Abstract: An injection seeded, single frequency ring laser source is presented wherein stabilization and single frequency control is accomplished by measuring the intensity or power of the portion of the high power laser beam generated in the ring slave laser and which is directed to return to the seed laser. When the intensity of the return beam falls below a preset threshold level, the in-phase operation of the laser system has been established and high energy single frequency pulses are generated and emitted.

Abstract: Frequency modulated radar transmitters with a repetitive linear increase in frequency with time, referred to as "frequency chirps", are required for many radar applications. The present invention provides a simple way of obtaining such a chirped frequency modulation for a laser radar transmitter or the like. The principle is to translate an optical wedge in the direction of its wedge gradient at constant velocity across the optical path of a laser resonator. The resulting increase or decrease in the effective optical length of the resonator causes frequency chips. In a first embodiment of the present invention, a rotating phase plate on the face of a rotating wheel with the added phase varying linearly with angular position around the wheel is placed within a laser's resonator cavity to tune the optical pathlength of the cavity and thereby the longitudinal mode of the resonator to produce the chirp. This embodiment can be used in either a reflective or a transmissive mode.

Abstract: The present invention provides various embodiments of laser systems for generating "chirp" signals. In the broadest sense, a diffraction grating is placed within a laser cavity on the face of a carrier and the motion of the carrier in its own plane causes the laser to chirp. Typically, the diffraction grating is placed in the end-reflector position of the optical path of the resonant cavity associated with the laser. By putting the diffraction grating on the outer peripheral rim of a wheel and rotating the wheel, a sequence of either up-chirp or down-chirp signals can be generated continuously. Similarly, the desired "chirped" signals can be generated by using a diffraction grating oriented radially on the face of a rotating wheel.

Abstract: A driver circuit of a laser diode. The laser diode has a first electrode structure for injecting a first drive current with a first magnitude and a second electrode structure separated from the first electrode structure for injecting a second drive current with a second magnitude. The second electrode structure is provided in correspondence to a location in diode at which said carriers are depleted most. The driver circuit comprises a presetting circuit for presetting a relationship between the first and second magnitudes, and a current distribution circuit controlled by the presetting circuit for producing the first and second drive currents with respective magnitude satisfying the relationship that is preset by the presetting means.

Abstract: A laser source comprises an optical fiber doped with a homogeneously broadened lasing medium, preferably with Erbium, pumped by a laser pump source and an intracavity acousto-optic modulator. When the acousto-optic modulator is driven by a variable frequency source, the Erbium fluorescence line emitted by the Erbium-doped optical fiber can be electronically tuned. In another embodiment, an electronic sweep waveform is used to frequency modulate the acoustic signal produced by the acousto-optic modulator. Without the low-rate frequency modulation, Erbium in a silica optical fiber is a mostly homogeneously broadened gain medium with a narrow laser linewidth. When measured on a long time scale, low-rate frequency modulation provides a broader spectral width, on the order of 19 nm, which makes such a source an ideal source for certain optical applications such as fiber optic gyroscopes.

Abstract: A wavelength monitor/stabilizer for narrowly controlling the bandwidth of laser; the monitor/stabilizer uses parameters Q, F or G derived by measuring diameters of interference fringes given by the beam of the wavelength-controlled narrow bandwidth laser e.g. excimer laser and those given by the reference light e.g. of a mercury lamp. The controlling is made by controlling the parameter to be in a predetermined range. An image sensing unit for detecting the interference fringes are splitted into plural image sensors with adjustable distance for enabling more rapid measurement by skipping the in-between part.

Abstract: A solid-state laser oscillator/amplifier system, which combines in a single laser crystal the operations of a narrow beam oscillator and a large volume amplifier, utilizes the polarization feature of the laser beam to effect coupling of an amplified beam out of the resonator in a manner which efficiently utilizes the whole volume of the active medium. The system generates a high brightness laser beam with high output energy contained in a small divergence angle.

