Abstract: A Fiber Bragg grating is sliced into small segments (such as 1 mm in length), the sliced fiber Bragg grating segments are used as external cavities for lasers to stabilize their center wavelength. In one embodiment, a semiconductor laser has an anti-reflection coating on the front facet and a high reflectivity coating on the back facet, a sliced fiber Bragg grating is used as a partial reflection mirror to form a lasing cavity. Since the sliced fiber Bragg grating has a very small wavelength drift with temperature change, the semiconductor laser has a stable center wavelength output. In the other embodiment, a solid state laser has an anti-reflection coating on the front facet and a high reflectivity coating on the back facet, a sliced fiber Bragg grating is used as a partial reflection mirror to form a lasing cavity. The solid state laser has a stable center wavelength output.

Abstract: According to an aspect of the embodiment, there is provided a semiconductor light emitting device including: a gallium nitride substrate; a multilayer film of nitride semiconductors provided on the gallium nitride substrate; a first film including a first silicon nitride layer; and a second film including a second silicon nitride layer and a laminated film provided on the second silicon nitride layer. The gallium nitride substrate and the multilayer film have a laser light emitting facet and a laser light reflecting facet. The first silicon nitride layer is provided on the laser light emitting facet. The multilayer film includes a light emitting layer, and the multilayer film has a laser light emitting facet and a laser light reflecting facet. The second silicon nitride layer is provided on the laser light reflecting facet, and the laminated film includes oxide layer and silicon nitride layer which are alternately laminated.

Abstract: The present invention is to provide a method for producing a semiconductor laser diode (LD) with an enhanced ESD resistance. The method includes a step for forming an aluminum film on a facet of the LD and a step for forming an aluminum oxide film on the aluminum film. The underlying aluminum film is oxidized during the formation of the aluminum oxide film to form a double aluminum oxide layer. The ratio of the oxide composition of the underlying aluminum oxide film is smaller than that of the upper aluminum oxide film.

Abstract: Single mode oscillation at a wavelength of about 1064.4 nm is enabled with no use of an etalon installed in an optical resonator by providing one of two ends of a Nd:YAG element, which acts as one end of the optical resonator, with an HR coating arranged for the wavelength of about 1064.4 nm and determining the thickness along the direction of transmission of light of the Nd:YAG element so that the peak of reflection appears at the wavelength of about 1064.4 nm but not at a wavelength of about 1062.8 nm.

Abstract: A first buffer layer (GaAs), a second buffer layer (AlGaAs), and a diffusion suppressing layer consisting of GaAs or AlGaAs are stacked on a GaAs substrate. The structure has a first cladding layer thereon. When AlGaAs is used for the diffusion suppressing layer, the Al ratio of AlGaAs is made smaller than in the second buffer layer. In such a structure, when a window region is formed, the diffusion rate of the impurity (Zn) can be lowered in the diffusion suppressing layer, and the diffusion of the impurity can be stopped at the second buffer layer.

Abstract: A GaN semiconductor laser, includes a coating film on a front end surface through which laser light is emitted. The coating film includes a first insulating film in contact with the front end surface and a second insulating film on the first insulating film. The sum of the optical film thicknesses of the first insulating film and the second insulating film is an odd multiple of ?/4 with respect to the wavelength ? of laser light produced by the semiconductor laser. The adhesion of the first insulating film to GaN is stronger than that of the second insulating film to GaN. The refractive index of the first insulating film is 1.9 or less and the refractive index of the second insulating film is 2 to 2.3.

Abstract: A semiconductor laser device comprises a GaN substrate having a refractive index of 3.5 or below, a semiconductor layer laminated on the substrate, and a pair of facets forming a resonator and in face-to-face-relation to each other in a direction perpendicular to the direction of the laminated layer. One of the facets of the resonator includes a low reflection film, of a first dielectric film, a second dielectric film, a third dielectric film, and a fourth dielectric film. When the refractive indexes of these films are taken as n1, n2, n3, and n4, n1=n3 and n2=n4. The following relationship between the first dielectric film and the third dielectric film, and between the second dielectric film and the fourth dielectric film is established, nd+n?d?=p?/4, where p is an integer, and ? is oscillation wavelength of a laser beam generated by the semiconductor laser device.

