Semiconductor laser device

Abstract

The objective of this invention is to provide a semiconductor laser device that reduces the non-uniformity of the threshold current at high temperatures. The semiconductor laser device (100) of the solution comprises a facet-emitting semiconductor laser element (200) with a relatively short oscillation wavelength at room temperature and a facet-emitting semiconductor laser element (200) with a relatively long oscillation wavelength at room temperature. The difference in oscillation wavelength at room temperature between the shorter wavelength semiconductor laser element (200) and the longer wavelength semiconductor laser element (200) is less than 20 nm. The reflective films on the emission side of the shorter wavelength semiconductor laser element (200) and the longer wavelength semiconductor laser element (200) differ in at least one of film thickness, refractive index, and number of layers. The emission side reflectivity of the shorter wavelength semiconductor laser element (200) at its upper operating temperature limit is higher than that of the longer wavelength semiconductor laser element (200) at its upper operating temperature limit.

Description

Technical Field

[0001] The present invention relates to semiconductor laser devices. Prior Art

[0002] In recent years, devices using semiconductor lasers have been strongly required to operate stably over a wide temperature range. Generally speaking, semiconductor laser elements have a characteristic in which the threshold current increases as the operating temperature rises. This increase in threshold current is caused by a phenomenon called carrier overflow, in which electrons in a high-energy state overflow into the coating layer. (Patent Document 1)

[0003] The temperature dependence of the threshold current is expressed by the following equation using the characteristic temperature T 0 . The characteristic temperature T0 of a red laser with a wavelength of 640 nm is about 80 K, and the characteristic temperature of a laser with a wavelength of 780 nm is about 150 K.

[0004] The increase in threshold current at high temperatures is largely dependent on the band gap difference ΔEc between the active layer and the coating layer. In particular, in 640nm red lasers, where ΔEc is small due to limitations in structural materials, the increase in threshold current with rising temperature becomes significant. This results in an increase in operating current, increased heat generation, and a shortened residual lifetime.

[0005] Furthermore, the temperature dependence of threshold current can lead to the following problems in devices incorporating multiple semiconductor laser elements. In such devices, when the oscillation wavelengths of multiple semiconductor laser elements vary from one element to another in manufacturing, the threshold current of elements with shorter oscillation wavelengths increases more significantly as temperature rises, while the threshold current of elements with longer oscillation wavelengths increases less as temperature rises. Therefore, when multiple elements are driven with the same current, the difference in light output between the elements becomes significant.

[0006] Furthermore, at high temperatures, operating currents closer to the threshold current are more effective than at room or low temperatures. This is because even at high temperatures, light output saturates even with increasing operating current, shortening the remaining lifespan as the operating current increases. Therefore, reducing threshold current variation is more effective in reducing light output variation than reducing slope efficiency variation.

[0007] As a method for reducing the threshold current during high-temperature operation, increasing the reflectivity of the laser's output facet (called output reflectivity) is a well-known method. This method increases the light density within the laser, thereby reducing the threshold current at high temperatures. However, increasing the laser's output reflectivity increases the light density near the output facet, which is required during operation at low temperatures to around room temperature. This increases the light density near the output facet, which can easily cause facet damage (COD).

[0008] To address this issue, a proposed method has been proposed to make the output reflectivity wavelength-dependent, increasing it with increasing wavelength (Patent Document 2). Generally, semiconductor lasers have a characteristic whereby their oscillation wavelength shifts toward longer wavelengths as the temperature rises. By utilizing this characteristic and increasing the output reflectivity with increasing wavelength (i.e., during high-temperature operation), light confinement can be increased at high temperatures, thereby reducing the increase in threshold current at high temperatures.

[0009] On the other hand, the oscillation wavelength during operation at low temperatures to around room temperature is shorter than that during operation at high temperatures, thereby suppressing the reflectivity at the output end and achieving high COD resistance. [Prior Art] [Patent Document]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-049420 [Patent Document 2] Japanese Patent Application Laid-Open No. 7-74427 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-111622 Summary of the Invention

[0011] [Problems to be solved by the invention]

[0012] The inventors of this case have identified that the following problems may occur when the technology described in Patent Document 2 is applied to a device in which a plurality of semiconductor laser elements are mounted.

