Abstract: An optical laser frequency stabilizer which is simple, inexpensive, produces an unmodulated output, and a highly controlled oscillation frequency, wherein signals supplied to a master laser are modulated with a signal which is switched between four or more different levels to control the oscillation frequency of the master laser to the frequency of an absorption line; and wherein the beat frequency of signals from the master laser and a slave laser is counted by an up-down frequency counter in synchronism with the modulation signal and, in response to the obtained total count, the oscillation frequency of the slave laser is controlled to a frequency based on the center frequency of the oscillation of the master laser so that an unmodulated output is generated which is not affected by variations in the powers of the laser beams. The laser frequency can be offset from the frequency of the absorption line, and also the offset frequency can be varied continuously.

Abstract: A laser system using non-linear crystals for second harmonic generation and solid state gain media is operated under data processor control so that a plurality of pump power modes are available. The data processor modulates the pump power in a low power mode, and supplies continuous pump power in combination with Q-switching in a high power mode. Alternatively, modulation may be used in both low power and high power modes, with the parameters of the modulation adjusted under program control. Second harmonic generation without a Q-switch in high power modes can be achieved as well. The data processing control of pump power allows optimization of pump energy consumption and the generation of waste heat so that the laser resonator may be air-cooled in many environments. Also other design objectives can be achieved for specific laser applications using the program controlled data processor to drive the pump power source.

Abstract: A miniature laser cavity in which a solid-state lasing gain element and a Q-switch have respective end surfaces at substantially the Brewster angle, parallel to and facing each other, and separated by a narrow gap occupied by a transparent low-index-of-refraction material.

Abstract: The present invention is a laser system that includes an acousto-optic device (24B) having an optical medium (40B) that maintains a substantially uniform index of refraction even when subjected to nonuniform thermal or mechanical stress. The acousto-optic device provides substantially distortion-free polarized output light that can be directed accurately to strike an intended target.

Abstract: A ring laser is disclosed that produces a single frequency of laser radiation in either the pulsed mode of operation or the continuous waveform (cw) mode of operation. The laser comprises a ring laser in a bowtie configuration, a birefringent gain material such as Nd:YLF, an improved optical diode that supports laser oscillation having a desired direction of travel and linear polarization, and a Q-switch. An output coupler (mirror) having a high reflectivity, such as 94%, is disclosed. Also disclosed is a self-seeded method of operation in which the laser can provide a pulse or a series of pulses of high power laser radiation at a consistent single frequency with a high degree of amplitude stability and temporal stability. In operation, the laser is operated in continuous waveform (cw) at a low power output with the Q-switch introducing a loss into the resonating cavity. Pumping is continued at a high level, causing the gain material to store energy.

Abstract: A length stabilized, dispersion compensated synchronously pumped mode locked dye laser is disclosed. The output of the dye laser is actively stabilized by monitoring the output power thereof and generating an error signal for actively adjusting the cavity length. The operation is enhanced by actively controlling the power of the pump pulses exciting the dye laser so that the power fluctuations in the dye laser are due primarily to fluctuations in cavity length. Stability is also enhanced by operating the cavity with a negative group velocity disperison. The resultant lengthening of the output pulses is compensated by a pulse compressor, located outside of the cavity, which adds a positive group velocity disperison to upchirp and shorten the pulses.

Abstract: An acousto-optical device includes a solid state substrate having optical characteristics affected by an acoustic wave in the substrate, and a Z-cut lithium tantalate transducer coupled to the substrate for inducing the acoustic wave. Lithium tantalate provides the transducer with a coupling coefficient and acoustic impedance mismatch which generate a very high finesse acoustic standing wave within the substrate. The lithium tantalate also provides low shear wave components with relatively high manufacturing tolerances. The acousto-optical device with a lithium tantalate transducer is also utilized as a high Q modelocker in a laser capable of producing short pulses of laser light.

Abstract: A room-temperature, laser-pumped, Q-switched, thulium-doped, solid state laser for producing pulses of laser emission at substantially 2 microns is disclosed. In a preferred embodiment, the laser comprises: a laser cavity defined by first and second reflective elements opposing each other on a common axis to form a reflective path therebetween; a laser crystal disposed in the laser cavity, the laser crystal having a host material doped with an amount of thulium activator ions sufficient to produce a laser emission at substantially 2 microns from the .sup.3 F.sub.4 to .sup.3 H.sub.

