Abstract: For optical data storage applications, for example, for holographic storage applications, a radiation beam (12) with a flat intensity profile is needed. The radiation source device (1) of the invention comprises a beam shaper element (5) and a collimating element (7) between a semiconductor laser (3) and an output coupler (9) and provides such a radiation beam (12) with an increased efficiency. An external resonator is thereby provided. Further, a relatively fast tuning of the wavelength of the output radiation beam (12) can be provided.

Abstract: A method of modulation terahertz radiation comprising: (A) generating Terahertz radiation by pumping nonequilibrium electrons into a Magnon Gain Medium (MGM), wherein propagation of nonequilibrium electrons in the MGM causes generation of nonequilibrium magnons, and wherein interaction between the nonequilibrium magnons causes generation of the Terahertz radiation; and (B) frequency modulating THz radiation generated in the MGM by applying longitudinal AC magnetic field, or by applying AC electrical field bias.

Abstract: The invention relates to a waveguide structure for upconversion of IR wavelength laser radiation and is characterized in comprising a) at least one base substrate layer made essentially out of a moisture-stable mechanically- and/or temperature-stable material b) at least one active layer made essentially out of a halide glass, preferably a fluoride glass located on the base substrate layer whereby the material of the at least one base substrate layer has a different composition from the material of the at least one active layer.

Abstract: A method relating to the calibration of tuneable lasers is described. The method provides for the provision of correct control currents so as to achieve each of desired output frequencies from the laser. The correct currents are determined by forming a matrix of the output characteristics of the laser at specific tuning currents and processing that matrix to determine stable operating points within the matrix.

Abstract: A surface-emitting type semiconductor laser includes a substrate, a first distributed Bragg reflection type mirror formed above the substrate, an active layer formed above the first mirror, a second distributed Bragg reflection type mirror formed above the active layer, and an insulation layer having an opening section that is formed in one of the first and second mirrors, wherein light generated from the active layer is emitted as a lower order mode laser beam lower order modeor a higher order mode laser beamhigher order mode, and the first mirror is formed with a number of pairs greater than the number of pairs of the second mirror such that the lower order mode laser beamlower order mode can be emitted in an upward direction of the substrate, and the opening section in the insulation layer is formed to have a size that enables the higher order mode laser beamhigher order mode to be emitted in a downward direction of the substrate.

Abstract: An optical spread spectrum communication system includes a tunable laser which sequentially outputs optical signals having different wavelengths. The laser produces a frequency spectrum having a plurality of closely spaced modes relative to optical frequencies. The system further includes an optical modulator and a frequency synthesizer. The frequency synthesizer controls the optical modulator to allow specific modes from the frequency spectrum to pass through. Additionally, the system includes a tunable filter and a phase locked loop (PLL) control circuit. The PLL control circuit controls the filter to select specific channels. The selection of the specific modes by the modulator and the selection of channels by the tunable filter are performed independent of each other and are based on randomly assigned codes generated in accordance with one or more algorithms.

Abstract: In one aspect the invention relates to a frequency varying wave generator. The generator includes a gain element adapted to amplify a wave having a wavelength; a time varying tunable wavelength selective filter element in communication with the gain element, the tunable filter element adapted to selectively filter waves during a period T; and a feedback element in communication with the tunable filter element and the gain element, wherein the tunable wavelength selective filter element, the gain element and the feedback element define a circuit such that the roundtrip time for the wave to propagate through the circuit is substantially equal to a non-zero integer multiple of the period T.

Abstract: Methods and systems for control and monitoring processing of semiconductor materials with a focused laser beam. Laser light may be focused on a sample to excite optical emission at the sample surface during processing, which may include laser processing. Optical emission spectra produced may be analyzed for various properties effectively during the process. For example, process effects such as chemical composition analysis, species concentration, depth profiling, homogeneity characterization and mapping, purity, and reactivity may be monitored by optical spectral analysis. The wavelength may be selected to be appropriate for the process effect chosen.