Abstract: A GaN laser, includes a coating film on a front end surface through which laser light is emitted. The coating film includes a first insulating film in contact with the front end surface and a second insulating film on the first insulating film. The optical film thickness of the second insulating film is an odd multiple of ?/4 with respect to the wavelength ? of laser light produced by the semiconductor laser. The adhesion of the first insulating film to GaN is stronger than the adhesion of the second insulating film; to GaN. The refractive index of the second insulating film is 2 to 2.3 thick. The first insulating film is 10 nm or less. The first insulating film is an oxide film having a stoichiometric composition.

Abstract: A semiconductor laser device includes a cavity extending in a propagation direction of a laser beam (X-direction). A front facet is on one end of the cavity through which the laser beam is emitted. A rear facet is on the other end of the cavity. An anodic oxide film is provided on at least one of the front facet and the rear facet, and the anodic oxide film preferably has a thickness of ?/4n or an odd integer multiple thereof, where ? is the wavelength of the laser beam and n is the refractive index of the anodic oxide film.

Abstract: A semiconductor laser device includes a cavity extending in a propagation direction of a laser beam (X-direction). A front facet is on one end of the cavity through which the laser beam is emitted. A rear facet is on the other end of the cavity. Further, an adhesive layer and a coating film are on the front facet, and an adhesive layer and a coating film are on the rear facet. The adhesive layers preferably have a thickness of 10 nm or less and preferably include an anodic oxide film of one of Al, Ti, Nb, Zr, Ta, Si, and Hf.

Abstract: In a coherent light source in which limitations on the wavelength of emitted light are relaxed, a coherent light source for simultaneously emitting a first light (3) and a second light (4) having a wavelength shorter than that of the first light (3), includes: a light source main body emitting at least the first light (3); a mirror (5) which transmits or reflects the first light (3); and a functional film (6) provided on at least a part of the mirror (5). The functional film (6) has a photocatalytic effect to be induced by the second light (4).

Abstract: A method of fabrication of laser gain material and utilization of such media includes the steps of introducing a transitional metal, preferably Cr2+ thin film of controllable thickness on the ZnS crystal facets after crystal growth by means of pulse laser deposition or plasma sputtering, thermal annealing of the crystals for effective thermal diffusion of the dopant into the crystal volume with a temperature and exposition time providing the highest concentration of the dopant in the volume without degrading laser performance due to scattering and concentration quenching, and formation of a microchip laser either by means of direct deposition of mirrors on flat and parallel polished facets of a thin Cr:ZnS wafer or by relying on the internal reflectance of such facets.

Abstract: Provided is a semiconductor laser device, a semiconductor laser device package including the semiconductor laser device and methods of manufacturing the same. A semiconductor laser device may include a light emission structure including a first clad layer, an active layer and a second clad layer sequentially deposited on a substrate, a submount to which the light emission structure bonded, and a light shield plate in the submount, wherein the light shield plate blocks an end of the substrate on a light emission face of the light emission structure and blocks light leaked through the end of the substrate.

Abstract: A laser diode capable of effectively inhibiting effects of return light is provided. A laser diode includes a substrate, and a laminated structure including a first conductive semiconductor layer, an active layer having a light emitting region, and a second conductive semiconductor layer having a projecting part on the surface thereof, on the substrate, wherein a return light inhibition part is provided on a main-emitting-side end face, and effects of return light in the vicinity of lateral boundaries of the light emitting region are inhibited by the return light inhibition part.

Abstract: One facet of a nitride based semiconductor laser device is composed of a cleavage plane of (0001), and the other facet thereof is composed of a cleavage plane of (000 1). Thus, the one facet and the other facet are respectively a Ga polar plane and an N polar plane. A portion of the one facet and a portion of the other facet, which are positioned in an optical waveguide, constitute a pair of cavity facets. A first protective film including nitrogen as a constituent element is formed on the one facet. A second protective film including oxygen as a constituent element is formed on the other facet.

Abstract: On a first region that is a part of one main face of a semiconductor substrate 1, a first semiconductor laser structure 10 is formed so as to have a first lower cladding layer 3, a first active layer 4 with a first quantum well structure and first upper cladding layers 5, 7, which are layered in this order from the semiconductor substrate side, thereby forming a first resonator. On a second region that is different from the first region, a second semiconductor laser structure 20 is formed so as to have a second lower cladding layer 13, a second active layer 14 with a second quantum well structure and a second upper cladding layer 15, 17, which are layered in this order, thereby forming a second resonator. End face coating films 31, 32 are formed on facets of the first and the second resonators, and a nitrogen-containing layer 30 is formed between the facets of the first and the second resonators and the facet coating film.

