Provided is an optical parametric oscillation laser based on I-type quasi-phase matching. The optical parametric oscillation laser comprises a femtosecond laser pumping source (1), an input coupling mirror (3), an Mg:PPLN crystal (4), an output coupling mirror (7) and a beam splitter prism (12), wherein the femtosecond laser pumping source (1) of a synchronous pump, the input coupling mirror (3), the Mg:PPLN crystal (4), the output coupling mirror (7) and the beam splitter prism (12) are sequentially placed. Group velocity mismatching between near-infrared pump light and intermediate infrared signal light in the intermediate infrared optical parametric oscillation laser is eliminated by using the dispersion relationship between the crystal and the temperature and in a manner of adjusting the working temperature of the crystal, so that an optical parametric oscillation process can satisfy phase matching and group velocity matching at the same time, and therefore intermediate infrared ultrashort pulse laser with high power and wide spectrum is obtained.

A system for conversion or amplification using quasi-phase matched nonlinear optical wave-mixing includes a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, a bent structure for receiving the pump radiation beam and the signal radiation beam, and an outcoupling radiation propagation portion for coupling out an idler radiation beam generated in the bent structure. A radiation propagation portion of the bent structure is made of a uniform three-dimensional material at least partly covered by a two-dimensional or quasi-two-dimensional material layer and has a dimension taking into account the spatial variation of the nonlinear optical susceptibility along the radiation propagation portion as experienced by radiation traveling along the bent structure for obtaining quasi-phase matched nonlinear optical wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for the nonlinear optical process.

In a laser device, a different refractive index region 6B of a photonic crystal layer is arranged at a lattice point position of a square lattice. In the case where a plane shape of the different refractive index regions 6B is a nearly isosceles right triangle, two sides forming a right angle extend along longitudinal and horizontal lateral lines of the square lattice. A direction parallel to or vertical to an oblique side of the triangle and a direction of polarization in the periodic polarization inversion structure of a nonlinear optical crystal NL are the same.

A waveguide includes an array of p-i-n junctions formed by ions implanted into the waveguide. The p-i-n junctions concentrate electric fields applied on the waveguide to convert the third order susceptibility .sup.(3) into the second order susceptibility .sup.(2) and induce the DC Kerr effect. The periodic electrical fields concentrated by the p-i-n junctions effectively create a wave vector, which together with the wave vectors of optical beams in the waveguide satisfies phase matching conditions for nonlinear optical effects. The phase matching can significantly enhance the efficiency of the nonlinear optical effects, such as second harmonic generation, sum frequency generation, difference frequency generation, and four-wave mixing. Waveguides with arrays of PIN junctions can also be used in phase modulators, amplitude modulators, and filters.

A method and system for generating femtosecond (fs) ultraviolet (UV) laser pulses enables stabile, robust, and optically efficient generation of third harmonic fs laser pulses using periodically-poled quasi-phase-matched crystals. The crystals have different numbers of periodically poled crystalline layers that enable a long conversion length without back-conversion and without a special phase-matching direction. The fs UV laser may have a high conversion efficiency and may be suitable for high power operation.

A high harmonic optical generator comprising a laser arrangement for emitting a beam of polarized radiation at a fundamental frequency and an optical waveguide having a hollow core for a gaseous harmonic generation medium for the generation of high harmonics of the fundamental frequency, the optical waveguide having an optical propagation axis along the hollow core, the laser arrangement is configured to couple the beam of polarized radiation along the propagation axis of the hollow core optical waveguide to provide a beam of optical driving radiation for the high harmonic generation, the optical driving radiation having a plane of polarization that rotates about the propagation axis.

Systems and techniques relating to automatically-locked homodyne detection are described. A described system includes a first nonlinear element, a filter, and second nonlinear elements. The first nonlinear element can produce, based on an input signal and a first continuous wave (CW) signal, a first output signal that includes the input signal and a phase conjugate copy of the input signal. The filter can produce a filtered signal based on the first output signal and can be programmable to adjust an induced delay between the input signal and the phase conjugate signal. The second nonlinear elements can produce second output signals based on a second CW signal and differently weighted combinations of signal components within the filtered signal. The second output signals can include an in-phase output signal based on an in-phase version of the filtered signal and a quadrature output signal based on a quadrature version of the filtered signal.

Disclosed is a method for fabricating a wavelength conversion device that is capable of suppressing unintended and random polarization reversal due to heating thereby achieving higher wavelength conversion efficiency. The method includes: forming an insulating layer on one place of a crystal substrate naturally and uniformly polarized in a thickness direction; forming an insulating layer pattern with line-and-space by photolithography; then supplying conductive fluid to both planes of the crystal substrate to apply voltage to the crystal substrate, thereby a wavelength conversion device that is periodically polarization-reversed is fabricated. When temperature of the crystal substrate decreases after heating, an ionizer supplies ions to a surface of the crystal substrate, negative ions collect on +z plane, and positive ion collect on z plane, thereby unintended and random polarization reversal is suppressed.

A periodic polarization reversal electrode, periodic polarization reversal structure forming method and periodic polarization reversal element. The element includes a plurality of stripe electrode sections with a stripe shape extending in parallel at a gap from each other, arranged in contact with the +Z surface of a ferroelectric crystal substrate; an insulation film arranged over the +Z surface so as to cover the plurality of stripe electrode sections; and an equipotential electrode section which has a portion that opposes at least a part of each of the plurality of stripe electrode sections across the insulation film and is arranged over the insulation film without contacting the ferroelectric crystal substrate or the plurality of stripe electrode sections, wherein an electric field is generated in the area of the ferroelectric crystal substrate directly below the plurality of stripe electrode sections by applying a voltage to the equipotential electrode section.

A cw terahertz image beam is upconverted by a nonlinear optical process (e.g., sum- or difference-frequency generation with a near IR cw upconverting beam). The upconverted image is acquired by a near IR image detector. The bandwidths and center wavelengths of the terahertz image beam and the upconverting beam are such that wavelength filtering can be employed to permit an upconverted image beam to reach the detector while blocking or substantially attenuating the upconverting beam.