Abstract: A package structure for horizontal cavity surface emitting laser diode with monitor photodiode chip includes a header with a plurality of conductive pins, where three conductive pins extend onto the surface of the header. One of the conductive pins is attached to a stage with a slope and a monitor photodiode chip is placed on the top of the stage. A submount is placed among the three conductive pins and is attached to a laser diode chip. The back facet of the laser diode chip is facing the stage. The upward surface emission light of the laser diode chip is focused outside the transparent window by the lens on the transparent window and the horizontal emission light of the laser diode chip is incident on the monitor photodiode chip, whereby the power of the light can be detected.

Abstract: The present invention is directed to a method and system for providing a three-level current scheme to a semiconductor laser to control beam wavelength and laser temperature. A first current is received into a gain section of the semiconductor laser and at least one other current is received into a DBR and/or phase section of the semiconductor laser. This other current(s) is pulse-width modulated based upon a required temperature value. An output beam is generated by the semiconductor laser based upon the received first current and the received pulse-width modulated current(s).

Abstract: To make a terahertz wave generation system capable of easily illuminating terahertz wave on an arbitrary position and to easily realize the system for practical use by effectively using existing systems and devices, the terahertz wave generation system has: a two-wavelength oscillation laser device capable of simultaneously oscillating laser light having two wavelengths and varying the wavelengths; an optical fiber that transmits laser light having two wavelengths, which has been output from the two-wavelength oscillation laser device; and wavelength conversion means for generating terahertz wave by difference frequency generation using the laser light having two wavelengths, which has been transmitted by the above-described optical fiber.

Abstract: A method and apparatus for controlling bias and alignment in an optical signal transmitter for providing intensity modulation and DPSK modulation to an optical signal, e.g. in an RZ-DPSK modulation format. Output power in dither signals applied to the bias signals may be detected by a low speed photodetector. One or more of the bias signals may be adjusted in a low speed control loop in response to an error signal obtained by mixing the detected signal with the low frequency dither signals.

Abstract: The present invention relates to a single mode light source device having an external cavity. The single mode light source device according to the present invention includes a laser diode, an integrated lens, and an optical fiber. The optical fiber has an incidence surface cleaved at a predetermined angle, such that a portion of light emitted from the laser diode is reflected to return to the laser diode. An internal cavity embedded in the laser diode is combined with an external cavity, thereby selecting only an optical signal of a single mode (wavelength) and outputting the selected optical signal. The external cavity is formed between a light emitting surface of the laser diode using multi mode oscillation and the incidence surface of the optical fiber. According to the present invention such constructed, the single mode light source can be embodied easily at a low price and also can be used as a variable wavelength light source.

Abstract: A waveguide to waveguide coupled hybrid master oscillator power amplifier (MOPA) includes a wavelength locked laser master oscillator (MO) first chip including a semiconductor substrate, a waveguide region having a gain section, one side of the MO including an integrated wavelength selective feedback element and the other side of the MO including an integrated reflective or coupling element on one side the waveguide and an emitting surface opposite the integrated reflective or coupling element for emitting light. A power amplifier (PA) second chip is stacked above or below the MO. The PA includes a semiconductor substrate including a waveguide region having a gain section, an integrated reflective or coupling element on a side of the PA aligned with light emitted from the emitting surface of the MO and a coupling grating or turning mirror and integrated lens on an opposite side of the PA for emitting an output beam.

Abstract: Devices and techniques for achieving signal filtering in RF or microwave frequencies by optical filtering using two separate optical paths. Each optical path may include one or more optical resonators to achieve desired optical filtering.

Abstract: A laser frequency stabilizing apparatus stabilizes an oscillation frequency of laser light by varying a resonator length on the basis of a saturated absorption line included in an optical output signal. The optical output signal is obtained by irradiating an absorption cell with the laser light. The laser frequency stabilizing apparatus includes: a light detecting section for detecting the optical output signal; a differential signal detecting section for detecting a differential signal of the optical light signal; an actuator for varying the resonator length; a drive section for driving the actuator; and a control section for controlling the drive section on the basis of the differential signal.