Abstract: The operating point is stabilized at the MAX or the MIN of its optical frequency discriminating characteristic. Under the stabilized operating point, the detected difference between the average of the light intensity and a set value is fed back to a data modulator so that the average value converges on a set value when a predetermined optical frequency deviation is produced. The operating point is also stabilized at the MED of said characteristic. Under the stabilized operating point, a low-frequency signal component is extracted from an electric signal output by means of synchronous detection. The operating point is stabilized at the MAX or the MIN of said characteristic. Under the stabilized operating point, a low-frequency signal component is twice in frequency by means of synchronous detection. In the fourth and fifth aspects, means such as synchronous detection is not required for the stabilization control of an operating point.

Abstract: A system for the generation of modulated optical signals, wherein to the d.c. bias current of a semiconductor laser (1) associated with an opto-electronic feedback circuit (2) including a delay, there are superimposed the variations of a current obtained by detecting an optical signal resulting from the combination of an optical, amplitude-modulated input signal and of the optical signal present in the feedback circuit. By a suitable choice of the modulation frequency (f2) of the input signal and of the low-frequency gain (B) of the feedback loop (2), the laser output signal is amplitude-modulated at a frequency equal to the modulation frquency (f2) of the input signal.

Abstract: A laser source comprises an optical fiber doped with a homogeneously broadened lasing medium, preferably with Erbium, pumped by a laser pump source and an intracavity acousto-optic modulator. When the acousto-optic modulator is driven by a variable frequency source, the Erbium fluorescence line emitted by the Erbium-doped optical fiber can be electronically tuned. In another embodiment, an electronic sweep waveform is used to frequency modulate the acoustic signal produced by the acousto-optic modulator. Without the low-rate frequency modulation, Erbium in a silica optical fiber is a mostly homogeneously broadened gain medium with a narrow laser linewidth. When measured on a long time scale, low-rate frequency modulation provides a broader spectral width, on the order of 19 nm, which makes such a source on an ideal source for certain optical applications such as fiber optic gyroscopes.

Abstract: Coupling apparatus for a large bore metal vapor laser is disclosed. The coupling apparatus provides for coupling high voltage pulses (approximately 40 KV) to a metal vapor laser with a high repetition rate (approximately 5 KHz). The coupling apparatus utilizes existing thyratron circuits and provides suitable power input to a large bore metal vapor laser while maintaining satisfactory operating lifetimes for the existing thyratron circuits.

Abstract: A semiconductor optical amplifier is utilized for optical amplification and for detection of an optical signal at the current injection electrode of the optical amplifier. A wide detection bandwidth is provided by utilizing an impedance transformer between the current injection terminal and the detection circuit. The impedance transformer typically has an input impedance of about 1 to 15 ohms. The impedance transformer can be a bipolar junction transistor circuit, a microstrip transmission line impedance transformer or a hybrid impedance transformer. A wide detection bandwidth is also obtained by providing a semiconductor optical amplifier having two current injection electrodes. A bias current is supplied through both current injection electrodes, and both electrodes produce optical gain. However, only one of the electrodes is used for optical signal detection. The detection electrode has a relatively high junction resistance and a relatively high series resistance.

Abstract: A drive current is modulated by a current modulator, and the modulated drive current is supplied to a laser beam generator so that the laser beam emitted by the laser beam generator is varied in wavelength. The laser beam is applied to a frequency converter, and the maximum intensity of the laser beam from the frequency converter is detected by the light detector. Based on the detected intensity, the temperature of the laser beam generator is regulated by a temperature regulator. The wavelength of the laser beam generated by the laser beam generator is thus controlled so as to be best suited to the phase matching condition of the frequency converter. The harmonic generator is simple in arrangement and small in size, and can operate stably over a long period of time without deterioration due to aging.

