to each ridge portion is equalized, and it is possible to drive at a constant voltage without providing a voltage adjusting mechanism such as a resistor for each ridge portion.

  In addition, it is preferable that the width of the ridge portion of the semiconductor laser element disposed at the center portion is larger than the width of the ridge portion of the semiconductor laser element disposed at the end portion. In general, a semiconductor laser device in which a plurality of semiconductor laser elements are arranged has a property that heat dissipation is low in the central portion and heat dissipation is high in the end portion. For this reason, since the width | variety of the ridge part of a center part is comparatively large, heat dissipation becomes lower. On the contrary, since the width of the ridge portion at the end is relatively small, the heat dissipation is further improved. Therefore, a large difference in height occurs depending on the operating temperature between the central portion and the end portion. Therefore, the spectral bandwidth of the oscillation wavelength is expanded more effectively.

  Further, when the metal layer is provided on the side where the plurality of ridge portions of the semiconductor layer are provided, the thermal conductivity is increased in the region between the adjacent ridge portions. In a region where the width of the ridge portion is relatively large, heat hardly reaches the metal layer, and the region where the metal layer is formed is relatively small. On the other hand, in the region where the width of the ridge portion is relatively small, heat easily reaches the metal layer and the region where the metal layer is formed is relatively large. Therefore, the height difference due to the difference in heat dissipation of the semiconductor laser device as a whole becomes larger, which is advantageous for securing the spectral bandwidth.

  In the laser module of the present invention, a plurality of semiconductor laser devices connected in parallel have at least two types of semiconductor laser elements having different ridge widths, thereby causing a difference in operating temperature. The oscillation wavelength shifts to the longer wavelength side when the temperature increases, and conversely shifts to the shorter wavelength side when the temperature decreases, so that the spectral bandwidth of the oscillation wavelength is expanded in each semiconductor laser device. In particular, when the spectral bands of the light emitting layers of the plurality of semiconductor laser devices are different from each other, the spectral bandwidth of the synthesized light output from the plurality of semiconductor laser devices is used when each semiconductor laser device is used alone. Enlarged compared to

  According to the semiconductor laser device and the optical device of the present invention, a plurality of semiconductor laser elements each having a ridge portion and a current injection layer for injecting a current into the ridge portion include at least two kinds of ridge portions having different widths. Since the semiconductor laser element is included, there is a difference in operating temperature between the semiconductor laser elements having different ridge widths. Therefore, the spectral bandwidth of the oscillation wavelength is expanded, and speckle can be suppressed.

  According to the laser module of the present invention, a plurality of semiconductor laser arrays connected in parallel are respectively provided in a plurality of stripe-shaped ridge portions arranged in an array, and each ridge portion has a constant stripe width. A current injection layer and a light emitting region corresponding to each current injection layer, and the stripe width of the ridge portion arranged at the center of the plurality of ridge portions is larger than the stripe width of the ridge portion arranged at the end portion Because the spectral bands of the oscillation wavelength of multiple semiconductor laser arrays are different from each other, the spectral bandwidth is expanded and speckle is more efficient than when these semiconductor laser arrays are used alone. Can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional configuration of a semiconductor laser device 1 including a semiconductor laser array 10 according to an embodiment of the present invention. In the semiconductor laser device 1, for example, the semiconductor laser array 10 is placed on a heat sink 19 with a ridge portion 13 side down through a metal layer 18. The semiconductor laser array 10 has a light emitting region for each ridge portion 13 and includes a plurality of semiconductor laser elements.

  The semiconductor laser array 10 has a semiconductor layer 12 formed on one surface side of a substrate 11. The semiconductor layer 12 has a lower clad layer, an active layer, an upper clad layer (not shown) and the like laminated on the substrate 11 in this order, and has a plurality of ridge portions 13 above the upper clad layer. Yes.

  The substrate 11 is made of, for example, n-type GaAs. The n-type impurity is, for example, silicon (Si) or selenium (Se).

  The semiconductor layer 12 is made of, for example, an AlGaInP semiconductor. Note that an AlGaInP-based semiconductor is a compound semiconductor containing aluminum (Al), gallium (Ga), or indium (In) as a group 3B element and phosphorus (P) as a group 5B element in the long-period periodic table. Say.