Abstract: The present photonic RF generation and distribution system provides a system and method for distributing an RF output signal. The photonic RF distribution system includes two optical sources for generating optical signals. A first optical source (42) is operable to generate a first optical signal having an operating frequency. A second optical source (44) is operable to generate a second optical signal having an operating frequency. A modulator (46) is operable to impress an RF modulation signal on a tapped portion of the first optical signal such that a modulated signal is generated. A first coupler (52) combines the modulated signal with a tapped portion of the second optical signal, thereby forming a combined signal having a difference frequency component. A control photodetector (50) is responsive to the combined signal to generate a tone signal.

Abstract: Particular embodiments of the present invention relate generally to semiconductor lasers and laser scanning systems and, more particularly, to schemes for controlling semiconductor lasers. According to one embodiment of the present invention, a laser is configured for optical emission of encoded data. At least one parameter of the optical emission is a function of a drive current IGAIN injected into the gain section of the semiconductor laser and one or more additional drive currents I/VPHASE, I/VDBR. Mode selection in the semiconductor laser is altered by perturbing at least one of the additional drive currents I/VPHASE, I/VDBR with a perturbation signal I/VPTRB to alter mode selection in the semiconductor laser such that a plurality of different emission modes are selected in the semiconductor laser over a target emission period.

Abstract: An apparatus and method for measuring CPT is disclosed. The apparatus includes a quantum absorber that is irradiated by radiation from an electromagnetic radiation source. The quantum absorber includes a material that exhibits CPT. The electromagnetic radiation source generates electromagnetic radiation having first and second CPT-generating frequency components. The first CPT-generating frequency component has a frequency ?L??, and a first CPT component amplitude. The second CPT generating frequency component has a frequency ?L+? and a second CPT component amplitude. The apparatus also includes a detector for generating a detector signal related to the power of electromagnetic radiation that leaves the quantum absorber. The detector signal exhibits an asymmetry as a function of frequency ? in a frequency range about a frequency ?0. The apparatus includes an asymmetry servo loop that alters one of ?L, the first CPT component amplitude, and the second CPT component amplitude to reduce the asymmetry.

Abstract: A multi-section laser diode control system comprising a multi-section laser diode (10), microprocessor controller (24), digital-to-analogue converter (28), driver circuit (30) and wavelength locker (14) is modified by inclusion of a locking circuit (40) which generates an analogue correction signal . . . 1 V ph responsive to measurements of the laser output made by the wavelength locker. The analogue correction signal is added to the preset phase voltage V ph asserted by the microprocessor controller to provide fast feedback that bypasses the microprocessor controller. This novel feedback is made possible by avoiding the use of the standard prior art control algorithm which requires a division calculation to be performed. Instead, novel control algorithms based purely on additions, subtractions and multiplications are used. The laser can thus be locked to its target output frequency without having to place slow analogue-to-digital and digital-to-analogue converters in the feedback control path.

Abstract: A photonic integrated circuit (PIC) chip comprising an array of modulated sources, each providing a modulated signal output at a channel wavelength different from the channel wavelength of other modulated sources and a wavelength selective combiner having an input optically coupled to received all the signal outputs from the modulated sources and provide a combined output signal on an output waveguide from the chip. The modulated sources, combiner and output waveguide are all integrated on the same chip.

Abstract: An optical transmitter module includes a semiconductor laser for outputting forward outgoing light and backward outgoing light, a temperature control device for controlling a temperature of the semiconductor laser, a beam splitter plate for receiving incidence of the backward outgoing light and outputting split light, which is reflected part of the backward outgoing light and transmitted light, which is part of the backward outgoing light, a first photoelectric conversion element for converting the split light into an electric signal. The beam splitter plate includes an anti-stray-light structure for preventing the transmitted light reflected by an incident surface of a wavelength filter from entering the first photoelectric conversion element through a side end surface portion of the beam splitter plate.

