Abstract: Disclosed herein is an optically locked photon echo apparatus and method, which can solve the problem of limited echo efficiency and can overcome constraints on the conventional storage time being limited to the spin dephasing time. The optically locked photon echo apparatus of the present invention includes a nonlinear optical medium and an optical pulse generation unit. The nonlinear optical medium is provided with three energy levels |1>, |2>, and |3>, and is configured to receive optical pulses from an optical pulse generation unit and generate output light (E) which satisfies a phase matching condition. The optical pulse generation unit is configured to generate five or more optical pulses which resonate between the energy levels of the optical medium.

Abstract: A synchronously-pumped optical parametric oscillator (OPO 10) driven by the second harmonic output of a Kerr-lens-mode-locked Ti:sapphire laser (12) generates femtosecond pulses with wide tunability in the visible and ultraviolet spectrum. The OPO uses bismuth triborate, BiB3O6 (or BIBO) or a substituted form thereof, in collinear critical phase-matching as the nonlinear gain crystal (24). Using simple crystal rotation at room temperature, a continuous tuning range from 480 nm to 710 nm is achieved with a single BIBO crystal (24) and a single set of mirrors (26, 28, 30) for the OPO cavity. The OPO (10) generates up to 27 OmW of average power across the available tuning range and can deliver femtosecond pulses at a repetition rate of 76 MHz.

Abstract: A tunable multiple laser pulse scanning microscope and a method of operating the same is described, applying two pulsed laser beams with distinct wavelengths incident on a scanning spot of a sample to be imaged simultaneously or at a specific time delay. The microscope comprises at least two pulsed laser light sources emitting laser light of distinct wavelengths, an acousto-optic tunable filter (AOTF) for tuning at least one of the laser pulses, a delay stage provided upstream of the AOTF, and an actuator for moving delay stage depending on the time delay. As a result, the wavelength of at least one type of pulses is tuned, and the delay between at least two pulses of distinct wavelengths is adjusted.

Abstract: Seed light pulses and pump light pulses are generated; the seed light pulses are preferably chirped; and both are directed into an enhancement cavity at a full repetition rate. The enhancement cavity defines a closed optical path that contains a nonlinear medium that provides phase matching at a wavelength different from both the central seed wavelength and the central pump wavelength. The generation of the pump light pulses and the seed light pulses are synchronized to pass the seed light pulses through the nonlinear medium simultaneously with the pump light pulses to parametrically amplify the seed light pulses in the nonlinear medium to produce an amplified signal pulse and idler pulse. Increased conversion with low average pump power can be achieved, as well as gain bandwidth enhancement approaching octave-spanning levels.

Abstract: The present invention relates to an OPCPA apparatus. The OPCPA of the present invention includes an optical pulse stretcher (100) for outputting chirped laser light using odd-order dispersion (third-order dispersion is mainly used). A pump laser (200) outputs pump laser light. An OPA unit (300) receives the pump laser light and the chirped laser light (signal), amplifies the signal using the pump laser light, and generates an idler. An optical signal separation unit (400) separates output light of the OPA unit into the signal, the idler, and remaining light (pump). An optical pulse compressor (600) compensates for pulse chirping caused by odd-order dispersion that is imparted by the optical pulse stretcher, thus temporally compressing the signal and the idler, which overlap each other.

Abstract: A coherent light source is provided for producing narrow-linewidth output, continuously tunable within a broad (at least one-octave-wide) range of optical wavelengths. The source is based on type-I or type-0 near-degenerate optical parametric oscillator (OPO), which uses a nonlinear optical crystal with either birefringent phase matching or quasi phase matching. The pump wavelength is chosen such that the OPO degeneracy wavelength (at twice the pump wavelength), is close to the point of zero group-velocity dispersion. That results in an extremely broad OPO bandwidth. Fast OPO wavelength tuning is achieved by rotating an intracavity diffraction grating. In accordance with the invention, the choice of a nonlinear crystal and a pump source determines the overall tuning range. For example, the use of lithium niobate provides tuning over the range of 1.3 to 3 microns, ZGP—3.8 to 8 microns, gallium arsenide—4 to 12 microns, CGA—6 to 13 microns.