Abstract: A laser diode capable of improving surge withstand voltage by preventing damage to a rear end surface, and a method of manufacturing the same are provided. A laser diode includes a laser resonator between a first end surface as a main emission end surface and a second end surface facing the first end surface, and the laser diode includes a light absorption inhibition region on the second end surface side of the laser resonator.

Abstract: A nitride-based semiconductor laser device includes a front facet located on a forward end of an optical waveguide and formed by a substantially (000-1) plane of a nitride-based semiconductor layer and a rear facet located on a rear end of the optical waveguide and formed by a substantially (0001) plane of the nitride-based semiconductor layer, wherein an intensity of a laser beam emitted from the front facet is rendered larger than an intensity of a laser beam emitted from the rear facet.

Abstract: The semiconductor laser device includes a cavity structure having a first clad layer, an active layer and a second clad layer formed on a substrate. The second clad layer has a stripe portion extending between the front end face from which laser light is extracted and the rear end face opposite to the front end face. The stripe portion has a first region located closer to the front end face, a second region located closer to the rear end face and a change region whose width changes located between the first and second regions. The effective refractive index difference between the inside and outside of the stripe portion in the change region is greater than that in the first region.

Abstract: A package structure of a compound semiconductor device comprises a thin conductive film with a pattern, a die, at least one metal wire or metal bump and a transparent encapsulation material. The die is mounted on the first surface of the thin conductive film, and is electrically connected to the thin conductive film through the metal wire or the metal bump. The transparent encapsulation material is overlaid on the first surface of the conductive film and the die. A second surface of the conductive film is not covered by the transparent encapsulation material, and is opposite the first surface.

Abstract: A nano-resonating structure constructed and adapted to include additional ultra-small structures that can be formed with reflective surfaces. By positioning such ultra-small structures adjacent ultra-small resonant structures the light or other EMR being produced by the ultra-small resonant structures when excited can be reflected in multiple directions. This permits the light or EMR out put to be viewed and used in multiple directions.

Abstract: A nitride semiconductor laser element, comprises; nitride semiconductor layers in which a nitride semiconductor layer of a first conduction type, an active layer, and a nitride semiconductor layer of a second conduction type that is different from the first conduction type are laminated in that order; a cavity end face formed by the nitride semiconductor layers; and a protective film formed on the cavity end face, the protective film has a region in which an axial orientation of crystals is different in the direction of lamination of the nitride semiconductor layers.

Abstract: A nitride semiconductor laser element comprises; a nitride semiconductor layer that includes a first nitride semiconductor layer, an active layer, and a second nitride semiconductor layer, and that has a cavity with end faces, and a first protective film that is in contact with at least one end face of the cavity, wherein the first protective film has a film structure in which bright and dark parts comprising a region in contact with the active layer and a region in contact with the first and second nitride semiconductor layers are observed under scanning transmission electron microscopy, or the first protective film has a film structure in which the crystallinity at a portion adjacent to the active layer is different from that at portions adjacent to the first and second nitride semiconductor layers.

Abstract: A method and structure for producing lasers having good optical wavefront characteristics, such as are needed for optical storage includes providing a laser wherein an output beam emerging from the laser front facet is essentially unobstructed by the edges of the semiconductor chip in order to prevent detrimental beam distortions. The semiconductor laser structure is epitaxially grown on a substrate with at least a lower cladding layer, an active layer, an upper cladding layer, and a contact layer. Dry etching through a lithographically defined mask produces a laser mesa of length lc and width bm. Another sequence of lithography and etching is used to form a ridge structure with width won top of the mesa. The etching step also forming mirrors, or facets, on the ends of the laser waveguide structures. The length ls and width bs of the chip can be selected as convenient values equal to or longer than the waveguide length lc and mesa width bm, respectively.

Abstract: There is provided a nitride semiconductor light emitting device having a light emitting portion coated with a coating film, the light emitting portion being formed of a nitride semiconductor, the coating film in contact with the light emitting portion being formed of an oxynitride. There is also provided a method of fabricating a nitride semiconductor laser device having a cavity with a facet coated with a coating film, including the steps of: providing cleavage to form the facet of the cavity; and coating the facet of the cavity with a coating film formed of an oxynitride.

