Abstract: A method of altering a refractive index, as for an optical waveguide, as in a buried heterostructure laser, by inducing disordering in a region of a semiconducotr body comprises exposing a surface portion of the semiconductor body to plasma etching, coating at least a part of the surface portion with an oxide layer, heat treating the semiconductor body.

Abstract: A gain waveguide type semiconductor laser oscillating visible light has an N type GaAs substrate of, and a double-heterostructure provided above the substrate to include an InGaP active layer, and first and second cladding layers sandwiching the active layer. The first cladding layer consists of N type InGaAlP, whereas the second cladding layer consists of P type InGaAlP. A P type InGaP layer is formed as an intermediate band-gap layer on the second cladding layer. An N type GaAs current-blocking layer is formed on the intermediate band-gap layer, and has an elongated waveguide opening. A P type GaAs contact layer is formed to cover the current-blocking layer and the opening.

Abstract: An InGaAlP NAM structure laser is formed with a double-heterostructure section disposed on an n-type GaAs substrate. The double-heterostructure section includes a first cladding layer of n-type InGaAlP, a non-doped InGaP active layer, and a second cladding layer of p-type InGaAlP. An n-type GaAs current-blocking layer having a stripe opening and a p-type GaAs contact layer are sequentially formed on the second cladding layer by MOCVD crystal growth. A low-energy band gap region is defined in a central region of the active layer located immediately below the stripe opening. A high-energy band gap region is defined in a peripheral region of the active layer corresponding to a light output end portion of the laser and located immediately below the current-blocking layer. Therefore, self absorption of an oscillated laser beam at the output end portion can be reduced or prevented.

Abstract: A semiconductor structure having a face with macroscopic parallel steps and its method of making. The structure is formed by cutting a face on a crystal at a vicinal angle, that is, being misoriented from a major crystal face by a few degrees. Atomic sized microsteps are formed in the vicinal face. Parallel grooves or other regular irregularities are etched in the vicinal face. Subsequent epitaxial growth causes the microsteps to coalesce into macroscopic steps. Alternatively, etching or annealing can accomplish the same coalescing. Novel electronic structures can be fabricated on the stepped structure.

Abstract: The invention relates a method of manufacturing a semiconductor laser device having a coating on surfaces of a semiconductor body intended for emanation of a laser beam.

Abstract: A method of producing a semiconductor laser including deposition a first film as a source of n type impurities on a portion of a semiconductor structure produced by growing at least a p type lower cladding layer, a quantum well active layer, and an n type upper cladding layer successively on a substrate, depositing a second film as a source of p type impurities at least on the surface of the semiconductor structure on both sides of and on the first film and annealing to diffuse p and n type impurities at the same time, thereby disordering portions of the quantum well except for the portion becoming an active region with p type impurities reaching at least the p type lower cladding layer, n type impurities reverting the portions of the n type cladding layer to which p type impurities have diffused to n type, and the n type impurities reaching the n type cladding layer but not reaching the active layer.

Abstract: Proposed is a method of fabricating semiconductor devices involving vapor etching of channels and/or growth of layers in a substrate. The etch or growth rate is controlled by opening up additional regions in the mask which are separated from the opening used to define the active region. The etching or growth in the additional exposed regions of the substrate consumes a certain amount of reactant and controllably reduces the amount available for etching or growth in the active region.

Abstract: A two dimensional, surface-emitting array of semiconductor lasers. Lasers disposed on a semiconductor substrate emit light in a direction substantially parallel to the substrate surface into a high index material in which the lasers are embedded. Internal reflectors composed of a low index material, also embedded in the high index material, reflect the laser beams to the surface of the array. The indexes of the low index material and the high index material are chosen so that none of the light enters the internal reflector, and all light is reflected to the laser array surface.

Abstract: A semiconductor laser device includes a current blocking structure having a p-n-p-n structure, provided on a first conductivity type semiconductor substrate, an active region buried in a stripe shaped groove produced in the current blocking structure, a lower cladding layer grown by liquid phase epitaxy approximately filling the stripe groove, an active layer on the lower cladding layer in the stripe groove, a waveguide layer on the active layer completely filling the groove, and a diffraction grating on the waveguide layer.