Here, the lower cladding layer is made of, for example, n-type Al _a Ga _1-ab In _b P (0 <a <1, 0 <b <1). The active layer is made of, for example, Ga _c In _1-c P (0 <c <1) that does not contain impurities. This active layer has a stripe-shaped light emitting region S corresponding to each ridge portion 13. That is, each light emitting region S is formed in the common semiconductor layer 12. The light emitting region S corresponds to a current injection region into which a current confined by the ridge portion 13 is injected. The upper cladding layer is made of, for example, p-type Al _d Ga _1-de In _e P (0 <d <1, 0 <e <1). The p-type impurity is zinc (Zn), magnesium (Mg), beryllium (Be), or the like.

  A plurality of stripe-shaped ridge portions 13 extending in the laser beam emission direction (axial direction) are formed in parallel on the upper clad layer. Each ridge portion 13 limits the current injection region of the active layer and guides it in the axial direction by the lateral refractive index confinement action. The configuration of the ridge portion 13 will be described later. Hereinafter, a direction in which the semiconductor layers 12 are stacked is referred to as a vertical direction, and an axial direction and a direction perpendicular to the vertical direction (arrangement direction of each ridge portion 13) are referred to as a horizontal direction.

  Such a semiconductor laser array 10 has an upper electrode 16 and a lower electrode 17. The upper electrode 16 is integrally provided so as to cover all the ridge portions 13, and serves as a common electrode for each ridge portion 13. The upper electrode 16 has, for example, a structure in which titanium (Ti), platinum (Pt), and gold (Au) are stacked on the semiconductor layer 12 in this order. Further, in this embodiment, in order to adjust the balance of the voltage applied to each laser, the upper electrode 16 is configured to be electrically separated for each ridge portion 13, and a resistor or the like is provided for each electrode. There is no need.

  The lower electrode 17 is formed on the back side of the substrate 11. The lower electrode 17 has, for example, a structure in which AuGe, Ni, and Au are stacked in this order, and is electrically connected to the substrate 11. The upper electrode 16 and the lower electrode 17 are connected to a single power source (not shown) via a wire (not shown).

  The metal layer 18 is made of, for example, a connection metal such as solder, an alloy containing gold, tin (Sn), silver (Ag), or the like. The heat sink 19 is a heat radiating member for radiating heat generated from each light emitting region S of the semiconductor laser array 10 from the semiconductor laser array 10. The metal layer 18 connects the upper electrode 16 of the semiconductor laser array 10 and the heat sink 19. Further, for example, a cooling element such as a Peltier element may be used, or a structure connected to another substrate such as a submount instead of the heat sink 19 may be used.

  Next, the configuration of the ridge portion 13 will be described. Assuming that the central region in the semiconductor array 10 is G1, the end region is G3, and the intermediate region between these regions is G2, the stripe width W1 of the ridge portion 13 of the central region G1 is the width of the ridge portion 13 of the end region G3. It is larger than the stripe width W3. Preferably, the stripe width of the ridge portion 13 gradually decreases from the central region G1 to the end region G3. More preferably, the number of ridge portions 13 included in each region is relatively large in the central region G1.

  For example, the stripe width of the ridge portion 13 in each region is configured to gradually decrease from the central region G1 to the end region G3 so as to satisfy the relationship of W1> W2> W3. Further, the number of ridge portions 13 arranged in the central region G1 is five, the number of ridge portions 13 arranged in the intermediate region G2 is two, and the number of ridge portions 13 arranged in the end region G3 is two. Thus, the number of ridge portions 13 in the central region G1 is the largest.

  In the present embodiment, the plurality of ridge portions 13 are provided at equal intervals (interval P). That is, the light emitting regions S are formed at equal intervals corresponding to the ridge portions 13.

Here, FIG. 2A shows an enlarged view of a cross-sectional configuration example of each ridge portion 13 when the stripe width W is relatively wide, and FIG. 2B shows a case where the stripe width W is relatively narrow. As shown in these drawings, a current injection layer 14 is provided on the ridge portion 13 of the semiconductor layer 12. An insulating layer 15 is provided along the ridge shape in the region where the current injection layer 14 is not formed on the semiconductor layer 12. The insulating layer 15 is made of, for example, SiO ₂ . The upper electrode 16 is provided adjacent to the current injection layer 14 and the insulating layer 15 so as to integrally cover the plurality of ridge portions 13.

The current injection layer 14 is made of, for example, p-type Al _f Ga _{1 -fg} In _g P (0 <f <1, 0 <g <1) or p-type GaAs. The current injection layer 14 functions as a contact layer between the semiconductor layer 12 and the upper electrode 16 and limits the current injection region of the active layer.

