Abstract: Terahertz radiation generation systems and methods are implemented using a variety of methods and devices. According to an example embodiment of the present invention, method for generating terahertz radiation is implemented where the wavelength of an optical pulse is controlled, and where the wavelength is controlled as a function of the group velocity dispersion in a nonlinear crystal. The optical pulse is then directed through consecutively-inverted parallel domains in the nonlinear crystal.

Abstract: A nonlinear frequency conversion system includes a first element including a first medium configured to perform type II birefringent phase matching (BPM) of a pump beam to provide corresponding seed beams having at least first and second polarization states. A second element includes a second medium configured to perform quasi phase matching (QPM) of the seed beams. The second element amplifies at least one of the seed beams to provide corresponding output beams, and at least one of the output beams has a predetermined wavelength that is different from the wavelength of the pump beam. The nonlinear frequency conversion system can be implemented in an optical resonator to provide an optical parametric oscillator.

Abstract: A method for generating THz radiation comprises illuminating a semiconductor crystal with an optical pulse train. The semiconductor crystal comprises alternating parallel crystal domains, with each domain having a crystal orientation inverted with respect to adjacent domains. The optical pulse train propagates substantially perpendicularly relative to domain boundaries in the semiconductor crystal. The THz radiation is generated from the optical pulse train by optical down-conversion mediated by the semiconductor crystal. Optical path lengths through the crystal domains at least in part determine a frequency of the generated THz radiation. THz generation efficiency may be enhanced by placing the semiconductor crystal within an external resonant cavity, by placing the semiconductor crystal within a laser cavity, or by placing the semiconductor crystal within an OPO cavity. The semiconductor crystal may comprise zinc-blende, III-V, or II-VI semiconductor.

Abstract: An optical frequency mixer according to one embodiment of the present invention comprises a V-shaped resonant cavity including a first reflective surface, a second reflective surface and an output coupler, a pumping unit configured to emit a pumping wave to the laser gain medium to generate a resonating wave in the resonant cavity, a nonlinear crystal positioned on an optical path of the resonating wave in the resonant cavity, and an input interface configured to emit a mixing wave into the resonant cavity. Preferably, the output coupler can be a plano-concave lens having a concave surface configured to reflect the resonating wave and to focus the resonating wave such that the spot size of the resonating wave is matched the spot size of the pumping wave. Particularly, the nonlinear crystal is positioned between the output coupler and the input interface.

Abstract: An optical frequency mixer according to one embodiment of the present invention comprises a V-shaped resonant cavity including a first reflective surface, a second reflective surface and an output coupler, a pumping unit configured to emit a pumping wave to the laser gain medium to generate a resonating wave in the resonant cavity, a nonlinear crystal positioned on an optical path of the resonating wave in the resonant cavity, and an input interface configured to emit a mixing wave into the resonant cavity. Preferably, the output coupler can be a plano-concave lens having a concave surface configured to reflect the resonating wave and to focus the resonating wave such that the spot size of the resonating wave is matched the spot size of the pumping wave. Particularly, the nonlinear crystal is positioned between the output coupler and the input interface.

Abstract: A wavelength converter device is provided for generating a converted radiation at frequency ?g through interaction between at least one signal radiation at frequency ?s and at least one pump radiation at frequency ?p, including an input for the at least one signal radiation at frequency ?s, a pump light source for generating the at least one pump radiation at frequency ?p, an output for taking out the converted radiation at frequency ?g, a structure for transmitting the signal radiation, including two optical resonators having a non-linear material, having an optical length of at least 40*?/2, ? being the wavelength of the pump radiation, and resonating at the pump, signal and converted frequencies ?p, ?s and ?g, wherein by propagating through the structure, the pump and signal radiation generate the converted radiation by non-linear interaction within the optical resonators.

Abstract: Optical frequency conversion by four-wave mixing in a fiber is considered. If the frequencies and polarizations of the waves are chosen judiciously, four-wave mixing enables the translation of individual and entangled states, without the noise pollution associated with parametric amplification (modulation instability or phase conjugation) and with reduced noise from stimulated Raman scattering.

Abstract: A tunable coherent light source includes a pump laser for generating a pump beam and an optical parametric oscillator including a crystal exhibiting an output curve for a pump beam of a defined wavelength, the output curve defining wavelengths of signal and idler outputs based on periodically poled grating periods of the crystal. The crystal has a plurality of segments associated with a plurality of grating periods of the output curve, each segment of the plurality of segments having a different crystal structure. At least one of the plurality of segments comprises a crystal structure combining at least two of the grating periods A heating device heats the crystal to an elevated operating temperature and is adjustable for adjusting the output wavelengths of each of the segments.