Abstract: A buried stripe semiconductor light emitting device and a method for producing the device in which the buried stripe functions as an internal resonator, and the device has window regions interposed between the resonator and facets on the external surface of the device. A first phase crystal growth is conducted in which a first cladding layer is grown on a doped substrate. Thereafter, a doped stripe of impurities is introduced into the first cladding layer in electrical contact with the doped substrate. The doped stripe extends longitudinally but terminates short of the facets so that later out-diffusion from the doped stripe will form the window regions. A second phase crystal growth is then conducted which buries the doped stripe internal to the semiconductor, i.e., not projecting through any external surface. The second phase crystal growth comprises an active layer, a second cladding layer and a contact layer successively grown on the first cladding layer.

Abstract: A buried heterojunction semiconductor laser appropriate for integration with other electronic circuitry and method of producing same, in which the width of a central stripe of the active region can be reduced beyond the physical size limitations of the connecting electrode so as to allow the semiconductor laser to oscillate in a stable manner and with low threshold current. The semiconductor laser is provided with a portion of the surface of the upper cladding layer located above the disordered active layer regions electrically connected with the upper cladding layer located above the nondisordered central stripe. As a result, the central stripe electrode can be of a width larger than that of the central stripe itself.

Abstract: A method for manufacturing a surface emitting type AlGaAs/GaAs semiconductor LASER diode by a selective epitaxy method which is capable of forming naturally a 45.degree. mirror reflective face during the epitaxy method itself. The method comprises the steps of forming a silicon oxide or silicon nitride layer on one side of a n-type single crystal GaAs substrate as a mask, removing the mask of the regions each for forming a 45.degree. mirror reflective face and a LASER diode by use of a photolithography and a chemicaletching, forming the two layers by removing the photoresistor on the remaining mask after a selective epitaxy process and converting a slant face of the LASER diode into a vertical face, depositing a n-type metal layer on the other side of the substrate, and carrying out a heat treatment.

Abstract: A semiconductor laser and a method of producing the same wherein the semiconductor laser is produced by forming a stripe-shaped projection on the surface of a semiconductor substrate, and forming multilayered thin films with a double heterostructure including an active layer on said semiconductor substrate by using the metal organic chemical vapor phase epitaxial growth method or the molecular beam epitaxial growth method. Thus, a buried stripe-structure semiconductor laser can be produced by a sequence of crystal growth processes.

Abstract: A high-power AlGaAs/GaAs laser device comprises: a ridge formed on the top surface of a substrate from one end to the opposite end, thereof wherein the width of the ridge is made narrower in regions near both the ends and wider in a middle region; a depression is formed in the wider region of the ridge; a clad layer is grown epitaxially over the top surface of the substrate; and an active layer is grown epitaxially on the clad layer, wherein the thickness of the active layer is thinner in portions just above the narrower ridge regions and relatively thicker in a portion just above the wider ridge region.

Abstract: A monolithic integrated structure in which a compound semiconductor (III-V or II-VI material) optoelectronic device (laser) is formed in the shape of a mesa-like structure projecting from an etch pit in an Si substrate. A method for sonically removing cantilevered beams formed on said optoelectronic device, to provide laser end facets, is also described.

Abstract: A planar process for fabricating an optoelectronic integrated circuit device is described. The process includes the in situ formation of laser diode mirror facets comprising the steps of providing a semi-insulating gallium arsenide substrate having thereon layers of n-doped gallium arsenide, n-doped aluminum gallium arsenide, and undoped gallium arsenide; patterning and etching the undoped gallium arsenide layer into a mandrel having substantially vertical walls; establishing insulator sidewalls on the vertical walls; removing the mandrel, thereby exposing the inner walls of the insulator sidewalls and leaving the insulator sidewalls self-standing; removing the aluminum gallium arsenide using the insulator sidewall as a mask; and forming a laser diode within the region between the insulator sidewalls and creating the mirror facets with the inner walls of the insulator sidewalls. Mirror facets formed in accordance with this process are substantially free of contaminants.

Abstract: A method of making semiconductor laser arrays having an impurity disordered pattern of waveguides at least some of which are directly joined at branching junctions. The region near the branching junctions provides a phase boundary condition in which lightwaves propagating in adjacent waveguides are in phase. Using one impurity dose and one disordering depth in a first portion of the pattern and another in a second portion of the pattern provides a combination of strong and weak waveguiding with strong waveguides that eliminate evanescent coupling from occurring at least in the branching junction regions, and with weak guides near one or both end facets permitting evanescent coupling. The evanescent coupling between adjacent weak waveguides preserves the in phase relationship that was established in the Y-junction regions, resulting in a diffraction limited single lobe far field output.

