Abstract: A laser control system with multiple CPU's having shared memory on a common bus to provide high performance, relatively lost-cost, laser control. In the system disclosed, a first CPU which handles most, if not all, communication to and from the laser control system and which may communicate with one or more additional CPU's through the shared memory, so as to be capable of providing the software and operating commands to one or more additional processors on the common bus. A second processor is provided to control the intensity and repetition rate of a gas laser responsive to the program and commands made available thereto through the shared memory by the first processor. In addition, the second processor may directly respond to specific controls provided thereto to allow operation of the laser directly in response to control signals provided thereto from the outside, rather than based on parameters provided thereto by the first processor.

Abstract: An optical clock regenerator using a laser includes an optical modulator for mode locking in a laser resonator. The optical modulator is driven by an intensity-modulated optical signal. When an intensity-modulated optical data pulse train including a clock frequency component close to a frequency n (n is an integer) times or one-nth times a resonance frequency of the laser resonator is input to the optical modulator, the laser outputs clock pulse light locked by the frequency n times or one-nth times a clock frequency of the optical data pulse train. The optical data pulse train and the laser resonator are spatially separated from each other.

Abstract: An optical amplifier pumping system with built-in redundant reliability for lightwave communication system provides plural levels of redundancy. A first level of redundancy deals with redundancy in the form of plural primary laser diode sources in the lightwave communication system. A second level of redundancy deals with redundancy of multiple single mode laser emitters on the same chip or bar sufficiently segmented so as not to interfere with operation of or cause failure to adjacent or neighboring emitters on the same chip or bar. A third level of deals with redundancy of a plurality of fiber pump sources for pumping a plurality of serially connected injection signal fiber amplifiers.

Abstract: A power monitoring system including a first substrate having a first vertical cavity surface emitting laser and a second vertical cavity surface emitting laser formed thereon and being generally identical. A second substrate having a photodiode formed thereon. The second substrate is flip chip mounted on the first substrate with the photodiode in optical alignment the second vertical cavity surface emitting laser. The output of the photodiode is used to control emissions of the first and second vertical cavity surface emitting lasers.

Abstract: A carbon dioxide gas laser oscillation apparatus having one or more discharge tubes each having a pair of anode and cathode electrodes at least one of which is non-grounded and one or more high voltage DC power sources each connected between the pair of electrodes of each discharge tube provides with one or more conductors each being arranged on each discharge tube in the vicinity of the non-grounded electrode of the pair of electrodes but on one side of the non-grounded electrode opposite to a space between the pair of electrodes. The CO.sub.2 gas laser oscillation apparatus further provides with one or more current detection circuit for detecting a current flowing between zero-potential terminal and ground terminal of the high voltage DC power source, thereby enabling to detect an abnormal discharge within each discharge tube.

Abstract: An apparatus using a semiconductor laser comprises a measuring unit for measuring a slope efficiency of the semiconductor laser; a determination unit for determining whether or not the measurement value reaches a specified value; and a notification unit for notifying the determination result of said determination unit.

Abstract: A laser diode array assembly includes a laser diode array and a memory device integrally packaged with the array. The memory device includes operational information concerning the array. The memory device is accessible by a host external operating system which determines the manner in which the array is to be powered based on the operational information. The memory device may have the capability to be written to such that the external operating system can record in the memory device significant events such as extreme operational conditions, operational faults, and the on-time or shot-count of the array. The assembly may include sensors to which the operating system is coupled. The assembly may further include a processing means to monitor the sensors and provide real-time updates to the external operating system such that laser diode array is continuously powered in an optimal manner.

Abstract: A temperature controlled mounting package for a fiber optic communication laser, mounted within an adapter, which is in thermal contact with a heat exchange element. The heat exchange element may be a thermoelectric cooling element or a resistance heater which maintains the laser within a temperature band. By keeping the temperature bandwidth to 40 degrees Centigrade, the signal variations are held to within 1 dB in fiber-optic applications.

Abstract: A travelling-wave semiconductor laser amplifier having suppressed self-oscillation is provided. When incorporated into a master oscillator power amplifier device, such a device has improved light output versus amplifier current characteristics. Also provided is a method for suppressing self-oscillation in travelling-wave semiconductor laser amplifier structures for improving the characteristics of the device into which the amplifier is incorporated.