[0013] When comparing individuals with shorter oscillation wavelengths with those with longer oscillation wavelengths, the longer wavelength shift amplitude during operation from room temperature to high temperature moves in parallel, so the difference in the rate of increase of the threshold current at high temperature does not decrease, and as a result, the problem of light output difference cannot be solved.

[0014] The present disclosure is invented in view of the relevant situation, and one of its exemplary purposes is to provide a semiconductor laser device with reduced variation in threshold current at high temperatures. [Methods used to solve the problem]

[0015] A semiconductor laser device according to one embodiment of the present disclosure includes a first semiconductor laser element of the edge-emitting type having a relatively short oscillation wavelength at room temperature, and a second semiconductor laser element of the edge-emitting type having a relatively long oscillation wavelength at room temperature. The difference in oscillation wavelength between the first and second semiconductor laser elements at room temperature is 20 nm or less. The reflective film on the output side of the first semiconductor laser element and the reflective film on the output side of the second semiconductor laser element differ in at least one of film thickness, refractive index, and number of layers. The reflectivity of the output side of the first semiconductor laser element at the upper operating temperature limit is higher than the reflectivity of the output side of the second semiconductor laser element at the upper operating temperature limit.

[0016] Another aspect of the present disclosure is also a semiconductor laser device. This semiconductor laser device comprises a plurality of semiconductor laser elements having different oscillation wavelengths at room temperature. The reflective films on the output side of the plurality of semiconductor laser elements differ in at least one of film thickness, refractive index, and number of layers. Statistically, the reflectivity of the output side of the semiconductor laser element with a shorter oscillation wavelength at room temperature is higher than the reflectivity of the output side of the semiconductor laser element with a longer oscillation wavelength at room temperature.

[0017] Furthermore, any combination of the above-mentioned components, or any substitution of components and expressions between methods, devices, systems, etc., may also be effective as aspects of the present invention. Furthermore, the description in this section (means for solving the problem) does not represent all the features that are essential to the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Effects of the Invention]

[0018] According to certain aspects of the present disclosure, the variation in threshold current at high temperature is reduced. Simple diagram description

[0019] [Figure 1] A diagram showing a semiconductor laser device according to embodiment 1. FIG2 is a diagram showing the wavelength dependence of the reflectance R on the output end side of the short-wavelength element and the long-wavelength element of Comparative Technology 1. ... FIG3 is a diagram showing the IL (current-light output) characteristics of a semiconductor laser device having the reflectivity R shown in FIG2 . FIG4 is a diagram showing the wavelength dependence of the reflectance R on the output end side of the short-wavelength element and the long-wavelength element of Comparative Technology 2. FIG5 is a diagram showing the IL characteristics of a semiconductor laser device having the reflectivity R shown in FIG4 . FIG6 is a diagram showing the wavelength dependence of the output-end reflectivity RS of the short-wavelength element and the output-end reflectivity RL of the long-wavelength element in Embodiment 1. FIG7 is a diagram showing the IL characteristics of a semiconductor laser device having the reflectivity characteristics of FIG6 . [Figure 8] A diagram showing a wafer. [Figure 9] A diagram showing the wavelength dependence of the output-end reflectivity RS of the short-wavelength element and the output-end reflectivity RL of the long-wavelength element in Embodiment 2. FIG10 is a diagram showing a semiconductor laser device according to a modified example. [Figure 11] A three-dimensional view of a semiconductor laser package. Implementation Method

[0020] (Overview of Embodiments)

[0021] This summary describes several exemplary embodiments of the present disclosure. This summary serves as a prerequisite for the detailed description that follows, and is intended to provide a basic understanding of the embodiments. It simplifies several concepts related to one or more embodiments and does not limit the scope of the invention or disclosure. Furthermore, this summary is not an all-inclusive overview of all conceivable embodiments, nor does it define essential structural elements of an embodiment. For ease of explanation, "one embodiment" may be used to refer to one embodiment (an embodiment and its variations) or multiple embodiments (an embodiment and its variations) disclosed in this specification.