Abstract: A semiconductor laser includes a semiconductor substrate on which a longitudinal groove is provided in the resonator direction, a first semiconductor layer disposed on a region of the semiconductor substrate where the groove is not provided and forming a rectifying junction therewith, a first cladding layer provided on the semiconductor substrate in the groove, an active layer provided on the first cladding layer in the groove, and a second cladding layer provided directly on the active layer and opposite the first semiconductor layer with an interposed insulating layer, such as a gap void of solid material or a gap and current blocking material having only negligible parasitic capacitance.

Abstract: A method for forming a semiconductor waveguide includes forming a layer of expitaxial silicon over a substrate. The impurity concentration of the layer is higher than that of the substrate. A second layer of epitaxial silicon is disposed over the upper surface of the layer with a higher resistivity than that of the substrate. A masking layer is then disposed over the substrate and then patterned, and then the layer selectively etched down to the upper surface of the layer. The layer is then porified to form an insulating layer from the layer. The porous film is then converted by oxidation to a silicon dioxide layer. The sidewalls of the resulting ridge are then oxidized to form sidewall layers and then the masking layer removed from the upper layer. The upper surface of ridge is oxidized to form an upper insulating layer to extend the sidewall layer over the entire upper surface and sidewalls of the ridge. A layer of insulating material is then disposed over the substrate.

Abstract: A double heterostructure stack comprising confinement layers (CC) enclosing active layers (CA) is formed on a substrate (S), e.g. a N+ type gallium arsenide substrate. Selective etching is performed so as to lay bare the confinement layers at different depths, e.g. CC4, CC3, CC2. The confinement layers initially receive contact layers (CP) made of P-type gallium arsenide. Regions R1, R2, and R3 are formed through the contact layers to constitute junctions with the uppermost active layers (respectively CA1, CA2, CA3). Valleys (V10, V21, V32) are formed to isolate the above-defined elementary stacks. After a metal contact layer has been formed, and after the end surfaces have been optically prepared, a multi-wavelength laser device is obtained.

Abstract: Bars of integral laser diode devices cleaved from a wafer are placed with their p regions abutting and n regions abutting. A thin BeCu mask having alternate openings and strips of the same width as the end facets is used to mask the n region interfaces so that multiple bars can be partially coated over their exposed p regions with a reflective or partial reflective coating. The partial coating permits identification of the emitting facet from the fully coated back facet during a later device mounting procedure.

Abstract: A method for separating laser diodes. The diodes are monolithically produced from a semiconductor substrate wafer which through an epitaxy process has been provided with a layer sequence suitable for laser operation. First, the semiconductor substrate wafer is covered with a first mask which defines the interspaces between the mirrors of adjacent laser diodes. Then the mirror surfaces are etched out of the semiconductor substrate wafer. Thereafter, the wafer is covered with a second mask for defining separation trench areas between the mirror surfaces of adjacent laser diodes and for protecting the remaining wafer parts. Then, separation are etched into the trench area. Finally, the laser diodes are separated by breaking the wafer along the trenches. In a preferred embodiment, the wafer thickness is at most twice the distance between the mirror surfaces of adjacent laser diodes and the trench depth is at least one fourth of the wafer thickness.

Abstract: A method of producing a semiconductor laser which comprises sequentially depositing a lower cladding layer, an active layer, and an upper cladding layer on a substrate, forming a V shaped groove in the deposited layers at least reaching the lower cladding layer, the groove extending in a direction perpendicular to the direction between the surfaces that are to become resonator end surfaces, growing a semiconductor layer having a larger energy band gap than that of the active layer in the groove while retaining the V shaped groove, and cleaving the substrate and layers along the V shaped groove.

Abstract: Different diffusion rates can be made operative relative to diffusion disordering in designated areas of a thin active layer or of quantum well feature compared to thermal disordering in other areas thereof where disordering is not desired by the selective placement of migratory defects in a semiconductor support means, such as a semiconductor substrate or semiconductor support layer for supporting subsequently epitaxially deposited semiconductor layers. Such migratory defects as used herein are intended to include impurities and/or other lattice defects initially introduced into the semiconductor support means prior to epitaxial deposition of semiconductor layers constituting the semiconductor structure, wherein at least one of such layers comprises a thin active layer (i.e.