Abstract: A device for preventing laser beam leakage, which excludes a danger that a laser beam emitted from a laser source directly attacks eyes of an operator when an external connector is connected to or disconnected from an internal connector, aiming at being inexpensive and excellent in operability, and having a high safety. When the external connector has been removed from the optical transmission apparatus, a pair of movable shield plates are constantly urged in respective directions for closing a receiving opening of the apparatus to bring joining portions of the movable shield plates into close contact with each other, thereby preventing dust from entering the inside of the apparatus and the laser beam from being leaked.

Abstract: A resonant power circuit which supplies pulsed power to a load, such as a pulsed laser, from a d.c. supply by cyclically charging a capacitor. The capacitor is discharged through the load on closure of a switch which should then open to allow the capacitor to re-charge. Occasionally the switch fails to open and the circuit of the invention then develops and applies a reverse voltage to the switch to force it to become open circuit.

Abstract: An optical transmission device which is used for a short range optical data link or an optical communication system for subscribers and more particularly requires no automatic optical power control minimizes the turn-on delay time of a laser diode and allows unformatted optical signal transmission by fixed level decision receiving system. By applying a fixed-bias electric current which is not more than the electric threshold current value of the laser diode to the laser diode, the turn-on delay time of the laser diode can be minimized, and the extinction level can be lowered by it, and the fixed level decision receiving system can be used, and the optical receiver circuit can be simplified more.

Abstract: Electron orbits from a helical axial wiggler in an axial guide field are absolutely unstable as power is extracted from the particles. For off-axis beams an axial FEL mechanism exists when the axial electric field in a TM mode is wiggled to interact with the axial velocity of the electrons that form the beam. The interaction strength is comparable to that for helical FELs and is insensitive to beam orbit errors. The orbits for this mechanism are extremely stable in the absence of space charge and lead to high extraction efficiencies without particle phasing incoherence or interception. This interaction mechanism is suitable for use with intense annular electron beams for high power generation at microwave frequencies.

Abstract: An external control system for a laser system, used as an illumination source for a stepper system, is provided. The external control allows for a measuring of the energy actually distributed to a wafer and a correction of the energy dose distribution based upon this measurement. In this way, a more precise energy dose control is achieved. The external control communicates with the laser's own internal control system to provide serial inputs which allow for corrections to be made to the High Voltage setting based upon the aforementioned measurements, and coordinates with the laser's internal control system to initiate laser operation at the required intervals.

Abstract: A trial writing operation is performed on a phase-change optical disc using write and erase light-emitting powers, which together are varied according to predetermined variation ratios respectively. Signals relevant to said trial writing operation are reproduced from said disc. Optimum ones of the write and erase light-emitting powers are determined using the thus-reproduced signals. The predetermined variation ratios for the write and erase light-emitting powers may be the same as each other. Alternatively, the trial writing operation may be performed on a phase-change optical disc using write and erase light-emitting powers which are individually varied according to predetermined variation ratios respectively.

Abstract: A laser system capable of providing light of high intensity is disclosed. This system includes a laser gain medium and three reflectors. A first reflector and a second reflector spaced from the first reflector define a laser cavity that contains the laser gain medium. The second reflector has a reflectivity (R.sub.2) larger than the reflectivity (R.sub.1) of the first reflector such that light emitted from the laser gain medium resonates in the laser cavity. A third reflector having a reflectivity (R.sub.3) larger than the reflectivity of the first reflector (R.sub.1) is spaced from the second reflector to define a resonant cavity external to the laser cavity. Light passes from the laser cavity to resonate in the external resonant cavity. Part of the light passes from the external resonant cavity to the laser cavity to optically lock the laser gain medium.