Abstract: Methods of controlling semiconductor lasers are provided where, the time-averaged optical spectrum of the semiconductor laser is broadened by modulating the drive current at a relatively high frequency. Generally, the frequency of the drive current modulation is high enough to induce wavelength chirping within the data periods encoded in the gain current signal. Laser controllers and projections systems operating according to the disclosed methodology are also provided.

Abstract: An ultra-low heat laser that does not rely on florescence cooling. Generally, the inventive laser includes a pump source operable at a pump frequency and a gain medium disposed to receive energy from the source and lase at a frequency close to the pump frequency. In the illustrative embodiment, the laser is a solid state laser having a gain medium which is resonantly pumped to lase at a frequency within 5% of the pump frequency. However, in the best mode and in accordance with the present teachings, the gain medium lases at a frequency within 1% of the pump frequency. In the illustrative embodiment, the laser gain medium ion has a rich Stark energy level structure and the laser active gain medium has oscillator strengths at transitions wavelengths that allow an ultra-low quantum defect operation. The pump source has a wavelength output centered to correspond to a predetermined pump band and an emission band subtended by an absorption bandwidth thereof.

Abstract: Optical communication apparatuses and optical communication methods are provided. According to one aspect, an optical communication apparatus includes a communication path configured to communicate a first signal; a signal generator configured to provide a second signal; a combiner configured to combine the first signal with the second signal to provide a composite signal; and a light source coupled with the combiner and configured to receive the composite signal and to output an optical signal corresponding to the composite signal to an optical conduit, wherein the signal generator is configured to monitor the application of the optical signal to the optical conduit and to alter the second signal responsive to the monitoring.

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 driving method for laser light source device includes: providing a laser light source device including a laser light source, a wavelength conversion element converting the wavelength of the light emitted from the laser light source, and a resonator mirror constituting a resonator structure between the laser light source and the resonator mirror, and driving the laser light source so as to cause the amount of light to decrease depending on the passage of time, compared with the amount of light by the initial driving of the laser light source.

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: A laser beam source device includes a light source that emits light of a first wavelength, a wavelength converting element that converts a wavelength of the light of the first wavelength entered into a second wavelength, a multi-layer film mirror having a characteristic of reflecting light of the first wavelength and transmitting light of the second wavelength, a band-pass filter having a band-pass characteristic near the first wavelength is formed, a reflection mirror that branches the light transmitted through the multi-layer film mirror to the first optical path and a second optical path, a laser-power measuring unit that measures power of the light branched to the second optical path, and a control unit that performs angle adjustment for displacing a tilt angle of the band-pass filter.

Abstract: A method of generating coherent radiation, wherein a first fundamental beam of radiation from a four level laser and a second fundamental beam of radiation from a three level laser are mixed in a non-linear body to obtain an output beam at the sum frequency of the two fundamental beams. The invention also relates to an arrangement for carrying out the method.

Abstract: A method for effective injection seeding is based on continuous wavelength sweeping for matching the injected seeds with one or more longitudinal mode(s) of the slave oscillator in every pulse. This is achieved through rapidly varying laser drive current, as a result of RF modulation. Depending on the modulation parameters, the seeder may be operated in CW or quasi-CW or pulsed mode, with a narrow or broad bandwidth, for injection seeding of single longitudinal mode or multimode. The wavelength and bandwidth of the laser output can be tuned according to the needs. Injection seeding of high repetition rates is achievable. From pulse to pulse, the master-slave resonance persists though may occur at different longitudinal modes upon cavity length fluctuations. Cavity length control and phase locking schemes are consequently not required.

Abstract: An image display device includes a laser light source, a wavelength conversion element converting a wavelength of a light beam emitted from the laser light source into a predetermined wavelength, and a light modulating device modulating the laser beam output from the wavelength conversion element, wherein the laser beam emitted from the laser light source has a frequency of integral multiplication of the maximum modulation frequency of the light modulating device, and has a pulse width narrower than a time period during which the light modulating device is in a stable state.

