Abstract: A single mode laser implementation and associated method are disclosed. The laser may accommodate a frequency multiplying material to provide an intracavity doubled single frequency laser. The laser implementation includes an input mirror and an output mirror defining a resonant cavity and a light path within the resonant cavity and between the mirrors. A lasant material is positioned in the light path for lasing at a desired fundamental wavelength and possibly other, unwanted wavelengths. A first birefringent member is also positioned in the light path for refracting in different directions the different wavelengths of light which are present along the path.

Abstract: A Yb-doped cladding pumped fiber laser includes a reflective grating located at each distal end of the laser cavity. Each reflective grating can reflect light propagating inside a fiber core and at a desired wavelength range. A plurality of band-rejecting gratings are disposed between the reflective gratings, whereby the band-rejecting gratings can couple light at an undesired wavelength range and out of the fiber core. When the band-rejecting gratings are in an end-to-end relationship, they are separated by a distance of approximately L whereby L=[(.sigma..sub.e.sup.d +.sigma..sub.a.sup.d)ln 1/T]/[n(.sigma..sub.a.sup.d .sigma..sub.e.sup.u -.sigma..sub.e.sup.d .sigma..sub.a.sup.u)], n is a concentration of ions subject to excitation, .sigma..sub.a.sup.d is an absorption cross section at said desired wavelength range, .sigma..sub.e.sup.u is an emission cross section at said undesired wavelength range, .sigma..sub.e.sup.d is an emission cross section at said desired wavelength range, .sigma..sub.a.sup.

Abstract: In order to obtain a high-power laser beam with a high beam quality with use of a small-sized and low-cost apparatus, there has been disclosed a laser resonator which is constructed so as to produce a single high-order transverse mode laser beam, and a technique for converting the laser beam with a single high-order transverse mode into a laser beam with a high beam quality. The laser resonator is provided with a regulating plate of a high-order transverse mode which is constructed so as to produce a laser beam in a single high-order transverse mode. A phase adjusting plate inverts a phase for each region of the laser beam divided depending upon a lateral mode thereof to match the phase for each region of the laser beam, and subsequently, a traveling direction of the laser beam is changed for each position thereof by means of the first binary optics element, and further, the laser beam is converted into a parallel beam by means of the second binary optical element.

Abstract: A very narrow band pulse excimer laser capable of producing pulses at a rate in the range of about 500 to 2000 Hz with enhanced energy dose control and reproducibility. A prior art burst mode "slug effect" occuring at one gas circulation time after the beginning of a burst of pulses is eliminated by the addition of a minute quantity of oxygen. In a preferred embodiment very narrow bandwidth is achieved by reducing fluorine partial pressure to less than 0.10 percent and by increasing the reflectance of the output coupler to greater than 25 percent. In a preferred embodiment, prior art fused silica beam expansion prisms used in the prior art line narrowing module were replaced with calcium fluoride prisms.

Abstract: A laser crystal (25) having a relatively short optical length functions as a seed laser (1) and simultaneously establishes the wide separation between longitudinal modes. Pulsed operation causes multiple longitudinal modes to co-exist before competition acts to extinguish modes. The seed laser (1) is isolated from the relatively higher peak power output beam (4). Further, the injection seeded slave resonator (6) optical cavity length is adjusted by mechanical, electromechanical and/or electro-optical component(s) to harmonize the slave resonator optical cavity to the seed laser (1) optical cavity. A number of widely separated longitudinal modes are simultaneously output as a pulsed, high optical quality beam having a broad frequency range, short temporal coherence, and stable simultaneous operation of the several modes.

Abstract: A microlaser cavity including an entry mirror, an exit mirror (36), an active laser medium. Also included is a mechanism for selecting cavity transverse modes when the cavity is pumped, in order to enable oscillation of one or several cavity transverse modes and to prevent oscillation of other cavity transverse modes.

