A hollow-core anti-resonant-reflecting fibre (HC-AF) includes a hollow-core region, an inner cladding region, and an outer cladding region. The hollow-core region axially extends along the HC-AF. The inner cladding region includes a plurality of anti-resonant elements (AREs) and surrounds the hollow-core region. The outer cladding region surrounds the inner cladding region. The hollow-core region and the plurality of AREs are configured to provide phase matching of higher order hollow-core modes and ARE modes in a broadband wavelength range.

The invention relates to an arrangement and a method for efficient, non-linear light conversion. The object of the present invention of specifying an arrangement for efficient, non-linear light conversion, which simultaneously optimally fulfills the local conversion rate, the interaction scale, and the dispersive properties, is achieved in that the arrangement is provided in the form of a component, which comprises an optical waveguide or an optical fiber with or without cavities, wherein said arrangement consists of fiber cladding substrate or waveguide substrate (IV) with an adapted geometry, which defines the light-guiding properties of the fiber mode with designed dispersion properties (VI), and wherein the waveguide or the core carries a grown, atomically-thin layer of transition metal dichalcogenides in the form of crystallites, wherein this layer completely or partially covers the waveguide or the core.

An optical structure includes a refractive material, a Fresnel surface, a dichroic reflective coating and a second coating. The refractive material has a refractive index. The Fresnel surface is formed in the refractive material and the Fresnel surface includes active surfaces and draft surfaces. The dichroic reflective coating is selectively disposed on the active surface. A second coating is selectively disposed on the draft surfaces.

A self-referencing nonlinear frequency converting photonic waveguide includes: a supercontinuum input optical taper; a supercontinuum nonlinear optical member that produces supercontinuum light spanning an optical octave with respect to input light; and a supercontinuum output optical taper; a second harmonic input optical taper; a second harmonic nonlinear optical member that receives the supercontinuum light and produces second harmonic light from the supercontinuum light, the second harmonic light including a second harmonic of the supercontinuum light; and a second harmonic output optical taper that receives the second harmonic light, the supercontinuum light, and the input light and co-propagates the second harmonic light, the supercontinuum light, and the input light from the second harmonic generator section as output light.

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).

A nonlinear optical crystal (NLO) with a phase matching angle that is corrected with a source laser beam for harmonic conversion. The source laser only has to be within a wavelength range depending on the dispersion of the crystal while the crystal is tilted to the calculated expected conversion angle of the source laser as reference. The angle correction is accomplished with a parallel kinematic motion device to which a nonlinear crystal is mounted on a platform, to determine the wavelength- and temperature-specific angle with active laser alignment and subsequent precision resurfacing. The invented phase matching angle correction is applicable to any uniaxial and biaxial NLO crystals in a wide range of wavelengths, e.g., from far ultraviolet to visible to far infrared. It is of most value for NLO crystals of large walk-off and is applicable to any prior art frequency converting architectures.

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

A method for extending and enhancing bright coherent high-order harmonic generation into the VUV-EUV-X-ray regions of the spectrum involves a way of accomplishing phase matching or effective phase matching of extreme upconversion of laser light at high conversion efficiency, approaching 10.sup.−3 in some spectral regions, and at significantly higher photon energies in a waveguide geometry, in a self-guiding geometry, a gas cell, or a loosely focusing geometry, containing nonlinear medium. The extension and enhancement of the coherent VUV, EUV, X-ray emission to high photon energies relies on using VUV-UV-VIS lasers of shorter wavelength. This leads to enhancement of macroscopic phase matching parameters due to stronger contribution of linear and nonlinear dispersion of both atoms and ions, combined with a strong microscopic single-atom yield.

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 nonlinear optical crystal (NLO) with a phase matching angle that is corrected with a source laser beam for harmonic conversion. The source laser only has to be within a wavelength range depending on the dispersion of the crystal while the crystal is tilted to the calculated expected conversion angle of the source laser as reference. The angle correction is accomplished with a parallel kinematic motion device to which a nonlinear crystal is mounted on a platform, to determine the wavelength- and temperature-specific angle with active laser alignment and subsequent precision resurfacing. The invented phase matching angle correction is applicable to any uniaxial and biaxial NLO crystals in a wide range of wavelengths, e.g., from far ultraviolet to visible to far infrared. It is of most value for NLO crystals of large walk-off and is applicable to any prior art frequency converting architectures.