The invention is a nonlinear Raman optical device generating zig-zag radiation beam paths in a nonlinear medium having dichroic coatings reflecting at a pump radiation wavelength, with a first mirror between an injected beam of pump radiation and a first end of the nonlinear medium and a second mirror at a second end of the nonlinear medium, the second mirror being partially reflecting at a first Stokes wavelength of the pump radiation.

A system for determining a second-order nonlinear susceptibility of a material includes a laser light source, a polarization modulator, a light collector, a polarization detector and a controller. The controller can obtain the second-order nonlinear susceptibility of the sample to be tested according to the test data. The system for determining the second-order nonlinear susceptibility of a material can directly test a material (block or film) with a thickness of hundreds of nanometers, and draw a second-order nonlinear susceptibility fitting curve of the material according to the test results of the optical system.

In a terahertz wave generation apparatus including a first non-linear optical crystal 3 on which first laser L1 and second laser L2 from laser generation means 2 are incident to generate terahertz wave TH1, the laser generation means includes a second non-linear optical crystal 7 on which laser having the same wavelength as that of the second laser is incident to generate idler light L1 including a plurality of wavelengths, and makes the idler light L1 generated from the second non-linear optical crystal incident on the first non-linear optical crystal as the first laser L1, to generate terahertz wave including a plurality of wavelengths from the first non-linear optical crystal 3, and wavelength selection means including a transmission section which transmits an idler light having the specific wavelength in the idler light including the plurality of wavelengths can be provided, as needed. Thus, terahertz wave having a high output power and including a plurality of wavelengths can be obtained, and the wavelength selection means easily obtains a required terahertz wave having the specific wavelength.

A method of creating difference frequency (DF) laser pulses (1) by difference frequency generation (DFG) comprises the steps of providing ultrashort laser pulses (2) having a spectral bandwidth corresponding to a Fourier limit of below 50 fs and containing first spectral components and second spectral components having larger frequencies than the first spectral components, and driving a DFG process by the ultrashort laser pulses (2) in an optically non-linear crystal (10), wherein the DF laser pulses (1) are generated in the crystal (10) by difference frequencies between the first and second spectral components, resp., said difference frequencies comprising third spectral components being lower in frequency than the first and second spectral components, wherein at least one enhancement cavity (20) with resonator mirrors (Mil to Ml4) spanning a beam path (22) is provided and the crystal (10) is placed in the beam path (22) of the enhancement cavity (20), the ultrashort laser pulses (2) are input coupled and coherently added in the at least one enhancement cavity (20), at least one circulating ultrashort laser pulse (3) is created in the at least one enhancement cavity (20), which drives the DFG process in the crystal (10) for generating the DF laser pulses (1), and the at least one enhancement cavity (20) is adapted for recycling the at least one ultrashort laser pulse (3) passing through the crystal (10). Furthermore, a photonic source (100) for creating DF laser pulses (1) is described, including one or more enhancement cavities.

The multi wavelength laser device includes a laser light source 10 that emits a plurality of laser lights 20 whose fundamental wavelengths differ from one another, a dispersing element 30 that changes the traveling direction of each of the plurality of laser lights according to the wavelength and the incidence direction, and that emits the laser lights in a state in which the laser lights are superposed on the same axis, and a wavelength conversion element 40 that has a plurality of polarization layers disposed therein and having different periods, and that performs wavelength conversion on the fundamental wave laser lights emitted from the dispersing element 30 and placed in the state in which the laser lights are superposed on the same axis, and emits a plurality of laser lights 50 acquired through the wavelength conversion in a state in which the laser lights are superposed on the same axis.

A supercontinuum light source can include a seed laser arranged to provide seed pulses with a pulse frequency F.sub.seed; a pulse frequency multiplier (PFM) arranged to multiply the seed pulses by converting pulses having the pulse frequency F.sub.seed to pump pulses with a pulse frequency F.sub.pump, where F.sub.pump is larger than F.sub.seed; and a non-linear element arranged to receive said pump pulses and convert said pump pulses to pulses of supercontinuum light. The PFM can further include a splitter for splitting pulses into first and second sub beams each having the same pulse frequency, where the PFM is configured such that the sub beams experience different delays; and a combiner for combining said first and second sub beams into a beam having the pulse frequency that is greater than said same pulse frequency. The splitter can have an uneven splitter ratio.

A wavelength conversion optical element using a nonlinear optical effect of a device structure in which wavelength conversion efficiency rises as targeted when the length of a waveguide is increased is provided. The element adopts a waveguide structure using lithium niobate of a second-order nonlinear optical material. Wavelength conversion regions are formed to correspond to two linear waveguides extending in parallel to each other on a plane of the planar structure and correspond to the lengths of the two linear waveguides. One end side of the linear waveguide is an incident side of excitation light and one end side of the linear waveguide is an emission side of wavelength converted light. The linear waveguides excluding the incident side and the emission side are joined by a bent waveguide. Second-order nonlinear optical media forming the linear waveguides have polarization inversion structures in which directions of spontaneous polarization are periodically inverted with respect to a propagation direction of light.

A nonlinear crystal including stacked Strontium tetraborate SrB.sub.4O.sub.7 (SBO) crystal plates that are cooperatively configured to create a periodic structure for quasi-phase-matching (QPM) is used in the final frequency converting stage of a laser assembly to generate laser output light having a wavelength in the range of 125 nm to 183 nm. One or more fundamental light beams having fundamental wavelengths between 1 and 1.1 μm are doubled and/or summed using multiple intermediate frequency conversion stages to generate one or more intermediate light beam frequencies (e.g., second through eighth harmonics, or sums thereof), and then the final frequency converting stage utilizes the nonlinear crystal to either double a single intermediate light beam frequency or to sum two intermediate light beam frequencies to generate the desired laser output light at high power and photon energy levels. A method and inspection system incorporating the laser assembly is also described.

An optical filter includes a substrate; a first mirror on the substrate; a cavity layer on the first mirror; and a second mirror on the cavity layer. Each of the first and second mirrors provide high reflection, low transmission and low absorption over a targeted stopband. The cavity layer defines a resonant transmission band within the targeted stopband with the resonant band wavelength depending on the optical thickness of the cavity layer. The cavity layer includes a material having a non-linear response to incident irradiance such that cavity absorption changes with irradiance and suppresses cavity resonance at high irradiance. The material having the non-linear response to the incident irradiance includes a two-dimensional (2D) material.

Apparatus and methods for improved HHG of ultrashort pulse laser beams. A HHG assembly includes a gas distribution block and a waveguide cartridge having a HHG hollow core waveguide. The waveguide cartridge is attached to the gas distribution block and may be removed and replaced, while the gas distribution block remains affixed within the apparatus. The gas distribution block is configured to maintain a pressure profile within the hollow core fiber. The system also includes two operating beam sensors and two actuatable mirrors. The operating beam sensors are fixed with respect to the HHG assembly. The system is aligned before operation by adjusting the actuatable mirrors to optimize a sample beam through the waveguide and recording the position of the beam on the operating beam sensors. In operation, the mirrors are actuated to maintain the same positions of the input beam on the operating beam sensors.