Abstract: An optical frequency measurement apparatus of the present invention includes: a coarse light frequency measurer that computes coarse light frequency (Fw) of measured input light based on a reference wavelength that is a wavelength of reference light; a pulsed light source that generates pulsed light including a plurality of optical frequency components with different repetition frequency (fs1) based on reference frequency (Fs) that is frequency of the reference light; a first beat signal generating section that generates a first beat signal having a first difference frequency (fc) that is difference frequency between optical frequency of the pulsed light closest to optical frequency of the measured input light among the plurality of optical frequency components and the optical frequency of the measured input light; a frequency measurer that measures the first difference frequency (fc) of the first beat signal; and an arithmetic section that computes the fine light frequency (Fx) based on the coarse light freq

Abstract: A method of tuning optical components integrated on a monolithic semiconductor chip having a plurality of first optical components integrated on the chip with each fabricated to approximate an emission wavelength along a given wavelength grid and together forming a first optical component wavelength grid. A second optical component is integrated on the chip with and optically coupled to the group of first optical components. The second optical component has a second optical component wavelength grid approximating the given wavelength grid where at least one emission peak along the second optical component wavelength grid is within an acceptable wavelength tolerance range of a particular first optical component of the first optical component wavelength grid but not the same as a corresponding emission wavelength of a particular first optical component.

Abstract: A DBR semiconductor laser is controlled in an image projecting apparatus, which includes the DBR laser having a phase and DBR region, a light wavelength converting device for converting fundamental-wave light emitted from the DBR laser into second harmonic wave light, an optical deflector for scanning the second harmonic wave in a one or two-dimensional manner, and a modulating portion for modulating the DBR laser. Coefficient calculating and wavelength adjusting steps are performed within a non-drawing time. The coefficient calculating step calculates at least one coefficient in a relationship between a DBR current to be injected into the DBR region and a phase current to be injected into the phase region for continuously shifting the wavelength of the fundamental-wave light. The wavelength adjusting step changes DBR current injected into the DBR region and phase current injected into the phase region based on the relationship.

Abstract: An optical signal emitted from a semiconductor laser is converged by a lens and then received by a single uniaxial birefringent crystal having a C axis that is inclined at an angle other than 90 degrees against a laser optical axis to output an optical signal having a polarized wave component of constant intensity corresponding to the wavelength of the optical signal regardless of temperature changes. The optical signal has an ordinary ray vibrating in a direction perpendicular to a plane including both the C axis and the laser optical axis, and an extraordinary ray vibrating in a direction perpendicular to both the ordinary ray and the laser optical axis. A first main photo detector detects the intensity of a p-polarized component of the optical signal that has passed through a polarizer and a second photo detector directly receives the optical signal converged by the lens.

Abstract: A high finesse optical resonator is used to store optical pulses of a mode-locked laser. The mode-locked laser is frequency stabilized by monitoring an optical attribute of the high finesse optical resonator indicative of a difference between a center frequency of the mode-locked laser and a resonant frequency of the high finesse optical resonator. In one embodiment FM sideband modulation is used to stabilize the mode-locked laser pulses.

Abstract: A self-contained module injects seeds into a slave laser for applications such as single mode or multimode injection seeding, master oscillator power amplifiers, regenerative amplifiers, optical parametric oscillators, Raman lasers, and LIDAR systems. The injection source provides a continuous wavelength sweeping for master-slave resonance to replace conventional cavity length control of the slave laser and phase locking schemes. The inventive module can be operated remotely as a separate unit or be packaged as a subsystem in the injection seeding system. The salve can be used as it is. Modifications of the slave laser and/or additional efforts are not needed.

Abstract: An integrated circuit lithography technique called spectral engineering by Applicants, for bandwidth control of an electric discharge laser. In a preferred process, a computer model is used to model lithographic parameters to determine a desired laser spectrum needed to produce a desired lithographic result. A fast responding tuning mechanism is then used to adjust center wavelength of laser pulses in a burst of pulses to achieve an integrated spectrum for the burst of pulses approximating the desired laser spectrum. The laser beam bandwidth is controlled to produce an effective beam spectrum having at least two spectral peaks in order to produce improved pattern resolution in photo resist film. Line narrowing equipment is provided having at least one piezoelectric drive and a fast bandwidth detection control system having a time response of less than about 2.0 millisecond.