Abstract: An optical parametric oscillator includes a source of coherent energetic pump optical signals and an optical resonator cavity which includes a set of optical parametric amplifying (OPA) crystals and a set of optical elements such as mirrors disposed along an optical path. The optical elements are configured (1) to direct an oscillation optical signal generated by the OPA crystals along the optical path, (2) to provide input coupling of the energetic pump optical signals such that each energetic pump optical signal travels through only one of the OPA crystals to result in a corresponding depleted pump optical signal, and (3) to provide output coupling of the depleted pump optical signals to prevent each depleted pump optical signal from traveling through more than one of the OPA crystals. Resonator cavities have multiple-leg configurations, including “L” and “U” shapes, and either linear (or standing-wave) or ring architectures.

Abstract: Optical parametric oscillators (OPO) and systems are provided. The OPO has a non-linear optical material located between two optical elements where the product of the reflection coefficients of the optical elements are higher at the output wavelength than at either the pump or idler wavelength. The OPO output may be amplified using an additional optical parametric amplifier (OPA) stage.

Abstract: WDM optical signals are amplified using optical parametric amplification by applying an appropriate separation of those optical signals according to their carrier angular frequencies. These angular frequencies are within the two principal amplification bands defined by the non-linear optical medium used for optical parametric amplification. It is advantageously proposed to launch into the non-linear optical medium in one direction the optical signals of carrier frequencies within the one amplification band, and in the opposite counter-propagating direction the optical signals of carrier angular frequencies within the other amplification band. The required pump radiation is launched co-linearly with the respective optical signals to be amplified.

Abstract: A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

Abstract: The present invention relates a wavelength conversion apparatus capable of making the wavelength of output light constant even when the wavelength of input light is changed. The wavelength conversion apparatus comprises a first wavelength converter and a second wavelength converter which are provided in series between an input terminal and an output terminal. The first wavelength converter generates four-wave mixing by input light and a first pumping light, generates an intermediate light having a new wavelength by the four-wave mixing, and outputs the intermediate light and the input light. The second wavelength converter generates four-wave mixing by the intermediate light and the input light, respectively outputted from the first wavelength converter, and a second pumping light, generates output light having a new wavelength by the four-wave mixing, and outputs the generated output light.

Abstract: The present invention provides a cesium-lithium-borate crystal, which can be used as a high-performance wavelength converting crystal, having a chemical composition expressed as CsLiB6O10, and substituted cesium-lithium-borate crystals expressed by the following formula: Cs1?xLi1?yMx+yB6O10 or Cs2(1?z)Li2LzB12O20 (where, M is an alkali metal element, and L is an alkali earth metal element); a method for manufacturing same by heating and melting; and an optical apparatus using such crystals.

Abstract: Fiber Bragg writing devices comprising solid state lasers are provided. The solid state lasers comprise optical parametric oscillators and emit moderate peak-power output beams at wavelengths which are suitable for efficient production of fiber Bragg gratings without causing embrittlement of the optical waveguide. These solid state lasers generate output beams with wavelengths of approximately 240 nm, in order to match the primary absorption peak in the ultraviolet range for a typical optical waveguide. Some of these solid state lasers generate tunable wavelength beams using an optical parametric oscillator (“OPO”), then generate harmonics of these tunable beams. Other lasers mix the tunable beam with fixed wavelengths derived from the pump laser to reach the desired output wavelength.

Abstract: A white light source has a light emission device, in particular an IR laser diode, whose emitted radiation beam is converted, in a nonlinear-optical element and a conversion element, into a radiation beam with wavelengths ?1, . . . ?n which can be perceived as white light and can have a higher power rating.

Abstract: A high-efficiency multiple-pass nonlinear wavelength converter and amplitude modulator employs a variable dispersion element between adjacent passes of a nonlinear wavelength conversion process in a single nonlinear optical material substrate. When controlled by a voltage via the electro-optic effect, the variable dispersion element dynamically alters the phase matching condition of the multiple-pass nonlinear wavelength conversion process and thus modulates the laser output amplitude. When the phase mismatch between passes is completely compensated by the variable dispersion element, the multiple-pass nonlinear wavelength converter achieves its maximum efficiency.

