A nonlinear crystal grating assembly including two integral nonlinear crystal grating structures having inverted crystal axes and having parallel spaced-apart mesas with predetermined mesa widths arranged such that, when assembled in an interdigitated configuration, the mesas of the two grating structures form an alternating grating pattern that is aligned with a propagation direction of input light, thereby creating a periodic structure for quasi-phase-matching (QPM). The nonlinear crystal grating structures are formed using strontium tetraborate, lithium triborate or another nonlinear crystal material. The nonlinear crystal grating assembly is utilized in a laser assembly in which fundamental wavelengths are doubled and/or summed using intermediate frequency conversion stages, and then a final frequency converting stage utilizes the nonlinear crystal grating assembly to double or sum one or more intermediate light beam frequencies to generate laser output light at high power and photon energy levels. A method and inspection system are also described.

In one aspect, a device is disclosed that includes one or more input ports structured to receive a pumping light at a pumping wavelength and a signal light at a signal wavelength, and one or more output ports structured to output light including an amplified signal light at the signal wavelength and a second harmonic idler light. The device includes a nonlinear optical material to mix the pumping light and the signal light and to cause nonlinear conversion of the pumping light into the amplified signal light and generate an idler light at an idler wavelength. The nonlinear optical material is further structured to convert the idler light into the second harmonic idler light which eliminates the idler light at the one or more output ports and prevents back-conversion of the amplified signal light and idler light to the pumping wavelength.

A wavelength conversion device that includes a plurality of crystal layers adjacent to one another such that crystal-axis orientations thereof are alternately arranged, the plurality of crystal layers each including a first-thickness portion having a first thickness and a second-thickness portion having a second thickness smaller than the first thickness; and an adhesive layer in at least part of a gap between adjacent second-thickness portions of the plurality of crystal layers and with which the plurality of crystal layers are bonded to one another.

A pulsed laser output section outputs a laser beam having a predetermined wavelength as first pulses. An optical path determining section receives the first pulses and determines one among a plurality of optical paths for each of the first pulses for output. A parallelizing section parallelizes a traveling direction of light beams traveling, respectively, through the plurality of optical paths. A wavelength changing section receives outputs from the parallelizing section and changes the outputs to have different wavelengths for output. A focusing section receives and focuses outputs from the wavelength changing section. An optical fiber receives an output from the focusing section at a core end face. A timing control section is arranged to time outputs from the optical path determining section to the output of the first pulses. The focusing section is arranged to focus the outputs from the wavelength changing section on the core end face.

A wavelength conversion device includes a second-order nonlinear optical medium with a polarization inversion structure, wherein the wavelength conversion device performs wavelength conversion between three wavelengths according to a relationship of 1/λ.sub.1=1/λ.sub.2+1/λ.sub.3, a polarization inversion period Λ of the polarization inversion structure is divided into 2a regions, and when the 2a regions divided from the polarization inversion period Λ each has a width ratio of an inverted region and a non-inverted region of r to 1−r (where 0≤r≤1), a ratio value r is set such that, when one period in phase of a sine function from 0 to 2π is divided into 2a regions, a value of the sine function in a center of each divided region is (1−2r)±0.1.

A nonlinear crystal grating assembly including two integral nonlinear crystal grating structures having inverted crystal axes and having parallel spaced-apart mesas with predetermined mesa widths arranged such that, when assembled in an interdigitated configuration, the mesas of the two grating structures form an alternating grating pattern that is aligned with a propagation direction of input light, thereby creating a periodic structure for quasi-phase-matching (QPM). The nonlinear crystal grating structures are formed using strontium tetraborate, lithium triborate or another nonlinear crystal material. The nonlinear crystal grating assembly is utilized in a laser assembly in which fundamental wavelengths are doubled and/or summed using intermediate frequency conversion stages, and then a final frequency converting stage utilizes the nonlinear crystal grating assembly to double or sum one or more intermediate light beam frequencies to generate laser output light at high power and photon energy levels. A method and inspection system are also described.

In one aspect, a device is disclosed that includes one or more input ports structured to receive a pumping light at a pumping wavelength and a signal light at a signal wavelength, and one or more output ports structured to output light including an amplified signal light at the signal wavelength and a second harmonic idler light. The device includes a nonlinear optical material to mix the pumping light and the signal light and to cause nonlinear conversion of the pumping light into the amplified signal light and generate an idler light at an idler wavelength. The nonlinear optical material is further structured to convert the idler light into the second harmonic idler light which eliminates the idler light at the one or more output ports and prevents back-conversion of the amplified signal light and idler light to the pumping wavelength.

Provided is a wavelength conversion element capable of achieving highly efficient wavelength conversion, without relying on a method of applying electric fields. A wavelength conversion element is formed of a second-order nonlinear optical crystal and has a z-axis, running along a direction of spontaneous polarization, within a substrate plane. The wavelength conversion element includes a waveguide in which, when a plurality of circles having their centers on a straight line parallel to the z-axis and having the same radius are depicted so that circumferences of the plurality of circles contact each other, semicircular waveguides corresponding to one semicircles of the circumferences with the straight line as a boundary, are alternately connected.

An exemplary system can be provided which can include, for example, a plurality of source arrangements configured to provide a plurality of electro-magnetic radiations to at least one of at least one sample or at least one reference structure, a first arrangement configured to receive a first radiation(s) from the reference structure(s), a second arrangement configured to receive a second radiation(s) from the sample(s), where a portion(s) of the second radiation(s) can be in an invisible spectrum, a third arrangement configured to combine the first radiation(s) and the second radiation(s) into a third radiation(s), and a fourth arrangement configured to convert the third radiation(s) into a further radiation in a visible spectrum based on the at least one portion.

A wavelength converter stabilizes output light intensity in which the light coupling efficiency to a light waveguide core is not easily varied. A mounting structure is adopted in which a substrate of a wavelength conversion element is a material with a lower refractive index for signal light than that of the core, and a support structure that suppresses elastic deformation by supporting the element through a contact at a tip end surface at a position corresponding to both end portions of the core at the occurrence of elastic deformation due to the thermal stress of the element is provided. The support structure is provided at a portion apart from a temperature control element at the top surface of a metal housing bottom surface member, and its top surface is disposed in the vicinity of a portion corresponding to both end portions of the core of the element in a support member.