[0022] A semiconductor laser device according to one embodiment includes a first semiconductor laser element of the edge-emitting type having a relatively short oscillation wavelength at room temperature, and a second semiconductor laser element of the edge-emitting type having a relatively long oscillation wavelength at room temperature. The difference in oscillation wavelength between the first and second semiconductor laser elements at room temperature is 20 nm or less. The reflective film on the output end side of the first semiconductor laser element and the reflective film on the output end side of the second semiconductor laser element differ in at least one of film thickness, refractive index, and number of layers. The reflectivity of the output end side of the first semiconductor laser element at the upper operating temperature limit is higher than the reflectivity of the output end side of the second semiconductor laser element at the upper operating temperature limit.

[0023] According to this structure, the difference in threshold current between the first semiconductor laser element and the second semiconductor laser element at high temperature can be reduced.

[0024] In one embodiment, multiple semiconductor laser devices may be diced from the same wafer. In this case, the multiple semiconductor laser devices exhibit uneven oscillation wavelengths at room temperature due to process nonuniformity. The oscillation wavelengths of the multiple semiconductor laser devices vary depending on their position on the wafer before dicing. Therefore, devices located in regions of the wafer that tend to have shorter oscillation wavelengths form a reflective film with a relatively high reflectivity on the output side at high temperatures, while devices located in regions of the wafer that tend to have longer oscillation wavelengths form a reflective film with a relatively low reflectivity on the output side at high temperatures.

[0025] A semiconductor laser device according to one embodiment may include three or more semiconductor laser elements. The first semiconductor laser element may be the one having the shortest oscillation wavelength at room temperature among the plurality of semiconductor laser elements, and the second semiconductor laser element may be the one having the longest oscillation wavelength at room temperature among the plurality of semiconductor laser elements.

[0026] In one embodiment, the oscillation wavelength can be 600 nm to 700 nm. Semiconductor laser devices whose active layers are formed of AlGaInP-based materials are particularly temperature-sensitive. Therefore, applying the disclosed technology to semiconductor laser devices with this oscillation wavelength can significantly improve their effectiveness.

[0027] In one embodiment, the reflectivity of the output end of the first semiconductor laser element may increase with longer wavelengths. In other words, in one embodiment, the reflectivity of the output end of the first semiconductor laser element at room temperature may be lower than the reflectivity at the upper operating temperature limit. Generally, light output is higher at room temperature, so high COD resistance at room temperature is important. On the other hand, reducing the threshold current is more important to suppress a decrease in light output at high temperatures. Considering this balance, by lowering the reflectivity of the output end at room temperature and increasing it at high temperatures, COD resistance can be improved while lowering the threshold current at high temperatures.

[0028] In one embodiment, the difference between the reflectivity of the output end of the first semiconductor laser element at room temperature and the reflectivity of the output end of the second semiconductor laser element at room temperature may be smaller than the difference between the reflectivity of the output end at the upper operating temperature limit of the first semiconductor laser element and the reflectivity of the output end at the upper operating temperature limit of the second semiconductor laser element. The difference in reflectivity at room temperature affects COD resistance, so the difference in reflectivity at room temperature between the shorter and longer wavelengths is preferably as small as possible. Furthermore, since the variation in threshold current at room temperature is smaller than the variation in threshold current at high temperature when comparing the shorter and longer wavelengths, the difference in reflectivity at high temperature between the shorter and longer wavelengths may be larger.

[0029] In one embodiment, in a graph plotted with the oscillation wavelength on the horizontal axis and the reflectivity on the output end side on the vertical axis, the slope of the graph for the first semiconductor laser element may be greater than the slope of the graph for the second semiconductor laser element. The rate of increase in wavelength with temperature changes is greater for shorter-wavelength elements than for longer-wavelength elements. Therefore, by increasing the slope for longer-wavelength elements to a greater value than that for shorter-wavelength elements, the variation in threshold current between shorter-wavelength elements and longer-wavelength elements can be reduced over a wide temperature range.