Abstract: A phasor can be employed within the resonator of an optical parametric oscillator (OPO) to adjust the absolute and relative phase of OPO beams. An embodiment of the invention comprises an OPO having at least one phasor for receiving and adjusting the phase of one or more beams resonating within the optical cavity which forms part of the OPO. Smooth alteration of the phases of the OPO beams using the at least one phasor facilitates continuous tuning of the wavelength of at least one of the beams. In another embodiment, the at least one phasor may be a translatable wedge or have adjustable refractive index to alter the phases of the OPO beams. In an additional embodiment, each at least one phasor may be comprised of more than one material, held fixedly together.

Abstract: An optical parametric amplifier (OPA) driven with at least two pump waves. The pump waves may be configured such that the OPA produces uniform exponential gain over a range of wavelengths that extends, for example, at least 30 nm on either side of the average pump-wave wavelength. In addition, since the Brillouin scattering limit applies to each pump wave independently, substantially twice the amount of energy may be pumped into an OPA of the present invention compared to that in the corresponding single pump-wave OPA of the prior art. An OPA of the present invention may be used in a WDM communication system and configured for simultaneous signal amplification and wavelength conversion.

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 multi-pump phase modulator apparatus and operating method uses only one phase modulator to eliminate SBS without degrading idler(s). The single phase modulator phase modulates multiple pump signals to form multiple phase modulated pump signals using a modulation signal having a modulation period. A delay apparatus delays a first wavelength group by the modulation period relative to other wavelength groups. A combiner combines the delayed first wavelength group with the other wavelength groups to form a combined modulated multiple pump signal. In one embodiment a multi-pump phase parametric apparatus comprises the multi-pump phase modulator apparatus combined with a parametric apparatus to generate an amplified input signal and one or more idlers. Other embodiments of the multi-pump phase conjugator apparatus are used as part of an Optical Switch, Sampler, Tributary Extractor, and Regenerator.

Abstract: A method and apparatus for transferring information of an optical information-bearing signal from a first wavelength to a second wavelength. The method is implemented in an all-optical wavelength converter circuit which includes a laser diode in communication with a polarization controller. An information-bearing signal having a first wavelength is input to the circuit. A polarization controller adjusts the polarization of the information-bearing signal. The laser diode receives the polarization-adjusted information-bearing signal and generates a converted information-bearing signal by transferring the information of the polarization-adjusted information-bearing signal from the first wavelength to the second wavelength. The polarization controller receives the converted information-bearing signal from the laser diode, and polarizes the converted information-bearing signal.

Abstract: A method for thermally stabilizing an optical parametric oscillator (OPO) 10 to maintain constant optical path length for stable high power output places a beam dump 32 outside an OPO cavity 18. The OPO 10 has a nonlinear crystal 22 within cavity 18 for splitting a single input pump beam 14 into lower energy signal and idler beams 16, 18. The method includes providing a cavity exit port for unconverted pump and generated idler beams, and absorbing unconverted beams in beam dump 32. The method includes athermalization by actively cooling surfaces used as an optics mounting base, and athermalization by constraining the size of cavity 18 by using thermally stiff members, guiding pins or rails, or by using bimetallic materials with different expansion.

Abstract: An optical signal amplification device for outputting an output signal light which has the same wavelength as an input signal light and an intensity variation identical in phase with an intensity variation of the input signal light.

Abstract: A nonlinear optical conversion device includes a nonlinear crystal having entrance and exit surfaces allowing input and output laser beams to propagate in the phase-matching plane for a desired nonlinear generation process. The nonlinear generation process involves a nonlinear interaction in the nonlinear crystal and resultant conversion of power in one or two input beams into power in the output beam. The nonlinear crystal is characterized by absorption and resultant modification of the crystal properties by the power in the output beam, the modification with the potential for reducing the efficiency of the nonlinear process in the crystal, and the nonlinear process involving critical phase-matching in the nonlinear crystal in which the powers in the output beam and input beam or beams propagate in different directions through the process of Poynting vector walk-off. The input beam or beams are of a sufficiently small beam dimension in the phase-matching plane.

Abstract: The present invention discloses a means of the generation of tunable femtosecond pulses from 380 nm to 465 nm near the degenerate point of a 405-nm pumped type-I BBO non-collinearly phase-matched optical parametric amplifier (NOPA). The tunable UV/blue radiation is obtained from sum frequency generation (SFG) between the OPA output and the residual fundamental beam at 810-nm and cascaded second harmonic generation (SHG) of OPA. With a pumping energy of 75 mJ at 405 nm, the optical conversion efficiency from the pump to the tunable SFG is more than 5% and the efficiency of SHG of the OPA is about 2%.