Abstract: A nonlinear harmonic generation system is provided. The nonlinear harmonic generation system includes a waveguide channel receives and propagates electromagnetic signals. A resonant cavity is coupled to the waveguide channel. The resonant cavity structure includes a plurality of resonant modes into which electromagnetic energy is coupled during the operation of the system. One of the resonant modes includes a resonant frequency that changes during operation of the system to reach either an input-signal frequency or a harmonic frequency for a majority of the time in which harmonic generation is occurring. Both reflected and harmonic fields are emitted back into the waveguide channel so as to allow efficient harmonic generation at a specified critical input power.

Abstract: A compact source of polarization-entangled photons includes a laser source, producing a laser beam, a pair of nonlinear crystals, in optical contact with each other, with one of the pair of nonlinear crystals having an input face, with the laser beam incident on the input face, and another of the pair of nonlinear crystals rotated 90°, along an axis perpendicular to the input face, with respect to each other and a fiber coupling point, configured to receive a pair of single-mode fibers. Pairs of polarization-entangled photons are produced through spontaneous parametric down conversion of the laser beam and provided to the fiber coupling point.

Abstract: A system and method for improving conversion efficiency of a difference frequency generator (DFG) and/or for outputting a desired shape of the output signal, where the method includes providing a pump source, modifying the pump pulse temporal shape for optimal DFG conversion efficiency, and providing the modified pump pulse to the DFG. The pump source may be, for example, a MOPA laser or a diode or any other suitable source. In one embodiment, the pump pulse shape is modified such that an initial gain within the DFG is high, followed by a lower level signal for efficient conversion within the DFG. An example of such a shape is a double square pulse. Other configurations are possible as well such as a single rectangular pulse shape.

Abstract: A wavelength conversion system includes a Mach-Zehnder interferometer including two optical waveguides, a non-linear medium provided on one of the two optical waveguides, and a branching ratio adjuster for adjusting the branching ratio of multiplexed light produced by multiplexing signal light and pumping light so that the powers of the signal light and the pumping light which are to be emitted from the two optical waveguides are equal to each other. The multiplexed light whose branching ratio is adjusted by the branching ratio adjuster is introduced into the two optical waveguides such that the non-linear medium generates phase conjugation light of the signal light and the light guided through the one optical waveguide and the light guided through the other one of the two optical waveguides interfere with each other so that the phase conjugation light is extracted as wavelength conversion light.

Abstract: A non-linear optical device includes a frequency-conversion waveguide and first and second input waveguides. The longitudinal axes of the input waveguides are inclined to that of the frequency-conversion waveguide such a first transverse mode is excited in the latter at the input frequency in operation of the device. The frequency-conversion waveguide supports a second transverse mode at an output frequency of the device, such that the phase velocity of the second transverse mode at the output frequency is substantially equal to that of the first transverse mode at the input frequency, thus providing phase-matching by balancing the effects of chromatic and modal dispersion.

Abstract: Embodiments of parametric chirped pulse amplifiers seeded with a single pulse source which is subsequently split into a signal arm and a pump arm with appropriate signal and pump conditioning stages are disclosed, which advantageously improve the utility of high average power and/or high energy ultrafast amplification systems. In various embodiments, at least one of the signal or the pump conditioning stages is non-linear, allowing for a great range of seed sources to be utilized. Chirped pulse amplification in the pump conditioning stage may be used to simplify the parametric amplification of pulses with pulse widths of the order of 10 fs. The parametric pump can include coherently combined fiber arrays, hybrid fiber solid-state amplifiers, and/or cryogenically cooled solid-state amplifiers to increase or optimize the energy extraction of high average powers.

Abstract: An optical parametric oscillator including a nonlinear crystal pumped by a laser source and an optical resonator, including an optical interferometer, which determines a level of output coupling of the oscillator, allowing high stability, broad wavelength tuning, and output power level optimization.

