Abstract: A laser-radiation source includes a laser delivering an output beam, a lens, and an optical arrangement for dividing the output beam into a main beam and an auxiliary beam. The main and auxiliary beams are coupled by the lens into entrance faces of respectively a main optical fiber and an auxiliary optical fiber. The entrance face of the main optical fiber is located on the optical axis of the lens. The entrance face of the auxiliary optical fiber is laterally displaced from the optical axis of the lens.

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: An actuator for continuously aligning the primary mirror relative to the scraper the other resonator mirrors and the feedback mirror in a high power laser resonator, comprised of extended portions of the resonators primary mirror, feedback mirror and scraper mirror for a low power laser beam to travel parallel to but offset from the high power laser beam for aligning the mirrors. The low power laser beam is used to measure the position of the mirrors in the resonator. The low power beam is split into a beam which is incident on a quadrant cell for measuring the tip and tilt of the feedback mirror relative to the primary mirror and a beam which measures the translation of the feedback mirror relative to the primary mirror. A controller receives the data form the quadrant cells and sends signals to actuators on one mirror to move it relative to the other thus keeping the mirrors in constant alignment.

Abstract: A compactly constructed configuration for coupling radiation into an optical fiber in a highly effective manner has a semiconductor laser with a radiation exit window, and an optical fiber having a radiation entry end. The radiation exit window of the semiconductor laser faces the radiation entry end of the optical fiber. A resonator is provided and has an end mirror and an output mirror, between which the semiconductor laser is disposed. The output mirror of the resonator is formed by the optical fiber. An optical device is disposed between the semiconductor laser and the optical fiber and serves for imaging only the fundamental mode of the radiation of the semiconductor laser onto the radiation entry end of the optical fiber.

Abstract: A light emitting module packaging two light sources emitting two light beams of different wavelengths, and a compatible optical pickup device adopting the module are provided. The light emitting module includes a base, first and second light sources installed on the base, for emitting laser beams in different wavelength regions, a beam splitter and a monitoring photodetector for monitoring the optical outputs of the first and second light sources by receiving the beams emitted from the first and second light sources and split from the beam splitter in one direction.

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: The present invention is directed to a large area single-mode (LASM) laser system that provides a laser having a wider gain region and thus a higher power output without introducing the second transverse mode into the optical signal. The laser system of the present invention also reduces the laser junction temperature, thereby improving the reliability of the laser and of laser systems constructed therefrom. The present invention also provides a stabilized spectrum in an optical signal by providing a means for feeding back from an external fiber grating to the laser only a single mode and a selective spectrum of an optical signal generated by the laser.

Abstract: The present invention is an optical turn used to the monitor the output of a light source such as a VCSEL. Light incoming to the optical turn is reflected off of a totally internally reflecting surface towards a window-mirror, where the light is partially routed to an output lens, and partially diverted to a monitor lens where the diverted light can be focused onto a monitoring device, such as a photodiode. In an alternative embodiment of the present invention, the optical turn is modified to monitor an incoming light array. In another alternative embodiment, the optical turn monitors an incoming light array, and further includes a zigzag multiplexer that is used to carry out Coarse Wavelength Division Multiplexing (CWDM). CWDM is the combination of different wavelengths of light into one beam.

Abstract: If an optical path length of an optical system is reduced and a length of a laser light on an irradiation surface is increased, there occurs curvature of field which is a phenomenon that a convergent position deviates depending on an incident angle or incident position of a laser light with respect to a lens. To avoid this phenomenon, an optical element having a negative power such as a concave lens or a concave cylindrical lens is inserted to regulate the optical path length of the laser light and a convergent position is made coincident with a irradiation surface to form an image on the irradiation surface.

Abstract: An optical configuration to illuminate an etalon in a laser wavemeter with a minimum level of light intensity. The system includes optical components to direct a portion of the laser output beam representing the entire cross section of the beam, through an etalon positioned in an etalon housing and onto a photodetector. A first lens condenses the size of the beam sample, and a second lens re-collimates the beam which then passes into the etalon housing, ensuring that all of the spatial components of the beam are adequately sampled. A diffractive diffusing element is incorporated into the optical path. In a preferred embodiment, the diffractive diffusing element is placed within the etalon housing between said plano-concave lens and the etalon. In another preferred embodiment, the diffusing element is located up stream but outside the housing in the optical path.