Abstract: When forming a periodically-poled structure on a nonlinear optical crystal 1 that permits wavelength conversion and/or optical computing, the group velocity matching conditions are determined to synchronize the group velocity of the incident light L1 with that of the outgoing light L2, and the polarization reversal period of the periodically-poled structure is determined to satisfy quasi-phase matching conditions for the aforementioned wavelength conversion and/or optical computing. As a result, the problems associated with wavelength conversion of the pulsed light due to a difference in the group velocity are suppressed.

Abstract: A method and apparatus for controlling an optical gain difference and an optical phase difference in a semiconductor optical amplifier—Mach-Zehnder interferometer (SOA-MZI) wavelength converter having two arms and that outputs probe output signals POH and POL, corresponding to pump input signals of logic high and logic low, respectively. The controlling includes detecting an optical power level of the output probe signals and controlling at least one of an optical gain difference between the two arms and an optical phase difference between the two arms in accordance with a detected optical power level of the probe output signal.

Abstract: A wavelength conversion device including a nonlinear medium having quantum dots uses a tunable laser as an excitation light source of optical four wave mixing, and performs wavelength conversion for a wide bandwidth signal light with optical four wave mixing by employing a control apparatus for controlling an optical system including an optical path of a signal light and an optical system including an optical path of an excitation light in correspondence with a wavelength of a signal light that is to be wavelength converted.

Abstract: A laser having an optical parametric oscillator for providing a preselected wavelength beam is provided. A nonlinear crystal cut for phase matching condition preferably cut for noncritical phase matching conditions for the fundamental beam wavelength and the preselected wavelength beam is located in both the optical parametric oscillator cavity and laser resonator cavity. The optical axis of the laser resonator and the optical axis of the optical parametric oscillator cavity are at least partially separate and partially overlap. The laser crystal is located in the laser resonator cavity but not in the optical parametric oscillator cavity. Each end of the OPO nonlinear crystal that intersects the optical axes has a Brewster cut for both the fundamental and preselected wavelength beams so that the fundamental and preselected wavelength beams incident on the nonlinear crystal at approximately the Brewster angle and pass through without substantial reflection loss.

Abstract: A wavelength converter using difference frequency generation (DFG) is disclosed. In one embodiment, the wavelength converter comprises (a) a first optical filter configured to filter out one or more lightwaves requiring wavelength conversion from wavelength-division multiplexed (WDM) lightwaves, and (b) a broadband multi-channel simultaneous wavelength conversion portion comprising a pump source that generates pump light for use in the process of the DFG, a first optical combiner for combining said pump light with said filtered lightwaves, a high non-linear medium configured to generate wavelength converted lightwaves from said filtered lightwaves using the DFG, and a second optical filter for filtering said wavelength converted from said filtered lightwaves.

Abstract: A multi-frequency light producing method and apparatus multiplies the number of optical channels present in an incident wavelength division multiplexed (WDM) signal light source by four-wave mixing (FWM) the WDM signal with at least one pump lightwave at least one time. By FWM the WDM light and a pump lightwave multiple times, wherein each FWM process is executed with a pump lightwave having a different frequency, either in series or parallel, the number of optical channels produced as a result of FWM effectively increases the number of optical channels present in addition to those from the WDM signal. The light producing method and apparatus can be employed in a telecommunications system as an inexpensive light source producing a plurality of optical frequencies.

Abstract: A method and device for tuning the wavelength of an optoelectronic component arrangement including at least two optoelectronic components. The characteristic wavelength for each optoelectronic component is adjusted using a respective resistance device which is connected between a common voltage/power source and a respective heating device associated with each optoelectronic component. Heating capacity is modified by changing the overall resistance of the respective resistance device (RM) in order to adjust wavelength. The wavelength of semiconductor lasers, filters, wavelength multiplexers and waveguides may be tuned.

Abstract: An apparatus for generating a specified number of photons whose generating time is known, and further an apparatus for generating a specified number of photons in the known schedule are provided. The particularly important specified number is 1 and it is able to be applied to quantum cryptographic communication. The apparatus comprises a photon pair source for generating a photon pair that comprises a signal photon and an idler photon and correlates with the generating time, photon number detectors for detecting the photon number of idler photons, a controller for controlling the gate device in conformity with the information on the photon number form the photon number detector, and a gate device for controlling the emission of the signal photon.