Abstract: A number of embodiments provide multi-Wavelength Laser Source (MWLS) designs based on Super Continuum (SC) generation using Highly Non-Linear optical Fiber (HNLF). Advantageously, in some embodiments this technology only needs a single wavelength locking mechanism to tune and lock the whole set of channels to the ITU grid. Furthermore, in some embodiments, this laser system is able to provide wavelength channels in all the S, C and L bands. In this design, the optical signal provided by an initial seed laser source goes through a wavelength channel multiplier stage based on HNLF and is expanded in the frequency domain to cover a wider wavelength range. The wavelength channel multiplier consists of a number of optical fibers including various combinations of HNLF, single mode fiber and dispersion shifted fibers.

Abstract: Thermo-optic tuning apparatuses and techniques that may be used in external cavity lasers are provided. A wavelength selection device may be placed in the external cavity and may include a thermally responsive substrate and tunable optical elements extending therefrom. Heating and heat monitoring actuators may be formed in the substrate itself, with the tunable optical elements being mechanically positioned in the recesses of the substrate for thermo-optic tuning. In some examples, a separate optical path length adjustment element is also placed in the thermally responsive substrate, or elsewhere, for separate frequency tuning. This adjustment element may be part of a control that is detangled from the normal servo controls used in laser tuning.

Abstract: A wavemeter and method for measuring bandwidth for a high repetition rate gas discharge laser having an output laser bean comprising a pulsed output of greater than or equal to 15 mJ per pulse, sub-nanometer bandwidth tuning range pulses having a femptometer bandwidth precision and tens of femptometers bandwidth accuracy range, for measuring bandwidth on a pulse to pulse basis at pulse repetition rates of 4000 Hz and above, is disclosed which may comprise a focusing lens having a focal length; an optical interferometer creating an interference fringe pattern; an optical detection means positioned at the focal length from the focusing lens; and a bandwidth calculator calculating bandwidth from the position of interference fringes in the interference fringe pattern incident on the optical detection means, defining a DID and a DOD, the respective distances between a pair of first fringe borders and between a pair of second fringe borders in the interference pattern on an axis of the interference pattern, and acc

Abstract: The object of the present invention is to provide an optical module for the WDM communication system, in which the oscillation wavelength is on the grid of the WDM regulation, moreover the optical output power and the oscillation wavelength can be controlled independently. The present module comprises a semiconductor light-emitting device, a wedge shaped etalon device and two light-receiving devices. The etalon device contains a first portion, on which the anti-reflection films are coated, and a second portion. One of the receiving devices detects light transmitted through the first portion of the etalon device, while the other device detects light through the second portion. Signal from the former device controls the output power of the light-emitting device, while the signal from the latter receiving device controls the oscillation wavelength of the laser.

Abstract: The multi-channel optical transmitter is composed of a tunable optical signal source, an optical multiplexer and an intensity reducer. The tunable optical signal source includes a tunable laser, and additionally includes an optical signal output through which it outputs an optical signal to one of the inputs of the optical multiplexer. The intensity reducer is for reducing the intensity of the optical signal output by the optical signal source during tuning of the tunable laser. The intensity reducer prevents the tunable optical signal source from injecting high levels of noise into the channels during tuning of the tunable optical signal source.

Abstract: A system for locking the operating wavelength of an optical transmission source, the system including: a pattern of nanostructures being optically coupled to the optical transmission source and adapted to perform notch filtering; at least one photodetector optically coupled to the pattern of nanostructures; and, at least one controller operatively coupled to the photodetector and optical transmission source to operate the optical transmission source responsively to the at least one photodetector.