Abstract: The present invention provides a directly modulatable wavelength variable laser that enables long distance and large volume communication with a simple and compact configuration. The wavelength variable laser includes a semiconductor optical amplifier, an optical filter, and a frequency-amplitude converter. The semiconductor optical amplifier produces optical gain of the light signal. The optical filter configured by multi-stage connected waveguide ring resonators performs frequency modulation on the light signal. The frequency-amplitude converter performs amplitude modulation on the light signal frequency modulated in the optical filter.

Abstract: In a first embodiment, the invention makes use of a Neodymium doped YAG (Nd: YAG) gain medium placed in an optical resonant cavity formed by two mirrors. Power extraction is maximized for a specific laser cavity. In particular the concave curvature on the rod ends contributes a negative lensing component to modify the strength of the thermal lens. In a second embodiment the present invention uses an amplifier rod medium with curved ends to act as lensing elements to collect emission from the laser gain medium and/or oscillator described in the first embodiment of the invention. The combination of thermal lens and curved rod ends produces a lensing effect which allows light to be directly coupled from a laser. In addition, variation of the input pump power allows for control of the thermal lens formed within the amplifier rod.

Abstract: A CO2 laser reference oscillator (RO) can provide injection seeding to a Q-switched (QS) or Q-switched cavity dumped (QSCD) CO2 laser, where the output frequency of the RO laser is locked to the peak of the laser line by the use of appropriate electronics to dither one of the resonator mirrors of the reference oscillator. This injected radiation seeds the radiation building up within the Q-switched laser cavity, such that the oscillating frequency favors the wavelength of the injected radiation. An electronic feedback control circuit can be used to lock an axial mode of the Q-switched laser to line center. The change in build-up time of the pulses within the QS laser can be used to maintain cavity length at a value that enables oscillating at the peak of the same laser line that is injected into QS laser.

Abstract: Described are an optical transmitter and a method for generating a single sideband optical signal. The method includes generating a data signal at a first power level and at a second power level with a predetermined ratio being defined between the power levels. The data signal at the first power level is applied to a phase module disposed in a laser cavity of a semiconductor laser to generate a frequency modulated laser signal having a double sideband. The intensity of the frequency modulated laser signal is modulated in response to the data signal at the second power level to yield the single sideband optical signal. Optical transmitters implementing the method have an increased manufacturing yield and reliability, a lower fabrication cost and a decreased size compared to other optical single sideband optical transmitters.

Abstract: Provided is a millimeter-wave band frequency optical oscillator that can be used as an oscillation frequency signal source for a millimeter-wave forwarded to wireless subscribers from a base station of a millimeter-wave wireless subscriber communication system for a next generation (e.g., fifth generation) ultra-high speed wireless internet service. A pair of an optical fiber amplifier and an optical fiber grating mirror is connected to each of input/output ports of a loop mirror in parallel, so that a dual mode laser resonator is formed which can make simultaneous oscillation in two laser modes suitable for each wavelength. Accordingly, it is possible to obtain a light source that is modulated to a ultra-high frequency (over 60 GHz) by a beat phenomenon between the two laser modes.

Abstract: An apparatus for adjusting the wavelength of a laser capable of lasing at multiple wavelengths by using a single acousto-optical modulator and a pair of optical reflectors inside a laser cavity. By adjusting the frequency and amplitude of the radio-frequency source to the acousto-optical modulator, undesired wavelengths are suppressed in the laser cavity, leaving appreciable gain only at the desired wavelength.

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: 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 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: A frequency modulated (FM) vertical cavity surface emitting laser (VCSEL). The frequency modulated VCSEL includes a mirror region that has an active region. The frequency modulated VCSEL also includes a phase adjustment region for use in altering the characteristics of the VCSEL. For example, by changing the index of refraction in the phase adjustment region, the wavelength of the VCSEL can be changed, resulting in frequency modulation.