Abstract: Multibeam coupling in a Kerr medium of nonlinear characteristics and finite response time is disclosed together with two different frequency spectrum examples of its use. In the first spectrum example, the modes are equally spaced and in the second spectrum the frequency separations are all unequal. In either case, as the beams propagate, both input spectra eventually reach a saturation characterized by a cascading of energy into the lowest frequency if the Kerr constant is positive. The direction of cascading of energy transfer is reversed to the highest frequency if the Kerr constant is negative. The examples disclosed include a typical Kerr medium and are representative of a multimode, equally spaced laser source and an unequally spaced source. For the equally spaced case, the optimum medium response time for conversion of Gaussian spectra is disclosed. If the frequencies are unequally spaced general conditions to be satisfied are disclosed, along with examples.

Abstract: A method for controlling a narrow-band oscillation excimer laser which is suitable for control of an excimer laser used as a light source of a reduced projection exposer, and a system thereof. At least two wavelength selective element are disposed within a laser oscillator. There are provided a center wavelength control for causing an oscillation center wavelength determined by these wavelength selective elements to coincide with a desired value, an overlapping control for overlapping the transmission wavelengths of these wavelength selective elements, and a power control for controlling a voltage applied to electrodes located within a laser chamber to thereby control a laser output. Partial gas replacement is carried out when the application voltage to the electrodes within the laser chamber becomes high.

Abstract: A method and apparatus using sinusoidal cross-phase modulation, provides a laser pulse having a very broad bandwidth while substantially retaining the input laser's temporal shape. The modulator may be used in a master oscillator system for a laser having a master oscillator-power amplifier (MOPA) configration. The modulator utilizes a first laser providing an output wavelength .lambda. and a second laser providing an output wavelength shifted by a small amount to .lambda.+.DELTA..lambda.. Each beam has a single, linear polarization. Each beam is coupled into a length of polarization-preserving optical fiber. The first laser beam is coupled into the optical fiber with the beam's polarization aligned with the fiber's main axis, and the second beam is coupled into the fiber with its polarization rotated from the main axis by a predetermined angle. Within the fiber, the main axis' polarization defines an interference beam and the orthogonal axis' polarization defines a signal beam.

Abstract: A sensor is disclosed for detecting a physical magnitude, comprising a mechanical resonator, adapted to be subjected to a mechanical stress representative of the magnitude to be measured, and means for causing the resonator to oscillate and maintaining its oscillations at a resonance frequency representative of the magnitude to be measured, wherein the resonator is made from a solid laser material and said oscillation means comprise means for feeding the laser resonator with a continuous pumping light beam.

Abstract: An apparatus for generating a relatively high-power, modulated optical beam s disclosed. The apparatus comprises a first element for emitting a relatively low-power laser beam at a preselected wavelength, means for focusing the laser beam into a focused beam, a damage-resistant integrated optic modulator responsive to the focused beam for developing a modulated beam, optical means for shaping the modulated beam into a shaped modulated beam, and semiconductor means having a large active area responsive to the shaped, modulated beam for producing a relatively high-power, output modulated beam. In a first embodiment, the semiconductor means is a semiconductor amplifier which amplifies the modulated beam to produce the high-power, modulated output beam.

Abstract: A method for stabilizing an oscillation frequency separation among a plurality of laser devices wherein a plurality of laser devices are controlled to emit light outputs each having a predetermined frequency so that a frequency separation is stabilized, wherein the plurality of laser devices are divided into a plurality of groups, in each of which the frequency separation is stabilized in accordance with a reference light output of one reference laser device. On the other hand, a plurality of the reference laser devices are controlled to stabilize a frequency separation each other, so that relative frequency separation among the plurality of groups of the plurality of laser devices are stabilized. As a result, a frequency separation of a large number of laser devices is stabilized.

