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.

A doubly resonant optical parametric oscillator (1) includes 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). The crystal (5, 55, 105) has 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 optical parametric oscillator (1) has a 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, the 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 the first straight line (108) towards the entrance face (59) of the crystal (105).

Optical transmitters and optical receivers utilizing long wave infrared light for use with an earth-orbiting satellite communication system, and a structure including an intracavity optical nonlinear process, are described herein. The transmitters include a pumping laser diode with a fast-axis collimating lens and a pumping wavelength λ0, operating in a continuous wavelength (CW) mode. The transmitters also include a laser cavity having a beam combiner or a dichroic mirror, a laser crystal with a lasing wavelength λ1 and a difference frequency generation orientation patterned semiconductor to generate long wave-IR light. The transmitters also include a second laser at a wavelength λ2, operating in a modulation mode. The receivers have a similar structure to the transmitters, utilizing a sum frequency generation orientation patterned semiconductor to convert long wave-IR light into the short wave-IR.

According to a laser beam output apparatus, a pulsed laser output section outputs a laser beam having a predetermined wavelength as first pulses. An optical path determining section receives the first pulses and determines one among a plurality of optical paths for each of the first pulses for output. A parallelizing section parallelizes the traveling direction of light beams traveling, respectively, through the plurality of optical paths. A wavelength changing section receives outputs from the parallelizing section and changes the outputs to have their respective different wavelengths for output. A focusing section receives and focuses outputs from the wavelength changing section. An optical fiber receives an output from the focusing section at a core end face. The focusing section is arranged to focus the outputs from the wavelength changing section on the core end face.

An object is to provide, for example, an optical wavelength conversion device capable of highly efficient wavelength conversion on the surface of, or inside, the main body of any of various shapes, such as a bulky shape and a fiber shape. The optical wavelength conversion device includes a main body configured to allow light to propagate therein, and a plurality of crystal regions arranged inside the main body along a propagation direction of the light. The plurality of crystal regions each have a spontaneous polarization oriented along the propagation direction (i.e., spontaneous polarization having a polarization orientation coinciding with the propagation direction).

Systems and methods for generating infrared radiation are provided. The systems and methods may generate, via one or more pump sources, one or more pump beams. The one or more pump beams may define a single beamline. The systems and methods may further generate, via a nonlinear optical converter, a first signal wavelength, a first idler wavelength, a second signal wavelength, and a second idler wavelength based, at least in part, on the one or more pump beams. The first signal wavelength and the first idler wavelength may be independently variable from the second signal wavelength and the second idler wavelength. The systems and methods may further output, via the nonlinear optical converter, a mid-wave infrared (MWIR) beam including three or more wavelengths in the single beamline.

An optical parametric device (OPD), which is selected from an optical parametric oscillator (OPO) or optical parametric generator (OPG), is configured with a nonlinear optical element (NOE) which converts an incoupled pump radiation at first frequency into output signal and idler radiations at one second frequency or different second frequencies, which is/are lower than the first frequency, by utilizing nonlinear interaction via a random quasi-phase matching process (RQPM-NOE). The NOE is made from a nonlinear optical material selected from optical ceramics, polycrystals, micro and nanocrystals, colloids of micro and nanocrystals, and composites of micro and nanocrystals in polymer or glassy matrices. The nonlinear optical material is prepared by modifying a microstructure of the initial sample of the NOE such that an average grain size is of the order of a coherence length of the three-wave interaction which enables the three wave nonlinear interaction with a highest parametric gain achievable via the RQPM process

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 fiber laser system includes a high power pump laser, an optical fiber that is aligned to receive output from the high power pump laser. The fiber laser system includes a first pair of orthogonally opposed, periodic electrode structures longitudinally aligned on opposite first and second sides of the optical fiber. The fiber laser system includes a controller that is communicatively coupled to the first pair of periodic electrode structures. The controller performs variable period poling of the first pair of periodic electrode structures to achieve quasi-phase matching (QPM).

A cylindrical electrode module of a fiber optic laser system includes an inner cylinder having an inner repeating pattern of longitudinally-aligned positive and negative electrodes on an outer surface of the inner cylinder. The cylindrical electrode mode includes an outer cylinder that encloses the inner cylinder. The outer cylinder that has an outer repeating pattern of longitudinally-aligned negative and positive electrodes on an inner surface of the inner cylinder that are in corresponding and complementary, parallel alignment with the positive and negative electrodes of the inner repeating pattern on the outer surface of the inner cylinder. The cylindrical electrode module includes an optical fiber having an input end configured to align with and be optically coupled to a high power pump laser. The optical fiber is wrapped around the inner cylinder within the outer cylinder to form a cylindrical fiber assembly. The electrodes are activated to achieve quasi-phase matching.