Abstract: An improved laser diode assembly includes a laser diode unit which is mounted directly on a compact thermoelectric cooler, which is mounted on a heat sink. A thermally insulating gasket, mounted around the thermoelectric cooler, seals the thermoelectric cooler from the ambient environment, thereby preventing condensation from forming on the cold face of the thermoelectric cooler. A bushing concentrically positions the laser diode unit in the proper optical alignment with respect to the optical assembly, while thermally and electrically insulating the laser diode. A thermally conductive gasket, mounted around the circumference of the laser diode window, returns heat from the heat sink to the window to prevent condensation from forming on the window. The laser diode is the only component cooled by the thermoelectric cooler. Since a portion of the heat transferred by the thermoelectric cooler is utilized to warm the laser diode window, a separate heating element is not required.

Abstract: Apparatus, and a related method, for compensating for birefringence introduced in a birefringent medium, such as a solid-state amplifier. The invention includes the combination of a quarter-wave plate, a Faraday rotator and a mirror, which may be a phase conjugation cell. Light passing through the quarter-wave plate is substantially circularly polarized, which is advantageous if the mirror is a phase conjugation cell using stimulated Brillouin scattering (SBS). A second pass through the quarter-wave plate provides a linearly polarized beam of which the polarization angle is orthogonally related to that of the original beam, to facilitate out-coupling of energy from the apparatus. The Faraday rotator effects a total polarization angle rotation of 90.degree. in two passes and helps compensate for birefringence when the beam is passed through the birefringent medium again on the return pass.

Abstract: To adapt temperature control of a secondary cooling water to the temperature of a primary cooling water: A control apparatus computes duty factor D from measured open time period T.sub.ON and closed time period T.sub.OFF of a solenoid valve (step B3) for each cycle of the solenoid valve operation (step B2). The apparatus classifies the computed duty factor into one of a plurality of predetermined ranges and conditionally updates the reference temperature Pt of the secondary cooling water based on the classification (B5, B6, B7). If the reference temperature has reached an upper limit P.sub.MAX and if the duty factor has exceeded an upper limit, e.g., 95 percent (B8), the apparatus stops the operation of a laser oscillator and provides an alarm.

Abstract: A package for a high power semiconductor laser comprising a hermetically sealed container filled with a dry gaseous medium containing oxygen. The presence of oxygen in the laser atmosphere is counter to standard practice in the art which teaches the use of an atmosphere of a dry inert gas. The package also includes a getter for organic impurities, e.g., a getter composed of a porous silica or a zeolite. The hydrogen content of the materials used to form the package are reduced by baking at an elevated temperature for an extended period of time, e.g., at 150.degree. C. for 200 hours.

Abstract: An apparatus and method for stabilizing the transverse mode of laser oscillation in a vertical cavity semiconductor laser and a microchip laser are disclosed. A preferred embodiment includes a quantum-well region formed over a semiconductor substrate. A first reflective surface is formed over the quantum-well region, and a second reflective surface is formed over the substrate, opposite the first reflective surface, forming a laser cavity. The quantum-well region is optically pumped, producing laser oscillation. The absorbed pump power causes a thermal lensing effect within the semiconductor material, stabilizing the transverse spatial mode of the laser cavity. The radius of curvature of the thermal lens is a function of absorbed pump power. Maximum power conversion efficiency is achieved if the pump power is controlled such that the diameter of the oscillating mode matches the diameter of the pump beam. The invention has applications in optical communication and laser printing.

Abstract: A current detector detects a driving current Im flowing through a light emitting device (laser diode); a temperature sensor is arranged in the vicinity of the light emitting device; a microcomputer is supplied with the outputs of the current detector and temperature sensor; a temperature correction coefficient specific to the light emitting device, obtained based on a driving current value IT1 at a temperature T1 and a driving current value IT2 at a temperature T2 (>T1), is stored in memory; a deterioration threshold current Id for a detected temperature Ti is calculated; and when the deterioration threshold current Id for the detected temperature Ti is exceeded by the detected current, a driver is controlled so as to inhibit the supply of the driving current to the light emitting device. Since the operating temperature also is taken into consideration, deterioration of the light emitting device can be accurately estimated, thereby preventing erroneous recording/reproduction of data.