Abstract: An optical frequency comb generator includes a laser device arranged for generating input laser light having a predetermined input light frequency, a dielectric micro-resonator having a cavity exhibiting a third order nonlinearity, so that the micro-resonator is capable of optical parametric generation providing parametrically generated light, and a waveguide optically coupled to the micro-resonator, the waveguide being arranged for in-coupling the input laser light into the micro-resonator and out-coupling the parametrically generated light out of the micro-resonator, wherein the laser device, the waveguide and the micro-resonator being arranged for resonantly in-coupling the laser input light to a mode of the micro-resonator with a minimum power level so that an optical field inside the cavity exceeds a predetermined cascaded parametric oscillation threshold at which the parametrically generated light includes frequencies of frequency sidebands of the input light frequency and of the sidebands thereof.

Abstract: An intra-cavity optical parametric oscillator. The oscillator includes means for providing a non-linear loss for suppressing relaxation oscillations.

Abstract: A wavelength converter which performs simultaneously wavelength conversion for a plurality of input light wavelengths that are unequally intervals, is provided. The nonlinear material of the wavelength converter has a modulation structure which has modulation of a nonlinear optical constant at a period ?0 in a propagating direction of light, a phase being continuously changed each period ?0 and a continuous phase modulation for a different period ?ph being added to the modulation structure. The nonlinear material has a modulation structure obtained by changing a modulation curve for the phase modulation, wherein a phase mismatch ?? is represented by ??=2?(n3/?3?n2/?2?n1/?1), and at least three peaks at unequally intervals within a plurality of peaks for conversion efficiency represented by 2?/?0+2?i/?f (i=m, m+1, . . . , n: where m and n are positive or negative integers) have highest conversion efficiency.

Abstract: In an optical parametric amplifier of the invention, pumping light which is amplified using a practical optical amplifier such as an EDFA is supplied together with signal light having a wavelength outside the amplification band of the optical amplifier, to a nonlinear optical medium via a multiplexer, to thereby amplify the signal light by an optical parametric amplification effect due to the pumping light in the nonlinear optical medium. As a result, the amplification band of a practical optical amplifier such as an EDFA, can be extended, and the noise characteristics can be improved.

Abstract: Devices, systems and methods of using same where hybrid substrate materials are provided with a substantially uniform surface to provide uniformity of properties, including interaction with their environments. Uniform surfaces are applied as coatings over, e.g., hybrid metal/silica, metal/polymer, metal/metal surfaces to mask different chemical properties of differing regions of the surface and to afford a protective surface for the hybrid structure.

Abstract: Devices, systems and methods of using same where hybrid substrate materials are provided with a substantially uniform surface to provide uniformity of properties, including interaction with their environments. Uniform surfaces are applied as coatings over, e.g., hybrid metal/silica, metal/polymer, metal/metal surfaces to mask different chemical properties of differing regions of the surface and to afford a protective surface for the hybrid structure.

Abstract: Devices, systems and methods of using same where hybrid substrate materials are provided with a substantially uniform surface to provide uniformity of properties, including interaction with their environments. Uniform surfaces are applied as coatings over, e.g., hybrid metal/silica, metal/polymer, metal/metal surfaces to mask different chemical properties of differing regions of the surface and to afford a protective surface for the hybrid structure.

Abstract: A single-pass optical parametric amplifier is provided. The single-pass optical parametric amplifier comprises a light source emitting a fundamental wave having a wavelength range; a nonlinear material, which the fundamental wave passes therethrough to form a second harmonic generation wave having a light path; a supercontinuum generator extending the wavelength range of the fundamental wave to form a supercontinuum generation seed; and an optical parametric wavelength transformer transforming the supercontinuum generation seed and the second harmonic generation wave into a signal wave and an idler wave.

Abstract: A sample of nonlinear optical material for use in a nonlinear optical device contains a grating comprising alternating regions of inverted and non-inverted nonlinear coefficient of the material, with the regions separated by boundaries positioned such that the grating can provide quasi-phase matching of a selected nonlinear optical interaction, and compensate for phase mismatch arising from the Gouy phase shift of one or more focused optical beams involved in the interaction. The boundary positions can be calculated for second harmonic generation or optical parametric generation and oscillation.