[0030] A semiconductor laser device according to one embodiment includes a plurality of semiconductor laser elements having different oscillation wavelengths at room temperature. The reflective films on the output side of the plurality of semiconductor laser elements differ in at least one of film thickness, refractive index, and number of layers. Statistically, the reflectivity of the output side of the semiconductor laser element with a shorter oscillation wavelength at room temperature is higher than the reflectivity of the output side of the semiconductor laser element with a longer oscillation wavelength at room temperature.

[0031] (Implementation form) The present invention will be described below with reference to preferred embodiments and accompanying drawings. Identical or equivalent components, members, and processes shown in the various drawings are denoted by the same reference numerals, and duplicate descriptions will be omitted where appropriate. The embodiments are not intended to limit the disclosure; they are merely illustrative, and not all features or combinations described in the embodiments are necessarily essential to the disclosure.

[0032] The dimensions (thickness, length, width, etc.) of various components shown in the drawings may be exaggerated or reduced for ease of understanding. Furthermore, the dimensions of multiple components do not necessarily indicate a relative size. Even if component A is depicted as thicker than component B in the drawings, component A may still be thinner.

[0033] (Implementation form 1) FIG1 is a diagram illustrating a semiconductor laser device 100 according to Embodiment 1. The semiconductor laser device 100 includes a plurality of semiconductor laser elements 200_1 to 200_N, a heat sink 102, and a plurality of submounts 104_1 to 104_N. In this embodiment, N=3.

[0034] The semiconductor laser elements 200_1 to 200_N are edge-emitting lasers and are mounted adjacent to each other on the heat sink 102. The color of light emitted by the semiconductor laser element 200 is not particularly limited, and for example, it can be a red laser with a wavelength of 600 nm to 700 nm.

[0035] The semiconductor laser devices 200 are mounted on the submounts 104, which are mounted on the heat sink 102. The submounts 104 are also referred to as interposers.

[0036] The semiconductor laser device 200 includes a laser resonator formed on a semiconductor substrate. The type and structure of the laser resonator are not particularly limited, and various known technologies or future available structures can be used.

[0037] On the emission end face of the semiconductor laser element 200_i (i=1-N), a reflective film (emission end side reflective film) 202_i having a reflectivity lower than 100% is formed in order to extract light from the resonator.

[0038] Although the plurality of semiconductor laser elements 200_1 to 200_N are lasers of the same color manufactured by the same manufacturer, their oscillation wavelengths λ1 to λN at room temperature vary due to manufacturing tolerances. Due to manufacturing tolerances, the order of the lengths of the oscillation wavelengths λ1 to λ3 is essentially random.

[0039] Now, two are selected from the semiconductor laser elements 200_1 to 200_N. The one having a shorter oscillation wavelength λ at room temperature is called a short-wavelength element 200S, and the other having a longer oscillation wavelength λ at room temperature is called a long-wavelength element 200L.

[0040] In a semiconductor laser device 100 having N=3 or more semiconductor laser elements, for example, the short-wavelength element 200S may be the one having the shortest oscillation wavelength at room temperature among the three or more semiconductor laser elements, and the long-wavelength element 200L may be the one having the longest oscillation wavelength at room temperature among the three or more semiconductor laser elements.

[0041] As described above, the plurality of semiconductor laser elements 200_1 to 200_N are manufactured using the same process, so the variation in their oscillation wavelengths λ can be said to be within 20 nm. Therefore, the difference in the room temperature oscillation wavelengths λS and λL between the short-wavelength element 200S and the long-wavelength element 200L selected from the semiconductor laser elements 200_1 to 200_N is also less than 20 nm. Furthermore, product specifications sometimes specify oscillation wavelengths within ±10 nm. Furthermore, the term "same process" here does not simply refer to the same wafer; even different wafers, as long as they are the same laser element, are considered to be manufactured using the same process. Statistically, the in-plane variation in wavelength across wafers is generally less than 10 nm.