Abstract: Circuitry for controlling a diode optically coupled to an optical fiber suitable for transmitting digital light signals therethrough. The circuitry includes a temperature compensated driver when operating in the transmit mode and receiving circuitry for conditioning and amplifying electrical signals generated by the diode when it operates in a photodetection mode. A sweep circuit is provided for isolating amplifiers in the receiving circuitry and for discharging residual charge left in the diode during the transmission mode thereby reducing the signal-to-noise ratio.

Abstract: An apparatus for frequency conversion of a laser (1) in which one or more non-linear crystals (5, 6) are arranged in the laser beam (3), and the necessary power density is produced by an arrangement of a dedicated focussing lens (4), in the region of the focal point (14), with a collimator, which minimizes the divergence of the laser beam (3), an optical corrector, which shapes the cross section of the laser beam (3). A single focussing lens (4) is provided behind which a corrective lens (7) is arranged at an angle to the optical axis and at a distance which corresponds roughly to the sum of both focal lengths such that the focussing lens (4) and the corrective lens (7) form the collimator and the corrective lens (7) also functions as a corrector. In this way a laser is produced which is characterized by small size and a simple and economical construction.

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 laser marker includes a collimator lens converting laser light emitted from a broad area semiconductor laser into substantially parallel beams of light, a cylindrical concave lens permitting to pass therethrough the laser light having passed through the collimator lens and being perpendicular to a plane of an active layer of the semiconductor laser, the cylindrical concave lens serving as a concave lens for the laser light having passed through the collimator lens and being parallel to the plane of the active layer, a cylindrical convex lens permitting to pass therethrough the laser light having passed through the concave lens and being perpendicular to the plane of the active layer of the semiconductor laser, the cylindrical convex lens serving as a convex lens for the laser light having passed through the collimator lens and being parallel to the plane of the active layer, and a focusing lens focusing the laser light having passed through the cylindrical convex lens.

Abstract: Methods of and systems for illuminating objects using planar laser illumination beams having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of image formation and detection modules employed in such systems. Each planar laser illumination beam is produced from a planar laser illumination beam array (PLIA) comprising an plurality of planar laser illumination modules (PLIMs). Each PLIM comprises a visible laser diode (VLD, a focusing lens, and a cylindrical optical element arranged therewith. The individual planar laser illumination beam components produced from each PLIM are optically combined to produce a composite substantially planar laser illumination beam having substantially uniform power density characteristics over the entire spatial extend thereof and thus the working range of the system.

Abstract: A laser is disclosed for generating radiation having narrow band width and high spectral purity. The laser comprises a cavity (10) containing a lasing medium (12) in between two reflective elements (14, 16) and at least one wavelength-selective element (16) for extracting (coupling-out) radiation from the resonator. In one embodiment, said element for extracting radiation from the resonator comprises a prism (30; 60; 70) which is wavelength-selective on the basis of interference. According to another embodiment, the element (16′) for extracting radiation from the resonator comprises two transparent plates (40, 42) each of which is, at one side, partly reflective. According to another embodiment, said wavelength-selective element (50, 52) for extracting radiation from the resonator comprises an angled mirror (50) and a plate (52) arranged in front of that mirror.

Abstract: To restrain nonuniformity of irradiation when a linear laser beam is irradiated by scanning the beam, linear laser pulses are irradiated by scanning the pulses in an oblique direction by which irradiation is carried out without overlapping peaks periodically present in the longitudinal direction of the linear laser beam and accordingly, nonuniformity of irradiation can be restrained.

Abstract: An apparatus for combining the outputs from multiple gain elements of an array within a single resonator cavity to achieve a predetermined spectral output or improved output power is provided. The 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 gain element array and the output coupler are an optical element and a reflective diffraction grating. The optical element can be comprised of either a GRIN lens or a uniform index element with a shaped, reflectively coated back surface. The output coupler can be directly coupled to an optical fiber, for example by burying the output coupler into the entrance aperture of the fiber.