Abstract: An optical spectrum generator is disclosed, which is based on generating conjugate optical frequencies via the use of two or more nonlinear interactions, where filters are used to select the conjugate output of the preceding nonlinear interaction as the input to the following nonlinear interaction. The cascaded nonlinear interaction is seeded with an incoming optical beam and pumped with multiple pump beams. The conjugate output of the last nonlinear interaction can be fed-back to the input of the first nonlinear interaction thus creating a recirculating path. An add-drop multiplexer is implemented for efficiently combining the pump beams with conjugate beams. The generated output frequencies are related to the difference in frequency between the pumps which can be changed as a function of time to create a time-varying output frequency. The magnitude of the variation in output frequency can be magnified by recirculating the signal through the system multiple times.

Abstract: A wide-band ultrashort-pulse optical oscillator includes: an optical amplification medium 1 that optically amplifies an incident light having a wide band or a plurality of bands so as to be converted into an oscillation light emitted from an optical resonator; an energy injection element 2 that either injects energy into the optical amplification medium so that light energy is generated, or injects light energy into the optical amplification medium; a negative dispersion element 4 that imparts a negative dispersion to a pulse light of the oscillation light; a mode locker 9 that produces a mode-locking with respect to the pulse light; a positive dispersion element 11 that imparts a positive dispersion to the pulse light; and an optical system formed so that the pulse light passes through a loop-like optical path from the optical amplification medium via the negative dispersion element, the mode locker, and the positive dispersion element, back to the optical amplification medium in at least one of the stated d

Abstract: Certain embodiments relate to and involve producing broadband phase-locked frequency combs in the near-infrared and mid-infrared spectral ranges. One such embodiment is directed to a system, with a pump laser and an optical parametric oscillator (OPO) resonator, that is configured to produce broad-bandwidth frequency combs in the near-infrared and mid-infrared frequency ranges. The pump laser is configured to produce femtosecond pulses of light having a pulse repetition rate. The optical parametric oscillator (OPO) resonator that is coupled to the pump laser for facilitating synchronous OPO pumping by matching a roundtrip time of the pulses of light within the OPO resonator with the pulse repetition rate of the pump laser.

Abstract: The present invention provides methods, systems, and apparatus of improved fiber-based optical parametric oscillators (FOPOs). These oscillators can be used in the creation of short pulsed laser radiation, which are useful in numerous applications, such as characterization of materials and molecules. A relationship between fiber length and performance is realized, where shorter lengths counterintuitively provide greater power and width of output bands. This relationship is used to develop improved FOPOs. For example, fibers of 10 cm or less may be used to obtain superior performance in terms of wavelength tunability (e.g. bandwidth of 200 nm and greater) and output power (e.g. pulse power of 1 nJ). Other realized relationships between length and wavelength position of output bands are also used to select the wavelength range output from the FOPO. The diameter of the fiber may be selected to provide positioning (e.g. a centering) of the range of attainable output wavelengths.

Abstract: An optical antenna collects, modifies and emits energy at light wavelengths. Linear conductors sized to correspond to the light wavelengths are used. Nonlinear junctions of small dimension are used to rectify an alternating waveform induced upon the conductors by the lightwave electromagnetic energy. The optical antenna and junctions are effective to produce harmonic energy at light wavelengths. The linear conductors may be comprised of carbon nanotubes that are attached to a substrate material, which may then be connected to an electrical port.

Abstract: It is provided a device of oscillating an electromagnetic wave having a frequency of 0.1 THz to 3 THz from pump and idler waves by parametric effect. The device includes a supporting body 13, an oscillating substrate 11 of a non-linear optical crystal, an adhesive layer 12 adhering the supporting body 13 and oscillating substrate 11, and a film 15 reflecting the electromagnetic wave formed on a surface of the supporting body 13 on the side of the adhesive layer 12. The oscillating substrate 11 has an upper face, a bottom face and an incident face on which the pump wave is made incident. The adhesive layer 12 has a refractive index with respect to the pump wave lower than that of the oscillating substrate 13.