  In particular, the stripe width D of the current injection layer 14 is substantially uniform among the plurality of ridge portions 13. That is, when the stripe width W of the ridge portion 13 is wide (FIG. 2A) and when the stripe width W of the ridge portion 13 is narrow (FIG. 2B), the stripe width D of the current injection layer 14 is Are almost equal. In other words, the ratio of the stripe width D of the current injection layer to the stripe width W of the ridge portion 13 is different between the ridge portions 13 having different stripe widths. For example, the stripe width W of the ridge portion 13 is 300 μm in FIG. 2A and 80 μm in FIG. 2B, whereas the stripe width D of the current injection layer 14 is 60 μm in any case. Yes. Thus, the current injection layer 14 is provided with a constant width regardless of the stripe width W of each ridge portion 13. Note that “substantially uniform” is not limited to the completely identical case, and is a concept including manufacturing errors.

  Further, since the insulating layer 15 is provided in the region where the current injection layer 14 is not formed on the semiconductor layer 12, the upper electrode 16 and the semiconductor layer 12 are electrically connected only by the current injection layer 14. The For this reason, the stripe width of the light emitting region S is somewhat the same as the stripe width D of the current injection layer 14 although it slightly changes depending on the temperature distribution in the lateral direction.

  The semiconductor laser device 1 having the above configuration can be manufactured, for example, as follows.

First, the semiconductor laser array 10 is formed. The compound semiconductor layer on the substrate 11 is formed by, for example, MOCVD (Metal Organic Chemical Vapor Deposition) method. At this time, for example, trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMIn), and phosphine (PH ₃ ) are used as raw materials for the AlGaInP-based compound semiconductor as described above. For example, hydrogen selenide (H ₂ Se) is used, and dimethyl zinc (DMZ) is used as the acceptor impurity raw material, for example.

  Specifically, first, a lower clad layer, an active layer, an upper clad layer, and a current injection layer are laminated in this order on the substrate 11, and then the current injection layer 14 and the upper clad layer are formed using a mask 2 Each is selectively removed by step etching, for example, reactive ion etching (RIE). As a result, a plurality of stripe-shaped ridge portions 13 are formed in parallel in the upper cladding layer so that the stripe width in the central region G1 is larger than the stripe width in the end region G3. Subsequently, the insulating layer 15 is formed by a vapor deposition method or the like in a region of the upper clad layer where the current injection layer 14 is not formed.

  Next, the upper electrode 16 is formed by collectively forming a metal material on the plurality of ridge portions 13 by vapor deposition, sputtering, or the like so as to cover the formed current injection layer 14 and insulating layer 15. To do. Similarly, the lower electrode 17 is formed on the back surface of the substrate 11, and then a reflecting mirror film (not shown) is formed on the pair of end surfaces in the axial direction. In this way, the semiconductor laser array 10 is formed.

  Thereafter, the semiconductor laser array 10 and the heat sink 19 are connected by forming a metal layer 18 between the upper electrode 16 and the heat sink 19 by soldering, for example. Thus, the semiconductor laser device 1 shown in FIG. 1 is completed.

  Next, the operation of the semiconductor laser device 1 of the present embodiment will be described. In the semiconductor laser device 1, when a predetermined voltage is applied between the upper electrode 16 and the lower electrode 17, current is confined by the ridge portion 13, and current is injected into the current injection region (light emitting region S) of the active layer. This causes light emission due to recombination of electrons and holes. This light is reflected by a pair of reflecting mirror films (not shown), causes laser oscillation at a wavelength at which the phase change when it reciprocates once in the element is an integral multiple of 2π, and is emitted to the outside as a laser beam. The

  By the way, in general, in the semiconductor laser device 100 including the semiconductor laser 110 having the single ridge portion 113 and the heat sink 119 as shown in FIG. 9A, the upper electrode 116 and the lower electrode 117 are compared with each other. When a voltage is applied to output laser light from the light emitting region T corresponding to the ridge portion 113 in the semiconductor layer 112, the component that has not contributed to the light emission in the energy injected into the light emitting region T becomes heat. Therefore, the light emitting region T functions as a heat source that generates a calorific value with a distribution as shown in FIG. The heat generated in the light emitting region T is mainly dissipated to the heat sink 119 via the ridge portion 113 and the upper electrode 116, and part of it is dissipated outside via the substrate 111 and the lower electrode 117. As a result, the light emitting region T and the vicinity thereof have a temperature distribution as shown in FIG.