Abstract: Method and apparatus for integrating a VCSEL with a SOA, comprising positioning a collimating lens adjacent to the output of the VCSEL, positioning a focusing lens adjacent to the input of the SOA, and positioning a movable lens between the collimating lens and the focusing lens, where the movable lens has a focal length significantly longer than the focal length of the focusing lens; and moving the movable lens relative to the focusing lens so as to adjust the focusing spot on the input of the SOA.

Abstract: A partial reflective laser output device comprising a partial reflective unit mounted on a laser output device (such as a vertical cavity emitting laser), the partial reflective unit allowing the laser beam emitted from the laser output device to be partially reflected while the rest penetrating through. On one hand, this device decreases the intensity of output laser light so as to comply with the eye safety standard; the reflected light is absorbed by a photodiode (PD) to perform auto power control on the laser output device on the other. In addition, by adjusting the tilting angle of the partial reflective unit or making a curvature thereon, the reflected light can have no destructive interference with the output light and can even be focused onto the PD so that there would be no relative intensity noise problem and the size of the PD can be made smaller to lower the cost.

Abstract: A method and a system for generating grating images with an improved speed is disclosed. The system utilizes a coherent light source for providing a coherent beam L, an exposure control device for controlling the exposure of the coherent beam L, a beam guiding device for controlling the pitch and the orientation of each grating, a symmetrical beam generating device for splitting the coherent beam L into two symmetrical coherent beams, a local scan device for allowing the two coherent beams to intersect and form a standing wave, at different position in a small local scan area in order to combine different gratings in the local scan area, a photosensitive material for recording the standing wave, and a supporting device for supporting and moving the photosensitive material so as to combine different local scan area, and obtain a large scale grating image.

Abstract: [Summary]

Abstract: A Low loss resonator is provided, which consist of two confocal parabolic reflectors and two flat reflectors forming a closed cavity capable of direct to the output window, stimulated emissions generated in the axes parallels to the axis of symmetry and the radial axes, being the point of origin of the radial axes the common focal point of the parabolic reflectors. The Low loss resonator has the advantage of extract energy from the active medium more efficiently than cylindrical shaped resonators.

Abstract: A passive Q switch. The inventive Q switch includes a first wedge of material adapted to absorb electromagnetic energy. The first wedge has a first thickness on a first end thereof and a second thickness on a second end thereof diametrically opposite the first end. The first wedge has a first surface connecting the first and second ends and a second surface connected the first and second ends. The second surface is slanted relative to the first surface. A second wedge of material is included in the inventive passive Q switch. As per the first wedge, the second wedge has a first thickness on a first end thereof and a second thickness on a second end thereof diametrically opposite the first end. The second wedge has a first surface connecting the first and second ends and a second surface connecting the first and second ends. The second surface is slanted relative to the first surface.

Abstract: Laser light emitted from an LD apparatus is concentrated and applied onto a laser light path region A of a slab-shaped YAG crystal 21 and the neighborhood thereof with the use of a concave lens and a pair of reflecting mirrors, a duct lens, or a plurality of cylindrical lenses, whereby a concentrated applied light intensity distribution in the side surface width direction (y-axis direction) of the slab-shaped YAG crystal is formed as a double-peak distribution having maximum values P1 and P2 at opposite end portions A1 and A2 of the laser light path region of the slab-shaped YAG crystal or in the neighborhoods thereof.

Abstract: An optical membrane device and method for making such a device are described. This membrane is notable in that it comprises an optically curved surface. In some embodiments, this curved optical surface is optically concave and coated, for example, with a highly reflecting (HR) coating to create a curved mirror. In other embodiments, the optical surface is optically convex and coated with, preferably, an antireflective (AR) coating to function as a refractive or diffractive lens.