Abstract: It is provided a device of oscillating an electromagnetic wave having a frequency of 0.1 THz to 3 THz from pump and idler waves 3, 4 by parametric effect. The device includes a supporting body 13, an oscillating substrate 11 made of a non-linear optical crystal, and an adhesive layer 12 adhering the supporting body and oscillating substrate. The oscillating substrate 11 includes an upper face 11a, a bottom face 11f and an incident face 11c on which the pump wave 3 is made incident. The oscillating substrate 11 provides cut-off with respect to the electromagnetic wave 7 oscillated by parametric effect when the pump and idler waves 3, 4 propagate in parallel with the bottom face 11f.

Abstract: An oscillating device includes an oscillating substrate 11 of a non-linear optical crystal and having an incident face 11c where a pump wave 3 and an idler wave 4 are made incident; a first waveguide 24A provided in the oscillating substrate 11 and between the incident face 11c and an interacting part 20 of the pump wave 3 and idler waves 4; and a second waveguide 24B provided in the oscillating substrate 11 and between the incident face 11c and the interacting part 20. The first waveguide 24A guides the pump wave 3 and the second waveguide 24B guides the idler wave 4.

Abstract: A quantum entanglement generating system (30) comprises: a laser light source (1) for producing a light beam of light frequency 2f0; a ring interferometer (20) comprising a beam splitter (4) into which the light beam of light frequency 2f0 is incident and a plurality of mirrors (5, 7, 8), the beam splitter and the mirrors forming an optical path in the form of a ring; a parametric amplifier (6) inserted in the optical path of the ring interferometer for producing a beam of light of light frequency f0 upon receiving the light beam of light frequency 2f0 incident into the optical parametric amplifier; and a dispersive medium (9) inserted in the optical path of the ring interferometer for varying relative optical path length for the light beam of light frequency 2f0 and the light beam of light frequency f0, whereby two light beams of light frequency 2f0 split into at the beam splitter (4) so as to travel mutually contrariwise in direction of advance in the ring interferometer are incident into the optical parame

Abstract: The present invention discloses a structure and method for realizing electromagnetically-induced transparency. In the present invention, a first split-ring resonator and a second split-ring resonator form a resonance structure. The first split-ring resonator and the second split-ring resonator are made of a conductive material. The first split-ring resonator has a “U” shape with a containing space. The second split-ring resonator has a “rectangular loop” shape with a gap or has a “U” shape with an opening. The second split-ring resonator is inserted into the containing space with the gap or opening arranged inside the containing space and faced downward to form the resonance structure. The resonance structures are periodically arranged on a chip to form an array. Thereby, different-frequency electromagnetic waves can be used to generate electromagnetically-induced transparency via regulating the dimensions of the resonance structure.

Abstract: An optical parametric oscillator (OPO) comprises a resonant cavity for signal light, and an optically non-linear medium disposed in the resonant cavity for converting pump light into the signal light, wherein the resonant cavity is arranged so that in operation signal light is repeatedly output from and returned to the optically non-linear medium along a signal light path in a continuously repeating cycle, and the OPO comprises delay means for extending the time taken for signal light output from the optically non-linear medium in operation to return to the optically non-linear medium along the signal light path.

Abstract: A waveguide parametric device including a multi-mode waveguide having orientation layers formed in a propagation direction of a signal beam and a pump beam propagating down the waveguide. The orientation layers are oppositely oriented to provide non-linear coupling between the pump beam and the signal beam and have a periodicity that provides quasi-phase matching for a fundamental propagation mode, where the waveguide has a size to accommodate multi-mode wave propagation.