Abstract: A laser resonator includes a laser medium having opposite end faces inclined at Brewster's angle and disposed in optical alignment between spaced-apart and tilted first and second optical elements. A method for adjusting the optical alignment includes pumping the laser medium to produce a laser beam, and adjusting separation spacing between the two optical elements. Tilt of at least one of the optical elements is adjusted in response to any observed change in beam cross-sectional size. In an additional embodiment, the laser medium is initially positioned at about equal spacings between the first and second elements. Position of the laser medium is then adjusted, at a constant value of the separation spacing, to within a position range selected for a specific value of a ratio of intracavity peak power of circulation of the laser beam and a critical power for self-focusing to effect discrimination of mode-locked operation over continuous wave operation.

Abstract: A tunable laser and method for operating the same, wherein the tunable laser utilizes a tunable Fabry-Perot filter as its wavelength-selective component. In one form of the invention, the tunable laser is characterized by the provision of optical elements (hereinafter referred to as "optical operators" or just "operators") on either side of the tunable Fabry-Perot filter, whereby the tunable Fabry-Perot filter can be set at a right angle to the optical path of the laser without introducing reflection problems interfering with the optimum lasing.

Abstract: An intracavity doubled single longitudinal mode laser is disclosed which provides stable (i.e., low amplitude variation in its output beam intensity), efficient operation. An associated method is also disclosed. The laser includes an input mirror and an output mirror defining a resonant cavity and a light path within the resonant cavity and between the mirrors. The output mirror is configured to be substantially transparent to an output wavelength produced within the cavity. A lasant material is positioned in the light path for producing light at a desired fundamental wavelength and possibly other, unwanted wavelengths. Polarizing element and a type I doubling material are also positioned in the light path. During operation of the laser, the polarizing element polarizes the desired fundamental wavelength as well as the unwanted wavelengths of light produced by the lasant material. The type I doubling material then produces output wavelengths at twice the frequency of any wavelengths passing therethrough.

Abstract: A fiber optic system in accordance with the present invention includes an optical fiber, a coupling device, and a system for generating a pump signal. The optical fiber has a birefringence which preserves polarization and has a first polarization mode which is substantially perpendicular to a second polarization mode. The coupling device couples an input signal with an input wavelength into the optical fiber so that the input signal propagates in the first polarization mode in the optical fiber. The system for generating a pump signal generates a pump signal with a pump wavelength which is within a range of 50 nanometers (nm) to 300 nm less than the input wavelength and which has a first amount of pump power which is enough power to switch the input signal, but not enough to create higher order solitons. The coupling device also couples the pump signal into the optical fiber so that the pump signal propagates in the first polarization mode in the optical fiber.

Abstract: Longitudinal diode-pumped solid-state lasers currently have maximum power outputs of no more than a few watts. By using resonators with several reflection sites inside the active medium, the output power of these lasers can be boosted accordingly. The configuration proposed here differs from known designs in being far easier to handle and less costly to manufacture.

Abstract: A laser beam machining apparatus including an image-transfer optical system having a mask inserted in an optical path between a laser oscillator and a workpiece, and a lens for reducing and forming an image of the mask on a processing surface; a focusing optical system; a drive unit for selecting one of the image-transfer optical system and the focusing optical system; and a numerical controller for controlling the image-transfer optical system, the focusing optical system, and the drive unit, wherein one of the image-transfer optical system and the focusing optical system is selected in correspondence with the diameter and depth of a hole to be processed.

Abstract: An etalon is disposed in a resonator of a laser to make the laser oscillate in a single longitudinal mode. Opposite end faces of the etalon through which light travels are provided with coating by ion-assisted deposition to prevent output fluctuations of the laser due to changes in environmental moisture and/or aging of the laser. Preferably the coating is of HfO.sub.2 and SiO.sub.2. In accordance with a second aspect of the present invention, there is provided a single longitudinal mode laser comprising a resonator and an etalon which is disposed in the resonator to make the laser oscillate in a single longitudinal mode, wherein the improvement comprises that opposite end faces of the etalon through which light travels are provided with coating by ion-assisted deposition. Further, the resonator may be contained in an airtight casing.