Abstract: An acousto-optic tunable filter, for laser tuning, comprises an acoustic transducer connected to one face of an anisotropic crystal or Bragg cell which is cut at such an angle relative to its optic axis that an acoustic wave projected into the crystal normal to the face causes wavelength-specific diffraction of an incident optic wave (from a laser amplifying element) which nearly, but not completely, satisfies the parallel-tangents phase matching condition, thus preserving a substantial angular field of view, the angle also being such that the diffraction is polarization-insensitive.

Abstract: The invention is directed to a laser arrangement for converting frequency wherein the fundamental frequency or the converted frequency can be selectively emitted by means of an optical element which can be pivoted into and out of the beam path. An especially slim configuration of the overall arrangement is obtained with the aid of an additional deflection element.

Abstract: A laser system in which the laser medium is a single crystal of Cr.sub.3+ :Mg.sub.2 SiO.sub.4 is disclosed. In one embodiment, the system comprises a single crystal of chromium doped forsterite and a cavity which includes a pair of 30 cm. radius mirror having high transmission at 543 nm (the pump wavelength) and high reflectivity in the 1150-1350 nm range. Room temperature vibronic pulsed laser action is obtained with this cavity. Laser action has been observed at 1235 nm and a bandwidth of 25 nm. The wavelength range is suitable for transmission through optical fibers and is useful in laser ranging and remote sensing. Because of the ultrawide fluorescence bandwidth and a 15 fluoroescence lifetime the system is suitable for high intensity, tunable, cw, Q switched mode locked operation. In the mode locked operation pulses as short as 10-500 femtosecond may be generated. A number of different embodiments of the invention are described.

Abstract: A laser power beam control system includes a photodetector for generating an electrical signal which is proportional to the power level of the laser beam. The electrical signal is converted to a high frequency modulated signal which controls a single acousto-optical modulator. The acousto-optical modulator is in the laser beam path and controls the power level of the beam in response to the amplitude modulated signal. The system is particularly adapted to control a laser beam used in raster or vector scanning a laser for the formation of semiconductor integrated circuits.

Abstract: A microwave oscillator frequency modulates the output of the laser system to be controlled. The modulated output passes through a molecular gas cell. The output of the molecular gas cell is detected by a square law device, which produces a signal at the desired microwave frequency only when a sideband of the modulated laser output coincides with the desired molecular transition frequency. A quadrature signal pair is produced by mixing the filtered output of the square law device with two phase-shifted signals from the microwave oscillator. The dispersion signal can be used to control the output frequency of the laser system, since its magnitude and sign are uniquely related to the required direction of correction.

Abstract: A neodymium or other rare earth doped solid state laser is pumped by a matched high efficiency laser diode, including a diode array and a multi-spatial mode extended emitter diode, resulting in a compact, high efficiency and long lifetime laser assembly. The cavity mode volume is matched to a region of absorption in the pumping volume formed by the focused diode beam. Output is in the near infrared range, but can be converted to the visible spectrum by an intra-cavity frequency doubler. A doubling crystal, e.g., KTP, is placed in an optimum location in the laser cavity. Polarization of the beam for frequency doubling may be achieved by using a birefringent material for the rod or by stressing a non-birefringent rod. An amplitude noise suppression etalon may also be placed at an optimum position in the laser cavity. A folded cavity configuration produces a pair of beam waists in the cavity. Pulsed operation can be produced by means of a Q-switch.

Abstract: An optical system for producing an optical output having a beat frequency. The shifter has a beam splitter for splitting a laser radiation generated by a laser source, into a first and a second laser beam, and includes an acoustooptical modulator for deflecting the first laser beam and thereby changing the frequency of the first laser beam. The shifter further has an optical-path changing device such as a convex lens or parabolic reflector for changing an optical path of the first laser beam deflected by the acoustooptical modulator, into parallelism with the optical axis of the changing device. The focal point of the optical-path changing device is located at a point of emission of the deflected first laser beam. A mixer is provided for mixing the deflected first laser beam with the second laser beam, thereby causing an interference between the first and second laser beams, to produce a beat frequency equal to a difference between the frequencies of the first and second laser beams.