Abstract: The present invention relates to laser devices with increased cooling capability by means of largely extended cooling surfaces contacting the laser active medium. According to the present invention there is provided a laser device comprising a large active volume in conjunction with a compact structure of the device and outputting single mode radiation. The laser device according to the present invention comprises the following features. A laser active medium, an optical resonator system defining an optical axis, exciting means for exciting said laser active medium and enabling a stimulated emission of radiation of said laser active medium, and cooling means, having first and second cooling elements arranged in spaced opposing relationship with surfaces facing each other, wherein said laser active medium is provided between said cooling elements along said optical axis.

Abstract: In a solid laser with one or several pump light sources whose radiation is fed into a laser crystal with a high light density, a laser crystal and an optical resonator are provided. Each pump light source is formed of several laser diodes. The light from the laser diodes of each pump light source is in-coupled by means of a single optical waveguide.

Abstract: A mode locked semiconductor laser that can generate relatively high-power output pulses. The semiconductor mode locked laser is formed from an array of optical amplifiers that are coupled to a common resonant cavity by way of an optical channelizer or wavelength division multiplexer (WDM). By utilizing an array of optical amplifiers, the output pulses will have a relatively higher power than known mode locked lasers. As such, the mode locked semiconductor laser in accordance with the present invention does not depend on the power handling capability of the individual optical amplifiers and allows the average output power to be scaled, for example, up to the kilowatt range using semiconductor optical amplifiers. A mode locked laser in accordance with the present invention can be implemented with active mode locking, passive mode locking or a hybrid of the two. In embodiments utilizing active mode locking, the output pulse shape can be tailored by the amplifier drive current distribution.

Abstract: An object is to obtain an even energy distribution of a laser beam in one direction, thereby conducting a uniform laser annealing on a film. A laser irradiation apparatus comprising: a lens for dividing a laser beam in one direction; and an optical system for overlapping the divided laser beam, characterized in that the shape of the laser beam entering into the lens has edges vertical to the above-mentioned direction.

Abstract: The present invention provides an infrared laser optical element, in which a dense optical thin film with a low laser absorption and high moisture resistance is formed on the surface thereof, and a manufacturing method for the same. In this infrared laser optical element, the main surface of the optical substrate is smoothed, a BaF2 film formed on said main surface thereof and then a ZnSe film formed on said BaF2 film. The smoothing treatment for the main surface of the optical substrate is carried out by irradiating Xe gas ion beams. The BaF2 and the ZnSe films formed on said BaF2 film are formed on the main surface of the optical substrate, which has been smoothed, by Xe gas ion assisted vapor deposition. Superior performance can be achieved if the series of treatments are carried out under the specified conditions.

Abstract: A semiconductor laser module includes a semiconductor laser element, a lens system for condensing laser light onto an optical fiber, a band-pass filter for transmitting laser light having a predetermined wave length, and an optical fiber. The band-pass filter is held by a mechanism for tilting the band-pass filter at a desired angle relative to the traveling direction of the laser light. A reflecting element for reflecting part of the incident laser light is provided in a wave guide of the optical fiber so that a resonator is formed between the reflecting element and the emitting end face of the semiconductor laser element. The reflecting element utilizes a difference in refractive indices of materials forming the reflecting element to provide reflection. Preferably, control of the tilting mechanism is conducted via a control unit in response to an output from a thermal sensor.

Abstract: A laser beam in the ultraviolet region is generated at high power for along period. A green laser beam generated by a laser oscillator comes incident into a resonator from behind a first curved mirror, and circulates there, reflected by each mirror. By passing a barium borate crystal, it causes a secondary harmonic (a laser beam in the ultraviolet region) to be generated, which is taken out of the resonator via a second curved mirror. The beam waist of the laser beam passing the barium borate crystal is set to 46 &mgr;m, about double the conventional thickness, by adjusting the distance between the first curved mirror and a second flat mirror. As a result, the power density of the laser beam in the barium borate crystal is reduced to ¼ of the value according to the related art, and it is made possible to avoid rapid degradation of the barium borate crystal by excessive squeezing of the laser beam.