Abstract: An active layer is formed on an n-type InP buffer layer of a substrate. A pair of strip-shaped grooves are formed into the active layer to divide it into a contract portion and side portions. A p-type Inp cladding layer is deposited on the entire surface of the active layer and grooves. The cladding layer is selectively etched to form a mesa portion including the central active portion and expose the buffer layer. An insulating film is coated on the mesa portion and buffer layer, so that a semiconductor light-emitting device is manufactured.

Abstract: A method of manufacturing a semiconductor light emitting device by forming a compound semiconductor structure with homo- or heterojunction therein having a first p-type compound semiconductor crystal layer at the top of the structure, growing a second p-type compound semiconductor crystal layer on the structure in a reactor, wherein, before the beginning of the crystal growth step, a p-type dopant is caused to flow into the reactor in which the structure is placed. In some embodiments, the flow of the p-type dopant continues after the completion of the crystal growth.

Abstract: A triangular ring laser utilizing total internal reflection at two angled facets and a preselected amount of reflection at a third angled facet is disclosed. Partial transmission occurs through the third facet to reduce the threshold current required for achieving stimulated emission. The facets are at three corners of the triangular laser, and are formed by chemically assisted ion beam etching in which SiO.sub.2 is used as a mask, whereby smooth vertical walls are produced to form facets having reflective characteristics equivalent to those formed by cleaving.

Abstract: A semiconductor laser device of the buried heterostructure type in which leakage current is substantially reduced. A mesa portion carries the active lasing portion of the laser, and current blocking layers are grown at either side of the mesa portion. One of the current blocking layers has its conductivity type inverted to the opposite type to eliminate a current leakage path, thereby to provide a high efficiency low leakage current semiconductor laser. Conductivity inversion is accomplished by adjusting the impurity concentration levels in the layers on either side of the mesa portion, and controllably diffusing impurities from one layer to another until conductivity inversion is accomplished in a thin tip portion of one of the layers.

Abstract: In a method for Liquid Phase Epitaxy (LPE) of semi-insulating InP, a solution of P, Ti and a p-type dopant in molten In is cooled in a non-oxidizing ambient at a surface of a substrate to grow an epitaxial layer of doped InP on the surface. The concentration of p-type dopant in the solution is such as to provide a concentration of p-type dopant in the grown epitaxial layer greater than the aggregate concentration of any residual contaminants in the grown epitaxial layer, and the concentration of Ti in the solution is such as to provide a concentration of Ti in the grown epitaxial layer greater than the concentration of p-type dopant in the grown epitaxial layer. The required melt concentrations are determined empirically. The method can be performed at temperature below 650 degrees Celsius and is particularly suited to the LPE growth of semi-insulating InP to isolate InP-InGaAsP buried heterostructure lasers.

Abstract: A semiconductor optical element having a layer which exhibits a function of diffraction grating between a first cladding layer and a second cladding layer, wherein the layer which exhibits the function of diffraction grating consists of a superlattice layer in which crystal layers are periodically mixed to constitute a semiconductor grating layer.

Abstract: A masking layer is formed on the light-emitting mirror surface of a semiconductor laser body. The masking layer is capable of blocking or cutting off light emitted from the semiconductor laser body and of being made optically transparent by exposure to the light emitted from the semiconductor laser body dependent on the amount of energy of the emitted light. When the light is emitted from the semiconductor laser body on which the masking layer is deposited, a small light-emitting hole is defined in the masking layer, the light-emitting hole having a desired diameter commensurate with the amount of energy of the emitted light which is applied to the masking layer.

Abstract: A semiconductor laser having an internal current restriction includes a (100) face-oriented p-type GaAs substrate treated to have a groove or difference in level having an (n11) A face (n=1-5) as an inclined surface. An AlGaAs: Si layer, an AlGaAs:Be cladding layer, an AlGaAs active layer, and an AlGaAs:Sn cladding layer are grown on the substrate in the order mentioned. Since the Si acts as an n-type material on the (100) face and as a p-type material on the (n11) face, the AlGaAs:Si layer becomes a p-type layer solely in the groove, and it is in this portion that a current path is formed. The laser can be fabricated by molecular-beam epitaxy applied in a single step.