Abstract: A continuous-wave ultraviolet laser light generating apparatus includes a laser light source unit (1) for generating laser light from visible light to near-infrared light, a wavelength converting means (4) which includes an optical resonator (2) and a wavelength convertor (3) disposed in the optical resonator (2) for converting a wavelength of incident laser light and which converts the laser light from the laser light source unit (1) into continuous-wave ultraviolet laser light L.sub.UL to emit the latter, a locking means (5) for adjusting the optical resonator (2) so as to have a predetermined cavity length, and an electrooptic phase modulator (6) for modulating a phase of the laser light from the laser light source unit in response to a resonance frequency of the optical resonator. The electrooptic phase modulator (6) is made of an electrooptic crystal (11) having a composition of ATiOXO.sub.4 where A depicts any one of K, Cs and Rb and X depicts any one of P and As.

Abstract: A method and apparatus for operating a laser diode array in a laser thermal printer, wherein the laser diodes are formed on a common substrate, includes: generating digital image data signals for the individual diodes in the array; generating correction signals for each diode in the array, the correction signals being generated by weighting selected digital image data signals; summing the weighted correction signals with the digital image data signals for each diode in the array to produce control signals; employing the control signals to produce a driving current for each diode in the array; applying the driving currents to the diodes in the array.

Abstract: A method for avoiding damage to the eyes when using high-power lasers in the eye-transmissible spectral region is provided. By adding a laser or a radiation in the visible spectral region, the intensity of the radiation is increased as a function of time in the shape of a ramp from zero to higher values which lead to a conscious or reflex-type closing of the eyelids This therefore prevents the eyes from being damaged by the subsequent high-power laser beam.

Abstract: A device suitable for a laser-type bar code reader used in a POS (point of sales) system in the distribution industry, and more particularly, to a laser lighting control device in a laser scanner device which reads a bar code using a reflection light of a laser beam. A prolonged operational life and an improved reliability of the laser light source build-in device under intermittent light on/off control is achieved by monitoring its lighting time to execute the operational life control thereof. The laser lighting control device includes a laser light source, a drive unit for performing a light on/off drive of the laser light source to control the light on/off thereof, a control unit for outputting a light on/off command to the drive unit for laser light source control, and a timer unit for measuring the total lighting time of the laser light source.

Abstract: The present invention is a laser with a high reflector mirror and an output coupler mirror defining a laser resonator having an optical axis and optical path length. A gain medium, with a first refractive index and a first Verdet constant, is positioned in the resonator. The laser also includes an apparatus to excite and cause a population inversion in the gain medium to produce an output laser beam. An optically transparent medium is positioned in the laser resonator. The optically transparent medium has a second refractive index and a second Verdet constant. The second Verdet constant is typically larger than the first Verdet constant. One or more permanent and electromagnets are positioned at least partially around the exterior of the laser resonator.

Abstract: A solid-state laser architecture producing a beam of extremely high quality and brightness, including a master oscillator operating in conjunction with a zig-zag amplifier, an image relaying telescope and a phase conjugation cell. One embodiment of the laser architecture compensates for birefringence that is thermally induced in the amplifier, but injects linearly polarized light into the phase conjugation cell. Another embodiment injects circularly polarized light into the phase conjugation cell and includes optical components that eliminate birefringence effects arising in a first pass through the amplifier. Optional features permit the use of a frequency doubler assembly to provide output at twice optical frequencies, and an electro-optical switch or Faraday rotator to effect polarization angle rotation if the amplifier material can only be operated at one polarization.

Abstract: A laser package includes a housing and a subassembly to which the critical components of the laser package are mounted. The subassembly is structured to preserve component alignment even in the presence of thermal excursions by ensuring that any movement which might occur effects all the components in a way to preserve alignment. The subassembly is easily removable from the housing and thus permits replacement if a failure should occur. A reverse diode is included to provide a path for reverse currents which otherwise would be damaging to the active laser diode.