Abstract: An apparatus and method for coupling an array of light beams extending predominantly in one direction into an output port. The light beams are rearranged into a desired shape which extends more equally along two directions than does incident array of light beams. The operation of the rearranging is wavelength insensitive. The rearranged light beams are focused onto the output port. For output ports having a small interface, the focal length of a lens focusing the rearranged light beams to the output port should be as short as possible.

Abstract: A laser radiating optical system is composed of a laser diode and two mutually independent shaping optical systems. The laser diode emits a laser beam that has a Gaussian intensity distribution and that diverges with a large divergence angle in a first direction and with a small divergence angle in a second direction perpendicular to the first direction. The first shaping optical system makes the intensity distribution even with respect to the first direction, and the second shaping optical system makes the intensity distribution even with respect to the second direction. The shaping optical systems are each composed of a collimator lens and a diffractive element for shaping, and the diffractive elements of the two shaping optical systems are given substantially equal numerical apertures.

Abstract: There is provided a beam homogenizer which can unify the energy distribution of a linear laser beam in a longitudinal direction. In the beam homogenizer including cylindrical lens groups for dividing a beam, and a cylindrical lens and a cylindrical lens group for condensing the divided beams, the phases, in the longitudinal direction, of linear beams passing through individual cylindrical lenses of the cylindrical lens group for condensing the divided beams are shifted, and then, the beams are synthesized, so that the intensity of interference fringes of the linear beam on a surface to be irradiated is made uniform.

Abstract: A double-pass birefringent filter apparatus comprises an external-interface apparatus (illustratively including of a beam-displacer element and a waveplate element); a birefringent filter comprised of a series of several birefringent waveplates; and a wrap-around unit (illustratively comprised of a beam-displacer element and a retro-reflector). In response to an input beam received at the external-interface apparatus, the double-pass birefringent filter forms two output beams having complimentary intensities which vary periodically with frequency.

Abstract: In a solid-state laser in which a gain crystal is polished to have the Brewster angle or a solid-state laser comprising a dichroic concave mirror to which light enters at an incidence angle which is not zero, astigmatism generally occurs in pumping light. By tilting a focusing lens for pumping light with respect to the optical axis of the pumping light, the astigmatism is compensated. The tilting angle is determined in such a manner that synthetic focusing points in the sagittal and tangential planes, of a series optical system of a focusing lens, a dichroic concave lens, and a gain crystal are calculated and the focusing points almost coincide with focusing points in a cavity mode.

Abstract: A laser beam having a high power and preferable quality is obtained by a laser using a laser medium having a wide active region or a large mode volume. The laser includes a laser source, first and second resonator mirrors as a laser resonator optical system, an array illuminator optical system which is placed within the resonator optical system and places, at even spacing in a plane perpendicular to an optical axis of the resonator, complex amplitude distributions including only a fundamental transverse mode in a uniform phase similar to a fundamental transverse mode component of a laser beam emitted from the laser beam source. A higher-order mode component is diffracted in an angle larger than its diffraction angle and eliminated outside the resonator.

Abstract: In a device for optical coupling of a solid-state laser to an optical fiber, an anamorphic lens system is arranged between the output face of the solid-state laser and the input face of the optical fiber, the lens system converting differing apertures in the main sections of the solid-state laser into essentially identical apertures at the input face of the optical fiber. The lens system is composed of one anamorphic lens applied on the output face and a further lens applied on the input face.

Abstract: A method of correcting an optical axis of a laser projecting device is provided. According to this method, a cylindrical tubular member is provided, the tubular member made of a deformable material and having a base section, and a laser generation unit mounted inside the base section and adapted to project a laser beam along an optical axis. The tubular member is also provided with an extension section and a reduced-diameter circumferential groove between the base section and the extension section. Thereafter, the tubular member is rotated while projecting a laser beam from the tubular member towards a reference point in front of the tubular member that corresponds to a rotational axis of the tubular member.