Abstract: A method and apparatus are provided to modulate a beam of laser light. An acousto-optic modulator (AOM) is positioned to receive continuous-wave (CW) laser light at an angle approximating the Bragg angle. Fine tuning of the modulation is then used to compensate for any variations in the actual angle from the Bragg angle. A photodiode provides a feedback signal that may be used to tune or adjust the operation of the AOM. The photodiode is positioned to receive laser light at the first order diffraction and provide a signal indicative of the magnitude of the first order diffraction laser light produced by the AOM. The photodiode signal is coupled to an RF frequency generator so that the RF frequency may be adjusted to vary the acoustic wave in the AOM to compensate for any variations in the Bragg angle.

Abstract: A fiber Chirped Pulse Amplification (CPA) laser system includes a fiber mode-locking oscillator for generating a laser and stretching into a few hundreds ps-10 ns pulse by a fiber stretcher for projecting into an acoustic-optic (AO) functioning as a pulse picker for generated a modulated laser with a reduced repetition rate for projecting to a multiple stage amplifier. The multiple stage amplifier further includes a first high-energy amplifier implemented with a large mode area (LMA) fiber for amplifying the modulated laser up to a uJ level laser and a second amplifier implemented with a PCF based Yb doped fiber to further amplify the uJ level laser to a mJ level laser.

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 current output of a drive signal, modulated between two current settings, is applied to a laser diode, e.g. VCSEL. The settings are selected such that laser diode's power output meets the average power and peak power limits of the eye safety standards. The drive signal having a duty cycle toggling between the two settings. The duty cycle is selected such that the average and peak power limits are met for the given upper current setting. The drive circuit may include an analog modulator or digital analog converter (DAC) for maintaining the lower and upper current settings. When the drive circuit is implemented as an integrated circuit, the DAC may be incorporated into the IC. The sensitivity of the DAC is selected to maintain the desired lower and upper current settings.

Abstract: A laser diode module with a built-in high-frequency modulation IC used to remove the reflected noise generated as the laser beam reads the signal to be played back and directly packaged within a metal cap. The high-frequency modulation IC creates an electrical connection through wire bonding with several connection legs and the laser diode module. The packaged laser diode module has four connection legs. Two of these connection legs act as a positive and a negative terminal for supplying power to the built-in high-frequency modulation IC. The other two connection legs are electrically connected to an external automatic power control (APC) circuit and act as the positive terminal of the laser diode and the photo diode, respectively. In this way, the inconvenience of externally attaching a high-frequency current producing circuit board can be avoided, the productivity can be enhanced and the radiation of electromagnetic interference (EMI) can be reduced.

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 apparatus and a method for generating an optical carrier is disclosed. The apparatus includes: a light source generating a pump light; a SBS generator for stimulated Brillouin scattering the pump light to generate a stokes light from the light source; an attenuator for controlling an amplitude of the pump light from the light source to generate an amplitude controlled pump light; and a detector for heterodyne beating the stokes light and the amplitude controlled pump light to generate an optical carrier.

Abstract: An apparatus for controlling propagation of incident electromagnetic radiation is described, comprising a composite material having electromagnetically reactive cells of small dimension relative to a wavelength of the incident electromagnetic radiation. Each electromagnetically reactive cell comprises a metallic element and a substrate. An electron population within the substrate near the metallic element of at least one of the electromagnetically reactive cells is temporally controllable to allow temporal control of an associated effective refractive index encountered by the incident electromagnetic radiation while propagating through said composite material.

Abstract: The present invention discloses a low-cost light source for optical transmission systems and optical networks based on wavelength-division multiplexing (WDM) technology. A light source in accordance with the present invention is implemented by externally injecting a narrow-band incoherent light into a Fabry-Perot laser diode (F-P LD). After injection of narrow-band incoherent light, the output of F-P LD becomes wavelength-selective rather than multi-mode and the output wavelength of F-P LD coincide with the peak wavelength of the injected incoherent light. Multi-channel WDM light sources according to the present invention can be implemented using a single broadband incoherent light source and plurality of F-P LDs. An optical transmission system for upstream signal transmission in an passive optical network using the light source according the present invention is also disclosed.