Abstract: It is the object of the invention to suppress noises caused by reflections of a ray of light from a light receiving surface of a photodiode chip and inner and outer surfaces of a glass in a semiconductor light receiving apparatus. A construction of a light receiving apparatus is that, a photodiode chip 4 is mounted on a carrier 2 fixed to a stem 1, and a chip 4 is sealed up by a cap 7, which is provided with an opening 7a covered with glass 8. A ray of light transmits through an opening 7a, and incidents on a light receiving surface of a chip 4. A light receiving surface of a chip 4 and an outer surface of a glass 8 are inclined to the optical axis, where directions of inclinations are different to each other. An angle of inclination of a chip 4 is selected such that reflected rays from a chip 4 does not incident on an opening 7a. Accordingly, there is no ray which returns to a light source (not shown), and generation of delayed incidences to a chip 4 can be prevented.

Abstract: A decontaminate apparatus for a laser system includes a laser having a compartment housing having a base and walls formed into a cavity and having a compartment cover having at least a portion thereof porous to predetermined gases used in laser system optical cavities. The compartment housing cavity is filled with a selected decontaminating material held therein by the porous cover and is attached in the laser system housing so that selected contamination in the laser system optical compartment gas is absorbed by the selected material in the compartment. The compartment cover can be made of a porous silica.

Abstract: A gas laser 1 such as a .sup.13 CO.sub.2 -laser emits at two different wavelengths (.lambda..sub.1, .lambda..sub.2) with a sine-shaped adjustment of a resonator mirror or a grating 13 such as a Littrow grating. The gas laser emits radiation at the two desired wavelengths (.lambda..sub.1, .lambda..sub.2) in two mutually adjacent intervals of the resonator length L because of a suitable dimensioning of the grating 13 with respect to grating structure and angle position, the outcoupling factor of the outcoupling mirror 12, the resonator length L and the composition of the gas of the laser. The laser emission is inhibited at the crossover between the two intervals and the sine-shaped modulation (for example with a piezo element) of the resonator length L is essentially symmetrical about this crossover. The invention is also directed to an arrangement for detecting a substance such as NH.sub.3 in a flue gas.

Abstract: A semiconductor laser that includes a monolithic submount with a light emitting source aligned along one side thereby defining a radiation path over which the emitted light propagates. The submount includes two notches that flank the light emitting source. A micro-lens is mounted adjacent to the light emitting source by attaching to the submount with either epoxy or solder. Finally, the components of the semiconductor laser have matching coefficients of thermal expansion so that the optical alignment of the light emitting source and the micro-lens is maintained notwithstanding thermal cycling.

Abstract: In an optical soliton transmission system an optical transmitter (2) generating short pulses is coupled to a glass fiber cable (4) comprising sections of glass fiber (7, 9, 11, 13, 15) with interspaced semiconductor laser amplifiers (8, 10, 12, 14). An optical receiver (6) is connected to the end of the glass fiber cable (15). In optical soliton transmission Erbium doped fiber amplifiers and dispersion shifted fiber are currently used in the 1.5 .mu.m wavelength region. However, by utilizing standard fiber in the 1.3 .mu.m wavelength region it is possible to use a lower soliton power compared with a state-of the-art transmission system.

Abstract: A servo controlled laser system is provided which provides a laser output beam having reduced optical noise. The laser system may be any type of laser system and preferably is an ion laser system. The servo controlled laser system includes a laser head providing a laser output beam and a power driver coupled to the laser head which supplies input power to the laser head. The laser system also includes a light detector in the path of the output beam which generates an alternating current signal in response to the amount of optical noise detected in the laser output beam. A signal amplifier is coupled to the light detector for receiving and amplifying the alternating current signal. A wire couples the signal amplifier to power driver compensator circuitry which receives the amplified alternating current signal from the wire and, in response, adjusts the input power to reduce optical noise.

Abstract: A diode pumped laser system includes a laser cavity with an active laser medium. A laser diode, with an emitter region having an output facet that produces light at a frequency .lambda..sub.1, is the pump source for the laser medium. A coupling optics is positioned on an emission path of radiation from the emitter region and is optically coupled and spaced from the diode. The coupling optics produces stray radiation. An optical fiber, with a first end and a second end, is included. The first end of the fiber is oriented with respect to the coupling optics such that radiation from the emitter region is optically coupled into the optical fiber. The second end of the fiber is coupled to the laser cavity. A detector is positioned in a spaced, adjacent relationship to the coupling optics along an emission path of the stray radiation. The detector detects at least a portion of the stray radiation and produces a detected output in response to the stray radiation.

