Disclosed is a method of performing a measurement in an inspection apparatus, and an associated inspection apparatus and HHG source. The method comprises configuring one or more controllable characteristics of at least one driving laser pulse of a high harmonic generation radiation source to control the output emission spectrum of illumination radiation provided by the high harmonic generation radiation source; and illuminating a target structure with said illuminating radiation. The method may comprise configuring the driving laser pulse so that the output emission spectrum comprises a plurality of discrete harmonic peaks. Alternatively the method may comprise using a plurality of driving laser pulses of different wavelengths such that the output emission spectrum is substantially monochromatic.

The invention relates to a device comprising: a laser source emitting a first beam with a central wavelength λ.sub.1 lying between 1010 nm and 1050 nm, a spectral supercontinuum generator downstream of the laser source, generating a second beam with a central wavelength λ.sub.2 lying between 1670 nm and 1730 nm from a part of the first beam, an optical parametric amplification system downstream of the spectral supercontinuum generator, generating a third beam with a central wavelength λ.sub.3 lying between 2540 nm and 2690 nm from at least a part of the second beam and a part of the first beam, and a second harmonic generator downstream of the optical parametric amplification system, the second harmonic generator generating a fourth beam with a central wavelength λ.sub.4 lying between 1270 nm and 1345 nm from at least a part of the third beam.

A nonlinear optical crystal has a chemical formula Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or Rb. The nonlinear optical crystal belongs to tetragonal system with space group P4nc and Z=2. The unit cell parameters of Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 are a=b=11.3336(5) Å, c=5.0017(2) Å; and the unit cell parameters of Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12 are a=b=11.5038(6) Å, c=5.1435(3) Å. The two crystals are thermally stable and show strong second harmonic generation with high laser damage threshold.

A broad line red light generator is configured with a single mode (SM) pulsed ytterbium (“Yb”) fiber laser pump source outputting pump light in a fundamental mode (“FM”) at a pump wavelength which is selected from a 1030-1120 nm wavelength range. The disclosed generator further includes a SM fiber Raman converter spliced to an output of the Yb fiber laser pump source. The Raman converter induces an “n” order frequency Stokes shift of the pump light to output the pump light at a Raman-shifted wavelength within 1220 and 1300 nm wavelength range with a broad spectral line of at least 10 nm. The disclosed light generator further has a single pass second harmonic generator (“SHG”) with a lithium triborate (“LBO”) nonlinear optical crystal having a spectral acceptance linewidth which is sufficient to cover the broad spectral line of the pump light. The SHG generates a SM pulsed broad-line red light with a broad spectral line of at least 4 nm.

Embodiments of the disclosure provide an apparatus for emitting laser light and a system and method for detecting laser light returned from an object. The system includes a transmitter and a receiver. The transmitter includes one or more laser sources, at least one of the laser sources configured to provide a respective native laser beam having a wavelength above 1,100 nm. The transmitter also includes a wavelength converter configured to receive the native laser beams provided by the laser sources and convert the native laser beams into a converted laser beam having a wavelength below 1,100 nm. The transmitter further includes a scanner configured to emit the converted laser beam to the object in a first direction. The receiver is configured to detect a returned laser beam having a wavelength below 1,100 nm and returned from the object in a second direction.

A solid-state laser system may include first and second solid-state laser units, a wavelength conversion system, an optical shutter, and a controller. The first solid-state laser unit and the second solid-state laser unit may output first pulsed laser light with a first wavelength and second pulsed laser light with a second wavelength, respectively. The controller may perform first control and second control. The first control may cause the first and second pulsed laser light to enter the wavelength conversion system at a substantially coincidental timing, thereby causing the wavelength conversion system to output third pulsed laser light with a third wavelength converted from the first wavelength and the second wavelength, and the second control may prevent the first and second pulsed laser light from entering the wavelength conversion system at the coincidental timing, thereby preventing the wavelength conversion system from outputting the third pulsed laser light.

Disclosed is a non-linear optical crystal containing pyridinium represented by the following Formula (1), 4-substituted phenylsulfonate represented by the following Formula (2a), and 2,4,6-substituted phenylsulfonate represented by the following Formula (2b).

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A dual frequency optical resonator configured for optical coupling to light having a first frequency ω1. The dual frequency optical resonator includes a plurality of alternating layer pairs stacked in a post configuration, each layer pair having a first layer formed of a first material and a second layer formed of a second material, the first material and second materials being different materials. The first layer has a first thickness and the second layer has a second thickness, the thicknesses of the first and second layer being selected to create optical resonances at the first frequency ω1 and a second frequency ω2 which is a harmonic of ω1 and the thicknesses of the first and second layer also being selected to enhance nonlinear coupling between the first frequency ω1 and a second frequency ω2.

A method and apparatus to generate harmonically related laser wavelengths includes a pair of lenses at opposing faces of a non-linear optical material. The lenses are configured to promote incoming and outgoing beams to be normal to each outer lens surface over a range of acceptance angles of the incoming laser beam. This reduces reflection loss for higher efficiency operation. Additionally, the lenses allow a wider range of wavelengths for lasers for more universal application. Examples of the lenses include plano-cylindrical and plano-spherical form factors.

Single crystals of a new noncentrosymmetric polar oxysulfide SrZn.sub.2S.sub.2O (s.g. Pmn2.sub.1) grown in a eutectic KF-KCl flux with unusual wurtzite-like slabs consisting of close-packed corrugated double layers of ZnS.sub.3O tetrahedra vertically separated from each other by Sr atoms and methods of making same.