Abstract: The present invention relates to a device for outcoupling of light in an external cavity laser, which external cavity laser comprises at least one light source, at least one wavelength selective feedback element, at least one polarization selective beam-splitting optical element, and at least one Faraday-rotator element.

Abstract: A wavelength tuning system adjusts an external cavity of a laser about two orthogonal axes for aligning features of a diffractive optic with a third orthogonal axis about which the diffractive optic is pivoted for providing selected wavelength feedback to the laser. A laser mount supports the laser, and a mounting arm supports both the diffractive optic and a reflective optic in a fixed orientation with respect to each other. A flexural member forms at least part of a connection between the mounting arm and the laser mount in a relative orientation for optically coupling the diffractive optic to the laser within the external cavity. The mounting arm is pivoted with respect to the laser mount about the pivot axis by an actuator for varying a wavelength of a diffracted portion of the output beam returned to the laser without significantly varying an angular orientation of the output beam with respect to the laser mount as reflected from the reflective optic.

Abstract: A semiconductor laser diode module having high fabrication yields and high reliability is provided. A semiconductor laser chip is fixed on a substrate and a first lens and an optical isolator are disposed between the semiconductor laser chip and an optical fiber for receiving light emitted from the semiconductor laser chip. A lens holder fixed with the first lens and a housing fixed with the optical isolator are laser-welded and fixed to clamping parts of a lens holder retainer and an optical isolator retainer, respectively. Laser welding portions of the clamping parts of the lens holder retainer and the optical isolator retainer are formed to have a thickness thinner than that on the substrate side of the clamping parts and have almost the same thickness in the height direction. Curved surfaces, for example, which tilt in the direction thickening toward the lower side, are formed on the lower side thereof.

Abstract: This device comprises at least three pulsed lasers (2, 4, 6), in order to supply light pulses, and means (14) for directing these pulses substantially onto the same spot of a target (16) and substantially at the same time onto this spot. The lasers are pumped by diodes (40) operating continuously.

Abstract: A multimode diode package and pump-coupler package are provided with a beam rotator that facilitates efficient packaging of a multimode diode laser with a side-coupled optical fiber. The beam rotator comprises a pair of reflective surfaces that perform/a pair of “off-plane bounces” to rotate the beam's fast axis. In an XYZ coordinate system, if the diode lies in the XZ-plane and emits the beam along the Z-axis with its fast-axis along the Y-axis, the first reflective surface folds the beam along the Y-axis and its fast-axis along the Z-axis. The second reflective surface folds the beam along the X-axis and leaves the fast-axis along the Z-axis. The fiber is mounted in the XZ-plane along the Z-axis parallel to the fast-axis.

Abstract: A wavelength selectable light source is comprised of a two-dimensional (2-D) array of variable wavelength vertical-cavity surface-emitting lasers (VCSELs), wherein light beams emitted from the VCSELs are coupled into an output optical fiber. The light beams emitted from the VCSELs are collimated via a 2-D array of micro-lenses, the collimated light beams impinge upon a first fixed-position mirror that points each of the collimated light beams toward a second movable mirror located at a common focal point in a common area, and the second movable mirror redirects the collimated light beams into a lens coupled to the output optical fiber. By moving the second movable mirror, different ones of the collimated light beams can be directed into the output optical fiber, so that the second movable mirror performs a wavelength selection function.

Abstract: A semiconductor laser unit includes a plurality of semiconductor laser elements arranged parallel with one another in a laser beam-emitting direction, and a base for positioning and fixing the plurality of semiconductor laser elements. The plurality of semiconductor laser elements are arranged such that a laser beam emitted from the semiconductor laser element greatest in astigmatism, of the plurality of semiconductor laser elements, is coincident in its axis with a reference axis of the base. In the case that the semiconductor laser unit is arranged on an optical head device, the focusing characteristic on the plurality of laser beams can be improved.

Abstract: An optically-pumped semiconductor (OPS) laser includes a multilayer structure including a mirror-structure surmounted by a multilayer semiconductor gain-structure. A membrane mirror is spaced apart from the mirror structure to form a laser resonator between the mirror structure and the membrane mirror, with the gain-structure included in the laser resonant cavity. Pump light is transmitted through the membrane mirror into the gain structure. The membrane mirror includes a grating having parameters selected such that the membrane mirror has different reflectivities at the wavelength of the laser in two orthogonally-oriented planes of polarization. The membrane mirror is axially movable along the resonator axis for varying the resonator length to select the wavelength of the single lasing mode.