Abstract: A system is disclosed for minimizing the depolarization of a laser beam due to thermally induced birefringence in a rod-shaped gain medium over a wide range of excitation levels. After passing through the gain medium, the polarization of the beam is rotated by ninety degrees and either redirected back into the same gain medium or a substantially identical gain medium. By this arrangement, the portion of the beam that was radially polarized during the first pass is tangentially polarized during the second pass so that the original polarization is restored. In order to maximize the compensation, a relay image system is used to generate an image of the beam in the gain medium as it existed during the first pass and project that image into the gain medium during the second pass. The magnification of the relayed image is substantially one to one with respect to the actual image.

Abstract: According to a semiconductor laser device of the present invention, the thickness and carrier concentration of a current blocking layer are set so as to cause a punch through on the current blocking layer when the semiconductor laser device is driven at a current which is one to ten times as large as a maximum rated value of a DC driving current. Both a light absorbing layer and a photocurrent blocking layer are formed between the current blocking layer and a second clad layer in order to prevent a light turn-on phenomenon from occurring. The light absorbing layer contacts the second clad layer and is constituted of a semiconductor crystal of a p-type conductivity type, which is undoped or has a low concentration. The photocurrent blocking layer contacts the current blocking layer and is constituted of a semiconductor crystal of the p-type conductivity type. If the band gaps of the light absorbing layer, photocurrent blocking layer, and active layer are represented by E.sub.ab, E.sub.ocb, and E.sub.

Abstract: At least one coil (32) is located on an exterior side face (30) of a frame (12) of a ring laser gyroscope (10) such that a significant component of the magnetic field generated by the coil is colinear with the plasma discharge of the gyroscope, and by which dispersion equalization of the gyroscope can be effected. The coil may be supported by a magnetically permeable annular bobbin (40), which is set about a mirror (26) on side face (30) and which may be partly set within grooves in the side face, to reduce the current necessary to effect dispersion equalization and to provide shielding of the mirror from the effects of tangential and transverse fields, and to increase the shielding effects for the mirror, both from Faraday rotator magnets (16) and from external magnetic fields. For those mirrors where no coils are present, the annular bobbins are used solely for their shielding properties.

Abstract: In a of modulating a feedback signal in an optical amplifier, employing a laser diode LD, which can directly amplify an optical signal, the amplified optical signal is modulated by the feedback signal SV which is controlled in such a way as to compensate for the saturation characteristics of the laser diode LD to correctly modulate the feedback signal even if the laser diode is nearly saturated due to aging or fluctuations in temperature.

Abstract: A system for producing laser output from a solid-state laser is described. The laser output comprises two orthogonally polarized axial modes of light at different frequencies having linear polarization. In one embodiment, the two modes are at different frequencies and can be merged together to produce energy waves of variable frequency. This device has applications in microwave generation and velocity measurements.

Abstract: An electronic compensation circuit in which a simulation of a laser's thermal droop characteristics is used to adjust input to the laser and thereby compensate for the laser's thermal droop effects. The simulation circuit is connected to the laser either as an open loop circuit to provide a once only correction or as a closed loop feedback circuit to provide a continuous correction of the laser droop effects. The simulation circuit is designed using either analog or digital circuitry and is adjustable to provide compensation for lasers having different time constants of droop or different values of droop.

Abstract: A particular embodiment comprises:a semiconductor laser;a Mach-Zehnder type modulator;an analog adder for adding a modulation signal representing binary data with a DC bias voltage;a coupler for taking off a fraction of the modulated light signal;a photodiode;an amplifier;a bandpass filter tuned to a frequency equal to the binary data transmission rate;an amplifier;an amplitude detector;an amplifier; anda microprocessor associated with an analog-to-digital converter and with a digital-to-analog converter to modify the bias voltage so as to cause the amplitude of the spectrum line extracted by the filter and the amplitude detector to remain below a fixed threshold value. The invention is applicable to digital data transmissions.