Abstract: A method for manufacturing a semiconductor laser. As a preparative step for coating an end face of a resonator with a dielectric film, a cleavage plane of a semiconductor laminated structure that is to be the end face is subjected to a plasma cleaning to prevent a conductive film, which absorbs laser light, from attaching to the cleavage plane. During the plasma cleaning, a first process gas containing argon gas and nitrogen gas is introduced into a vacuumed ECR sputtering apparatus. After the cleavage plane is exposed to the first process gas in the plasma state for a certain time period without application of a voltage, a second process gas containing argon gas and oxygen gas is introduced, and the cleavage plane is exposed to the second process gas in the plasma state while a voltage is applied to the silicon target.

Abstract: The two-dimensional photonic crystal surface emitting laser according to the present invention includes a semiconductor substrate, a main laser section and a reflection film. The main laser section includes a lower cladding layer, an active layer, a two-dimensional photonic crystal layer, an upper cladding layer and a contact layer, which are all deposited on the semiconductor substrate. The reflection film, which surrounds the entire side surfaces of the main laser section, is made of a thin titanium-gold film deposited by sputtering.

Abstract: A semiconductor laser device includes a cavity extending in a propagation direction of a laser beam (X-direction). A front facet is on one end of the cavity through which the laser beam is emitted. A rear facet is on the other end of the cavity. An anodic oxide film is provided on at least one of the front facet and the rear facet, and the anodic oxide film preferably has a thickness of ?/4n or an odd integer multiple thereof, where ? is the wavelength of the laser beam and n is the refractive index of the anodic oxide film.

Abstract: A semiconductor laser device includes a cavity extending in a propagation direction of a laser beam (X-direction). A front facet is on one end of the cavity through which the laser beam is emitted. A rear facet is on the other end of the cavity. Further, an adhesive layer and a coating film are on the front facet, and an adhesive layer and a coating film are on the rear facet. The adhesive layers preferably have a thickness of 10 nm or less and preferably include an anodic oxide film of one of Al, Ti, Nb, Zr, Ta, Si, and Hf.

Abstract: A semiconductor laser device comprises a GaN substrate having a refractive index of 3.5 or below, a semiconductor layer laminated on the substrate, and a pair of facets forming a resonator and in face-to-face-relation to each other in a direction perpendicular to the direction of the laminated layer. One of the facets of the resonator includes a low reflection film, of a first dielectric film, a second dielectric film, a third dielectric film, and a fourth dielectric film. When the refractive indexes of these films are taken as n1, n2, n3, and n4, n1=n3 and n2=n4. The following relationship between the first dielectric film and the third dielectric film, and between the second dielectric film and the fourth dielectric film is established, nd+n?d?=p?/4, where p is an integer, and ? is oscillation wavelength of a laser beam generated by the semiconductor laser device.

Abstract: A semiconductor laser device has a front surface electrode formed by Au plating, a rear surface electrode formed by Au plating, an anti-adhesive film on the front surface electrode or the rear surface electrode and made of a material that does not react with Au, and a coating film that covers an end face on a light emitting side and an end face opposite the light emitting side. The anti-adhesive films may be located at least at the four corners of the front or rear surface electrode.

Abstract: According to an aspect of the embodiment, there is provided a semiconductor light emitting device including: a gallium nitride substrate; a multilayer film of nitride semiconductors provided on the gallium nitride substrate; a first film including a first silicon nitride layer; and a second film including a second silicon nitride layer and a laminated film provided on the second silicon nitride layer. The gallium nitride substrate and the multilayer film have a laser light emitting facet and a laser light reflecting facet. The first silicon nitride layer is provided on the laser light emitting facet. The multilayer film includes a light emitting layer, and the multilayer film has a laser light emitting facet and a laser light reflecting facet. The second silicon nitride layer is provided on the laser light reflecting facet, and the laminated film includes oxide layer and silicon nitride layer which are alternately laminated.

Abstract: A semiconductor laser comprising a laser-active layer sequence (1) having a first main face (1003), on which is arranged a heat conducting layer (3) containing carbon nanotubes (30) and a method for producing such a semiconductor laser.