  Therefore, as in the semiconductor laser device 200 shown in FIG. 10, when a plurality of ridge portions 113 having a constant stripe width are arranged at equal intervals, the temperature of the central region of the arrangement is increased due to thermal interference. It becomes higher than the temperature of the partial region. For example, the semiconductor laser array 210 is made of an AlGaInP / GaInP-based semiconductor material, the stripe width of each ridge 113 is 60 μm, the resonator length is 700 μm, the distance between the ridges 113 is 400 μm, the upper electrode 116 and the lower electrode When a driving current of 10 A is passed between the electrodes 117 and the temperature of the heat sink 219 is adjusted to 25 ° C., the center region and the end region of the semiconductor laser array 210 are separated as shown in FIG. A temperature difference of approximately 5 ° C. occurs.

  Here, in a general semiconductor laser, the oscillation wavelength of emitted light changes to the longer wavelength side as the temperature inside the ridge increases, and conversely, the oscillation wavelength decreases to the shorter wavelength side as the temperature inside the ridge decreases. It has the property of changing to Therefore, as described above, when a temperature distribution occurs in the horizontal direction, light having a wavelength corresponding to the temperature distribution is output from each light emitting region T. As a result, as shown in FIG. 11B, a wavelength difference of about 2 nm occurs between the central region and the end region due to the temperature distribution. Therefore, by arranging a plurality of semiconductor lasers in an array like the semiconductor device 200, the spectral bandwidth of the oscillation wavelength is expanded by about 2 nm due to the difference in operating temperature corresponding to the position.

  However, in actuality, as the temperature inside the laser increases, the light emission efficiency decreases, so that the emission intensity tends to be relatively low in the central region where the temperature is relatively high. For this reason, the emission intensity in the long wavelength region outputted from the light emitting region T in the central region becomes relatively low and the spectral distribution becomes non-uniform. Therefore, the effect of alleviating speckle noise with a spectral width of about 2 nm is rare.

  In contrast, in the present embodiment, among the plurality of ridge portions 13 provided in a stripe shape, the stripe width of the ridge portion 13 in the central region G1 is larger than the stripe width of the ridge portion 13 in the end region G3. It has become. As shown in FIG. 2A, when the stripe width W of the ridge portion 13 is large, the area (volume) of the ridge portion 13 in the semiconductor layer 12 becomes large, and the heat generated inside is thermally conductive. It becomes difficult to reach the high upper electrode 16 and the metal layer 18. For this reason, heat easily accumulates in the ridge portion 13 and heat dissipation is reduced. On the other hand, as shown in FIG. 2B, when the stripe width W of the ridge portion 13 is small, the area (volume) of the ridge portion 13 in the semiconductor layer 12 becomes small, and the heat generated inside is thermally conducted. It becomes easy to reach the upper electrode 16 and the metal layer 18 having high properties. For this reason, heat hardly accumulates in the ridge portion 13 and heat dissipation is enhanced. Accordingly, the operating temperature increases in the central region G1, and the operating temperature decreases in the end region G3.

  For example, the semiconductor laser array 10 shown in FIG. 1 is configured using an AlGaInP / GaInP semiconductor material, the stripe width W1 of the ridge portion 13 is 300 μm, the stripe width W2 is 180 μm, the stripe width W3 is 60 μm, and the ridge portion. The spacing between the electrodes 13 is 400 μm, the stripe width of the current injection layer 14 is 60 μm, the resonator length is 700 μm, a driving current of 10 A is passed between the upper electrode 16 and the lower electrode 17, and the temperature of the heat sink 19 is 25 ° C. When adjusted, the temperature distribution is shown in FIG. 3A and the wavelength distribution is shown in FIG. As shown in these drawings, a temperature difference of about 15 ° C. occurs between the central region G1 and the end region G3 of the semiconductor laser array 10, and accordingly, from the central region G1 to the end region G3. The oscillation wavelength of 640 nm to 645 nm. Therefore, the spectral bandwidth is expanded to about 5 nm.

  On the other hand, the stripe width of the current injection layer 14 provided for each ridge portion 13 is substantially uniform. For this reason, the magnitude and density of the current flowing through each ridge portion 13 are substantially equal regardless of the stripe width of the ridge portion 13. Thereby, each ridge part 13 can be driven with a uniform voltage.

  Here, when the stripe width of each ridge portion is different, a difference occurs in current density for each ridge portion. For this reason, when connected in parallel to a single power supply, the operating voltage differs for each ridge portion. For example, the upper electrode is formed electrically separated for each ridge portion, and a voltage drop resistor, etc. It is necessary to provide a new adjustment mechanism.