Abstract: A photonic integrated circuit (PIC) chip comprising an array of modulated sources, each providing a modulated signal output at a channel wavelength different from the channel wavelength of other modulated sources and a wavelength selective combiner having an input optically coupled to received all the signal outputs from the modulated sources and provide a combined output signal on an output waveguide from the chip. The modulated sources, combiner and output waveguide are all integrated on the same chip.

Abstract: A high resolution measurement method and apparatus for tracking wavelength transients in tunable lasers. The apparatus comprises a Mach-Zehnder interferometer (MZI) which is used to generate a self-heterodyne signal between the wavelength transient to be measured, which is effectively the laser signal passed along the time-delayed arm of the MZI, and the laser wavelength after the tuning transient has subsided, which is effectively the same laser signal passed along the direct arm of the MZI. The heterodyne signal is detected on a receiver, and can then be measured with the frequency resolution typical of electronic measurements, such as by means of an oscilloscope. The only laser required is the laser under inspection. The wavelength measurement accuracy is up to twice the laser linewidth, and is only effectively limited by the laser phase noise. The method can be used to implement an automatic frequency control system for tunable lasers.

Abstract: According to aspects of an embodiment of the disclosed subject matter, a line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control method and apparatus are disclosed which may comprise a bandwidth metrology module measuring the bandwidth of a laser output flight pulse beam pulse produced by the light source and providing a bandwidth measurement; a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal; an active bandwidth controller providing a fine bandwidth correction actuator signal and a coarse bandwidth correction actuator signal responsive to the bandwidth error. The fine bandwidth correction actuator and the coarse bandwidth correction actuator each may induce a respective modification of the light source behavior that reduces bandwidth error. The coarse and fine bandwidth correction actuators each may comprise a plurality of bandwidth correction actuators.

Abstract: Integrated opto-electronic oscillators that use micro resonators in the optical section of the opto-electronic feedback loop.

Abstract: A tunable laser module having two or more tunable lasers exhibiting different, possibly contiguous or partially overlapping wavelength regions. The lasers are integrated into a single package, thereby extending a total wavelength range for the package that is substantially beyond that covered by a single laser while—at the same time—providing gap-free wavelength range coverage. Of further advantage, the laser module employs a locking mechanism that is relatively immune from backscatter.

Abstract: Method and apparatuses for compensating for wavelength drift in a fiber-optic laser transmitter includes 1) controlling a temperature within the optoelectronic assembly at a defined level; 2) driving the optoelectronic assembly to emit light, wherein the emitted light has a wavelength that is within a channel of operation, the channel of operation including a range of wavelengths centered around a channel center wavelength; 3) accessing from memory within the optoelectronic assembly a control value associated with the temperature of the optoelectronic assembly at defined points within an operational lifetime of the optoelectronic assembly; and 4) recalculating the defined level by reference to the control value, whereby a wavelength of the optoelectronic assembly is maintained within the channel of operation despite an expected drift of wavelength.

Abstract: A frequency-stabilized laser source that is adapted for use as a frequency standard. The frequency of the laser source is locked and the laser beam delivered by the laser source on a transition of an absorber chemical element. The technique combines both operation with saturated absorption and synchronous detection, based on modulating said transition being saturated by the beam passing through the absorber chemical element. This produces a single frequency laser beam whose output frequency is stationary. The frequency is not continuously modulated and is more precise than that which would be obtained operating with single-pass absorption only. The laser source is thus adapted for making a frequency standard.

Abstract: A wavelength locker. The wavelength locker can be mounted within an optical transceiver on a submount with the laser diode. The wavelength locker utilizes light emitted by the back facet of the laser to monitor the wavelength and power of the laser. The light is separated into two portions, at least one of which is passed through a filter to shift the wavelength thereof. Separate monitor diodes or photosensitive areas of a single monitor diode are used to measure the output of each portion of light. The outputs are analyzed to determine the wavelength of the light emitted from the back facet as well as the power of the laser and a controller can then change the temperature of the laser or otherwise adjust the wavelength of the laser when the wavelength locker detects that the wavelength of the laser is changing.