Abstract: A robust, quickly tunable narrow-linewidth entangled photon source system based on Spontaneous Parametric Down Conversion (SPDC) of the pump light in periodically polled LiNbO3 (PPLN) waveguides. The photon source provides narrow-linewidth, entangled output photons having a wavelength in the telecom C-Band wavelength. To tailor the output spectrum of the output photons, the PPLN waveguide is arranged between two end waveguides having LiNbO3-embedded Bragg gratings, thereby forming a tunable Fabry-Perot cavity. The resulting narrow output linewidth of the output photons makes the system desirable for use in a long-distance quantum key distribution (QKD) system.

Abstract: Methods and apparatus for non-collinear optical parametric ampliffication (NOPA) are provided. Broadband phase matching is achieved with a non-collinear geometry and a divergent signal seed to provide bandwidth gain. A chirp may be introduced into the pump pulse such that the white light seed is amplified in a broad spectral region.

Abstract: In a branched resonator OPS-laser arrangement, a combination of intra-cavity optical parametric generation and intra-cavity frequency conversion provides output radiation in a range between about 550 nanometers about 800 nanometers from an OPS fundamental wavelength in a range between about 900 nm and about 1100 nm.

Abstract: Apparatus and method for producing quantum entangled signal and idler photon pairs is provided. The apparatus makes use of a nonlinear optical fiber to generate the entangled photons. The use of an external broad band light source for alignment of any downstream measurement apparatuses is disclosed. One or more polarized output signals can be generated at both the signal and idler wavelengths using the alignment source, allowing the downstream measurement apparatuses to be aligned using classical light. Multiple signal and idler wavelengths can be generated and aligned using such a system.

Abstract: The polarization direction of an optical signal is changed by a polarization controller so as to be orthogonal to a main axis of a polarizer. A control pulse generator generates control pulses from control beam with a wavelength which is different from the wavelength of the optical signal. The optical signal and the control pulse are input to a nonlinear optical fiber. In the nonlinear optical fiber, the optical signal, during a time period in which the optical signal and the control pulse coincide, is amplified with optical parametric amplification around a polarization direction of the control pulse. The optical signal, during the time period in which the optical signal and the control pulse coincide, passes through the polarizer.

Abstract: A wavelength conversion element includes a second harmonic wave generating element provided with an entrance surface and an emission surface, a function of converting an incident fundamental wave into a second harmonic wave with a different wavelength and emitting the second harmonic wave, and a cyclic polarization inversion structure configured so as to be able to match a phase of the second harmonic wave in a pseudo manner, and a first wavelength dispersive optical element disposed on the entrance surface side of the second harmonic wave generating element, having a first diffraction surface for diffracting an incident light beam with a diffraction angle increasing in accordance with a wavelength of an incident light beam to disperse the incident light beam by the wavelength of the incident light beam, and for emitting the light beam dispersed in the first diffraction surface towards the second harmonic wave generating element.

Abstract: The invention applies to doubly resonant optical parametric oscillators comprising a non-linear crystal (4) through which pass a pump laser beam (fp), a signal beam (fs), and a complementary beam (fc), and a device (5) that totally or partially reflects said beams emanating from the crystal such that, after reflection, they generate between them a relative phase-shifting value ??ar for a given functioning mode independent of the signal frequency or complementary frequency, and is characterized in that the reflecting device (5) is a metallic minor, or a combination of two scattering mirrors and a multilayer dielectric mirror placed downstream.

Abstract: An optical repeater device of the present invention comprises: a preamble compensating circuit 53, for taking out a normal data signal from burst signals propagating through a communication transmission path, and for adding a preamble signal before and/or after the data signal. Furthermore, the preamble compensating circuit 53 comprises: a detector circuit 53a, for inputting the burst signal, and for outputting only the normal data signal; a buffer circuit 53b, for storing the data signal output from the detector circuit 53a, and for outputting thereof; a preamble signal generation circuit 53d, for outputting at least one type of the preamble signal; and an data output select circuit 53e, for outputting the data signal at the time of the data signal input from the buffer circuit 53b, and for outputting the preamble signal from the preamble signal generation circuit 53d at any other time thereof.