Abstract: 1064-nm and 1319-nm light respectively generated by two lasers is combined and injected into a doubly resonant sum-frequency generator. The optical path length of the sum-frequency generator is adjusted responsive to feedback of the 1319-nm light to maintain 1319-nm resonance. Feedback of 1064-nm light is concurrently used to adjust the 1064-nm laser responsive to the optical path length to maintain 1064-nm resonance. Light output from the sum-frequency generator is compared to the sodium D2a wavelength i.e., approximately 589 nm, and the 1319-nm laser is responsively adjusted to eliminate any differential. This abstract is provided to comply with the rules requiring an abstract, and is intended to allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A wavelength conversion element which can set the wavelength of a pump light to a wavelength longer or shorter than the wavelength of a plurality of signal lights and a wavelength of a plurality of conversion lights present in an optical communication band, and a method for using such a wavelength conversion element are provided. A first pump light with a wavelength ?1 of 1.51 ?m, a second pump light with a wavelength ?2 of 1.57 ?m, and a signal light with a wavelength of ?S of 1.55 ?m are multiplexed in a multiplexer and introduced as an incident light into an optical waveguide of a wavelength conversion element. In the optical waveguide, an SF light with a wavelength ?SF of 0.77 ?m is generated by the SFG of the first pump light with a wavelength ?1 of 1.51 ?m and the second pump light with a wavelength ?2 of 1.57 ?m, the signal light is wavelength converted as a DF light (wavelength 1.53 ?m) by the DFG of the SF light and signal light, and this DF light is outputted as the converted light (wavelength ?C=1.

Abstract: An apparatus for generating at least three visible light beams of different output wavelengths for display purposes includes a passively mode-locked solid-state thin-disk laser and a device, including an optical parametric oscillator (OPO) for at least partially converting the primary light beam into electromagnetic radiation having the at least three different output wavelengths. The OPO is preferably an optical fiber feedback OPO. An optical fiber feedback OPO includes a nonlinear optical element and feedback device for feeding back at least a portion of the radiation emitted by the nonlinear medium to the nonlinear element. The feedback device includes an optical fiber.

Abstract: An optical parametric circuit including an optical coupler including a first output port and a second output port, and a nonlinear loop mirror on which an optical path which connects the first output port and the second output port is formed, in which the nonlinear loop mirror includes an optical dispersive medium and a second-order optical nonlinear medium through which the optical path passes, and in which an order of placement of the optical dispersive medium and the second-order optical nonlinear medium on the optical path in one direction from the first output port to the second output port is the reverse of an order of placement of the optical dispersive medium and the second-order optical nonlinear medium on the optical path in another direction from the second output port to the first output port.

Abstract: The problem of the low efficiency of large quantum defect optical parametric oscillators is solved by recycling unused photons in a process involving pumping additional parametric processes having a common resonant wavelength. In order to improve the efficiency, a series of optical parametric oscillators are pumped with unused signal photons which exist at the output of a previous optical parametric oscillator that generates both signal and idler outputs, with the idler constituting the desired output.

Abstract: An apparatus for generating a strong source of doubly or multiply entangled photons emitted non-collinearly or collinearly with respect to the pump light that is at frequency 2f includes a laser medium producing classical laser light at fundamental frequency f. A medium for second harmonic generation transforms the light at fundamental frequency f to its second-harmonic frequency 2f and emitting entangled photons non-colinearly with respect to the light at the second harmonic frequency. An optical cavity element around the laser medium and the medium for second harmonic generation includes of at least two mirrors that are highly reflective at the light frequencies f and 2f.

Abstract: An optical parametric oscillator apparatus utilizing self-seeding with an external nanosecond-duration pump source to generate a seed pulse resulting in increased conversion efficiency. An optical parametric oscillator with a ring configuration are combined with a pump that injection seeds the optical parametric oscillator with a nanosecond duration, mJ pulse in the reverse direction as the main pulse. A retroreflecting means outside the cavity injects the seed pulse back into the cavity in the direction of the main pulse to seed the main pulse, resulting in higher conversion efficiency.

Abstract: By substituting a ring optical parametric oscillator for the linear cavity, one eliminates the effects of feedback solved in the prior art by the use of isolators and by the purposeful off-axis alignment of the pump laser beam. The result is an exceedingly robust system with state-of-the-art efficiency for maximizing output power while preserving beam quality.