Abstract: A calcium fluoride crystal in which the light transparency does not deteriorate with consecutive irradiation by high output short wavelength light over long time periods. A calcium fluoride crystal in accordance with the present invention has an internal transmittance of 70% or more for light of a 135-nm wavelength or more. A calcium fluoride crystal contains any one of strontium, aluminum, silicon and magnesium, with the strontium content ranging from 1 ppm to 600 ppm, the aluminum content ranging from 1 ppm to 50 ppm, the silicon content ranging from 1 ppm to 50 ppm, or the magnesium content ranging from 1 ppm to 10 ppm. A calcium fluoride crystal has an internal transmittance of 70% or more for light of a 135-nm wavelength or more and contains 1 ppm or less of La and 10 ppm or less of Y. An optical system for an excimer laser in accordance with the present invention comprises a lens comprising any calcium fluoride crystal set forth above.

Abstract: A cost-effective and accurate light source deice for use in an image forming apparatus and including semiconductor lasers is disclosed. The device needs only a minimum number of parts, obviates displacements during assembly, and allows collimator lenses to be adhered by photo-curable adhesive. Even when temperature around the device varies, the distance between the semiconductor lasers in a beam pitch direction varies little.

Abstract: An optical beam deflector in which a crosssection of an incident optical (e.g., laser) beam is divided into a first plurality of portions (micro crosssections) by an array of first lenses, a plurality of phases of the optical beam in the first micro crosssections are respectively modified by an array of first optical phase modulators so that a desired phase distribution is realized over the crosssection of the optical beam, and thereafter the crosssection of the optical beam is further divided into a plurality of second micro crosssections, and a plurality of phases of the optical beam in the second micro crosssections are respectively modified by an array of second optical phase modulators. An array of second lenses is provided corresponding to the second optical phase modulators to collect a plurality of portions of the optical beam output from the second optical phase modulators.

Abstract: In a solid-state laser apparatus, an optical resonator 7a is formed into a stable resonator by combing a solid-state laser medium 3a, a thermal lens F1 generated in the solid-state laser medium 3a, a wavelength-converting device 17, a thermal lens F2 generated in the wavelength-converting device 17, a reflecting mirror 4a and a harmonic mirror 19.

Abstract: An exposure apparatus includes a first dispersing element for dispersing substantially parallel laser light, from a laser, with respect to the wavelength to provide light beams of wavelength units, a first optical system for collecting each light beam of a wavelength unit from the first dispersing element, a wavelength selecting device for passing a predetermined wavelength region of light, of the light beams of wavelength units each being collected by the first optical system, a second optical system for receiving the light from the wavelength selecting device and providing parallel light beams of wavelength units, and a second dispersing element for combining the parallel light beams of wavelength units from the second optical system, the second dispersing element having substantially the same angular dispersion as that of the first dispersing element and a direction of dispersion opposite to that of the first dispersing element.

Abstract: An optical communication device which has an optical module including an optical element and a lens system optically coupled through a space and housed in a package, a supporting member for supporting the optical module, and a fixing member directly placed over the optical module for removably fixing the optical module on the supporting member, wherein the optical module is securely sandwiched between the supporting member and the fixing member, and a method of fixing the optical module for use in the optical communication device.

Abstract: A compact solid-state laser has its cavity formed by the reflection surface of a gain crystal and the reflection surface of a chirped mirror. The pumping light is incident to the cavity through the reflection surface of the gain crystal or the chirped mirror, from which the laser output is led out. Forming the cavity solely by the gain crystal and chirped mirror enables the elimination of additional component parts for the compensation of dispersion, so that the whole laser system can be made compact and, consequently, the repetition frequency can be made higher.

Abstract: Heretofore, if the beam size of the resonance mode is made small in a long resonator length, there arises a problem that the operation of the laser resonator becomes easy to be unstable and hence the adjustment thereof becomes difficult. A laser resonance includes: a laser material; a telescope for magnifying a laser beam which has been made incident from the laser material and for reducing a laser beam which has been made incident from the side opposite thereto; a flat reflecting mirror for reflecting the laser beam which has been made incident from said telescope; a telescope for magnifying the laser beam which has been reflected by the flat reflecting mirror to be reduced by the telescope and to be amplified by the laser material to be made incident thereto; and a flat reflecting mirror for reflecting the laser beam which has been made incident from the telescope.

Abstract: A semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.