[0042] The reflective film 202 on the output end side of the short-wavelength element 200S and the reflective film 202 on the output end side of the long-wavelength element 200L differ in at least one of film thickness, refractive index, and number of layers, and the reflectivity (output end reflectivity) RS of the reflective film 202 on the output end side of the short-wavelength element 200S and the reflectivity RL of the reflective film 202 on the output end side of the long-wavelength element 200L have different wavelength dependencies.

[0043] Before describing the specific features of the semiconductor laser device 100, several comparative technologies are described.

[0044] (Comparative Technology 1) FIG2 is a graph illustrating the wavelength dependence of the reflectance R on the output end side of the short-wavelength element 200S and the long-wavelength element 200L of Comparative Technology 1.

[0045] In Comparative Technique 1, the reflective film 202 on the output side of the short-wavelength element 200S and the reflective film 202 on the output side of the long-wavelength element 200L have the same film thickness, refractive index, and number of layers, and their reflectivities R have the same wavelength dependence. In this example, the reflective film is designed to minimize wavelength dependence.

[0046] Materials for the reflective film include oxides or nitrides of Zr, Si, Nb, Pb, Ti, Ce, Hf, Al, Bi, Cr, In, Nd, Sb, Ta, Y, and V. Other materials include AlF3, BaF2, CeF2, CaF2, MgF2, NdF3, PbF2, SrF2, ZnS, and ZnSe. Furthermore, materials such as SiO2, SiN, SiON, AlN, Al2O3, AlON, ZrO2, TiO2, Nb2O5, and Ta2O5 can also be used.

[0047] Room temperature is, for example, 25° C. The oscillation wavelength λ S(25) of the short wavelength element 200S at room temperature is 641 nm, and the oscillation wavelength λ L(25) of the long wavelength element 200L at room temperature (25° C.) is 643 nm.

[0048] High temperature is the upper limit of the temperature range (upper limit of operating temperature) of the semiconductor laser device 100, for example, 85°C. In addition, the oscillation wavelength λ S (85) of the short wavelength element 200S in the high temperature state (85°C) is 653nm, and the oscillation wavelength λ L (85) of the long wavelength element 200L in the high temperature state (85°C) is 655nm. In general, the upper limit of the temperature range of red lasers is generally 40°C to 90°C due to product design. The upper limit of the operating temperature is determined based on the relationship between light output and life, and is usually recorded in the product specifications as the operating temperature range. In addition, when not clearly stated, it is evaluated in this specification as the reflectivity on the output end side when driven at 90°C. The same temperature is usually measured on the side of the package such as the socket, and is replaced by the temperature of the submount or heat sink arranged near the semiconductor laser chip, or the package such as the socket.

[0049] FIG3 is a graph illustrating the IL (current-light output) characteristics of semiconductor laser device 100 having the reflectivity R shown in FIG2 . In Comparative Technology 1, at 25°C, the IL characteristics of short-wavelength element 200S and long-wavelength element 200L are identical, with the threshold current of short-wavelength element 200S being 55 mA and the threshold current of long-wavelength element 200L being 56 mA.

[0050] The threshold current of the short-wavelength element 200S increases to 164 mA at a high temperature (85°C), while the threshold current of the long-wavelength element 200L increases to 143 mA at a high temperature (85°C).

[0051] Thus, the threshold current of lasers with shorter oscillation wavelengths increases more significantly with rising temperature, while that of lasers with longer oscillation wavelengths increases less. Therefore, at high temperatures, the difference in threshold current between two laser elements increases (21mA in the example in Figure 3). Driving multiple lasers with the same current increases the difference in light output between them.

[0052] (Comparative Technique 2) FIG4 is a graph illustrating the wavelength dependence of the reflectance R on the output end side of the short-wavelength element 200S and the long-wavelength element 200L of Comparative Technology 2.