Abstract: A laser array and method of making same has precision fiducial marks that aid in the alignment of the laser array. The invention requires forming additional optical features adjacent to the laser array that is used to write fiducial marks on an opposite surface in the medium containing the laser array. Fiducial marks are formed when high intensity collimated beams of light are directed through the optical features onto a treated portion of the transparent medium. Fiducial accuracies of 1 micron are possible by using this approach.

Abstract: The device comprises several resonant cavities of different lengths, in order to emit over several different wavelengths, depending on the length of the corresponding cavity. Each resonant cavity comprises a convex cap, preferably hemispherical, of transparent material for the emitted wavelengths. The convex cap defines, at one end of the cavity, an excessive thickness, of length li, which enables to vary the length of the corresponding cavity. The caps are, preferably, obtained by remelting cakes of preset dimensions, for example of selenium, on the material forming the cavities.

Abstract: Two or more laser diodes are combined by crossing their cavities, and the multiple lasers share a common outcoupling aperture. By controlling the quantum wells in the active region, crosstalk between the devices can be eliminated. The multiple devices can also be made to crosstalk, and can be made coherent with respect to one another by mixing enough photons to phase lock the devices.

Abstract: Monolithic structures for coupling either a vertical-cavity surface emitting laser (VCSEL) or a half-cavity vertical cavity surface emitting laser into a single-mode optical fiber are provided. The monolithic structures include a coupler, which comprises a pellet comprising a piece of solid silica glass and a length of graded-index multimode fiber serving as a gradient index lens. Various coupler configurations are provided for handling the cases in which the diameter from the VCSEL is larger or smaller than the diameter of the single-mode fiber. In the case of the half-cavity VCSEL, the single-mode optical fiber including therein an embedded Bragg grating, the Bragg grating reflecting the seed light from the VCSEL, thus providing feedback for laser action. The fiber-coupled laser evidences increased mode field diameter and single-mode operation.

Abstract: The present invention contemplates a method and apparatus to generate a laser probe beam free of speckles. The present invention employs a holographic phase plate inserted in a laser beam path to modulate the relative phase across the beam. The holographic phase plate is designed to optimize the phase modulation across the beam while to minimize the degradation of the beam quality. The modulated laser beam has only a small and confined divergent angle and can then be refocused or collimated into a narrow and near collimated probe beam. The present invention further rotates the holographic phase plate to randomize the speckles in a time sequence. As a result, the probe beam preserves substantially the beam quality of a laser and produces substantially no speckles on image of its, intersection with a surface or material.

Abstract: An optical pickup device includes a semiconductor laser, a collimater lens, an optical member, a halfmirror, an objective lens, a collecting lens and a photodetector. The collimator lens collimates a laser beam from the semiconductor laser. The optical member diffracts the laser beam which has been collimated by the collimator lens outward along the direction of the shorter diameter of the laser beam, and emits a laser beam having a prescribed aspect ratio. The halfmirror passes the laser beam from optical member and reflects one half the light reflected from a signal recording surface of an optical disk to the photodetector. The objective lens focuses the laser beam on the signal recording surface. The collective lens collects the laser beam from the halfmirror. The photodetector detects the laser beam.

Abstract: The present invention provides for the coupling of laser diodes into electromagnetic radiation transmitting fibers wherein coupling efficiency is improved by improving the spatial brightness of multi-mode diode lasers as they are coupled into double-clad fibers. A Bragg grating 100 is fabricated into the core 102 of a double-clad fiber 104 coupled to a multi-mode diode laser 106. The output 108 from the multi-mode diode laser 106 is coupled into the core 102 and inner cladding 110 of the double-clad fiber by proximity or by one or more focusing objectives 112. The Bragg grating 100 in the core 102 of the double-clad fiber 104 is written at the wavelength of the multi-mode diode laser 106. The original output 108 from the multi-mode diode laser 106 strikes the Bragg grating 100 which reflects feedback 114 back to the diode laser 106.