Abstract: There is disclosed a semiconductor layer which can emit a continuous laser beam in a visible wavelength range. The laser has an n-GaAs substrate. On this substrate, an n-InGaAlP cladding layer, an active layer, and p-InGaAlP cladding layers are sequentially formed, thus forming a double hetero-structure. A mesa-shaped, upper cladding layer is provided, defining a laser beam-guiding channel. A thin p-InGaAlP contact layer and a mesa-shaped, p-GaAs contact layer are formed on the top surface of the upper cladding layer. Two n-type semiconductive, current-blocking layers cover the slanted sides of the upper, mesa-shaped cladding layer and also the contact layer. They are made of the same n-GaAs compound semiconductor material as the substrate.

Abstract: A ridge waveguide laser structure is manufactured by a method including providing a photoresist stripe (8) on an exposed area of a p cap layer (4) of a multilayer laser wafer; etching channels (9) through the cap layer (4) and a p passive layer (3) using the stripe (8) and an oxide layer window (FIG. 4) as a mask; evaporating a passivating and insulating oxide (11, 11a) over the wafer, there being breaks (C) in the oxide where the stripe (8) is undercut during channel etching; and removing the stripe (8) and the oxide (11a) on it by a lift-off technique.

Abstract: A method for producing a semiconductor laser including successively growing at least two semiconductor layers simultaneously on a substrate, the finally grown layer not containing aluminum and the layer grown immediately before the finally grown layer containing aluminum, etching a stripe groove through the finally grown layer to expose part of the semiconductor layer containing aluminum, growing a second semiconductor layer not including aluminum on the finally grown layer and the exposed surface of the semiconductor layer containing aluminum, and growing a semiconductor layer including aluminum on the second semiconductor layer not containing aluminum.

Abstract: A method of making a semiconductor laser from a gallium arsenide substrate of a first conductivity type by depositing a first layer of semiconductor material having the composition Al.sub.x Ga.sub.1-x As of first conductivity type on the substrate and a thin second layer of semiconductor material for quantum confinement having the composition In.sub.y Ga.sub.1-y As on the first layer. This layer experiences sufficient strain in the semiconductor structure so as to minimize the threshold current density. The device is completed by depositing a third layer of semiconductor material having the composition Al.sub.x Ga.sub.1-x As and of second conductivity type on the second layer, and depositing a fourth layer of semiconductor material having the composition GaAs and of second conductivity type on the third layer.

Abstract: A method for producing a semiconductor laser comprising depositing a first semiconductor layer comprising n-type InP on an n-type InP substrate, depositing a diffraction grating of InGaAsP which includes or excludes doping impurities on the first semiconductor layer with irradiating interference fringes by a light excitation crystalline growth means, and burying a portion of the diffraction grating with InGaAsP including or excluding doping impurities with irradiating interference fringes reverse in light and darkness from said interference fringes used in depositing the diffraction grating.

Abstract: A distributed feedback (DFB) type laser and a method and apparatus for forming same wherein a quaternary semiconductor active lasing strip of material is buried between a substrate of binary compound of one type conductivity material and a mesa binary compound body of opposite type conductivity and a periodic grating structure is etched into the plateau of the mesa. In one embodiment, ohmic contacts are provided on either side of the grating structure and the mesa is undercut adjacent the active strip to partly isolate the ohmic contacts from the homojunction formed when the active strip is buried, preferably using a mass-transport process. In another embodiment, the ohmic contacts are formed on the top of a deeply etched grating structure. A buried layer double heterostructure (DH) laser is also described with DFB grating formed on the side walls of the layer. Additionally, a surface emitting diode laser with DFB is described.

Abstract: A semiconductor laser device comprises a substrate (7) formed of p type GaAs, a laser diode portion (10) capable of laser oscillation and a monitor photodiode portion (11) capable of photoelectric conversion formed on substrate (7). The laser diode portion (10) and the monitor photodiode portion (11) are both formed of an epitaxial separating layer (6) of p type AlAs, an epitaxial layer group (23) mainly formed of a material of AlGaAs system and an epitaxial window layer (9) formed on a cleavage plane of this epitaxial layer group (23). The cleavage plane of the epitaxial window layer (9) on the side of the laser diode portion (10) constitutes a laser resonator plane (16) for laser light output of said laser diode portion (10) while the cleavage plane of the epitaxial window layer (9) on the monitor photodiode portion (11) constitutes a light receiving plane (17) for receiving the laser light outputted from the laser resonator plane (16).