Abstract: A laser cavity assembly includes means (12, 13, 14; 14", 56, 57) defining respective optical resonance cavities (20, 22) for stimulated radiation of different wavelengths, which cavities include at least some common volume. Such means includes window means (13, 14) for emission of radiation amplified in the respective cavities. Means (15, 54) in one of said cavities is responsive to stimulated radiation emitted by a laser medium at one of the wavelengths to emit radiation at another of the wavelengths. Dual mode means (12, 54) has respective selectable first and second modes at which the laser cavity assembly is adapted to emit laser radiation predominantly at the respective wavelengths. Also disclosed are a novel Q-switch device and a combination laser oscillator and dual mode means.

Abstract: A single mode laser implementation and associated method are disclosed. The laser may accommodate a frequency multiplying material to provide an intracavity doubled single frequency laser. The laser implementation includes an input mirror and an output mirror defining a resonant cavity and a light path within the resonant cavity and between the mirrors. A lasant material is positioned in the light path for lasing at a desired fundamental wavelength and possibly other, unwanted wavelengths. A first birefringent member is also positioned in the light path for refracting in different directions the different wavelengths of light which are present along the path.

Abstract: A line narrowed laser having a grating based line narrowing module and etalon-based line narrowing output coupler and a technique for tuning the laser. The etalon based output coupler is adjusted to preferentially reflect light at or near the spectral maximum produced by the grating. Substantial improvement in line narrowing results from the amplification in the laser resonance chamber of light at or near the grating spectral maximum which is preferentially reflected by the etalon based output coupler. A special tuning technique takes advantage of the fact that a grating based line narrowing module naturally produces a laser beam having spacial variation in wavelength along a beam cross sectional direction. By comparing profiles of the beam into and out of the etalon in the output coupler, the grating and/or the etalon can be adjusted to achieve desired spectral performance.

Abstract: A laser includes a laser head and a power supply. At least two resonator mirrors define a resonator cavity. A gain medium is positioned in the resonator cavity. A temperature controller is positioned in the laser head and is coupled to the gain medium. The temperature controller maintains the gain medium at a temperature of 25 degrees C. or greater. A pump source supplies a pump beam to the gain medium and producing an output beam. The power source is coupled to the pump source.

Abstract: A laser includes a split-wave hybrid resonator that produces a high quality laser beam from a low gain laser medium. The split-wave hybrid resonator includes a resonator cavity formed by a pair of resonator mirror surfaces positioned at opposite ends of the laser medium and a pair of resonator walls positioned on opposite sides of the resonator cavity. The resonator walls are separated from each other by a separation distance such that the resonator cavity has a Fresnel number between approximately 0.5 and 1.5. At least one of the resonator walls includes a first ring oscillation filter adjacent to the lasing medium to filter out ring oscillations within the laser medium. One or more of the resonator walls may include first and second wall portions angled with respect to each other to form a wave-front splitting interferometer. The resonator mirrors are tilted off-axis with respect to the resonator walls.

Abstract: A laser device has a laser medium responsive to an excitation light for generating a laser beam consisting of a plurality of longitudinal modes when excited by an energy of the excitation light, two mirrors constituting a laser resonator for forming an optical path of the laser beam passing through said laser medium, and a nonlinear optical element, arranged in the laser resonator, for generating a second harmonic caused by one of the plurality of longitudinal modes constituting the laser beam generated in said laser medium and a sum-frequency caused by two of the plurality of longitudinal modes constituting the laser beam generated in said laser medium.

Abstract: A monolithically integrated vertical twin-waveguide structure reduces the sensitivity of the device performance characteristics due to the laser cavity length and variations in the layer structure. This is achieved by the introduction of an absorption or loss layer between the active and passive regions. This layer eliminates the propagation of the even mode, while having minimal effect on the odd mode. The threshold current densities and differential efficiencies of the devices are unaffected by the loss layer. A coupling efficiency of 45% from the laser to the external passive waveguide is obtained.

