A method, apparatus, and system for non-linear optical process. A first light of a first wavelength is routed in a first loop in a main nonlinear optical waveguide. The first loop has a first length for the first light of the first wavelength. A second light of a second wavelength is routed in a second loop that includes portions of the main nonlinear optical waveguide and a first extension optical waveguide. The second loop has a second length for the second light of the second wavelength. A third light of a third wavelength is routed in a third loop that include portions of the main nonlinear optical waveguide and a second extension optical waveguide. The third loop has a third length for the third light of the third wavelength.

Methods, systems and methods for reducing temporal coherence of laser systems are described. One example laser system includes a seed laser having a continuous wave output and operable at a first wavelength, a phase modulator positioned to receive laser light from the seed laser and to impart phase modulation to the seed laser. The laser system also includes an optical parametric amplifier positioned to receive phase-modulated laser light at one of its inputs and a pump laser light at another input, and to produce an output beam having spectral characteristics of the phase-modulated laser light that is amplified according to a temporal feature of the pump laser light. In the example laser system, an output of the optical parametric amplifier has a lower temporal coherence compared to the seed laser.

Methods, systems and methods for reducing temporal coherence of laser systems are described. One example laser system includes a seed laser having a continuous wave output and operable at a first wavelength, a phase modulator positioned to receive laser light from the seed laser and to impart phase modulation to the seed laser. The laser system also includes an optical parametric amplifier positioned to receive phase-modulated laser light at one of its inputs and a pump laser light at another input, and to produce an output beam having spectral characteristics of the phase-modulated laser light that is amplified according to a temporal feature of the pump laser light. In the example laser system, an output of the optical parametric amplifier has a lower temporal coherence compared to the seed laser.

An optical waveguide structure comprises a first coupler and a second coupler that, in combination, direct a first-wavelength light to travel through a nonlinear-optical waveguide, the two couplers and an extension waveguide but not a secondary waveguide, a first resonator loop is defined for which the first-wavelength light is resonant. The two couplers, in combination, also direct a second-wavelength light to travel through the nonlinear-optical waveguide, the two couplers and the secondary waveguide but not the extension waveguide, wherein a different second resonator loop is defined for which the second-wavelength light is resonant.

An optical waveguide structure comprises a first coupler and a second coupler that, in combination, direct a first-wavelength light to travel through a nonlinear-optical waveguide, the two couplers and an extension waveguide but not a secondary waveguide, a first resonator loop is defined for which the first-wavelength light is resonant. The two couplers, in combination, also direct a second-wavelength light to travel through the nonlinear-optical waveguide, the two couplers and the secondary waveguide but not the extension waveguide, wherein a different second resonator loop is defined for which the second-wavelength light is resonant.

A system for resonantly enhanced frequency conversion includes a nonlinear crystal for frequency converting a pump laser beam, and mirrors forming a ring resonator for the pump laser beam such that a closed propagation path of the pump laser beam, inside the ring resonator, passes through the nonlinear crystal. The mirrors include an adaptive mirror, a curved-mirror pair positioned in a first segment of the propagation path spanning between the adaptive mirror and the nonlinear crystal, and an input coupler for coupling the pump laser beam into the ring resonator. The curved-mirror pair forms an imaging system having conjugate planes at the adaptive mirror and the nonlinear crystal. The input coupler is positioned in a second segment of the propagation path that spans between the adaptive mirror and the nonlinear crystal and does not include deflection by the curved-mirror pair.

An optical waveguide structure comprises a nonlinear optical waveguide comprising a nonlinear optical material having a second order nonlinear coefficient that changes with a direction of light propagation. A first portion of the nonlinear optical waveguide in which a light propagating through the first portion is affected by a positive value of a second order nonlinear coefficient. A second portion of the nonlinear optical waveguide in which the light propagating through the first portion is affected by a negative value of a second order nonlinear coefficient, wherein a set of dimensions in the nonlinear optical waveguide in the first portion and the second portion is selected to cause the light to have a phase walk-off that is an odd multiple of 180 degrees.

An optical waveguide structure comprises a nonlinear optical waveguide comprising a nonlinear optical material having a second order nonlinear coefficient that changes with a direction of light propagation. A first portion of the nonlinear optical waveguide in which a light propagating through the first portion is affected by a positive value of a second order nonlinear coefficient. A second portion of the nonlinear optical waveguide in which the light propagating through the first portion is affected by a negative value of a second order nonlinear coefficient, wherein a set of dimensions in the nonlinear optical waveguide in the first portion and the second portion is selected to cause the light to have a phase walk-off that is an odd multiple of 180 degrees.

Provided are a high-energy and high-powered laser light source and a photoemission electron microscope using the laser light source. The laser light source 2 is intended for use in the photoemission electron microscope for emitting a quasi-continuous wave laser 7 and includes: a first laser light source 100 configured to emit a continuous wave coherent light 100a, an optical resonator 110 including an optical path in which the continuous wave coherent light 100a circulates and including a non-linear optical element 114 disposed on the optical path, and a quasi-continuous wave light source 120 configured to emit a quasi-continuous wave coherent light 120a having a wavelength shorter than that of the continuous wave coherent light 100a and having a near rectangular output waveform. When the quasi-continuous wave coherent light 120a is incident on the non-linear optical element 114 from outside the optical resonator 110 while the continuous wave coherent light 100a is entering the optical resonator 110 to circulate in the optical path, the quasi-continuous wave laser 7 having a wavelength shorter than that of the quasi-continuous wave coherent light 120a is emitted from the non-linear optical element 114.

A spectroscopic measurement apparatus includes a pulsed laser light source that emits pulsed laser light, a beam splitter that splits the pulsed laser light into pump light and probe light, a delay circuit that changes a delay time of the pump light with respect to the probe light, a chopper that intensity-modulates the pump light, a wavelength converter that wavelength-converts the probe light into vacuum ultraviolet light, an optical system that guides the pump light and the wavelength-converted probe light to a sample, and a detector that detects the probe light reflected by the sample.