Abstract: A semiconductor laser device comprises a substrate (7) formed of p type GaAs, a laser diode portion (10) capable of laser oscillation and a monitor photodiode portion (11) capable of photoelectric conversion formed on substrate (7). The laser diode portion (10) and the monitor photodiode portion (11) are both formed of an epitaxial separating layer (6) of p type AlAs, an epitaxial layer group (23) mainly formed of a material of AlGaAs system and an epitaxial window layer (9) formed on a cleavage plane of this epitaxial layer group (23). The cleavage plane of the epitaxial window layer (9) on the side of the laser diode portion (10) constitutes a laser resonator plane (16) for laser light output of said laser diode portion (10) while the cleavage plane of the epitaxial window layer (9) on the monitor photodiode portion (11) constitutes a light receiving plane (17) for receiving the laser light outputted from the laser resonator plane (16).

Abstract: Process for the production of a monolithic integrated optical device incorporating a semiconductor laser and an optical waveguide, as well as to a device obtained by this process.The substrate is given a profile having at least one step. On said substrate is deposited by a single epitaxy operation performed in the vapour phase and in a successive manner a first confinement layer, a guidance layer made from a material transparent for the radiation emitted by the laser, a second confinement layer, an active layer, a third confinement layer and a contact layer. The transparent material has a refractive index higher than the indices of the confinement layers surrounding the same. Thickness values are given to the different layers such that the active layer of the lower stack faces the transparent layer of the upper stack.Application to optical telecommunications.

Abstract: Room temperature laser action is achieved in a cathode ray tube (CRT) in which the target includes a plurality of semiconductor layers: a thin, wide bandgap buffer layer; a thicker, narrow bandgap active layer; and a much thicker wide bandgap cavity-length-adjusting layer. The light beam direction is essentially parallel to the e-beam direction and hence is scannable.

Abstract: A method of fabricating a semiconductor crystal mesa stripe whose waist section is narrower than the upper plane of said mesa stripe. The method comprises the steps of forming a first striped mask on the semiconductor crystal wafer in order to fabricate a prescribed mesa stripe, linearly arranging a plurality of second striped masks, narrower than said first striped mask by the prescribed waist width of the main mesa stripe, on the semiconductor wafer plane at prescribed intervals and in parallel with said first striped mask in order to fabricate monitor mesa stripes; and of subjecting said semiconductor wafer plane to mesa etching.

Abstract: A method of making an optically coupled semiconductor laser having cleaved facing end walls and precise alignment and spacing. An indium coated face of a semiconductor laser diode bar is placed on an indium coated support. A knife edge cleaves the bar into two closely spaced and aligned semiconductor diode laser bodies and concurrently cold bonds them to the support. The knife edge is used without deleteriously affecting their bonding to the support.

Abstract: An integrated quantum well laser structure which has a plurality of quantum well lasers for providing a plurality of light beams each having a different wavelength for use in wavelength division multiplexing.

Abstract: A method of making a ridge waveguide laser with the ridge being grown through a stripe opened in an oxide layer covering one of the cladding layers is described. In one embodiment, the cladding layer is corrugated and the ridge waveguide laser is a distributed feedback laser.

Abstract: Prior to packaging, semiconductor lasers are purged by being subjected first to high temperature and high current simultaneously so as to suppress stimulated emission and stress the shunt paths which allow leakage current to flow around the active region. A prudent, but nonessential, second step is to lower the temperature and/or current so that the lasers emit stimulated emission (preferably strongly, near the peak output power), thereby stressing the active region. Lasers subjected to such a purge exhibit stabilized degradation rates in short times (of the order of a few hours) and provide a robust population which meets the performance criteria of long lifetime systems.

Abstract: A method of producing a semiconductor laser device, comprisingdepositing a first cladding layer, an active layer, and a second cladding layer successively, which three layers having heterojunctions each between neighboring two layers, said first and second cladding layers being made of mixed crystals of a semiconductor material composing the active layer and another semiconductor material containing aluminum,depositing a fourth thin semiconductor layer on the second cladding layer, said fourth layer being made of material not including aluminum, and having charge carriers of the same type with that of the second cladding layer,depositing a fifth semiconductor layer on said fourth layer, said fifth semiconductor layer having charge carriers of the type opposite to that of the second cladding layer,forming a stripe-like groove by etching in said fifth semiconductor layer down to said fourth semiconductor layer, anddepositing a sixth semiconductor layer on said fifth semiconductor layer and on said groove, said

Abstract: An epitaxial layer is used to place the surface of a crystal in compression o as to greatly increase the durability of the crystal such as a laser medium crystal.