  On the other hand, since the stripe width of the current injection layer is substantially uniform, the spectral width of the ridge portion 13 is changed from the central region G1 to the end region G3 in order to increase the spectral bandwidth. However, the drive voltage in each ridge portion 13 can be equalized without providing a voltage adjustment mechanism as in the conventional configuration. This eliminates the need to electrically isolate each ridge portion 13, so that the upper electrode 16 can be integrally formed as a common electrode with the plurality of ridge portions 13. Therefore, only one power source is required to be connected to the upper electrode 16 and the lower electrode 17, and efficient driving can be performed.

  Furthermore, in the present embodiment, since the plurality of ridge portions 13 are provided at equal intervals, the light emission intensity distribution in the array becomes uniform, and the illumination intensity can be made uniform without using a complicated optical system. Become.

  As described above, according to the semiconductor laser device 1 of the present embodiment, the stripe width of the ridge portion 13 arranged in the central region G1 among the plurality of ridge portions 13 is the ridge arranged in the end region G3. By making it larger than the stripe width of the portion 13, the spectral bandwidth of the oscillation wavelength can be expanded by about 5 nm. On the other hand, since the stripe width of the current injection layer 14 provided in each ridge portion 13 is constant regardless of the stripe width of the ridge portion 13, the drive voltages in each ridge portion 13 are all equal, and the voltage adjustment mechanism, etc. It is not necessary to provide a new configuration. Therefore, speckle generation can be efficiently suppressed with a simple configuration.

  Next, a laser module 2 according to an embodiment of the present invention will be described with reference to FIG.

  In the laser module 2, semiconductor laser arrays 20 a and 20 b having different spectrum bands of combined light are connected in parallel to the same single power source 24. Further, for example, the semiconductor laser array 20a and the semiconductor laser array 20b are arranged so that the lower electrodes 17 face each other, and a heat sink 19 and a Peltier are provided on each upper electrode 16 as a mechanism for heat dissipation and cooling. The element 22 and the radiation fin 23 are laminated in this order. In FIG. 4 and the following description, the same components as those of the semiconductor laser array 10 described above are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The configuration of the ridges provided in the semiconductor layers 21a and 21b and the metal layer 18 formed between the upper electrode 16 and the heat sink 19 are omitted for the sake of simplicity. Assume that the configuration is the same as that of the array 10.

  The semiconductor laser array 20a and the semiconductor laser array 20b oscillate light in different spectral bands due to the different configurations of the active layer (not shown) including the light emitting region in the semiconductor layer 21a and the semiconductor layer 21b. Specifically, the active layer of the semiconductor layer 21a and the active layer of the semiconductor layer 21b include different strains. Here, “distortion” is a change in shape such as expansion and contraction caused by the action of an external force such as compression or tension. Such distortion can be added by utilizing a difference in thermal expansion coefficient between the semiconductor laser arrays 20a and 20b and the heat sink 19 connected by soldering, for example. Note that “differing in distortion” means that the degree represented by the ratio between the deformation amount and the initial shape, or the sign (elongation (+), shrinkage (−)) is different. The degree and sign of distortion can be adjusted by adjusting various conditions during soldering.

Here, FIG. 8 shows the relationship of the energy band gap (ΔE (eV)) to the strain (Strain (× 10 ⁻³ )) of the semiconductor material composed of Ga _x In _1-x P (Non-patent Document 1). As described above, the energy band gap changes depending on the degree of distortion and the sign, so that the oscillation wavelength band shifts. Therefore, by applying different strains to the active layers of the semiconductor layers 21a and 21b, the oscillation wavelength band can be made different between the semiconductor laser array 20a and the semiconductor laser array 20b.

For example, when the semiconductor layers 21a and 21b are composed of the same composition of AlGaInP / GaInP system and each active layer is represented by Ga _0.6 In _0.4 P, no strain is added to the active layer of the semiconductor layer 21a ( ± 0%), a strain of -1.7% is added to the active layer of the semiconductor layer 21b. In this case, the spectral band of the synthesized light in the semiconductor laser array 20a without distortion is, for example, 640 nm to 645 nm, and in the semiconductor laser array 20b including distortion of −1.7%, the spectral band of the synthesized light is, for example, 635 nm to 640 nm. It becomes. That is, between the two semiconductor laser arrays 20a and 20b, each has a spectral bandwidth of 5 nm in a different wavelength region, so that the spectral bandwidth is expanded to 10 nm in total. Further, since it can be connected to a single power supply 24, it can be driven without complicating the configuration.