Abstract: A surface emitting laser includes an n-side multilayered reflection film and an active layer which are formed on a substrate. On the active layer, a mesa region is formed by sequentially stacking an AlGaAs current blocking layer, a p-side multilayered reflection film, a p-type contact layer and the like. A groove is formed to separate the mesa region from an outside region. The mesa region and the outside region are connected to each other with a beam portion provided in the groove. A reflection film with a high Al composition ratio in the p-side multilayered reflection film in the beam portion is completely oxidized, and thus has a high resistance.

Abstract: A semiconductor laser device includes a coating film for adjustment in reflectance formed at a light-emitting portion of semiconductor, wherein the coating film has a thickness d set to satisfy R (d, n)>R (d, n+0.01) and d>?/n, where n represents a refraction index of the coating film for a lasing wavelength ?, and R (d, n) represents a reflectance at the light-emitting portion depending on the thickness d and the refraction index n.

Abstract: A semiconductor laser having a semiconductor chip (1) which contains an active layer (5) and emits radiation in a main radiating direction (6). The active layer (5) is structured in a direction perpendicular to the main radiating direction (6) in order to reduce heating of the semiconductor chip (1) by spontaneously emitted radiation (10).

Abstract: A method of fabricating a surface-emission type light-emitting device which emits light in a direction perpendicular to a semiconductor substrate, includes the following steps (a) to (e). (a) A step of forming a column-shaped section by etching at least a part of a multilayer film. (b) A step of forming a first resin layer so as to cover the column-shaped section. (c) A step of forming a second resin layer by changing the solubility of the first resin layer in a liquid. (d) A step of immersing, for a specific period of time, at least the column-shaped section and the second resin layer in a liquid in which the second resin layer dissolves, thereby removing the second resin layer at least in the area formed over the column-shaped section. (e) A step of forming an insulating layer by curing the second resin layer.

Abstract: The present invention relates to a multi-wavelength laser diode, in which an oscillating structure includes a semiconductor substrate, and a lower cladding layer, an active layer and a ridge formed in their order on the semiconductor substrate. A first metal layer is formed on a first face of the oscillating structure including one end of the ridge, and made of a metal having a high reflectivity in a first wavelength range of at least a predetermined wavelength. A second metal layer is formed on the first metal layer, the second metal layer being made of a metal having a high reflectivity in a second wavelength range under the predetermined wavelength. The multi-wavelength laser diode can improve-the reflective layer structure to achieve a high reflectivity in the entire visible light range.

Abstract: The present invention relates to a nitride semiconductor laser device provided with a window layer on a light-emitting end face of the resonator which comprises an active layer of nitride semiconductor between the n-type nitride semiconductor layers and the p-type nitride semiconductor layers, in which at least the radiation-emitting end face of said resonator is covered by said window layer comprising monocrystalline nitride of general formula AlxGa1?x?yINyN, where 0?x+y?1, 0?x?1 and 0?y<1, having a wider energy gap than that of the active layer and being formed at a low temperature so as not to damage said active layer. Formation of such a window layer improves significantly the performance of the nitride laser device according to the invention.

Abstract: A semiconductor laser device for emitting light at two wavelengths ?1 and ?2 comprises: a laser chip having a front end face and a rear end face; and a high reflectance film on the rear end face of the laser chip and including seven or more layers laminated one on top of another, the seven or more layers including a first layer and a last layer, the first layer being closest to the laser chip, the last layer being farthest from the laser chip. One or more of the seven or more layers of the high reflectance film, other than the first and last layers, has an optical thickness of n*?/2, where n is a natural number and ?=(?1+?2)/2. All of the seven or more layers of the high reflectance film, other than the one or more layers and other than the last layer, have an optical thickness of (2n?+1)*?/4, where n? is 0 or a positive integer. The last layer of the high reflectance film has an optical thickness of n*?/4.

Abstract: A distributed feedback laser diode comprises a phase-shifting portion in diffraction gratings. The magnitude of a phase shift in the phase-shifting portion is 8 ?/40 to 9 ?/40, ? representing twice the distance between the diffraction gratings. A main mode stands on a lower wavelength side than the center of a stop band when an injected current is of a level of a threshold current, whereas the main mode is shifted to the center of the stop band and a sub mode is suppressed from growing when the injected current is of a level of an operating current.

