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 doubling stage of a laser assembly to generate laser output light having a wavelength in the range of about 180 nm to 200 nm. One or more fundamental laser beams are frequency doubled, down-converted and/or summed using one or more frequency conversion stages to generate an intermediate frequency light with a corresponding wavelength in the range of about 360 nm to 400 nm, and then the final frequency converting stage utilizes the nonlinear crystal to double the frequency of the intermediate frequency light to generate the desired laser output light at high power. Methods, inspection systems, lithography systems and cutting systems incorporating the laser assembly are also described.

An illumination source is configured to illuminate a medium with light at a wavelength selected based on an emission band of a selected absorption band of the medium. The selected absorption and emission bands being associated with an electric-dipole-allowed transition of the medium. Upon illumination by the light the medium is cooled.

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.

A fiber laser system includes: an array of gain fibers configured to transmit signal light; and an array of tapered end caps configured to receive the signal light and output the signal light, wherein each gain fiber in the array of gain fibers is spliced to a respective tapered end cap of the array of tapered end caps. A counter-pumping light source is configured to output counter-pumping light. A dichroic mirror is configured to receive the counter-pumping light and the signal light from the array of tapered end caps. The dichroic mirror is further configured to either allow the counter-pumping light received by the dichroic mirror to pass through the dichroic mirror and reflect the signal light received by the dichroic mirror or allow the signal light received by the dichroic mirror to pass through the dichroic mirror and reflect the counter-pumping light received by the dichroic mirror.

A titanium-sapphire laser apparatus may include a continuous wave oscillation laser unit, an amplification oscillator, a pulsed laser unit, an error detector, an error controller, and an optical path length corrector. The amplification oscillator may include an optical resonator and a titanium-sapphire crystal that is provided in an optical path in the optical resonator. The error detector may be provided in an optical path of leak light of seed light from the optical resonator, and may detect an optical path length error between an optical path length in the optical resonator and a positive integer multiple of a wavelength of the seed light and output an optical path length error signal. The optical path length corrector may vary the optical path length in the optical resonator on a basis of a signal resulting from adding a correction value to the optical path error signal.

An object information acquiring apparatus is used which includes a laser medium that oscillates laser light, an excitation source that excites the laser medium, a voltage accumulator that applies a voltage to the excitation source, a voltage supplier that supplies a voltage to the voltage accumulator, a voltage controller that limits a maximum supplied voltage from the voltage supplier, a receiver that receives a photoacoustic wave generated by an object irradiated with the laser light, and a constructor that acquires characteristic information relating to the object in use of the photoacoustic wave, wherein the voltage controller compares a measured voltage value obtained by implementing division of a supplied voltage from the voltage supplier with a reference voltage value defining the maximum supplied voltage.

The system and method of producing a first path comprising a pulse stretcher for a mid-wave infrared (MWIR) signal, an optical parametric chirped-pulse amplification (OPCPA) amplifier, and a MWIR compressor for producing a first beam in a MWIR portion of the spectrum and a second path comprising a pulse stretcher for a long wave infrared (LWIR) signal, an OPCPA amplifier, and a LWIR compressor for producing a second beam in a LWIR portion of the spectrum. Each beam, on its own, is configured to produce laser-matter interactions at long range (100s of meters), having nonlinear effects and favoring supercontinuum generation spanning multiple octaves, that is temporally and spatially overlapped with the fundamental laser beam.

A multiple frequency comb source apparatus (100) for simultaneously creating a first laser pulse sequence representing a first frequency comb (1) and at least one further laser pulse sequence representing at least one further frequency comb (2), wherein at least two of the first and at least one further pulse sequences have different repetition frequencies, comprises a laser resonator device (10) comprising multiple resonator mirrors including first end mirrors EM.sub.1,OC.sub.1 providing a first laser resonator (11), a laser gain medium (21, 22) being arranged in the laser resonator device (10), and a pump device (30) being arranged for pumping the laser gain medium (21), wherein the laser resonator device (10) is configured for creating the first and at least one further laser pulse sequences by pumping and passively mode-locking the laser gain medium (21), the resonator minors of the laser resonator device (10) include further end minors EM.sub.2, OC.sub.2 providing at least one further laser resonator (12), the first laser resonator (11) and the at least one further laser resonator (12) share the laser gain medium (21), resonator modes of the first laser resonator (11) and the at least one further laser resonator (12) are displaced relative to each other, wherein the resonator modes are located in the laser gain medium (21) at separate beam path spots, and at least one of the first and further end minors EM.sub.1, EM.sub.2, OC.sub.1, OC.sub.2 is adjustable so that the repetition frequency of at least one of the first and at least one further laser pulse sequences can be set independently from the repetition frequency of the other one of the first and at least one further laser pulse sequences. Furthermore, a spectroscopic measuring method, a spectroscopy apparatus and a multiple frequency comb generation method are described.

A femtosecond pulse laser apparatus includes a pump light source configured to provide a pump light, a gain medium configured to obtain a gain of a laser light using the pump light, a first curved mirror and a second curved mirror, which are provided at both sides of the gain medium, an output mirror configured to transmit a portion of the laser light and reflect the other portion of the laser light to the gain medium, a mode locking portion configured to generate a femtosecond pulse of the laser light, and an acoustic wave generator configured to provide an acoustic wave into the gain medium so as to adjust self-phase modulation of the laser light.

A radially polarized optical parametric amplifier insensitive to polarization is provided by the present invention, which comprises a laser module and a nonlinear crystal satisfying the type-II phase matching or the type-II quasi-phase matching condition, wherein the laser module is configured to generate two laser beams, namely the pump light and the signal light with an arbitrary polarization state, the wavelengths of the pump light and the signal light are degenerate or nearly degenerate; and the nonlinear crystal is provided in the emergent beamline of the laser module to perform optical parametric amplification of the signal light by using the pump light.