  As described above, in the two semiconductor laser arrays 20a and 20b connected to the single power source 24, the active layers of the semiconductor layers 21a and 21b include different strains, so that the spectrum depends on the degree and sign of the strain. The band shifts. Thereby, the spectral bandwidths of the oscillation wavelengths of the semiconductor laser arrays 20a and 20b are expanded in different bands. The light with the expanded spectral bandwidth is synthesized after being output from each of the semiconductor laser arrays 20a and 20b. Since the spectral bandwidth of the light synthesized in this way is enlarged compared to the case where the semiconductor laser arrays 20a and 20b are used individually, the generation of speckle can be further reduced.

Alternatively, the oscillation wavelength band can be shifted by changing the composition of the active layers of the semiconductor layers 21a and 21b. For example, when the composition of the active layer in the semiconductor layer 21a is represented by Ga _0.6 In _0.4 P and the composition of the active layer in the semiconductor layer 21b is represented by Ga _0.58 In _0.42 P, the spectral band is the semiconductor laser array 20a. For example, 640 nm to 645 nm and, for example, 635 nm to 640 nm in the semiconductor laser array 20b.

  Next, an optical device 3 according to an embodiment of the present invention will be described with reference to FIG.

  The optical device 3 includes the semiconductor laser device 1 according to the present embodiment and an optical system that collects light output from the semiconductor laser device 1. As such an optical system, for example, there is an optical system in which a collimator lens 30 and a fly-eye lens 31 are arranged in this order from the semiconductor laser device 1 side. ing.

  The collimating lens 30 includes, for example, a vertical collimating lens having a convex shape in the vertical direction and a horizontal collimating lens having a convex shape in the horizontal direction, and suppresses beam divergence in the vertical direction and the horizontal direction. The vertical component and the horizontal component are converted into parallel light. The collimating lens 30 is disposed at a position suitable for the use of the optical device 3 and the like. For example, when the optical device 2 is used as a light source for a projection display or the like, as shown in FIG. 5, the collimating lens 30 has a part of the light output from each light emitting region S on the incident surface of the collimating lens 30. The light output from each region (the central region G1, the end region G3, and the region sandwiched between them) of each semiconductor laser array 10 overlaps with each other on the incident surface of the collimator lens 30. It is possible to arrange at a position where there is no.

  The fly-eye lens 31 includes a plurality of microlenses 31a arranged in an array, and the light beams collimated by the collimating lens 30 are divided into minute light beams by the individual microlenses 31a. Are combined on the irradiated surface B. Thereby, in the irradiated surface B, the in-plane intensity distribution of the synthesized light output from the semiconductor laser device 1 can be made uniform.

  In the optical device 3 having such a configuration, when a predetermined voltage is applied between the upper electrode 16 and the lower electrode 17 in the semiconductor laser array 10, the current is confined by the ridge portion 13, and the current injection of the active layer is performed. A current is injected into the region (light emitting region S), and light emission is caused by recombination of electrons and holes. This light is reflected by a pair of reflecting mirror films (not shown), and generates laser oscillation at a wavelength at which the phase change when it reciprocates once in the element is an integral multiple of 2π. Is output from. The light output from each light emitting region S is collected by an optical system including the collimating lens 30 and the fly-eye lens 31 and then irradiated on the irradiated surface B.

(Modification)
Hereinafter, a modification of the present embodiment will be described in detail with reference to FIG. 6 and FIG.

  FIG. 6 is a diagram illustrating a cross-sectional configuration of the semiconductor laser device 4 including the semiconductor laser array 40 according to a modification of the present embodiment. The semiconductor laser array 40 has the same configuration as that of the semiconductor laser array 10 except for the arrangement interval of the plurality of ridge portions 43 provided in the semiconductor layer 42. For this reason, the same components as those of the semiconductor laser array 10 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The upper clad layer of the semiconductor layer 42 has a plurality of stripe-shaped ridge portions 43. Similar to the semiconductor laser array 10, the plurality of ridge portions 43 have a stripe width in the central region G1 larger than a stripe width in the end region G3. Furthermore, in this modification, these ridge portions 43 are arranged “densely” in the central region G1 and “sparse” in the end region G3. That is, the interval between the ridge portions 43 arranged in the central region G1 is smaller than the interval between the ridge portions 43 arranged in the end region G3.

  Specifically, the interval P1 between the ridge portions 43 with the stripe width W1 arranged in the central region G1, the interval P3 between the ridge portions 43 with the stripe width W3 arranged in the end region G3, and between these The interval P2 between the arranged ridges 43 of the stripe width W2 is configured to satisfy P1 <P2 <P3. Further, in this way, the distance between the ridges 43 in each region (the central region G1, the end region G3, and the region sandwiched between them) is gradually reduced from the end region G3 to the central region G1. Is preferred.