Abstract: The present invention relates to a laser frequency modulator for modulating a laser cavity. It is known in the prior art to utilize a PZT (piezoelectric transducer) element in combination with a mirror to change the cavity length of a laser cavity (which changes the laser frequency). Using a PZT element to drive the mirror directly is adequate at frequencies below 10 kHz. However, in high frequency applications (100 kHz and higher) PZT elements alone do not provide a sufficient change in the cavity length.The present invention utilizes an ultrasonic concentrator with a PZT element and mirror to provide modulation of the laser cavity. With an ultrasonic concentrator, the mirror element at the end of a laser cavity can move at larger amplitudes and higher frequencies.

Abstract: In an optical heterodyne receiver having a local oscillating light source controlled by a driver circuit and which uses a polarity diversity technique thereby producing first and second intermediate frequency signals, an automatic frequency control circuit (AFC) controls the driver circuit by generating an error signal. The AFC includes two power regulators for generating respective fixed power signals based on the two intermediate frequency signals.

Abstract: In a laser emitter-receiver system, a tunable diode laser provides a beam of coherent light having a selected frequency. An infrared detector spaced from the source detects the light transmitted along the beam path between the source and the detector and produces a corresponding output in response thereto. A heating laser provides radiation to the diode laser to heat, and thereby to change the frequency of, the latter laser. The radiation from the heating laser is varied periodically to modulate the intensity of the radiation incident on the diode laser thereby to frequency-modulate the diode laser output over a selected tuning range. A controller responsive to the detector output regulates the current to the diode laser to minimize selected frequency components of the modulated light beam from that laser so that the power output of the diode laser varies minimally when that laser is tuned over the selected tuning range.

Abstract: A method and apparatus is presented whereby control of the frequency of pulses emitted by a resonant ring slave laser is forced to a single frequency defined by a seed laser through the control of the pathlength of the ring laser resonant path. By monitoring the time difference between turn on of a Q-switch within the laser resonant cavity and the time of occurrence of the output pulse of the slave laser, and effecting changes to the ring laser resonant path in a manner to minimize the measured time difference, the frequency of the output pulse from the slave laser is driven to a single frequency defined by the seed laser resonator.

Abstract: A semiconductor laser HL has an external resonator including a reflector R which reflects the emitted laser beam back into the front facet of the laser. The light emitted from the rear facet of the laser falls on a photodiode PD which generates a signal s which is evaluated by an evaluation unit AE. By differentiation or other processing of the shapes of pulses in the signal s, it is possible to determine the direction of change of any of several operating parameters of the laser system, such as the length L between laser HL and reflector R, the tilt angle of reflector R with respect to the optical axis of the laser or the refractive index n of the medium in the space N defined between the laser and the reflector. For example, one can detect when gas G is fed into space N to change the medium from ordinary air to carbon dioxide, or the reverse.

Abstract: A method and apparatus for selectively blocking light beams of different wavelengths with the use of a single color-sensitive filter by passing the beams through a multiple layer system consisting of an input polarization plate (12), an output polarization plate (14), a liquid crystal cell (18) sandwiched between voltage-controlled matrices (20a and 20b), and a mosaic color mask (34). The incident light is detected by a photoelectronic sensor (32) which sends voltage signals to respective pixels (22) which form the above-mentioned matrices. These signals selectively control the polarization states of the beams passed through the respective pixels. Depending on the polarization states of the beams, the output polarization plate can either block the light or pass it to a color mask (34). This mask consists of a periodical set of color cells, the amount and dimensions of which correspond to those of the pixels. As a result, the mask selectively filters the beam in accordance with its pattern.

Abstract: A semiconductor laser device of the field modulation type includes a structure in which the threshold carrier density for laser oscillation is reduced so as to enable an effective action of a modulated electric field applied externally on an active region for radiating light, thereby enabling an extremely high speed modulation. A quantum structure which does not fulfill the charge neutrality condition for free-carriers or a strained super lattice structure is adopted as the structure in which the threshold carrier density is reduced.