Abstract: A very narrow band excimer laser. The very narrow bandwidth is achieved by using an etalon as an output coupler in combination with a line narrowing element located at the rear of the laser. Preferred embodiments are capable of producing 10 mJ laser pulses at 1000 Hz with a 95% integral bandwidth of less than 1.5 pm.

Abstract: A semiconductor laser of the present invention includes a semiconductor laser structure having a waveguide extending along a resonance direction, an active layer provided at least partly in the waveguide, and a control unit for controlling the excited state of the semiconductor laser structure to change the relationship between wavelengths or propagation constants and threshold gains for transverse electric (TE) mode and transverse magnetic (TM) mode of the laser structure. The waveguide is designed such that threshold gains for the TE mode and the TM mode can be alternately made minimum under the control of the control unit.

Abstract: A Q-switched solid-state laser has a narrow-band laser diode (18) whose narrow-band output radiation serves as seed radiation for exciting a solid (14), with the result that only a single wavelength-stable longitudinal mode oscillates in the resonator (10, 12) of the solid-state laser and corresponding radiation (16) is emitted.

Abstract: An object of the present invention is to electrically tune and control an oscillating wavelength of a laser at high rate having a good reproducibility without providing any mechanically movable section in the laser resonator. To achieve the object, a laser oscillator is provided comprising a laser resonator composed of a mirror on the output side and a total reflection mirror, a Ti:Al.sub.2 O.sub.3 laser crystal disposed in the laser resonator, an acousto-optic crystal disposed in the laser resonator and to which are inputted the outputting light rays from the Ti:Al.sub.2 O.sub.3 laser crystal, a piezoelectric element mounted on the acousto-optic crystal to input acoustic waves thereto, and a diffraction light ray correcting prism disposed in the laser resonator and for correcting an angle of deflection of the diffraction light rays outputted from the acousto-optic crystal.

Abstract: An optical communications source has a laser optically coupled with an external optical modulator (25). The laser has a long optical cavity and a narrow spectral bandwidth Bragg reflector (24) so that the longitudinal mode separation of the laser emission is small compared with the spectral bandwidth of the reflector. This makes the laser operate multi-mode, but without any significant dispersion penalty.

Abstract: The laser apparatus according to the present invention comprises an output mirror for reflecting a portion of a laser beam and transmitting therethrough a remaining thereof; a full reflection mirror located at a position opposite to this output mirror for completely reflecting a laser beam and changing the curvature; a laser medium provided between the output mirror and the full reflection mirror for causing induced emission; an aperture means for deciding a beam mode of a laser beam generated between the output mirror and the full reflection mirror and changing the aperture diameter; and a converging means for converging an outgoing laser beam from the output mirror and changing a distance from the output mirror according to a machining path; and the laser apparatus changes a curvature of the full reflection mirror and also changes a diameter of the aperture means.

Abstract: To amplify and compress optical pulses in a multi-mode (MM) optical fiber, a single-mode is launched into the MM fiber by matching the modal profile of the fundamental mode of the MM fiber with a diffraction-limited optical mode at the launch end. The fundamental mode is preserved in the MM fiber by minimizing mode-coupling by using relatively short lengths of step-index MM fibers with a few hundred modes and by minimizing fiber perturbations. Doping is confined to the center of the fiber core to preferentially amplify the fundamental mode, to reduce amplified spontaneous emission and to allow gain-guiding of the fundamental mode. Gain-guiding allows for the design of systems with length-dependent and power-dependent diameters of the fundamental mode. To allow pumping with high-power laser diodes, a double-clad amplifier structure is employed. For applications in nonlinear pulse-compression, self phase modulation and dispersion in the optical fibers can be exploited.