[0053] In Comparative Technology 2, the reflectance R of the short-wavelength element 200S and the long-wavelength element 200L has the same wavelength dependence as in Comparative Technology 1. In this example, the reflective film is designed so that the longer the wavelength, the higher the reflectance.

[0054] FIG. 5 is a graph illustrating the IL characteristics of the semiconductor laser device 100 having the reflectivity R shown in FIG. 4 .

[0055] In Comparative Technique 2, the threshold current of short-wavelength element 200S at high temperature is 151 mA, while the threshold current of long-wavelength element 200L at high temperature is 131 mA. This reduces the increase in threshold current with rising temperature to a smaller magnitude than in Comparative Technique 1. However, when comparing the threshold currents of short-wavelength element 200S and long-wavelength element 200L at 85°C, the difference is 151 mA - 131 mA = 20 mA, which is not significantly different from the 21 mA in Comparative Technique 1. Therefore, in Comparative Technique 2, when operating short-wavelength element 200S and long-wavelength element 200L at high temperature with the same current, the difference in light output between the individual elements is significant.

[0056] The advantages of the semiconductor laser device 100 of the embodiment become more apparent by comparison with comparative techniques 1 and 2.

[0057] FIG6 is a diagram illustrating the wavelength dependence of the output-end reflectivity RS of the short-wavelength element 200S and the output-end side reflectivity RL of the long-wavelength element 200L according to the first embodiment.

[0058] In this embodiment, the output-end reflectivity RS of the short-wavelength element 200S and the output-end reflectivity RL of the long-wavelength element 200L have several characteristics.

[0059] (First Feature) In this embodiment, the output end side reflective film 202 is designed so that the output end side reflectivity RS (85) at the upper limit of the operating temperature of the short wavelength element 200S (85°C) is higher than the output end side reflectivity RL (85) at the upper limit of the operating temperature of the long wavelength element 200L.

[0060] FIG. 7 is a graph illustrating the IL characteristics of the semiconductor laser device 200 having the reflectivity characteristics of FIG. 6 .

[0061] The first feature reduces the difference in threshold current between the short-wavelength element 200S and the long-wavelength element 200L at high temperatures (85°C). Specifically, the threshold current of the short-wavelength element 200S at high temperatures (85°C) is 151 mA, while the threshold current of the long-wavelength element 200L at high temperatures (85°C) is 143 mA, reducing the difference in threshold current to just 8 mA. This reduces unevenness in light output when the short-wavelength element 200S and the long-wavelength element 200L are operated with the same current.

[0062] (Feature 2) Referring to FIG6 , it can be seen that the reflectivity RL of the long-wavelength element 200L on the output side has little wavelength dependence. In contrast, the reflectivity RS of the short-wavelength element 200S on the output side increases with increasing wavelength. In other words, the reflectivity RS (25) of the short-wavelength element 200S on the output side at room temperature is lower than the reflectivity RS (85) at the upper operating temperature limit. This is the second characteristic.

[0063] Generally, light output is higher at room temperature than at high temperatures, so high COD resistance at room temperature is important. On the other hand, in order to suppress the decrease in light output at high temperatures, it is more important to reduce the threshold current. Considering this balance, by reducing the reflectivity RS (25) on the output side at room temperature and increasing the reflectivity RS (85) on the output side at high temperatures, COD resistance can be improved while reducing the threshold current at high temperatures.

[0064] (Third Feature) 6 , it can be seen that the difference ΔR (25) (= |RS (25)-RL (25)|) between the output end side reflectivity RS (25) of the short wavelength element 200S at room temperature and the output end side reflectivity RL (25) of the long wavelength element 200L at room temperature is smaller than the difference ΔR (85) (= |RS (85)-RL (85)|) between the output end side reflectivity RS (85) at the upper limit of the operating temperature of the short wavelength element 200S and the output end side reflectivity RL (85) at the upper limit of the operating temperature of the long wavelength element 200L.