Abstract: Photoreceptor for frequency-modulated optical signals. The photoreceptor consists of a semiconductor laser (10) fed clearly beyond the threshold (12). The optical signal (20) to be demodulated is injected into the laser. The voltage (V) taken at the terminals of the latter reflects the frequency difference between the frequency of the signal (F1, F2) and the actual frequency (Fo) of the laser.

Abstract: A tunable laser having a range of possible emission frequencies has a Bragg cell mounted inside its laser cavity such that only light passing through the Bragg cell without Bragg deflection will be emitted by the laser.

Abstract: The injection current for a laser diode is modulated so that a pregiven coherence function is obtained which drops off continuously at both ends outside of the coherence length. Several laser diodes are used for a very short coherence length for which the modulated wave numbers of the emitted radiation follow one another or overlap.

Abstract: A CO.sub.2 waveguide laser frequency modulation (FM) system which applies the Fourier series components of a triangular drive waveform selectively to the tuning PZT at one end of the waveguide and the FM PZT at the other end to achieve an improvement over the waveform than can be achieved by applying the fundamental and its harmonics to the FM PZT alone. The system applies the fundamental component to the tuning PZT and the odd harmonics to the FM PZT. The frequency-separated drive signals are applied in proper phase to the PZT's at each end of the waveguide via waveform synthesizer, frequency splitter and amplifiers. The waveform synthesizer includes a ROM containing digitized values of segments of the waveform amplitudes and a digital-to-analog converter for converting the digital ROM data to an analog signal.

Abstract: A method and apparatus which corrects the amplutide variation in the output in an electro-optic modulated laser system (10). Birefringence within the electro-optic crystal (25) causes elliptical polarization of the linearly polarized laser light (22) produced by the laser gain medium (16), in turn causing a loss in the laser output (27). The loss owing to the elliptical polarization is corrected by either applying a D.C. bias from voltage source (30) directly to the electro-optic crystal (25) or by inserting a quarter-wave plate (32) within the laser's resonant cavity.

Abstract: In an optical communication system, in order to reduce simultaneously both second and third harmonic distortion in a light beam from a modulated semiconductor laser, a nonlinear interferometric deivce--such as a Fabry-Perot etalon--is inserted in the path of the beam. The parameters of the interferometric device--such as its phase and finesse--are selected such that, for a suitable laser bias current, the second and third harmonics produced by nonlinearities of the laser (plus nonlinearities of the transmission medium such as an optical fiber, if any, through which the beam propagates from source to receiver) are significantly compensated by nonlinearities of the interometric device.

Abstract: Apparatus and method for modulating the phase or the amplitude of a monochromatic light beam, the apparatus including in one embodiment a Mach-Zehnder interferometer that consists of two beam splitters or beam combiners, a fully reflective mirror and an electro-optical crystal for modulation of one of two beam components. The electro-optical crystal serves as an optical resonator for the portion of the light beam admitted into the crystal material, using total internal reflection of the light beam from two or more of the crystal surfaces. The crystal has a high finesse so that a relatively small change in voltage applied across the crystal produces a large (.apprxeq.180.degree.) change in the external phase shift associated with the modulated component of the light beam.

Abstract: Apparatus, and a corresponding method, for phase-modulating an optical carrier signal. An input data signal is passed through a derivative filter to obtain a time-differentiated data signal, for application directly to a laser diode, which functions inherently as a frequency modulator. The carrier signal is frequency-modulated by the time derivative of the input signal, and this is equivalent to being phase-modulated by the input signal.

Abstract: A stabilized helium-neon laser emits radiation in the ranges of ultra-violet, infra-red and visible other than red in at least two modes. A stabilizing system consists of an alignment heater (19) which bends the laser tubes toward optimum alignment, a coil heater (20) which cyclically varies the tube length and permanent magnets (24,25) which reduce instability of mode polarizations and to optimize relative intensities of the modes. The transmitted output is stabilized in frequency by control of the laser tube length, with the stabilization signal derived from the steady or varying intensity of intensities of one or both of two orthogonally polarized optical outputs. There are many potential uses for non-red helium-neon lasers in applications where non-red light is required, for example, in multi-wavelength interferometry.