Abstract: A micro-lens built-in vertical cavity surface emitting laser (VCSEL) includes a substrate and a lower reflector formed on the substrate. An active layer is formed on the lower reflector, generating light by a recombination of electrons and holes. An upper reflector is formed on the active layer including a lower reflectivity than that of the lower reflector. A micro-lens is disposed in a window region through which the laser beam is emitted. A lens layer is formed on the upper reflector with a transparent material transmitting a laser beam; the lens layer includes the micro-lens. An upper electrode is formed above the upper reflector excluding the window region a lower electrode formed underneath the substrate.

Abstract: A semiconductor laser device (10) includes a resonant cavity (12) in which a quantum well active layer (11) made up of barrier layers of gallium nitride and well layers of indium gallium nitride is vertically sandwiched between at least light guide layers of n- and p-type aluminum gallium nitride. An end facet reflective film (13) is formed on a reflective end facet (10b) opposite to a light-emitting end facet (10a) in the resonant cavity (12). The end facet reflective film (13) has a structure including a plurality of unit reflective films (130), each of which is made up of a low-refractive-index film (13a) of silicon dioxide and a high-refractive-index film (13b) of niobium oxide. The low-and high-refractive-index films are deposited in this order on the end facet of the resonant cavity (12).

Abstract: A near-field light source device including a semiconductor laser comprised of laminated semiconductor layers and having a ring-type optical resonator with a plurality of wave guides connected via mirror portions, a light blocking film formed in one of the mirror portions and having a small opening not greater than a wavelength size, and a diffraction grating formed on the light blocking film. The light oscillated from the semiconductor laser is diffracted by the diffraction grating, the diffracted light is coupled to a rotation mode in the ring-type optical resonator, and near-field light is generated via the small opening.

Abstract: In a semiconductor laser having a first facet (front facet) through which laser light is emitted and a second facet (rear facet), and a first coating film composed of a single-layer dielectric film on the first facet. The oscillating wavelength of the laser light is ? and the refractive index of the dielectric film is n. The thickness of the dielectric film is within a range between 5% and 50% of ?/4n.

Abstract: A manufacturing method, in which two device bars are bonded prior to facet coating to form a stacked bar pair. In one embodiment, each of the device bars has a p-side and an n-side, each side having a plurality of bonding pads, with at least some bonding pads located at the p-side of the first device bar adapted for mating with the corresponding bonding pads located at the p-side of the second device bar. Solder material deposited onto the p-side bonding pads adapted for mating is liquefied in a reflow oven, wherein surface tension of the liquefied solder self-aligns the device bars with respect to each other and keeps them in alignment until the solder is solidified to form a solder bond between the mated bonding pads. Two or more instances of the bonded bar pair are further stacked such that bonding pads located at the n-sides of adjacent bar pairs are mated in a relatively tight fit.

Abstract: A laser capable of improving surge withstand voltage by preventing damage to a read end surface, and a method of manufacturing the same are provided. A laser diode includes a laser resonator between a first end surface as a main emmission end surface and a second end surface facing the first end surface, and the laser diode includes a light absorption inhibition region on the second end surface side of the laser resonator.

Abstract: A semiconductor laser diode comprising a semiconductor substrate having an active layer with a pair of cavity facets opposed to each other on both ends of active layer as well as a first dielectric film of an oxide and a second dielectric film of an oxynitride successively stacked on one cavity facet has sufficient initial characteristics with a film structure having excellent heat radiability for allowing stable high-output lasing over a long period without reducing a catastrophic optical damage level on an emission end.

Abstract: An edge-emitting semiconductor laser includes a resonator structure having an active layer. A low reflection three-layer film is provided on in emitting edge face of the resonator structure and a high reflection multi-layer film is provided on a rear edge face of the resonator structure. The low reflection three-layer film is formed in an exemplary embodiment by sequentially stacking a first Al2O3 layer having a thickness of 10 nm, an Si3N4 film having a thickness of 190 nm, and a second Al2O3 layer having a thickness of 10 nm.

Abstract: A semiconductor laser device comprises an active layer, a cladding layer, an end face for emitting light. A low-reflective film is provided on the end face. The reflectance of the low-reflective film changes with wavelength. A wavelength at which the reference of the low-reflective film is minimized is on the long wavelength side of a wavelength at which the gain of the semiconductor laser device is maximized. The gain and the loss of the semiconductor laser device become equal at a wavelength only in a wavelength region in which the reflectance of the low-reflective film decreases with increasing wavelength. The reflectance of the low-reflective film is preferably set to 1% or less at the wavelength at which the gain of the semiconductor laser device is maximized.