[0065] The difference in reflectivity ΔR (25) at the exit end at room temperature affects the difference in COD tolerance, so it is best to minimize the difference in reflectivity ΔR (25) at the exit end at room temperature between the shorter wavelength individual and the longer wavelength individual. Furthermore, the difference in threshold current between the longer wavelength individual and the shorter wavelength individual at room temperature is smaller than the difference in threshold current at high temperature. Therefore, the difference in reflectivity ΔR (85) at the exit end at high temperature between the shorter wavelength individual and the longer wavelength individual may be greater than ΔR (25).

[0066] (Fourth characteristic) 6 , it can be seen that the slope of the graph of the short-wavelength element 200S is greater than the slope of the graph of the long-wavelength element 200L.

[0067] The rate of increase in wavelength relative to temperature changes is greater for shorter wavelength components than for longer wavelength components. Therefore, by increasing the slope of the longer wavelength component (long wavelength element 200L) to a greater value than that of the shorter wavelength component (short wavelength element 200S), the variation in threshold current between the shorter and longer wavelength components can be reduced over a wide temperature range.

[0068] Figure 8 illustrates a wafer 300. Numerous semiconductor laser devices 200 are cut from the wafer 300. The oscillation wavelength of the semiconductor laser devices 200 varies according to their position within the surface of the wafer 300 before cutting. In this example, the wavelength tends to be shorter near the center of the wafer 300 and longer near the periphery. In this situation, the wafer 300 can be divided into several regions RGN1, RGN2, etc. within the surface based on the oscillation wavelength distribution trend. In the example of Figure 8, the two regions RGN1 and RGN2 are divided. A reflective coating for the short-wavelength device 200S is formed on the semiconductor laser devices 200 cut from region RGN1, and a reflective coating for the long-wavelength device 200L is formed on the semiconductor laser devices 200 cut from region RGN2.

[0069] The oscillation wavelength distribution of regions RGN1, RGN2, etc. within the wafer surface and the oscillation wavelength for each wafer can be predicted before forming the reflective film on the end facet using a technique called photoluminescence. In the present disclosure, the reflective film for the short-wavelength element 200S or the reflective film for the long-wavelength element 200L can be appropriately selected based on the predicted oscillation wavelength for each wafer within the wafer surface. The semiconductor laser device 100 can also select semiconductor laser elements 200 from multiple wafers or different wafers.

[0070] In the above description, in the semiconductor laser device 100 including N=3 or more semiconductor laser elements, the short-wavelength element 200S is the one having the shortest oscillation wavelength at room temperature, and the long-wavelength element 200L is the one having the longest oscillation wavelength at room temperature. However, the present invention is not limited to this.

[0071] From another perspective, the semiconductor laser device 100 can also be said to be a semiconductor laser device 100 in which the relationship between the short wavelength element 200S and the long wavelength element 200L mentioned above holds true for any one or two of the plurality of semiconductor laser elements 200 .

[0072] (Implementation Form 2) The wavelength dependence of the reflectivity of the short-wavelength element 200S and the long-wavelength element 200L of the semiconductor laser device 100 is not limited to that shown in FIG. 6 .

[0073] FIG9 is a graph illustrating the wavelength dependence of the output-end reflectance RS of the short-wavelength element 200S and the output-end-side reflectance RL of the long-wavelength element 200L according to Embodiment 2. In Embodiment 2, the wavelength dependence of the output-end reflectance RS of the short-wavelength element 200S and the output-end-side reflectance RL of the long-wavelength element 200L satisfies only the first of the first to third characteristics described in Embodiment 1.

[0074] According to the second embodiment, the effect of the first feature can be obtained. That is, the difference in threshold current between the short wavelength element 200S and the long wavelength element 200L in the high temperature state can be reduced, and when operating with the same current, unevenness in light output can be suppressed.

[0075] (Variation) The structure and package form of the semiconductor laser device 100 are not particularly limited.

[0076] 10 is a diagram illustrating a semiconductor laser device 100A according to a modified example. The semiconductor laser device 100A includes a heat sink 102 and a plurality of semiconductor laser packages 400_1 to 400_N mounted on the heat sink 102 .