Abstract: Apparatus and method for producing quantum entangled signal and idler photon pairs is provided. The apparatus makes use of a nonlinear optical fiber to generate the entangled photons. The use of an external broad band light source for alignment of any downstream measurement apparatuses is disclosed. One or more polarized output signals can be generated at both the signal and idler wavelengths using the alignment source, allowing the downstream measurement apparatuses to be aligned using classical light. Multiple signal and idler wavelengths can be generated and aligned using such a system.

Abstract: A single-photon generator includes a single-photon generating device generating a single-photon pulse having a wavelength on the shorter wavelength side than a communication wavelength band, and a single-photon wavelength conversion device performing wavelength conversion of the single-photon pulse into a single-photon pulse of the communication wavelength band, using pump pulse light for single-photon wavelength conversion.

Abstract: The present invention purposes to provide a THz-wave generator capable of generating a THz-wave stably and efficiently, and particularly, to provide the THz-wave generator which is stable against a frequency shift of a laser source and which can easily vary the frequency of the THz-wave. A THz-wave generator, for inputting a laser beam from a light source unit A including a laser source to a THz-wave generating element D, and generating a THz-wave (fT) from the THz-wave generating element, wherein a light circulating unit including an SSB optical modulator, and wavelength selecting means C are disposed between the laser source A and the THz-wave generating element D, the laser beam is guided into the light circulating unit, a specific wavelength lightwave is selected out of lightwaves having a plurality of wavelengths generated in the light circulating unit by the wavelength selecting means, and the specific wavelength (f0, fn) lightwave is input to the THz-wave generating element.

Abstract: A parametric device having a non-linear material (4) for generating an idler wave and a signal wave (16) in response to a pump wave (14), the pump, idler and signal waves being non-collinear, the device having a cavity (10, 11) resonant at the pump wavelength and means for varying the angle between the propagation directions of the pump and idler waves.

Abstract: A doubly-resonant cavity structure includes at least one cavity structures so as to allow total frequency conversion for second or third-harmonic generation using ?(2) and ?(3) nonlinearities between the at least one cavity structures. The total frequency conversion is efficiently optimized by determining a critical power allowing for such total frequency conversion to occur depending on the cavity parameters of the at least one cavity structures.

Abstract: In a THz wave generator for generating a THz wave from a THz wave generating element by inputting a plurality of laser beams having different wavelengths to the THz wave generating element, all of the plurality of laser beams are formed into a pulse beam by the pulse generator and the pulse beam is amplified by a single optical amplifier E to which the laser beams are inputted with polarization planes of the laser beams being controlled, and then the pulse beam is inputted to the THz wave generating element F. Preferably, the plurality of laser beams having different wavelengths are generated by inputting single wavelength beam to a multi wavelength generator from single mode laser light source and by inputting light waves having a plurality of wavelengths generated from the multi wavelength generator to wavelength selecting means.

Abstract: A two-pump optical parametric device (OPD) having a nonlinear birefringent fiber, in which various four-wave mixing (FWM) processes can occur. The OPD applies, to the nonlinear birefringent fiber, two pump waves, each polarized at about 45 degrees with respect to a birefringence axis of the fiber, and a polarized input signal. A relevant FWM process couples the pump waves and the signal to cause the fiber to generate a desired output signal. In one configuration, the relevant FWM process is inverse modulational interaction, which causes the desired output signal to be generated through amplification or attenuation of the input signal. In another configuration, the relevant FWM process is phase conjugation, which causes the desired output signal to be generated through amplification of the input signal. In yet another configuration, the relevant FWM process is Bragg scattering, which causes the desired output signal to be generated as a corresponding idler signal.

Abstract: The invention relates to the field of optical parametric oscillators (OPO), especially to an essentially vertical monolithic system (S) for parametric conversion from a pump wave with a pump wavelength, said system comprising at least two resonant cavities (6, 7). Said cavities are coupled by at least one coupling mirror (3), at least one of the cavities comprising an active non-linear medium, and the at least one coupling mirror being arranged in such a way that the parametric frequencies associated with the pump wavelength are located in the stop line of the at least one mirror for an injection direction of the pump wave essentially according to the axis of the system.