Abstract: A harmonic system for use with metals and alloys such as titanium, steel, copper, gold, aluminum, etc. is disclosed. The harmonic laser system includes an oscillator cavity having a first end mirror and a harmonic separator mirror, an active medium positioned in the oscillator cavity, an electro-optic pump device for optically pumping the active medium to produce a first optical beam at a fundamental wavelength and a non-linear optical crystal positioned in the oscillator cavity to generate a second optical beam at a harmonic wavelength of the first optical beam, wherein the harmonic separator mirror outputs the second optical beam and reflects the first optical beam.

Abstract: An optical test system for use in testing fiber optical transmission systems and components comprises a modular construction in a single housing. The modular construction includes a plurality of laser source channels, a MUX, additional optical conditioning devices both upstream and downstream of the MUX, and a master controller for operating the system components in synchrony. The integral housing, together with the modular construction, provides increased structural density that occupies in many instances at least seventy percent less space than is required for other optical test systems. The use of a master controller to drive the system affords expanded system functionality.

Abstract: Methods and apparatus are provided for detecting an abnormality in a host medium, such as a tumor within a patient's breast. The host medium is initially illuminated at a plurality of different positions with light of at least two different wavelengths. Following the propagation of the signals through the host medium, the amplitude and phase of the signals are detected and, based upon the detected signals, a shadow image can be created in which the abnormality is depicted as a suspicious region. Once a suspicious region has been identified, at least that portion of the host medium that contains the suspicious region is again illuminated with frequency-swept modulated signals of at least two different wavelengths generated by the light source and modulated by a modulator, such as a network analyzer.

Abstract: A pump fiber is stripped of its cladding over the last section. This can occur by etching a coating off. The sheath is preferably etched off wedge-shaped. As a result thereof, the remaining pump power is eliminated into the environment. How much stray pump light still proceeds via the fiber core to the fiber exit can be monitored over a length of the fiber completely stripped of the protective sheath.

Abstract: Apparatus and method for stabilizing the wavelength of a tunable laser to a target wavelength, by correspondingly adjusting the electrooptical performance of the laser's gain medium, whereby to eliminate the frequency shift due to vibrational factors. The electrooptical performance of the laser's gain medium is adjusted, in the case of an electrically pumped laser, by changing the injection current used to pump the laser; and the electrical performance of the laser's gain medium is adjusted, in the case of an optically pumped laser, by changing the intensity of the pump laser used to energize the laser. The system is implemented with a feedback mechanism.

Abstract: A frequency synthesiser for generating wideband signals for zero Hz up to frequencies in the millimetre wave band provides the ability for arbitrarily fine increments in output frequency. The synthesiser has an optical comb generator that provides a set of reference signals at predetermined intervals. These reference signals are fed to two or more laser devices, at least one of which is a frequency selection and translation device capable of selecting a particular output line from the comb generator and shifting it by some desired frequency. The outputs from the laser devices are then combined and detected using a photodetector. The output from this is the system output. Various methods of producing the frequency selection and translation device are disclosed, as are various methods of producing the optical comb reference signal. Some possible applications of the invention are also disclosed.

Abstract: A laser tuning mechanism which embodies “spectrally dependent spatial filtering” (SDSF) and contemplates two key elements of the tuning mechanism. The first element of the SDSF tuning mechanism is a spectrally dependent beam distortion (i.e. alteration of the amplitude and/or phase profile of the beam) provided by an SDSF tuning element in a laser cavity. The second element of the SDSF tuning mechanism is an intracavity spatial filter which makes the round trip cavity loss a sensitive function of both beam distortion and cavity alignment. Such a laser can be aligned so that a specific beam distortion, which is provided by the SDSF tuning element at a tunable wavelength, is required to obtain minimum round trip cavity loss, thereby providing tunable laser emission. A preferred embodiment of the SDSF tuning mechanism is an external cavity semiconductor laser having a zeroth order acousto-optic tuning element.