Abstract: The present invention relates to a resonator for at least two laser modes from an optically pumped laser medium, in which each laser mode is reflected between a highly-reflective mirror and an output mirror. The laser resonator feeds back and separates at least two longitudinal laser modes having a given stable frequency difference between the modes by the laser medium being adapted to emit the concerned number of laser modes which are arranged to pass a Fabry-Perot etalon at different angles.

Abstract: A technique for operating a diode pumped solid state laser in a continuous-wave (cw) mode using diodes blocks (12) that are individually operated in a pulsed mode. For some high power laser applications, it is desirable to provide for operation in pulsed and cw modes, but pump diodes are typically designed for efficient operation in only one of these modes. The invention includes a controller (20) that pulses the individual diode blocks (12) on and off, but not necessarily in unison. For a pulsed mode of operation, the diodes (12) in an array are pulsed either at the same time, or sub-arrays are pulsed in a temporally interleaved manner for a higher effective pulse repetition rate. For the cw mode of operation, the diodes (12) are pulsed sequentially in sub-arrays (A-E), such that at least one sub-array is always energized and the complete array appears to be providing continuous pumping energy. In one embodiment, the sub-arrays (A-E) are columns of the array.

Abstract: Method for making a custom phase-conjugating diffractive mirror for a laser resonator comprising the steps of: (a) choosing a specified beam mode profile a.sub.1 (x,y) that will suit need of said designer, (b) calculating the mode profile b(x',y') which is a value of the specified beam a.sub.1 (x,y) that is propagated to the reflection surface of the diffractive mirror and (c) calculating mirror reflectance t(x',y') which reflects phase conjugate of b(x',y'). A method for fabricating such a mirror is shown. Another aspect of the invention is the addition of a phase adjusting element into a laser resonator, and compensating for the addition of a phase adjusting element in the design of other phase-adjusting elements such as the mirrors.

Abstract: A vertical-cavity surface-emitting laser that generates light having a fixed direction of polarization. The laser has a plane light-generating region sandwiched between a first conductive mirror region and a second conductive mirror region. The first conductive mirror region has an opposite conductivity mode from the second conductive mirror region. The first conductive mirror region has a remote surface substantially parallel to the light-generating region and an electrode formed on the remote surface. The electrode bounds a light emission port from which the light is emitted in a direction defining an axis. A reduced-conductivity region is formed in the first conductive mirror region surrounding the axis and extending from the remote surface towards the light-emitting region to define a core region in the first conductive mirror region. The light emission port and/or the core region has first and second dimensions in orthogonal directions in a plane parallel to the light-generating region.

Abstract: In a laser device, notably for optical pumping, the wafer includes an expansion segment adjacent the exit to prevent degradation of the exit facet of the semiconductor wafer that constitutes the amplifying part of the laser. The other facet is reflective and a Bragg grating is formed in a coupling fiber disposed near the exit facet. Applications include optical pumping of erbium-doped fiber amplifiers.

Abstract: Apparatus for generating laser light having a wavelength in the range of about 1012 to 1022 nm comprising a double clad optical fiber having a core doped with triply ionised ytterbium ions, a source of laser light emitting at a wavelength of about 800 to 1070 nm and coupled to launch the fight into the fiber, and fiber Bragg gratings written into the core region of the optical fiber so as to provide optical discrimination of the emission centered in the range of about 1012 to 1022 nm.

Abstract: A method of controlling the spatial mode of the output of a semiconductor laser including the steps of monitoring above threshold spontaneous emissions of a semiconductor laser. Identifying a point at which the rate-of-change, or the slope, of spontaneous emissions versus drive current abruptly changes. Employing feedback to maintain spatial mode control.