Abstract: A frequency tuning system for a laser includes mode-matched lasing and feedback cavities. A reflective facet of the feedback cavity is adjustable for retroreflecting different feedback frequencies to the lasing cavity without changing a fixed length of the feedback cavity. A selection among resonant frequencies of the feedback cavity provides for tuning the laser through discrete resonant frequencies of the lasing cavity.

Abstract: A system for detecting wavelength error that includes one or more ordered pairs of photodetectors each of which receives an individual optical signal and is used to detect a wavelength error in that optical signal. Each individual optical signal is directed towards a corresponding pair of photodetectors. The pair of photodetectors are positioned around a region of maximum constructive interference or minimum insertion loss. A feedback circuit analyzes output signals from the photodetectors and determines wavelength error based on differences between the output signals from the photodetectors.

Abstract: An optical transmitter comprises a monolithic transmitter photonic integrated circuit (TxPIC) chip that includes an array of modulated sources formed on the PIC chip and having different operating wavelengths approximating a standardized wavelength grid and providing signal outputs of different wavelengths. A wavelength selective combiner is formed on the PIC chip having a wavelength grid passband response approximating the wavelength grid of the standardized wavelength grid. The signal outputs of the modulated sources optically coupled to inputs of the wavelength selective combiner to produce a combined signal output from the combiner. A first wavelength tuning element coupled to each of the modulated sources and a second wavelength tuning element coupled to the wavelength selective combiner. A wavelength monitoring unit is coupled to the wavelength selective combiner to sample the combined signal output.

Abstract: Disclosed is a method for maintaining wavelength-locking of a Fabry-Perot laser regardless of a change of external temperature even though a temperature controller is not used, and a wavelength division multiplexing (WDM) light source using the method, as an economical light source used in a WDM optical communication field. The WDM light source comprises a Fabry-Perot laser for injecting spectrum-spliced incoherent light to amplify and output only an oscillation mode matching with a wavelength of the injected light, and a bias controlling unit for adjusting a bias current supplied to the Fabry-Perot laser to a value adjacent to a threshold current of the Fabry-Perot laser, whose threshold current is changed according to a temperature and a relationship between the injected light changed depending to a temperature and a wavelength of the oscillation mode.

Abstract: Techniques and devices based on holey fibers with internal holes that confine a gas medium for various applications.

Abstract: A method for stabilizing a laser frequency using sub-Doppler spectral spectrum of atoms, and a laser frequency stabilization device used in the method which is comprised of a gas charged cell, a laser, a laser frequency adjusting means, a laser beam dividing means for dividing the laser beam into a pump beam and a probe beam, a photo detector for measuring intensity of the probe beam after passed through the cell, an ON/OFF means for cutting off the pumping beam at a constant time interval, a computing means for obtaining the intensity of the probe beam, a demodulated signal of the probe beam, the difference in intensity between the probe and pumping beam, and a difference in demodulated signal, and a feedback means which feeds back the information to the laser frequency adjusting means, thereby stabilizing the frequency of the laser.

Abstract: A beam shaping optical arrangement combines three incoming laser beams that are mutually laterally offset in two orthogonal directions (X and Y), including an incoming first central laser beam and second and third incoming beams laterally offset in the X direction on either side of the central beam, into one outgoing combined laser beam. The arrangement includes two lateral displacement optical units though which the laterally offset incoming beams are transmitted and that laterally displace the two laterally offset incoming beams along the X direction towards the incoming central beam but which do not laterally offset the incoming central beam.

Abstract: The present invention relates to a method for revising a wavelength of the EML by controlling a working temperature based on arithmetic functional relations between the DC-Offset voltage and the wavelength and between the working temperature and the wavelength, and a computer-readable recording medium thereof. The method includes the steps of: re-setting initial values of a working temperature, a amplifying voltage and the DC-Offset voltage; determining a wavelength with respect to the re-set DC-Offset voltage based on a functional relation between the DC-Offset voltage and the wavelength of the EML; and determining the revising working temperature for the determined wavelength based on the functional relation between the working temperature and the wavelength of the EML, and re-setting the working temperature with the revising working temperature.

