This far-infrared spectroscopy device is provided with: a variable wavelength far-infrared light source that generates first far-infrared light; an illuminating optical system that irradiates a sample with the first far-infrared light; a detecting nonlinear optical crystal that converts second far-infrared light into near-infrared light using pump light, said second far-infrared light having been transmitted from the sample; and a far-infrared image-forming optical system that forms an image of the sample in the detecting nonlinear optical crystal. The irradiation position of the first far-infrared light on the sample does not depend on the wavelength of the first far-infrared light.

A tunable laser system includes a laser diode producing a light beam having a plurality of frequencies in a visible portion of a light spectrum. A collimating lens arranged in front of the laser diode produces a collimated light beam from the light beam produced by the laser diode. A partial reflector arranged in a path of the collimated laser beam reflects a first portion of the collimated light beam and passes a second portion of the collimated light beam as an output light beam. The first portion of the collimated light beam enters the laser diode and mixes with the plurality of frequencies of the light beam produced by the laser diode so that the laser diode produces a self-injection-locked light beam including at least two frequencies having a frequency difference in a terahertz frequency range. A translational stage adjusts a distance between the laser diode and the partial reflector. The laser diode or the partial reflector is mounted on the translational stage. The at least two frequencies of the self-injection-locked light beam are based on the distance between the laser diode and the partial reflector.

A technique to generate terahertz radiation is disclosed, where a pump beam (12) is coupled into an optical element (50) made of a medium with non-linear optical properties having plane-parallel front and rear boundary surfaces (51, 52), wherein the pump beam (12) is split into a set of partial pump beams (121) by reflection and/or diffraction on a periodic relief structure (53) of said optical element (50). The partial pump beams travels along a direction at an angle γ that satisfies the velocity matching condition of v.sub.p,cs, cos(γ)=v.sub.THz,f within the given medium, where v.sub.p;cs is the group velocity of the pump beam, v.sub.THz;f is the phase velocity of the terahertz radiation and the speed a planar envelope (212) travels toward the front boundary surface (51) of the optical element (50), and γ is the angle formed by the pulse front envelope and the phase front of the pump beam.

The present invention relates to an optical imaging device capable of responding to a writing long-wave radiation (w) emitted by any object or scene. Said device is configured to operate in reflection mode or in transmission mode and comprises a reading light unit (2), writing light unit (4), resonant optically-addressed spatial light modulator (ROASLM) (3) with an optically-responsive resonant structure (ORRS) (100) and a detector (40), wherein said (ORRS) (100) comprises: a photosensitive layer (101) deposited on a transparent substrate for absorbing the writing radiation (w) in a form of the long-wave image of the object or scene (1) and transforming said image into the stimulating signal across the ORRS (100), optical layers (102) for inducing resonance effect to the stimulating signal formed in the ORRS (100), optional alignment layers (103) for aligning liquid crystal molecules, and the conversion layer (104) for converting the resonant long-wave image of the object or scene (1) into a visible-range image.

A transceiver based on at least one optical source is provided to facilitate wireless communication in a wearable display device, where the wearable display device is embedded with one or more planar antennas. The transceiver operates in terahertz and may be coupled to two different antennas, one for transmission and the other for reception.

A terahertz wave lens includes a substrate having a surface provided with an uneven structure that changes a phase of the terahertz wave. The uneven structure includes a plurality of holes that are periodically arranged. The uneven structure includes a plurality of regions where the plurality of holes are arranged. A height of the hole in a thickness direction of the substrate and a width of the pillar differ for each of the regions. Outer end portions of the uneven structure in the thickness direction are located on the same plane.

An aspect of the present disclosure is related to a method for measuring and controlling linear chirp level of ultrafast laser pulse. The method includes steps as follows. A carrier-envelope phase-chirp (CEP-chirp) relation which serve as a chirp monitor is extracted, in which the CEP-chirp relation is generated from an ultrafast laser pulse. A linear chirp level of a target pulse is measured in response to the CEP-chirp relation. According to the measuring with respect to the linear chirp level of the target pulse, a dispersion element which the ultrafast laser pulse passes through is varied to control and stabilize the linear chirp level of the target pulse.

A terahertz wave lens includes a substrate having a surface provided with an uneven structure that changes a phase of the terahertz wave. The uneven structure includes a plurality of holes that are periodically arranged. The uneven structure includes a plurality of regions where the plurality of holes are arranged. A height of the hole in a thickness direction of the substrate and a width of the pillar differ for each of the regions. Outer end portions of the uneven structure in the thickness direction are located on the same plane.

A nonlinear fiber interferometer is disclosed suitable for fiber sensor and other applications. A first nonlinear fiber section amplifies probe and conjugate sidebands of a pump through four-wave mixing. A second section introduces a phase shift to be measured, for example from a sensor. A third nonlinear fiber section amplifies with phase-sensitive gain to increase signal-to-noise ratio. Based on phase-sensitive output power of probe and/or conjugate components, the phase shift can be measured. Superior performance can be obtained by balancing gain between the (first and third) nonlinear sections. Non-fiber, for example photonic integrated circuit, embodiments are disclosed. Differential sensing, alternative detection schemes, sensing applications, associated methods, and other variations are disclosed.

A photonic device and a continuous-wave THz signal generator using such photonic device. The photonic device includes an input waveguide arranged to receive input waves of at least two input frequencies and to generate photons at an output frequency associated with the at least two input frequencies; an output waveguide coupled to the input waveguide and arranged to collect the generated photons at the output frequency; wherein the output waveguide is further arranged to facilitate an amplification of the generated photons as the generated photons propagates along the output waveguide and arranged to output an amplified signal at the output frequency.