Abstract: A laser device according to the present invention having a semiconductor laser which has at least two longitudinal modes .lambda..sub.0 and .lambda..sub.1 both of which are able to oscillate, and oscillating at the single longitudinal mode .lambda..sub.0. The device further comprises input means which inputs a wave nearly coincident with .lambda..sub.1 to the semiconductor laser to switch the oscillating wavelength from .lambda..sub.0 to .lambda..sub.1. The semiconductor laser maintains its oscillating wavelength .lambda..sub.1 even if the intensity of said wave input from said input means reduces.

Abstract: Reference signals having a predetermined frequency interval are produced in use of a wavelength tunable laser device and an optical resonator. Plural laser devices are controlled to radiate light outputs with oscillation frequency separation. The light outputs and a frequency swept light output of the wavelength tunable laser device are combined, and then converted to beat signals. The reference signals and the beat signals are compared to detect time differences of signal occurrance timings. The plural laser devices are driven with the oscillation frequency separation, such that the time differences become a predetermined value. Where a beat pulse is not produced due to a fault in at least one laser device among the plural laser devices, a dummy pulse is produced to produce signal of the time differences. The laser device of the fault may be driven with an injecting current varying in a predetermined range to produce a beat pulse.

Abstract: A method and apparatus for locking the frequencies of a number of first beams of coherent radiation from respective sources. Typically, the sources will form local oscillators in respective transmitters. The apparatus includes a reference beam generator such as a HeNe laser which generates a primary reference beam fed to an interferometer which generates a second, reference beam composed of a number of reference frequencies. This second reference beam is caused to interfere with each of the beams from the local sources in an optical coupler and the resultant beam is detected with a photodiode. The electrical output signal of the photodiode is filtered and fed to a discriminator which controls the frequency of the local laser. The discriminator controls the laser to maintain the relationship between the frequencies of the laser and the reference laser substantially constant.

Abstract: A frequency control arrangement for a gas laser operable in two longitudinal modes of laser oscillation includes a receiver for generating a difference frequency signal formed from the two longitudinal modes and mixing the difference frequency signal with a reference signal. The resulting intermediate signal is used to control an adjusting element on the laser resonator so that the laser emission is held at a predetermined frequency value.

Abstract: The present invention relates to an analog frequency modulatable laser. The radiation of the lasing medium is analog frequency modulated by change of the optical path length by movement of reflective mirrors forming the resonant cavity at the frequency of radiation of the laser in a manner corresponding to an information signal. In one embodiment, a magnetostrictive material is deposited on and bonded to the outer periphery of an active lasing medium having appropriate mirrors on the ends thereof. The magnetostrictive material is exposed to an information encoded magnetic field and physically expands or contracts the physical length of the lasing medium along the optical axis of the lasing medium corresponding to the modulated information of the magnetic field.

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 transmitter utilizes optical far field combination of two independent lasers (80,90) and variation of RF exciting power (86) to one (80) to produce sufficient frequency modulation. Two bores (122,124) within the same dielectric body (120) are provided with two independent sets of electrodes (134,135, 138,139) and two independent RF power sources (150,152). The lasers are operated at different frequencies and the beams transmitted in parallel adjacent paths to provide a combined far field optical beam component at the beat frequency of the two lasers. Variation of the frequency of one of the lasers provides frequency modulation of the far field beat frequency, enabling reception and demodulation of the modulated beam without use of a local oscillator laser at the receiver. The transmitter may also be used in a laser radar.

Abstract: An optical device is disclosed wherein a Fabry-Perot etalon (12) is used as a spectral mode selector externally coupled to a source of modelocked optical pulses (10). By adjusting the cavity length of the etalon (12), a plurality of equally spaced predetermined modes output from the source are transmitted by the etalon. These modes which are transmitted combine coherently to create a stream of optical pulses (16) having a higher repetition rate than the repetition rate of the source.