Abstract: The invention provides a laser package having a single-mode laser diode for emitting light; a single-mode optical fiber comprising an uncoated microlens formed on an input end of said single-mode optical fiber, the microlens optically coupled to the laser diode for receiving the light, the microlens being constructed so as to reduce a level of back reflection into the laser diode so as not to disturb an operation of the laser diode, wherein a center axis of the single-mode optical fiber is co-planar with an optical axis of the laser diode; and a grating formed in the single-mode optical fiber for providing feedback to the laser diode to stabilize the emitted light from the laser diode. The single-mode optical fiber can include a length of polarization maintaining fiber between the grating and the single-mode laser diode.

Abstract: A monolithic laser configuration has a substrate, a laser diode disposed on the substrate for generating a light beam, a photodetector disposed on the substrate in the path of the light beam for receiving at least one part of the light beam, and a deflection device disposed on the substrate for deflecting the light beam substantially perpendicularly to the substrate surface. The monolithic laser configuration can advantageously be used in a coupling module with a plastic SMT housing of a standard configuration, it being possible to produce the optical access through an opening in the leadframe of the coupling module.

Abstract: A laser tuning mechanism which embodies “spectrally dependent spatial filtering” (SDSF) and contemplates two key elements of the tuning mechanism. The first element of the SDSF tuning mechanism is a spectrally dependent beam distortion (i.e. alteration of the amplitude and/or phase profile of the beam) provided by an SDSF tuning element in a laser cavity. The second element of the SDSF tuning mechanism is an intracavity spatial filter which makes the round trip cavity loss a sensitive function of both beam distortion and cavity alignment. Such a laser can be aligned so that a specific beam distortion, which is provided by the SDSF tuning element at a tunable wavelength, is required to obtain minimum round trip cavity loss, thereby providing tunable laser emission. A preferred embodiment of the SDSF tuning mechanism is an external cavity semiconductor laser having a zeroth order acousto-optic tuning element.

Abstract: A means for optically coupling a semiconductor laser to an optical fiber is disclosed. In one embodiment, a volume phase holographic element is disposed on a light-emitting surface of a semiconductor laser. The volume phase holographic element acts as an aberration-corrector for a lens that is disposed between the semiconductor laser and the optical fiber. In this way, an inexpensive lens that is not aberration free can be used. In some embodiments, the volume phase holographic element converts a Gaussian light beam emitted by the semiconductor laser into an annular beam that is more suitable for long distance transmission in multimode fibers.

Abstract: A light source apparatus equipped with a GaN type semiconductor laser, wherein deformation of the shape of the light spot due to fluctuations in the drive current of the light emitting element is prevented, is provided. A light source apparatus equipped with a GaN type semiconductor laser is provided with a slit panel or other spatial filter for eliminating stray light, which amounts to 20% or less of the total output occurring when the GaN type semiconductor laser is driven at maximum output, from the light emitted from the GaN type semiconductor laser.

Abstract: We disclose a new structure that allows the creation of sharp and asymmetric lineshapes in optical microcavity systems. In this structure, the response function can vary from 0% to 100% in a frequency range that is narrower than the full width of the resonance itself. Therefore, an optical switch, based upon this structure, may require far less frequency shift to operate, compared with conventional microcavity-based structures. This method may also be used to improve the sensitivity of optical sensors based upon microcavity structures.

Abstract: A laser diode collimating system comprises a collimating lens for receiving a laser beam from a laser diode LD. First and second orthogonally arranged cylindrical lenses are provided through which the laser beam passes. The cylindrical lenses are positioned so as to have a substantially common focal plane and operate substantially independently on the divergence and/or convergence of the laser beam in its fast axis and slow axis directions respectively. A convex lens, through which the beam passes, has a focus lying in the said common focal plane.

Abstract: The present invention relates to a continuously tuneable free space laser. An amplifying medium in free space is placed inside a Fabry-Perot cavity consisting of two reflectors. One of these two mirrors being partially translucent and makes up the output mirror of the laser. According to the invention, the output mirror is inserted into the core of a monomode optic fiber that constitutes an output optic fiber and a lens placed in the Fabry-Perot cavity. This ensures coupling in this fiber of the luminous fluxes transmitted by the amplifying medium and the second reflector is self-aligned.

Abstract: A bearing for a rotatable window in a laser enclosure includes a bearing shaft rotatably fitted in a bearing sleeve. The bearing shaft is in the form of a hollow cylinder and the window is held in the bearing sleeve. The bearing shaft and the bearing sleeve each include a circumferential generally V-shaped groove. The grooves are aligned with other and a coil spring in the form of a continuous loop is located in the grooves. Coils of the coil spring make point contact with sloping surfaces of the grooves and are under radial compression. This provides an axial and radial preload for the bearing. The radial and axial preload retain the bearing shaft in the bearing sleeve while maintaining alignment of the window as the bearing shaft is rotated.