  For example, the semiconductor laser array 40 is made of an AlGaInP / GaInP semiconductor material, the stripe width W1 of the ridge 43 is 300 μm, the stripe width W2 is 180 μm, the stripe width W3 is 60 μm, and the interval P1 between the ridges 43 is 400 μm, The interval P2 is 450 μm, the interval P3 is 480 μm, the stripe width of the current injection layer 14 is 60 μm, the resonator length is 700 μm, and a driving current of 10 A is passed between the upper electrode 16 and the lower electrode 17 and the temperature of the heat sink 19 is When adjusted to 25 ° C., a temperature difference of about 15 ° C. occurs between the central region G1 and the end region G3 of the semiconductor laser array 10 (FIG. 7A). As a result, the spectral bandwidth is expanded to about 5 nm (FIG. 7B).

  As described above, the distance between the ridge portions 43 is “dense” in the central region G1 and “sparse” in the end region G3, so that the temperature of the central region G1 further increases and the end region G3. The temperature of the is further reduced. However, when the temperature difference between the central region G1 and the end region G3 increases, the emission intensity in the long wavelength region output from the light emitting region S of the central region G1 is significantly reduced. The ridge portions 43 are densely arranged in the region G1 to increase the emission intensity of the entire central region G1, and conversely, the ridge portions 43 are sparsely arranged in the end region G3 to reduce the emission intensity of the entire end region G3. This compensates for the decline. Thereby, since the emission intensity of the laser light output from each region can be made uniform, the spectral distribution of the combined light of the light output from each light emitting region S can be made uniform. Accordingly, coherence can be greatly reduced.

  Although the present invention has been described with reference to the embodiment and the modification, the present invention is not limited to the above-described embodiment and the like, and various modifications can be made.

  For example, in the above-described embodiment and the like, the configuration in which the width of the ridge portion in the central region G1 of the array is larger than the width of the ridge portion in the end region G2 has been described. If the widths of at least two ridge portions of the portions are different from each other, a difference in heat dissipation occurs as a whole device, so that the effect of the present invention is achieved.

  Further, in each region from the central region G1 to the end region G3 of the array, a configuration in which the stripe width of the ridge portion changes stepwise, that is, a configuration in which a plurality of ridge portions having the same stripe width are provided for each region However, it is also possible to arrange the stripe width so as to be continuously reduced. That is, the stripe width of the ridge portion may be adjusted so as to gradually change one by one. Further, even if the stripe widths of the ridge portions arranged in each region are not the same, the average value may be gradually reduced from the central region G1 to the end region G3. In the above-described embodiment and the like, the case where the number of the ridge portions 13 is five in the central region G1, two in the intermediate region G2, and two in the end region G3 has been described. It is not particularly limited. In addition, the region in the semiconductor array has been described as being divided into the three regions of the central region G1, the intermediate region G2, and the end region G3. However, the present invention is not limited to this, and at least two regions of the central region and the end region are defined. If so, the effect of the present invention is achieved.

  Further, in the laser module in which two semiconductor laser arrays having different spectral bands are connected, the stripe widths and intervals of the ridges arranged in the respective laser arrays may be the same or different. Furthermore, in the above-described embodiment, the case where the strain is made different from the case where the composition ratio of the active layer is made different is described separately. However, both the strain and the composition ratio of the active layer may be made different. Good. In addition, the example in which the spectrum bands do not overlap each other between the two semiconductor laser arrays has been described, but the present invention is not limited to this, and there may be overlapping bands. That is, the spectral bandwidth of one semiconductor laser array is compared to the case where these semiconductor laser arrays are used alone, except that the spectral band of the other semiconductor laser array is completely included in the spectral band of one semiconductor laser array. The effect of the present invention is achieved.

  In the above embodiment, the semiconductor laser array is arranged on the heat sink with p side up, but conversely, it may be arranged on the heat sink with p side down.

  In the above embodiment, the present invention has been described by taking an AlGaInP compound semiconductor laser as an example. However, other compound semiconductor lasers, for example, red semiconductor lasers such as AlInP and GaInAsP, GaInN and AlGaInN The present invention is also applicable to II-VI group semiconductor lasers such as gallium nitride based semiconductor lasers and ZnCdMgSSeTe. The present invention is also applicable to semiconductor lasers whose oscillation wavelength is not always in the visible range, such as AlGaAs, InGaAs, InP, and GaInAsNP.