Abstract: A miniaturized Q-switch is added to the resonant cavity of a compact laser diode pumped solid state laser to produce short high peak power pulses which are input into a single mode optical fiber to form a compact continuum generator. Q-switching the compact laser diode pumped solid state lasers takes advantage of the relatively high gain and short cavity length to provide a desirable combination of pulsewidth and pulse energy. Nd:YAG or Nd:YLF are useful solid state laser materials for Q-switching, or other longer lifetime rare earth ions such as erbium or holmium for greater energy storage. The Q-switch is formed of a material such as TeO.sub.2, SF.sub.10, or LiNbO.sub.3 with an acoustooptic figure of merit substantially greater tha fused silica. The high peak powers of the lasers are sufficient to exceed the threshold for Raman conversion in the fiber which produces a series of red shifted bands ending in a continuum by stimulated Raman scattering.

Abstract: An ultrasonically modulated laser comprises a laser oscillation tube including opposing ends for generating a beam of planar polarized light having a plurality of wavelenghts; an output mirror at one end of the tube for reflecting the light beam; and a modulation device at the other end of the tube for simultaneously modulating a plurality of wavelengths of the light beams, including an acousto-optical prism having an incident surface for separating the beam into multiple wavelength components, a total reflection mirror for receiving and reflecting selected wavelength components impinging on the incident surface from the tube at a predetermined angle, and an ultrasonic transducer for generating standing means perpendicular to the selected wavelength components for modulating the reflected selected wavelength components.

Abstract: In an acoustooptic device for use in acoustooptically controlling a laser beam in response to an electric signal, an acoustooptic element is packaged in a housing which defines an internal space therein and which can circulate a coolant in the internal space through inlet and outlet portions to directly cool the acoustooptic element by the coolant. The housing comprises a case block providing the internal space and a pair of cap members which forms windows for the laser beam, respectively, and which is hermetically attached to the case block with a pair of seal members interposed between the case block and each of the cap members. Each seal member comprises a first O-ring placed around the window and a second O-ring placed outside of the first O-ring to hermetically seal the internal space.

Abstract: A miniaturized Q-switch is added to the resonant cavity of a compact laser diode pumped solid state laser to produce short high peak power pulses. Q-switching the compact diode pumped solid state lasers takes advantage of the relatively high gain and short cavity length to provide a desirable combination of pulsewidth and pulse energy. Nd:YAG or Nd:YLF are useful solid state laser materials for Q-switching, or other longer lifetime rare earth ions such as erbium or holmium for greater energy storage. The Q-switch is formed of a material such as TeO.sub.2, SF.sub.10, or LiNbO.sub.3 with an acoustooptic figure of merit substantially greater than fused silica. Pulsewidths of 10-50 ns are achieved at pulse energies of 10-20 microjoules. TEMOO output is easily produced by the compact laser pumped solid state resonator. Applications include materials processing, link blowing in semiconductor memories, marking and scribing, and optical time domain reflectometry.

Abstract: A neodymium or other rare earth doped solid state laser is pumped by a matched high efficiency laser diode, including a diode array and a multi-spatial mode extended emitter diode, resulting in a compact, high efficiency and long lifetime laser assembly. The cavity mode volume is matched to a region of absorption in the pumping volume formed by the focused diode beam. Output is in the near infrared range, but can be converted to the visible spectrum by an intra-cavity frequency doubler. A doubling crystal, e.g. KTP, is placed in an optimum location in the laser cavity. Polarization of the beam for frequency doubling may be achieved by using a birefringent material for the rod or by stressing a non-birefringent rod. An amplitude noise suppression etalon may also be placed at an optimum position in the laser cavity. A folded cavity configuration produces a pair of beam waists in the cavity. Pulsed operation can be produced by means of a Q-switch.

Abstract: The subject of the invention is a device synchronizing modes of the laser, fastened in its resonance cavity, in a housing 1 having its inner temperature stabilized, which contains an acousto-optical modulator whose buffer 5, functioning at the same time as a prism, together with a transducer 13 generating an acoustic wave for modulation of a light wave and with a back mirror 11 form an integrated optical element in the form of a prism with a trapezoid base.