Abstract: In a method for the automatic frequency control of semiconductor kasers, the signal emitted from the laser (1) is sent to an optical resonator (6) whose resonance frequency is modulated by a ramp signal, the signal outgoing from the resonator (6) is converted into an electrical signal, the derivative of such an electrical signal is calculated, the zero crossing of the derivative is detected, the ramp signal is sampled in corresponding with such a zero crossing, and the sample thus obtained is algebraically summed to a reference signal depenent on the nominal laser emission frequency, thus obtaining an error signal which is sent to devices (3) driving the laser (1). In case of a plurality of lasers (1a . . . 1n) the signals of which are wavelength multiplexed, the rame signal is sampled in correspondence with the derivative zero crossings corresponding with the emission frequencies of the individual lasers (1a . .

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: To overcome the deleterious effects of the nonuniform frequency modulation response in semiconductor lasers due to current injection in direct frequency modulation applications, it has been determined that the linewidth enhancement factor .alpha. be made as large as possible. In one embodiment, distributed feedback lasers well suited for frequency modulation lightwave communication systems are designed to have an integrated feedback element such as a corrugation grating whose effective pitch is selected to cause the Bragg wavelength and, therefore, the laser operating wavelength to be longer than the wavelength at substantially the maximum gain or gain peak in the semiconductor structure without the grating. That is, the wavelength of the grating is effectively detuned toward the longer wavelength and lower energy side of the peak of the gain profile.

Abstract: For stabilizing the frequency of a narrow-band Excimer laser beam the interference rings of a Fabry-Perot interferometer 16 are projected onto a solid-state image sensor 18 and by means of the solid-state image sensor an electrical signal is generated which is dependent on the frequency of the laser beam. The electrical signal is compared with a stored reference signal to derive an adjusting signal 32 for an optical reflection grating 38 with which the frequency of the laser beam 12 is regulated to a desired value. The absolute value of the frequency of the laser beam 12 is determined by means of the optogalvanic effect.

Abstract: To overcome the deleterious effects of the nonuniform frequency modulation response in semiconductor lasers due to current injection in direct frequency modulation applications, it has been determined that the linewidth enhancement factor .alpha. be made as large as possible. In one embodiment, distributed Bragg relector lasers well suited for frequency modulation lightwave communication systems are designed to have an integrated feedback element such as a corrugation grating whose effective pitch is selected to cause the Bragg wavelength and, therefore, the laser operating wavelength to be longer than the wavelength at substantially the maximum gain or gain peak in the semiconductor structure. That is, the wavelength of the grating is effectively detuned toward the longer wavelength and lower energy side of the peak of the gain profile.

Abstract: A phase-locked semiconductor laser array is dephased-locked by forming at least two p-type contacts electrically isolated from one another coupled to one side of the active region and a single contact layer coupled to the other side of the active region. The same current is applied to two p-type contacts to form a single phase-locked far-field lobe. A different current is applied to one of the two p-type contacts to drive one contact harder than the other to form a dephased multiple lobe beam. An effective aperture at the receiver receives the in-phase single lobe and blocks the multiple lobes to produce a modulation effect at the receiver.

Abstract: A radio frequency excited carbon dioxide laser (50) is stabilized by sensing (66) variation in output power to generate a feedback signal (68,78 ) that is employed to vary amplitude of the radio frequency exciting signal from a power source (62). Frequency modulation of the laser output is achieved by varying the amplitude of the radio frequency signal from a power source (62) in response to a frequency modulating control signal from a modulation source (74). Both stabilization and frequency modulation are accomplished by combining the sensed power feedback signal with the frequency modulation control signal in a summing circuit (70) and employing the combined signal to vary magnitude of the radio frequency exciting signal.