1 is a cross-sectional view illustrating a schematic configuration of a semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic configuration of each ridge portion of the semiconductor laser device of FIG. 1. FIG. 2 is a characteristic diagram showing temperature characteristics and wavelength distribution of the semiconductor laser device of FIG. 1. It is sectional drawing showing schematic structure of the laser module which concerns on one embodiment of this invention. It is sectional drawing showing schematic structure of the optical apparatus which concerns on one embodiment of this invention. It is sectional drawing showing schematic structure of the semiconductor laser apparatus which concerns on one modification of this invention. FIG. 7 is a characteristic diagram showing temperature characteristics and wavelength distribution of the semiconductor laser device of FIG. 6. It is a characteristic view showing the relationship between distortion and an energy band gap. It is a figure showing the cross-sectional structure of the conventional semiconductor laser apparatus, and the characteristic of a ridge part. It is sectional drawing showing schematic structure of the conventional semiconductor laser apparatus. It is a characteristic view showing the temperature characteristic and wavelength distribution of the semiconductor laser apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,4 ... Semiconductor laser apparatus, 2 ... Laser module, 3 ... Optical apparatus 10, 20a, 20b, 40 ... Semiconductor laser array, 11 ... Board | substrate, 12, 21a, 21b, 42 ... Semiconductor layer, 13, 43 ... Ridge , 14 ... current injection layer, 15 ... insulating layer, 16 ... upper electrode, 17 ... lower electrode, 18 ... metal layer, 19 ... heat sink, 22 ... Peltier element, 23 ... radiating fin, 30 ... collimating lens, 31 ... fly Eye lens, 31a... Micro lens, S.

Claims (16)

A semiconductor laser device comprising a plurality of semiconductor laser elements,
The semiconductor laser element is
The ridge,
A current injection layer for injecting current into the ridge portion;
The plurality of semiconductor laser elements include at least two types of semiconductor laser elements having different widths of the ridge portion. The semiconductor laser device according to claim 1, wherein the current injection layer has a substantially uniform width in the at least two types of semiconductor laser elements. 2. The semiconductor laser device according to claim 1, wherein in the at least two types of semiconductor laser elements, a ratio of a width of the current injection layer to a width of the ridge portion is different from each other. The width of the ridge portion of the semiconductor laser element disposed at the center portion of the plurality of semiconductor laser elements is larger than the width of the ridge portion of the semiconductor laser element disposed at the end portion. The semiconductor laser device described. 5. The semiconductor laser device according to claim 4, wherein widths of ridge portions of the plurality of semiconductor laser elements are gradually reduced from a central portion to an end portion. 5. The semiconductor laser device according to claim 4, wherein among the plurality of semiconductor laser elements, the number of semiconductor laser elements arranged in a central portion is relatively large. 5. The semiconductor laser device according to claim 4, wherein the plurality of semiconductor laser elements are arranged at equal intervals. The semiconductor laser device according to claim 4, wherein the plurality of semiconductor laser elements are arranged so as to be dense at a central portion and sparse at an end portion. An insulating layer provided along the shape of the ridge portion adjacent to the current injection layer;
The semiconductor laser device according to claim 1, further comprising a common electrode formed integrally with the plurality of semiconductor laser elements so as to cover the current injection layer and the insulating layer. The semiconductor laser device according to claim 9, further comprising a metal layer provided adjacent to the common electrode and along a shape of a ridge portion of the semiconductor laser element. A plurality of semiconductor laser devices connected in parallel;
Each of the semiconductor laser devices is composed of a plurality of semiconductor laser elements,
The semiconductor laser element is
The ridge,
A current injection layer for injecting current into the ridge portion;
The plurality of semiconductor laser elements include at least two types of semiconductor laser elements having different widths of the ridge portion,
The laser module, wherein the plurality of semiconductor laser devices have different spectral bands of oscillation wavelengths. The laser module according to claim 11, wherein a composition ratio of a material constituting the light emitting region is different for each of the plurality of semiconductor laser devices. The laser module according to claim 11, wherein the materials constituting the light emitting region have different strains for each of the plurality of semiconductor laser devices. The laser module according to claim 11, wherein the plurality of semiconductor laser devices are connected to the same single power source. A semiconductor laser device;
An optical system for collecting the light output from the semiconductor laser device,
The semiconductor laser device comprises a plurality of semiconductor laser elements,
The semiconductor laser element is
The ridge,
A current injection layer for injecting current into the ridge portion;
The plurality of semiconductor laser elements include at least two types of semiconductor laser elements having different widths of the ridge portion. The semiconductor laser device comprises a plurality of semiconductor laser arrays,
The optical device according to claim 15, wherein the plurality of semiconductor laser arrays have different spectral bands of oscillation wavelengths.

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