Abstract: The compensation amount of the pressure for keeping the index of refraction of the gas constant is calculated on the basis of the pressures and the temperatures that have been measured at different time. Only the pressure of the gas will be varied in accordance with the calculated compensation value of the pressure, whereby the index of the gas can be maintained constant and the oscillation frequency can be kept constant as the consequence. The pressure corresponding to a desired sweeping oscillation frequency is also calculated using the measured pressures and temperatures. The pressure of the gas is varied on the basis of the result of calculation. Synchronously with the variation of the pressure of the gas, the cavity length and the angle of the frequency selecting element are compensated.

Abstract: A multi-axial mode frequency conversion system includes two resonators. At least two resonator mirrors define a first resonator cavity. A gain medium is positioned in the first resonator cavity. A pump source supplies energy to the gain medium. The first resonator cavity produces a first beam with a plurality of axial modes that are incident on a doubling crystal in the first resonator and produce a frequency doubled output beam. The first resonator cavity provides a sufficient number of axial modes to oscillate so that the doubled output beam has a noise of less than 3% RMS. At least two resonator mirrors define a second resonator cavity coupled to the output beam from the first resonator cavity. The second resonator is configured to provide resonant enhancement of at least a portion of the plurality of axial modes. A non-linear optical material is positioned in the second resonator and configured to produce a harmonic output beam.

Abstract: A solid-state laser has a rod-shaped laser medium with planar end faces and a pumping radiation source whose pumping radiation reaches the laser medium by means of an optical element arranged in a longitudinal configuration adjacent to a planar end face of the laser medium. The optical element is arranged in thermal contact with a cooling element and is optically dimensioned so as to result in a minimum diameter of the transverse mode profile within the laser resonator.

Abstract: A waveguide laser (10) incorporates a guide (12) and two concave resonator mirrors (14, 16). The guide (12) is of square section with side (2a), and of length L equal to 4a.sup.2 /.lambda., where .lambda. is a laser operating wavelength. The mirrors (14, 16) are phase matched to respective Gaussian intensity profile radiation beams with beam waists at respective waveguide end apertures (20, 22). Each beam waist has a radius w.sub.0 in the range 0.1a to 0.65a to avoid waveguide edge effects and excitation of unwanted high order waveguide modes. The laser (10) has good transverse spatial mode characteristics.

Abstract: A laser mode control system for suppressing anti-symmetric resonance modes of a beam of radiation in a laser resonator cavity. The system includes a main resonator cavity in which a beam of radiation having symmetric and anti-symmetric resonance modes propagates. The main resonator cavity has at least one exit plane at a first end of the cavity through which the propagating beam of radiation passes. The system further includes an external cavity located outside of the main resonator cavity and adjacent to the exit plane. The external cavity includes a mirror for reflecting the beam of radiation passing through the exit plane and for flipping a mode profile associated with the beam of radiation upon the beam of radiation being reflected from the mirror. The external cavity also includes a partially transmissive medium between the mirror and the main resonator cavity for introducing losses to the beam of radiation in the external cavity.

Abstract: A semiconductor light emitting device includes a semiconductor light amplifier, a mirror which reflects light emanating from the rear end face of the semiconductor light amplifier to return the light to the rear end face of the semiconductor light amplifier, and a band pass filter which is inserted into the optical path of the light emanating from the rear end face of the semiconductor light amplifier and has a narrow transmission wavelength band.

Abstract: In a solid state laser, a solid state laser medium is pumped with a pumping source. A wavelength selector element is disposed in a laser resonator and a twisting element makes a mode of an oscillating beam a twisted mode in the laser resonator.

Abstract: An injection laser assembly mounted upon a crystal substrate [10] employing a back facet monitor is disclosed. A graded index lens [34] focuses light from the, typically, high in diversion and low intensity rays output from the back facet of the laser [30]. To allow repeatable and efficient coupling the graded index lens [34] is mounted within a groove defined in the crystal. Several configurations for mounting a photodiode sensor [P1,P2] are possible.