Abstract: A semiconductor optical source includes a first laser diode supplied with a signal current pulse and a first bias current for producing an output optical signal pulse in response to the signal current pulse, a first biasing circuit for supplying the first bias current to the first laser diode, a second laser diode supplied with a second bias current for producing an output optical beam in response thereto, a second biasing circuit for supplying the second bias current to the first laser diode; a heat sink for maintaining the first laser diode and the second laser diode at a substantially identical temperature; and a threshold detection circuit for detecting a threshold of laser oscillation of the second laser diode, wherein the threshold detection circuit controls the first biasing circuit such that the first bias current is maintained at a level that is related to the threshold of the second laser diode.

Abstract: An apparatus for and a method of controlling a laser oscillator for use as a laser source in a machining operation or the like is disclosed. In particular, the present invention compensates for a deviation of an actual input/output characteristic of a laser oscillator from a normal (expected) input/output characteristic due to, for example, aging and the like. The present invention approximates the actual input/output characteristic and stores the characteristic as a pattern in a storage device. In response to a detection of the actual laser output and an external intensity command signal, the present invention refers to the input/output characteristic pattern thus approximated and generates an input intensity command signal for controlling the laser oscillator to accurately produce the desired laser beam intensity irrespective of the deviation between the actual input/output characteristic and the normal characteristic.

Abstract: A laser diode assembly is disclosed which utilizes a feedback system which substantially reduces the dependency of the optical output power of the laser diode on laser junction temperature which is dependent on the pixel pattern. The feedback system of this invention utilizes a low pass filter to detect the low frequencies of the train of pixel information which cause a certain droop. The low pass filter generates a signal based on the detected frequencies which after being scaled will be used as a feedback signal. The feedback signal will be applied to the driver of the laser diode to adjust the driving current of the laser diode for the detected patterns to substantially reduce the droop and the cross talk.

Abstract: A ring laser angular rate sensor getter mounting clip is configured so that the susceptibility of the mounting clip to radio frequency (RF) energy used to activate the getter is minimized. The clip is configured so that opposing RF current flow is induced which prevents heating of the clip beyond force relieving temperatures for the clip material, whereby the clip maintains its retaining force within a getter well via three contact surfaces to more stably retain the getter in its proper position within the well.

Abstract: An exposure apparatus, such as a stepper, uses a laser light source requiring new gas introduction from time to time. The timing of new gas addition and partial gas replacement is controlled so that the exposure apparatus is not adversely affected. In one embodiment, the timing is such that gas introduction or replacement occurs during interruption of exposure operation, which does not start again until the fluctuation of the output of laser light caused by gas introduction or replacement is stabilized.

Abstract: A laser transmitter utilizes a laser diode which is biased to its stimulated (laser) emission mode of operation by the application of current from a source of one or more operating voltages. The failure of any of these voltages and over temperature conditions of the laser are detected by an optical AND gate which switches the operating voltage off when any one of them is absent. The temperature of the laser is also detected and applied to one of the optos in the chain of the AND gate such that an over temperature condition also results in the switching off of the operating voltage and shut down of the laser. The temperature detection is by way of a circuit having hysteresis such that the optical AND gate is not enabled until the temperature the laser decreases below the initial cut off temperature. Operating current for biasing the laser for laser emission is applied gradually over a period from one to five seconds by connecting the switched operating voltage source to the laser through a slow start circuit.

Abstract: Light from a laser (10) is divided by a beam splitter (12) to provide signal (15) and reference (14) channels. The signal channel light is expanded (11) to illuminate an acousto-optic (AO) device (13). This leads to a spatial distribution of Doppler shifted frequencies. This spatial distribution then illuminates a spatial light modulator (SLM) (19) such that a number of parallel and discrete optical channels (112) emerge. In a local area network (LAN) the optical signal channels are coupled into a single mode optical fibre (22) and then heterodont to the reference laser light from a further optical fibre (23) in an optical coupler (25). In a receiver the modulated light is detected (32) and the detected signal connected to the transducer of an AO device (35). The AO device (35) is illuminated by a receiver laser light (36) and the emerging modulated light is incident on a focal plane detector array (39) where each detector (310) then receives light corresponding to each of the transmitted channels (311).