A quantum absorption spectroscopy system (100) includes a laser light source (1), a quantum optical system (201), a photodetector (31), and a controller (4). The laser light source (1) emits pump light. The quantum optical system (201) includes a nonlinear optical crystal (23) that generates a quantum entangled photon pair of a signal photon and an idler photon by irradiation with pump light, and a moving mirror (25) that changes a phase of the idler photon, and causes quantum interference between a plurality of physical processes in which the quantum entangled photon pair is generated. The photodetector (31) detects the signal photon when the phase of the idler photon is changed by the nonlinear optical crystal (23) in a state where a sample is disposed on an optical path of the idler photon, and outputs a quantum interference signal corresponding to the detected number of photons. The controller (4) calculates an absorption spectroscopy characteristic of the sample by performing Fourier transform on the quantum interference signal.

An entanglement-enhanced interferometry system includes a source of correlated photons configured to two-mode squeezed vacuum (TMSV), a polarizing splitter or off-axis polarizing coupler configured to separate the correlated photons into two paths, a polarization control device configured to rotate polarization of photons on one of the two paths relative to the photons on the other of the two paths in order to make photons indistinguishable, a coupler configured to entangle the indistinguishable photons, and a polarization maintaining fiber-based interferometer configured to use the entangled photons as the input state. The source of correlated photons might be a nonlinear element such as a periodically poled element such as a lithium niobate bulk crystal or waveguide. The interferometer might be a Mach-Zehnder or a common path configuration. The coupler might be a 50:50 coupler or a polarizing coupler 45 degrees off-axis.

A method of performing heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and a second precursor gas, to form a heteroepitaxial growth of one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN on the substrate; wherein the substrate comprises one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN; wherein the carrier gas is Hz, wherein the first precursor is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the second precursor is one of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), H.sub.2Te (hydrogen telluride), SbH.sub.3 (hydrogen antimonide), H.sub.2S (hydrogen sulfide), and NH.sub.3 (ammonia). The process may be an HVPE (hydride vapor phase epitaxy) process.

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 crystal quartz element includes a main face provided with a plurality of polarity inverted regions and a polarity non-inverted region, the plurality of polarity inverted regions are spaced apart from each other via the polarity non-inverted region, and the main face is a plane face. A method for manufacturing a crystal quartz element includes: preparing a crystal quartz body including a first main face which is a plane face, and a first pressing jig including a first pressing face on which a plurality of first projections are provided; and forming a plurality of polarity inverted regions corresponding to the plurality of first projections in the crystal quartz body by heating and pressing the first main face by the first pressing face.

Systems and methods for measuring or inspecting semiconductor structures using broadband infrared radiation are disclosed. The system may include an illumination source comprising a pump source configured to generate pump light and a nonlinear optical (NLO) assembly configured to generate broadband IR radiation in response to the pump light. The system may also include a detector assembly and a set of optics configured to direct the IR radiation onto a sample and direct a portion of the IR radiation reflected and/or scattered from the sample to the detector assembly.

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 method of performing heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and a second precursor gas, to form a heteroepitaxial growth of one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN on the substrate; wherein the substrate comprises one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN; wherein the carrier gas is H.sub.2, wherein the first precursor is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the second precursor is one of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), H.sub.2Te (hydrogen telluride), SbH.sub.3 (hydrogen antimonide), H.sub.2S (hydrogen sulfide), and NH.sub.3 (ammonia). The process may be an HVPE (hydride vapor phase epitaxy) process.

An apparatus and method for wavelength conversion of a signal, for example, a dual-polarization signal, is disclosed. The apparatus implements a single-loop counter-propagating wavelength conversion scheme which provides both up-conversion and down-conversion of the signal within the same loop. Nonlinear wavelength conversion devices in the loop provide both up-conversion and down-conversion of the polarization components of the signal within the loop depending on whether the polarization component travels through the nonlinear conversion device in a clockwise or a counter-clockwise direction. The wavelength-converted signal is available to be extracted from the wavelength-conversion loop. An all-optical wavelength-division multiplexing transponder based on the wavelength-conversion scheme is also disclosed.