The invention relates to a doubly resonant optical parametric oscillator (1) comprising a fan-out crystal (5, 55, 105) having an optical non-linearity of order 2 and placed in an optical cavity (6) able to reflect a pump (2), said crystal (5, 55, 105) comprising an entrance face (59) and an exit face (60), through which faces the optical axis passes, an upper face (57) and a lower face (58).

The main feature of an optical parametric oscillator (1) according to the invention is that said crystal (105) includes a grating of polarity-inverted lines (106) originating separately and in a narrowly spaced manner at a fictional upper line (61) that is parallel to the upper face (57) of the crystal (105), and ending separately and in a widely spaced manner either at a fictional lower line (63) that is parallel to the lower face (58) of the crystal (105), or at the entrance face (59) of the crystal, two successive lines (106) making between each other a constant angle, said grating starting with a first line (108) originating at the exit face (60) of the crystal (105) and extending towards the lower fictional straight line (63) while diverging from said exit face (60), all the other lines gradually and monotonically inclining from said first straight line (108) towards the entrance face (59) of the crystal (105).

An optical crystal for converting an input light beam, the crystal having an ingress surface, an egress surface, and a fan-out grating has a fan-out pattern oriented at an offset angle in the range of 1 to 45 with respect to a beam entry plane at a beam ingress location.

Provided herein is a wavelength converter capable of producing shorter wavelengths by wavelength conversion than in related art. A wavelength converter of the present disclosure includes: a first layer formed of a single crystal represented by general formula RAMO.sub.4; and a second layer formed of a single crystal represented by the general formula RAMO.sub.4 and having a direction of polarization reversed 180 from a direction of polarization of the first layer, wherein, in the general formula, R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and a lanthanoid element, A represents one or more trivalent elements selected from the group consisting of Fe(III), Ga, and Al, and M represents one or more divalent elements selected from the group consisting of Mg, Mn, Fe(II), Co, Cu, Zn, and Cd.

A system includes a waveform generator configured to generate a pulsed laser beam at a first wavelength. The system also includes at least one splitter configured to split the laser beam into multiple beams at the first wavelength. The system also includes at least one wavelength shifter configured to shift at least one of the multiple beams to another wavelength. The system also includes at least one combiner configured to combine the multiple beams into a multi-wavelength beam in which multiple wavelengths are co-aligned and propagating parallel to each other. The system also includes at least one nonlinear crystal configured to receive the multi-wavelength beam and generate multiple co-propagating beams using nonlinear wavelength conversion.

An embodiment of the invention relates to an optical device which is capable of realizing a secondary nonlinear optical phenomenon. The optical device is a fiber-type optical device which is comprised of glass containing SiO.sub.2, and includes a core region, a first cladding region, and a second cladding region. At least a part of a glass region configured by the core region and the first cladding region has such a repetition structure that a first section serving as a poled crystal region and a second section serving as an amorphous region are alternately disposed along a longitudinal direction of the optical device.

An SrB.sub.4O.sub.7 or PbB.sub.4O.sub.7 crystal is configured with a plurality of domains with respective periodically alternating polarity of the crystal axis so that the disclosed crystal is capable of quasi-phasematching (QPM). The disclosed crystal is manufactured by a method including patterning a surface of a crystal block of SrB4O7 or PbB4O7, thereby providing patterned uniformly dimensioned regions with a uniform polarity sign on the surface. The method further includes generating a disturbance on the patterned surface, thereby inverting a sign of crystal polarity of every other region to form the SrB.sub.4O.sub.7 or SrB.sub.4O.sub.7 crystal with a plurality of domains with alternating polarity enabling a QPM mechanism.

An optical wavelength converter of one embodiment comprises: a substrate comprised of a crystalline material or an amorphous material; plural first crystal regions each having a radial first polarization-ordered structure; and plural second crystal regions each having a radial second polarization-ordered structure. In the substrate, a first and second regions are defined to be directly adjacent to each other with a virtual axis therebetween when the substrate is viewed from a reference direction orthogonal to the virtual axis. Radial centers of the first polarization-ordered structures located in the first region and radial centers of the second polarization-ordered structures located in the second region are alternately arranged along the virtual axis. The plural first crystal regions partially protrude to the second region. The plural second crystal regions partially protrude to the first region.

An optical imager comprising an input lens system, a non-linear optic crystal, a pump source, and a photodetector array; the input lens system coupling input or incident light onto the non-linear optic crystal, the pump source providing pump light for the non-linear optical crystal, the non-linear optical crystal producing output light from a combination of the input light and the pump light, and the photodetector array detecting the output light produced by the non-linear optic crystal. The non-linear optic crystal preferably has a waveguided structure. The non-linear optic crystal has an optical cavity which is preferably shared with optical cavities of a plurality of lasers generating the pump light.

A visible-to-ultraviolet band optical frequency converter. The processing period of a nonlinear optical crystal is controlled to provide an additional period phase to meet a phase matching condition so as to realize effective optical frequency conversion. The additional period phase is characterized in that phase gratings periodically arranged according to different refractive indexes are formed in the crystal through technologies, including laser micro-processing, ion etching and the like, a nonlinear frequency conversion inverse process is avoided through the periodic structure damage of the crystals in the phase gratings and an additional period phase is provided, phase mismatch caused by the insufficient double refraction of the nonlinear optical crystal is avoided, and efficient frequency doubling or sum frequency output is realized.

An object is to provide, for example, a method for manufacturing an optical wavelength conversion device having a structure that enables efficient formation of crystal regions on the surface of, or inside, an amorphous material. An amorphous main body is intermittently irradiated with a first laser beam for generating a high-density excited electron region inside the main body and a second laser beam for heating the high-density excited electron region, with respective focus regions of the first and second laser beams overlapping each other. During the intermittent irradiation with the first and second laser beams, the relative position of the main body and the overlapping focus region of the first and second laser beams are varied. This enables part of the main body where the overlapping focus region moves to serve as a heat source for forming a crystal region.