Abstract: The present invention provides a method and apparatus for transmission of optical communications. The present invention provides an optical transmitter which includes a control circuit to enhance the stability of output power levels, a modulator circuit with precise impedance matching for high frequency performance, and an optical coupling mechanism that relaxes the alignment tolerances between the laser and the fiber and decreases the sensitivity of the gain medium to feedback from devices coupled to the fiber. These features allow the transmitter to deliver an optical output beam which can be modulated over a wide range of frequencies, duty cycles and amplitudes with very precise definition of the rising and falling edges of the waveform. In combination these features result in an optical transmitter that may be fabricated with relatively low cost and a reduced form factor when compared with prior art optical transmitters.

Abstract: A laser device has a laser diode with an optical resonator. The resonator has an exit side for emitting light into an optical system. A monitor diode is provided and has a light-sensitive face for measuring optical quantities of the laser diode. The light-sensitive face of the monitor diode is optically coupled to a backside of the laser diode, on the other side from the light exit side of the resonator, the backside also emitting light. This configuration permits a space-saving SMD layout for the laser device.

Abstract: A surface emitting semiconductor laser of the present invention has a resonator including a pillar-form portion, and an emission portion having a convex lens form is formed on an upper surface of the pillar portion. The pillar-form portion has an embedded structure, with the periphery of the pillar-form portion embedded in an embedding layer. The embedding layer is formed of a substance having non-affinity with the material used to form the emission portion.

Abstract: A display apparatus, includes a laser light source for emitting a light beam; a beam expander for expanding the light beam; a spatial light modulator; beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator, the beam shaping optics including a fly's eye integrator having an array of lenslets; and a moving diffuser located in the laser beam between the laser light source and the spatial light modulator.

Abstract: A light source device has a semiconductor laser for emitting an elliptical divergent beam having a light intensity distribution in an elliptical form; and a beam shaping element for converting an elliptical divergent beam from said semiconductor laser into an approximately circular divergent beam having a light intensity distribution in an approximately circular form; wherein the beam shaping element has a first surface formed of a cylindrical surface and a second surface formed of an anamorphic surface, in order from said semiconductor laser side, and satisfies the predetermined conditional expressions.

Abstract: A tunable laser comprised of a gain section for creating a light beam by spontaneous emission over a bandwidth, a phase section for controlling the light beam around a center frequency of the bandwidth, a cavity for guiding and reflecting the light beam, a front mirror bounding an end of the cavity, and a back mirror bounding an opposite end of the cavity. The back mirror has a &kgr;effB approximately equal to &agr;Tune, where &kgr;effB is an effective coupling constant and &agr;Tune is the maximum amount of propagation loss anticipated for an amount of peak tuning required, and a length of the back mirror is made to produce greater than approximately 80% reflectivity.

Abstract: A hermetically sealed photonic device submount includes a photonic device mounted on a substrate material and sealed in a flexible hermetic seal. In one configuration, the photonic device is configured to emit or to receive light through the substrate material. In this configuration, the photonic device is covered with an adhesive layer and a metal layer deposited onto the adhesive layer. In another configuration, the photonic device is configured to emit or to receive light in a direction substantially vertically upward from the substrate material. In this configuration, a cover is placed over the photonic device, then the cover is hermetically sealed to the substrate material with an adhesive layer and a metal layer depositd onto the adhesive layer. In both configurations, the photonic device submounts are hermetically sealed according to various aspects of the present invention on the substrate material without using a separate package.

Abstract: A folded cavity laser for generating a laser beam, includes a substrate provided with a distributed Bragg reflector (DBR); an active medium formed above the DBR for amplifying the laser beam; a first and a second mirrors formed on sides of the active medium, respectively, for making a horizontal cavity and for reflecting the amplified laser beam to the DBR; and a microlens, formed on the substrate opposite the DBR, for making the amplified laser beam astigmatic after passing therethrough.