Abstract: A laser diode package couples laser diode outputs into a plurality of fibers, and these are bundled and brought to an output face that produces a divergent composite beam from the fiber ends. The beam end pumps a solid-state laser across a gap, and the divergence allows a wide tolerance in alignment of the pump and crystal. Preferably, one cavity mirror is a focusing mirror that reconcentrates residual pump light in the desired mode. In a preferred embodiment, the output face of the package is at a short stub or ferrule that provides a simple and effective pump beam centering alignment. The solid-state laser may be a rod or crystal and is preferably sufficiently short, in relation to pump beam diameter and divergence in the rod, that the pump beam within the rod lies in the TEM.sub.OO mode volume of the laser cavity. A concave mirror then refocuses residual pump light back into that mode. The rod preferably has a high index at the pump wavelength, but need not have high absorption.

Abstract: A semiconductor laser device that is modular can readily be changed to produce laser configurations for a broad spectrum of applications, using a minimum of components. A set of semiconductor modules covering wavelengths and polarizations of interest in specific technologies can be coupled to one of two beam shaping modules and projected through a selected objective optics module to provide large and small circular beams as well as broad and narrow line segments. Resolution enhancing and diffraction limiting filters may be included in the objective optics.

Abstract: Apparatus for improving the bias stability of a ring laser gyro by selecting a secondary transverse mode and controlling the path length of the gyro to maintain the selected mode.

Abstract: A semiconductor lasing device is formed by disposing a quantum well or quum wire array between positive and negative ohmic contacts such that different potentials are applied along the array to establish a transverse electromagnetic (TEM) mode of the optic signal (i.e. where the field components lie in a plane perpendicular to the direction of propagation). Thus, the light confinement l will be on the order of the electron confinement a. By applying different potentials via the positive and negative ohmic contacts to multiply connected waveguides, the established TEM mode does not have a cut-off frequency, and therefore, the gain of device can be greatly enhanced while still providing increased anisotropy and a low threshold current.

Abstract: A single longitudinal mode Nd:YAG laser oscillates in the range around 0.9 .mu.m and its oscillation mode is brought to a single longitudinal mode by an etalon disposed in a resonator. The thickness, reflectivity and inclination of the etalon and the separation of the resonator longitudinal modes are adjusted to meet conditions,0.6%.ltoreq.R.sub.N .ltoreq.3%, 0.2.degree..ltoreq..theta..ltoreq.1.degree.wherein R.sub.N represents the effective reflectivity of the etalon at a wavelength .lambda.=.lambda..sub.0 .+-..DELTA..lambda.c deviated from the resonance wavelength .lambda..sub.0 of the etalon by the separation .DELTA..lambda.c of the resonator longitudinal modes and .theta. represents the inclination of the optical axis of the etalon to the optical axis of the resonator.

Abstract: A high power diode pumped laser is disclosed which has at least one resonator mirror and an output coupler. At least one laser crystal with strong thermal focussing properties is included. The laser includes at least one diode pump source supplying a pump beam to the laser crystal, producing a thermal lens in the laser crystal. The combination of the laser crystal, thermal lens, resonator mirrors and output coupler create a confocal-to-concentric resonator. An output beam is generated, which may be polarized. Further, a Q-switch may be included in the resonator, particularly when the laser crystal is Nd:YAG.

Abstract: A method of using a distributed saturable absorber added to a laser cavity, which by nonlinear wave-mixing of the counterpropagating beams (or spatial hole-burning) promotes a reduction of the linewidth and a single mode operation.

Abstract: A pulsed laser comprises a laser rod (6), and is pumped by diode array (3) selected such that with additional components (7, 9) only a maximum of two longitudinal modes are generated between mirror (1) and output coupler (2). By slow Q-switching Q-switch (9) hoped to get a single longitudinal mode output pulse. However if on the onset of the relaxation pulse mode beating is detected by detector (28), indicating that two longitudinal modes are present, then the optical path length of the resonator is changed by quarter of one wave length, by applying an electrical signal to a pulse length control means (10), such that one of the modes is suppressed prior to the Q-switch being fully opened. The output may be amplified by amplifier arrangement (24).