[0077] 11 is a perspective view of a semiconductor laser package 400. The semiconductor laser package 400 is a CAN package and includes a semiconductor laser element 200. An emission-side reflective film 202 is formed on the emission-side end surface of the semiconductor laser element 200.

[0078] The technology disclosed herein can also be applied to such a semiconductor laser device 100A.

[0079] Furthermore, the embodiments merely disclose the principles and applications of the present invention, and many variations and configuration changes may be made to the embodiments without departing from the technical concept of the present invention as defined in the scope of the claims.

[0080] 100:Semiconductor laser device 100A:Semiconductor laser device 102: Heat release plate 104: Sub-base 104_1~104_N: Sub-base 200:Semiconductor laser device 200_1~200_N: Semiconductor laser device 200S: Short wavelength components 200L: Long wavelength components 202: Reflective film (reflective film on the output end side) 200_1~200_N: Reflective film (reflective film on the output end side) 300: Wafer 400:Semiconductor laser packaging 400_1~400_N: Semiconductor laser packaging 402: Secondary base RGN1:region RGN2: Region

Claims

1. A semiconductor laser device, characterized by comprising: a first semiconductor laser element of the end-face emission type, which has a relatively short oscillation wavelength at room temperature; and a second semiconductor laser element of the end-face emission type, which has a relatively long oscillation wavelength at the aforementioned room temperature, wherein the difference between the oscillation wavelengths of the first semiconductor laser element and the second semiconductor laser element at the aforementioned room temperature is less than 20 nm, wherein the reflective film on the emission end side of the first semiconductor laser element and the reflective film on the emission end side of the second semiconductor laser element are different in at least one of film thickness, refractive index, and number of layers, and the reflectivity on the emission end side of the first semiconductor laser element at the upper limit of its operating temperature is higher than the reflectivity on the emission end side of the second semiconductor laser element at the aforementioned upper limit of its operating temperature.

2. The semiconductor laser device as described in claim 1, wherein, It has three or more semiconductor laser elements, wherein the first semiconductor laser element is the one with the shortest oscillation wavelength at room temperature among the three or more semiconductor laser elements, and the second semiconductor laser element is the one with the longest oscillation wavelength at room temperature among the three or more semiconductor laser elements.

3. The semiconductor laser device as described in claim 1 or 2, wherein, The aforementioned oscillation wavelength is 600nm to 700nm.

4. The semiconductor laser device as described in claim 1 or 2, wherein, The reflectivity of the aforementioned first semiconductor laser element at the emission end is higher the longer the wavelength.

5. The semiconductor laser device as described in claim 1 or 2, wherein, The difference between the reflectivity of the first semiconductor laser element at the aforementioned room temperature and the reflectivity of the second semiconductor laser element at the aforementioned room temperature is smaller than the difference between the reflectivity of the first semiconductor laser element at the upper limit of its operating temperature and the reflectivity of the second semiconductor laser element at the aforementioned upper limit of its operating temperature.

6. The semiconductor laser device as described in claim 1 or 2, wherein, In a graph plotted with the horizontal axis set to the oscillation wavelength and the vertical axis set to the reflectivity at the emission end, the slope of the graph for the first semiconductor laser element is greater than the slope of the graph for the second semiconductor laser element.

7. A semiconductor laser device, characterized by comprising: a plurality of semiconductor laser elements having different oscillation wavelengths at room temperature; the reflective films on the emission end side of the plurality of semiconductor laser elements having at least one difference in film thickness, refractive index, or number of layers; the difference in oscillation wavelengths of the plurality of semiconductor laser elements at the aforementioned room temperature being less than 20 nm; and statistically, the reflectivity of the emission end side of the semiconductor laser element with a shorter oscillation wavelength at the aforementioned room temperature at the upper limit of its operating temperature is higher than the reflectivity of the emission end side of the semiconductor laser element with a longer oscillation wavelength at the aforementioned room temperature at the aforementioned upper limit of its operating temperature.

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