Abstract: Apparatus is provided for rapidly switching among discrete wavelengths within the output spectrum of a gas laser. A portion of the radiation in a primary optical cavity of a laser is transmitted by a partially reflective surface into a secondary cavity which includes a reflector element and one or more Bragg deflector cells. The Bragg cells are positioned between the primary cavity and reflector element, and frequency shift radiation passing between the primary cavity and reflector element. Each Bragg cell is selectably driven by an RF driver to enhance radiation of a predetermined wavelength within the range of the laser spectrum. Consequently, radiation injected back into the primary cavity from the secondary cavity is essentially of the predetermined wavelength.

Abstract: An active Q-switch integral laser cartridge is made of an acoustic transmitting body having a photoelastic laser medium in a part thereof for propagating and coupling both optical and acoustic waves. The photoelastic laser medium and the acoustic transmitting body may be made of substantially the same or similar base material.

Abstract: A mode-locked laser light source, i.e. a light source in which resonant longitudinal modes of the laser cavity are synchronized in phase to produce a pulsed laser output, is provided with an optical phase-lock loop, to lock the optical output pulse train to the mode-locking radio frequency drive signal. The invention provides a highly stable laser source for light pulses of picoseconds duration.

Abstract: By applying to a laser Q-switch a staircase-shaped control signal, a plurality of laser pulses are emitted with controlled energy and time separation. Compared with conventional Q-switching, the invention enables the laser to emit pulses with shorter time intervals, narrower linewidths, higher output energy, and more uniform power density across the laser beam cross section. The apparatus and method are particularly well-suited for use with low-gain lasers, such as alexandrite.

Abstract: A frequency shifted cavity apparatus for electromagnetic radiation. The cavity filters electromagnetic radiation wherein the instantaneous frequency increases and changes non-linearly in time. The cavity can optionally include an optical amplifier with sufficient gain to cause oscillation of at least one cavity mode.

Abstract: A laser system and method is disclosed which is capable of producing high peak power, high pulse rates, and narrow pulses. The invention comprises an acousto-optic shutter and a frustrated total internal reflectance Q-switch in a unique configuration which allows maximum power to be obtained from the laser device while still achieving high pulse rate and narrow pulse width.

Abstract: A method for controlling exposure light beams for use in a picture reproducing machine such as a color scanner and a color facsimile, wherein a light beam is supplied to an acoustooptical deflector and is deflected thereby to obtain diffraction light beams which are incident to fixed light paths and are used for exposing a recording film, and wherein the diffraction light beams are controlled by varying a frequency of a supersonic wave supplied to the acoustooptical deflector so that each diffraction light beam may be or may not be incident to the respective light path.

Abstract: The Q-switched laser gating pulses of an acousto-optic Q-switch are synchronized electrically to the phase of the RF signal driving the Q-switch by applying the RF oscillator output signals to the clock input of an integrated circuit D-type flip-flop and the laser gating pulses to the D input of the flip-flop, whereby the leading edge of each output gating pulse from the flip-flop always occurs at a particular place on the RF waveform. In another embodiment, the RF signals are synchronized to the phase of the gating pulses by applying the output of a repetition rate oscillator to the RF oscillator.

Abstract: A circuit arrangement for controlling a multi-beam acousto-optical cell in which Bragg diffraction is used for the generation of a plurality of outgoing laser beams, in which the acousto-optical cell has at least one ultrasonic transducer from which the outgoing laser beams are coming out in a common plane, the circuit arrangement comprises VHF or UHF oscillators coupled through respective control stages to the ultrasonic transducers. The frequency of each oscillator defines the diffraction angle of an associated outgoing laser beam the intensity of which is dependent from the amplitude of the oscillator. The passage of the oscillator outputs towards the respective ultrasonic transducers is controlled by the control stages according to predetermined operational requirements.

Abstract: The initially high amplitude laser output pulses at the start of a string of pulses from a continuously pumped, repetitively, Q-switched Nd:YAG laser are reduced in amplitude by reducing the current to the krypton arc lamp pumping light source by about 5 amperes for a time of about one-half to about one millisecond prior to gating the Q-switch.