Abstract: A method and apparatus for reducing speckle uses polarization averaging. A polarizing beam splitter divides a first polarized laser output into a second polarized laser output and a third polarized laser output. A plurality of mirrors creates an optical path difference between the second and third polarized laser outputs. The optical path difference is at least about a coherence length for the first polarized laser output. The second and third polarized laser outputs are combined into a fourth laser output, which illuminates a depolarizing screen. If a human eye or an optical system having a intensity detector views the depolarizing screen, the eye or the intensity detector will detect reduced speckle, which results from uncorrelated speckle patterns created by the second polarized laser output and the third polarized laser output. A first alternative embodiment of the invention functions without the optical path difference being at least about the coherence length.

Abstract: An optoelectronic integrated circuit includes a resonant cavity formed on a substrate. A heterojunction thyristor device is formed in the resonant cavity and operates to detect an input optical pulse (or input electrical pulse) and produce an output optical pulse via laser emission in response to the detected input pulse. The heterojunction thyristor device includes a channel region that is coupled to a current source that draws current from the channel region. Time delay between the input pulse and output optical pulse may be varied by configuring the current source to draw constant current from the channel region and modulating the intensity of the input pulse, or by varying the amount of current drawn from the channel region by the current source. The heterojunction thyristor device may be formed from a multilayer structure of group III-V materials, or from a multilayer structure of strained silicon materials.

Abstract: There is provided a millimeter wave band frequency optical oscillator predicted to be used as a millimeter wave oscillating frequency signal source in a base station of a millimeter wave wireless transmission system. The optical oscillator has a double resonator structure in which a pair of wavelength tunable fiber grating mirrors are inserted into a unilateral fiber-ring laser resonator in order to internally and additionally form a linear laser resonator. The double resonator structure composed of the two stable laser resonators can oscillate laser of two modes. Due to a beat phenomenon occurring between the two modes, received laser is modulated to an ultra-speed frequency of 60 GHz or greater. A variation in the gain within a resonator is induced by a polarization controller using the dependency of laser modes upon polarization. A modulation frequency is consecutively changed from 60 GHz to 80 GHz by controlling the wavelength of light reflected by the fiber grating mirrors.

Abstract: A distributed feedback laser device inhibiting beam coupling coefficient variation resulting from fabrication dispersion and improving fabrication yield. The distributed feedback laser device includes cladding layers provided on an InP substrate and located on both sides of an active layer and a diffraction grating having grating bars, different in refractive index from the cladding layers, in either cladding layer and extending in a direction perpendicular to a light emission direction at a prescribed pitch in the emission direction, as well as at least one light distribution control layer, located in the cladding layer, spaced from the diffraction grating and having the same composition as the diffraction grating.

Abstract: A broadband laser source comprising: a resonant cavity (1) containing a medium (2) which emits optical energy (3) in a continuum of wavelengths in response to application of pump energy (4) to the medium (2); a source of pump energy (5) for producing said optical energy (3); a frequency shifter (6) within the resonant cavity (1); and a tuneable spectral filter (7) within the resonant cavity (1), and the apparatus being such that in use the tuneable spectral filter (7) has a peak wavelength which is repeatedly swept in a substantially resonant fashion over a wavelength range equal to, or a fraction of, a linewidth of the broadband source such that the rate of change of the peak wavelength of the tuneable spectral filter (7) is substantially equal to the rate of change of the frequency of the optical energy (3) as it is frequency shifted within the resonant cavity (1) by the frequency shifter (6).

Abstract: A tunable laser device produces a laser energy over a range of frequencies. A property of an ultrasonic transducer or, more specifically, the frequency of an ultrasonic wave created by the ultrasonic transducer is altered to change the laser frequency of the tunable laser device. The ultrasonic transducer may couple its ultrasonic wave directly into the laser source or may form a tunable acousto-optic modulator external to the laser source. In both cases, the ultrasonic wave creates an index of refraction perturbation in an optical substrate, through which the laser energy of the laser source passes. Changes in the ultrasonic wave cause changes in the perturbation through which the laser energy passes, which in turn, changes the frequency of the laser energy, thereby enabling the frequency of the laser to be tuned.