Abstract: The present invention relates to an optical parametric oscillator including a non-linear optical crystal and two glass substrates surface contacted to the opposite ends of said crystal. The substrates include mirrors on their outer surfaces so that the combination of the mirrors, substrates and the crystal functions as the parametric oscillator. The invention also relates to the method of producing such an oscillator that overcomes the problems of surface contact bonding and laser damage threshold by use of an alkaline polishing compounds on the crystal ends.

Abstract: An apparatus and method for optically, parametrically amplifying a small-signal. A small-signal optical parametric amplifier (OPA) includes a narrowband pump source, means for suppressing stimulated Brillouin scattering (SBS) (e.g., a phase modulator), coupled to the narrowband pump source, a booster amplifier, coupled to the SBS-suppressed pump output, a bandpass filter, coupled to the booster amplifier, a low-loss coupler, coupled to the bandpass filter and the receiving end of a small-signal transmission line, and means for performing non-linear mixing, coupled to the injection coupler. The narrowband pump source produces a pump output. The booster amplifier amplifies the SBS-suppressed pump output to a sufficient power level for achieving parametric gain. The bandpass filter bandpass filters the amplified, SBS-suppressed pump output and suppresses amplified spontaneous emission (ASE) in the pump output.

Abstract: A fiber optical parametric oscillator is formed using photonic crystal fibers, also known as microstructure fibers or holey fibers. The optical parametric oscillator includes only a few meters of microstructure fiber. In one embodiment, the microstructure fiber is disposed between a highly reflective mirror and a diffraction grating in a simple Fabry-Perot configuration wherein the diffraction grating is tuned to reflect a particular wavelength of the signal wave back to the microstructure fiber. In another embodiment, the microstructure fiber is disposed in a ring cavity and the parametric oscillator is synchronously pumped. The parametric oscillator may be implemented with free space optics or use all fiber optic components.

Abstract: The present passively Q-switched laser comprises a condensing optical system for condensing a laser beam emitted from a laser light source onto the surface of the solid-state laser medium. The surface of a solid-state laser medium is disposed off the condensation position of the laser beam produced by the condensing optical system.

Abstract: An optical device comprises a cavity resonator and an intracavity ridge waveguide. The ridge waveguide includes a monolithically integrated intersubband core region and a nonlinear mixing region (NMR). In response to external pumping energy the core region generates laser light at a first frequency and in a first transverse mode. In response to the laser light the NMR generates parametric light at a second frequency and in a second transverse mode. For phase matching the effective-refractive-index-versus-ridge-width characteristics of the modes of the laser and the parametric light intersect one another at a phase matching width and so that, at greater widths, the effective refractive index of the mode of the higher frequency light is less than that of the lower frequency light. For true phase matching the width of the ridge is made to be essentially equal to the phase matching width.

Abstract: A method and a nonlinear frequency mixer employing the method to generate at least one output light from at least one input light with the aid of a quasi-phase-matching (QPM) grating for quasi-phase-matching the input and output light involved in a nonlinear frequency mixing operation such as three-wave mixing, four-wave mixing or other nonlinear operation mediated by a susceptibility of the nonlinear optical material. The QPM grating has a beam-modifying pattern with features for wave front shaping. More specifically, the features shape the wave fronts of the output light by diffraction or phase front shaping to thereby modify its propagation. This modification of propagation can be used to steer, focus, defocusing, split and/or collimate the output light.

Abstract: Wavelength stability of an optical oscillator has been enhanced by feedback from an external position-sensing detector to control the position or tilt of an intracavity optical element, such as a mirror. The wavelength stability results from stabilization of the intracavity beam position relative to an aperture in the oscillator. The wavelength selectivity of the aperture results from incorporation of a dispersive element in the oscillator cavity that produces a mapping of wavelength to beam position at the aperture.

Abstract: An optical wavelength converting apparatus comprising first and second light sources and a nonlinear optical material. Beams from the two light sources, incident on the material, generate sum frequency light of these beams. The nonlinear optical material is provided with a periodic structure that matches phases of the beams from the two light sources with a phase of the sum frequency light of these beams. Also, wavelengths of the beams from the two light sources and of the sum frequency light of these beams, polarization directions of these three beams in the material, and propagation directions of these three beams in the material are determined such that an efficiency of conversion into sum frequency light does not change even with a change in one of the defining parameters, thus providing an advantageous pumping light source.