The disclosed laser system is configured with a laser source outputting light at a fundamental frequency. The output light is incident on a frequency converter operative to convert the fundamental frequency to a higher harmonic including at least one frequency converting stage. The frequency converter is based on a SrB.sub.4O.sub.7 (SBO) or PbB.sub.4O.sub.7 (PBO) nonlinear crystal configured with a plurality of domains. The domains have periodically alternating polarity of the crystal axis enabling a QPM use and formed with each with highly parallel walls which deviate from one another less than 1 micron over a 10 mm distance.

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.

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 alkali metal monohydrogen cyanurate compound of the chemical formula AM(HC.sub.3N.sub.3O.sub.3).nH.sub.2O (specifically such as KLi(HC.sub.3N.sub.3O.sub.3).2H.sub.2O, RbLi(HC.sub.3N.sub.3O.sub.3).2H.sub.2O, RbNa(HC.sub.3N.sub.3O.sub.3).2H.sub.2O) and a nonlinear optical crystal thereof are related to optoelectronic functional materials. Measured using a powder frequency doubling test method, and the powder frequency doubling effect of the nonlinear optical crystal is about 2-3 times that of KH.sub.2PO.sub.4 (KDP). The ultraviolet absorption edge of the nonlinear optical crystal is shorter than 250 nm. The nonlinear optical crystal can achieve the harmonic generator of double, triple, or quadruple frequency for Nd:YAG (λ=1.064 μm). Moreover, the nonlinear optical crystal is of a single crystalline structure, is colorless and transparent, and does not deliquesce in air.

Methods, devices and systems for improving single-frequency operation of diode lasers are described. One such method includes ramping up an operational current of a diode laser for a first predetermined number of steps, and measuring an associated current value indicative of optical power within the laser diode for each of the first predetermined number of steps. Next, operational current of the diode laser is ramped down for a second predetermined number of steps, and an associated current value indicative of optical power within the laser diode is measured for each of the second predetermined number of steps. Using the measured data current values at which a mode hop or a multimode operation is likely to occur are identified, and a contiguous range of operating currents that is devoid of identified likely mode hops or multimode regions of operation is determined as the operating current range of the diode laser.

A method for extending scatterometry measurements of periodic structures created on a substrate into the deep UV and soft X-ray regions of the electromagnetic spectrum is presented. The method comprises measuring the scattering of a high harmonic generated (HHG) beam, which is created by a driving laser, that is scattered from the structures on the substrate. The scattered HHG beam is measured by a spectrometer or a detector sensitive to HHG radiation. Also presented is a system for carrying out the method.

An illumination source apparatus (500), suitable for use in a metrology apparatus for the characterization of a structure on a substrate, the illumination source apparatus comprising: a high harmonic generation, HHG, medium (502); a pump radiation source (506) operable to emit a beam of pump radiation (508); and adjustable transformation optics (510) configured to adjustably transform the transverse spatial profile of the beam of pump radiation to produce a transformed beam (518) such that relative to the centre axis of the transformed beam, a central region of the transformed beam has substantially zero intensity and an outer region which is radially outwards from the centre axis of the transformed beam has a non-zero intensity, wherein the transformed beam is arranged to excite the HHG medium so as to generate high harmonic radiation (540), wherein the location of said outer region is dependent on an adjustment N setting of the adjustable transformation optics.

A method and a system for generating intense, ultrashort pulses of XUV and soft X-ray radiation via high-order harmonic generation (HHG), the method comprising selecting a nonlinear solid target and a laser source; separating a beam from the laser source into a first laser beam and a second laser beam; focusing the first laser beam onto the nonlinear solid target, thereby generating a laser ablated plume; and compressing and frequency-doubling the second laser beam and directing a resulting second compressed and frequency-doubled laser beam to the laser ablated plume, thereby yielding high-order harmonic generation of radiation of photon energies in a range between 12 eV and 36 eV. A high-order harmonic source of radiation, comprising a nonlinear solid target; a laser source; a beam splitter separating a beam from the laser source into a first beam line and a second beam line; the first beam line comprising a first focusing unit directing a first, uncompressed, laser beam onto the nonlinear solid target, to generate a laser ablated plume; and the second beam line directing a second, compressed and frequency-doubled laser beam, to the laser ablated plume, yielding high-order harmonic generation of radiation of photon energies in a range between 12 eV and 36 eV.

A pyramidal growth method for long-seed KDP-type crystal. In the growth method provided by the present invention, the lower end of the long-seed crystal is restricted by a lower tray, and the upper end is free to grow into a pyramidal. At the same time, the four prismatic faces at two directions of [100] and [010] can grow, avoiding growth stress problem during crystal growth, and all cut optical elements have high optical quality. Because the growth process is that four prismatic faces with highly similar growth environments grow at the same time and stirring is applied by blade-like stirring paddles during the crystal growth process, the cut optical elements have high optical uniformity.

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.