Abstract: A high power diode laser array system utilizes an external cavity to narrow the spectral width of a high power diode laser array to change the output power normally produced by the diode array from a broad spectrum to a very narrow spectrum. The power output of the laser array system is concentrated over a narrow spectral range which falls within the useable range for particular applications such as optical pumping of noble gas samples for magnetic resonance imaging. The output of the array is received by a collimating element, which collimates the light in a direction perpendicular to the direction of the length of the array of emitters and directs the light on a beam path to a diffraction grating which is oriented at an angle to the incident beam.

Abstract: A semiconductor laser module comprises a laser diode that emits light in a frontward direction and a rearward direction, an optical fiber that transmits the light emitted in the frontward direction by the laser diode, and a monitor photodiode that receives the light emitted in the rearward direction by the laser diode. The monitor photodiode is characterized in that its sensitivity characteristic has a negative temperature coefficient.

Abstract: A surface emitting laser is coupled to an external modulator. The laser and the modulator aligned by photolithographically defined features. In a preferred embodiment, the electromagnetic output of the laser is reflected at a right angle from a mirror mounted on a substrate. The reflected output enters a modulator mounted on the same substrate as the mirror. A circuit coupled to the modulator controls the modulation undergone by the electromagnetic output. The modulated output is coupled to an optical fiber for transmission.

Abstract: A laser module wherein a platform supports an optical fiber component having a cantilever portion. The cantilever portion has a length sufficient to provide alignment of the optical fiber component with a laser. Alignment may be, for example, in an X-direction, Y-direction, or both. The platform may be housed in a compliant case. Also disclosed is a method of monitoring the coupling efficiency between, and the alignment of, the laser and optical fiber component.

Abstract: The present invention relates to systems of microneedle arrays to align and form optical components. Active components such as lasers are combined with optical fibers. Microneedles are fabricated using techniques such as laser drilled Kapton, and combined with optical fiber, using bump bonding and UV curing adhesives to manufacture a variety of optical components.

Abstract: An optical semiconductor device (100) includes an optical semiconductor structure (120) and a light reflector (110) monolithic with the optical semiconductor structure (120). The light reflector (110) is disposed to direct light to and/or from the optical semiconductor structure (120).

Abstract: A highly compact laser scanner with no moving parts includes a vertical cavity surface emitting laser (VCSEL). A microlens is mounted directly to the light emitting surface of the VCSEL via flip chip bonding. The VCSEL array may be one or two dimensional. The laser array may be used in a variety of applications including free space optical communications.

Abstract: A laser diode module includes a laser diode, a lens located on an optical path of light emitted from the laser diode, and an optical fiber located to receive the emitted light concentrated by the lens. The optical fiber includes a fiber grating having a reflection center wavelength greater than the cutoff wavelength of the laser diode and having a half-width of reflection spectrum ranging from twice the spacing of longitudinal modes of the laser diode to 10 nm.

Abstract: An F2-excimer laser has multiple closely-spaced spectral lines of interest around 157 nm, and one of the lines is selected by wavelength selection optics. The wavelength selection optics of a first preferred embodiment include a birefringent Brewster window enclosing the laser gas volume of the discharge chamber. The window preferably comprises MgF2 and is located at one end of the discharge chamber. One line is selected of the two when the optical thickness of the window is selected in coordination with rotatably adjustable, orthogonal refractive indices of the window. The transmissivity of the window is dependent on the orthogonal refractive indices and the optical thickness of the window. The wavelength selection optics of a second preferred embodiment include are at least partially within the laser active volume. In this way, line selection is performed in a manner which optimizes the combination of optical and discharge efficiency, resonator size and cost.

Abstract: A line narrowed laser system having a spatial filter to filter light at wavelengths greater and/or smaller than a desired range of wavelengths. The laser system is line narrowed with a line narrowing mechanism having a dispersive element which disperses laser light into wavelength dependent directions. By spatially filtering the resulting beam the bandwidth of the beam can be reduced substantially. There is also a reduction of beam energy as a result of the spatial filtering but this reduction is substantially less than some other known techniques for reducing bandwidths. A preferred spatial filter, for reducing the bandwidth of a line narrowed gas discharge laser, includes two cylindrical mirrors separated by a distance equal to their focal lengths with a slit aperture positioned at the common focal line.