Abstract: An object of disclosed technology is to control lasing wavelengths so that a wavelength shift does not occurs. Another object is to permit wavelengths of a light source for wavelength division multiplexing optical-fiber communication system to be variable in response to an ITU-TS grid. A means for achieving the objects is as follows: locating an etalon in a light path of diode laser light, which is a parallel plane wave changed by a collimator lens; generating a wavelength error signal from a difference between both of divided pieces of light from transmitted light or reflected light; and locking a wavelength of a diode laser device according to the wavelength error signal.

Abstract: The invention relates to a method for checking the regulation state of a frequency-stabilised laser system comprising a laser (2). At least one first sidebrand frequency VHF is modulated to the laser beam (1) of said laser, the laser beam being guided through an absorption material (13) comprising a plurality of absorption lines in a detuning region of the laser (2), said absorption lines being arranged at different distances from each other. The laser frequency VL is detuned and, as a regulation signal for the laser frequency VL, it is determined whether there has been an absorption in the absorption material.

Abstract: Electro-optic amplitude varying elements (AVEs) or electro-optic multi-function elements (MFEs) are integrated into signal channels of photonic integrated circuits (PICs) or at the output of such PICs to provide for various optical controlling and monitoring functions. In one case, such PIC signal channels may minimally include a laser source and a modulator (TxPIC) and in another case, may minimally include a photodetector to which channels, in either case, an AVE or an MFE may be added.

Abstract: A method and assembly for frequency stabilization of an optical signal especially from a laser, the assembly (11) comprising beam splitter (15), a passive frequency discriminator (16), and a pair of photodiodes (17 & 18). The beam splitter (15) in use receives a collimated optical beam (B) and diverts a sample beam (B1) which is directed towards the discriminator (16) which transmits a portion (B2) of said sample beam to one of the photodiodes (17) and reflects a second portion (B3) of said sample beam to the other photodiode (18). A control signal (S3) is derived from the respective intensities of the transmitted and reflected portions of the sample beam, and utilized to operate the electronic control to adjust the frequency of the laser output signal, if required, to maintain a specified frequency.

Abstract: Information of oscillation frequency of a laser beam source in a predetermined range including usable oscillation frequency that takes into consideration an output quality of the laser beam source, such as information on a relationship between oscillation frequency and output quality, is stored in a memory. Then, when the laser beam source is controlled, based on the information stored in the memory, a particular frequency range where the output quality of the laser beam source deteriorates or becomes good is specified, and a decision is made whether or not oscillation frequency f, which is going be used, is within the particular frequency range. Then, according to the results, the oscillation frequency is set, avoiding a frequency range where the output quality deteriorates or within a frequency range where the output quality becomes good according to the result. Thus, a laser beam source whose output quality is always good can be used.

Abstract: An injection locked dual opto-electronic oscillator having a master oscillator which generates a high Q RF output signal with a plurality of harmonic signals within a predetermined pass band. A slave oscillator has a modulation input coupled to the output signal from the master oscillator as well as an output signal. The slave oscillator has a cavity length selected to produce a single mode operation within the pass band. An electronic phase shifter in the slave oscillator is adjustable to produce constructive interference at a single harmonic of the output signal from the master oscillator and destructive interference of all other harmonics within the pass band and to bring the slave oscillator into injection locked condition with the master oscillator. Therefore the slave OEO is used as a filter for the spurious radiation generated by the master OEO and at the same time preserves the high Q of the RF carrier signal from the master OEO.

Abstract: A wavelength filter is disposed between a laser diode and a photodiode that receives the rear-facet output light of the laser diode. Either a part on one side of an input or an output surface of the wavelength filter is bounded to a protrusion provided in a metal holder for holding the wavelength filter. As a result, a support structure is obtained that does not bring a damage on the wavelength filter caused by degradation of optical characteristics or temperature variation of the wavelength filter when support-fixing a wavelength filter having a complex refractive index crystal.