Abstract: An apparatus, system, and method for precision positioning and alignment of a lens in an optical system, wherein a first support for coupling to the peripheral edge of the lens is connected to a concentric second support using a plurality of positioning devices. At least one positioning device is configured to move the first support in an axial direction relative to the second support. Each positioning device comprises a lever, an actuator, and a flexure. The lever has a pivot point and is mounted on the second support. The actuator is connected to the lever and used to operate the lever about its pivot point. The flexure has a first end connected to the lever between the actuator and the pivot point. A second end of the flexure is connected to the first support. A second positioning device is used to move the first support relative to the second support in a direction substantially perpendicular to the axial direction.

Abstract: A laser cavity assembly for high power optical range-finders consisting of two rods of lasing material co-axially mounted on a thin substrate of the same or thermally equivalent material, selected end-faces of the rods being bonded to layers or wafers of optical materials chosen from a group consisting of materials used in Q-switches, filters, matching transformers, linear polarizers and reflecting mirrors.

Abstract: An excimer or molecular fluorine laser includes a discharge chamber filled with a gas mixture, multiple electrodes within the discharge chamber connected to a power supply circuit for energizing the gas mixture, and a resonator including the discharge chamber and a pair of resonator reflectors for generating an output laser beam. The resonator includes an interferometric device, which may be a resonator reflector such as an output coupling interferometer or HR reflector, or a transmissive intracavity component, including a pair of opposing reflecting surfaces tuned to produce a response maximum at a selected wavelength for narrowing a linewidth of the output laser beam. One of the pair of opposing reflecting surfaces is preferably configured such that the opposing reflecting surfaces of the interferometer have a varying optical distance therebetween over an incident beam cross-section which serves to suppress at least one side band or outer portions of the response maximum to reduce spectral purity.

Abstract: A semiconductor laser module including a semiconductor laser device having an integrated diffraction grating configured to output a multiple mode laser beam in the presence of a driving current, an optical fiber configured to guide the multiple mode laser beam to an output of the laser module, and an optical attenuation device configured to attenuate the multiple mode laser beam by an amount sufficient to provide a predetermined output power from the output of the laser module. The optical attenuation device may be an optical coupling lens offset from an optimum coupling position by an amount sufficient to provide the predetermined output power, or an optical attenuator interrupting the optical fiber and configured to attenuate the multiple mode laser beam by an amount sufficient to provide the predetermined output power.

Abstract: An optical transmitter is equipped with a laser diode and a light detector provided on a packaging base, in which the light detector has a semiconductor substrate side arranged on a packaging base side, a semiconductor junction plane, a side surface which is roughly orthogonal to the semiconductor junction plane, and a facing surface which faces the side surface, wherein the facing surface is partially or completely inclined to reflect the output light from the laser diode incident from the side surface to the semiconductor junction plane of the light detector.

Abstract: An illumination system includes a multimode diode-laser and two optical fibers. Light from the diode-laser is directed into the first optical fiber having a first core diameter. The light exits the first optical fiber and is directed by an optical system into a second optical fiber having a core diameter greater than the first optical fiber and a numerical aperture greater than the numerical aperture of the optical system. A light beam exiting the second optical fiber has an intensity distribution having sharp edges and uniformity better than plus or minus ten percent over a central ninety percent of the beam.

Abstract: A method and apparatus is provided that enables an IBC system to operate over a large field angle. As a consequence, wide laser gain arrays can be used providing greater control over the output power and the bandwidth of the IBC system. The IBC resonator cavity is comprised of a reflector, preferably deposited on the back facets of the gain element array, and an output coupler. Interposed between the array and the output coupler is a wavelength dispersive element, such as a diffraction grating, and a collimating optic. A lens system, comprised of either a single cylindrical lens, a single cylindrical lens in combination with an array of orthogonally positioned cylindrical lens elements, or an array of individual lens elements, is located between the laser gain array and the collimating optic. At a minimum, the lens system reduces the divergence of the light from each emitter in the fast axis, thus allowing smaller, less optically complex optics to be used for the IBC resonator optics.

Abstract: A narrow band excimer laser and a wavelength detecting apparatus are suitable for use as a light source of a reduction projection aligner of a semiconductor device manufacturing apparatus. In the excimer laser, the ruling direction and the beam expanding direction of a prism beam expander are made substantially coincide with each other, and a polarizing element causing selective oscillation of a linearly polarized light wave substantially parallel with the beam spreading direction of a prism beam expander is contained in a laser cavity. A window at the front or rear side of a laser chamber is disposed such that the window make a Brewster's angle with respect to the axis of the laser beam in a plane containing the beam expanding direction of the prism expander and the laser beam axis.