THz device includes: a semiconductor substrate; a first semiconductor layer disposed on the semiconductor substrate; an active element formed by being laminated on the first semiconductor layer; a second electrode connected to the first semiconductor layer to be connected to a cathode K of the active element, the second electrode disposed on the semiconductor substrate; a first electrode connected to an anode A of the active element, the first electrode disposed on the semiconductor substrate to be opposite to the second electrode; a rear reflector metal layer disposed on a back side surface of the semiconductor substrate opposite to the first semiconductor layer, wherein the active element forms a resonator between the second and first electrodes, wherein electromagnetic waves are reflected on the rear reflector metal layer, and electromagnetic waves have a surface light-emission radiating pattern or surface light-receiving pattern in a vertical direction to the semiconductor substrate.

An apparatus includes a non-linear optical crystal configured to perform harmonic wavelength conversion. The apparatus also includes first and second heaters contacting opposite sides of the optical crystal, where the first and second heaters are configured to heat the optical crystal. The apparatus further includes first and second backing plates configured to hold the first and second heaters in contact with the optical crystal. The apparatus also includes an internal mount defining a space configured to receive at least a portion of the optical crystal. In addition, the apparatus includes an external cover around at least a portion of the internal mount.

A nonlinear crystal comprising a first end face and an opposing second end face is described. The first and second end faces are separated along an optical axis of the nonlinear crystal by a length in the range of 0.25 mm and 2 mm. Although the length of the nonlinear crystal results in a reduction in the nonlinear effects induced on an optical field propagating through the crystal it also provides for reduced deviation experienced by the generated optical field when the nonlinear crystal is rotated. Therefore, when the nonlinear crystals are incorporated within an enhancement cavity their reduced length allows for the deviation of the output field to be minimised by servo control electronics arranged to adjust a single cavity mirror. This significantly reduces the complexity, and thus expensive of the servo control electronics when compared to those employed with the prior art enhancement cavities.

A wavelength conversion system according to an aspect of the present disclosure includes a first crystal holder holding a first non-linear crystal, a second crystal holder holding a second non-linear crystal, a third crystal holder holding a third non-linear crystal, and a container housing the holders. The container has an entrance window and an emission window. The first non-linear crystal, the second non-linear crystal, and the third non-linear crystal are disposed in this order on an optical path of a laser beam traveling from the entrance window to the emission window. The crystal holders are rotatable. A first rotational axis that is a rotational axis of the first crystal holder is orthogonal to a second rotational axis that is a rotational axis of the second crystal holder, and the first rotational axis is parallel to a third rotational axis that is a rotational axis of the third crystal holder.

A wavelength conversion apparatus according to an aspect of the present disclosure is a wavelength conversion apparatus that performs wavelength conversion of light through a non-linear crystal and including a first non-linear crystal, a container in which the first non-linear crystal is housed, a crystal holding member provided inside the container for fixing the first non-linear crystal, a first window provided to the container for guiding light to the first non-linear crystal from outside of the container, a second window provided to the container for guiding light output from the first non-linear crystal to outside of the container, a first heater provided inside the container for heating the first non-linear crystal, a battery that supplies electric power to the first heater, and a first controller that controls electric power supply to the first heater.

A laser source includes a first laser device configured to generate a first laser beam having a first wavelength, a second laser device configured to generate a second laser beam having a second wavelength, which is different from the first wavelength, and a non-linear crystal configured to receive simultaneously the first and second laser beams and to generate a third laser beam that has a third wavelength, which is larger than each of the first and second wavelengths. The non-linear crystal has a length and a width, and a variable poling period is distributed across the width so that the third wavelength varies within a given wavelength range based on an incident position of the first and second laser beams along the width of the non-linear crystal.

An optical arrangement for enlarging spectral bandwidths by nonlinear self-phase modulation for shortening ultrashort pulses using a multipass cell and a nonlinear medium. The nonlinear medium is arranged within the multipass cell, and a laser beam having ultrashort pulses passes through the nonlinear medium multiple times. The laser beam is coupled into the multipass cell by way of a shaping optical unit. The laser beam is shaped into an astigmatic beam and coupled into the multipass cell by way of the shaping optical unit.

An inspection device includes: a light source for outputting pulsed excitation light with a time width of 10 picoseconds to 10 nanoseconds; a nonlinear optical crystal for generating a terahertz wave by optical wavelength conversion of the excitation light; and a detector for detecting a reflected wave of the terahertz wave reflected by an inspection target.

A cavity-enhanced frequency mixer includes an input optical fiber, a waveguide, and an output optical fiber. The waveguide has an input end and an output end, the input end is connected to the input optical fiber, and a surface of the input end of the waveguide is coated with a highly reflective coating. The output optical fiber is formed with a fiber Bragg grating structure. The highly reflective coating and the fiber Bragg grating structure form a pair of reflective surfaces for resonant optical parametric oscillation under a low threshold situation, so that one of the beams generated by the input beam is reflected inside the partially reflective surfaces. Operated above a pump power threshold, the cavity-enhanced frequency mixer is tantamount to a compact, low-power budget optical parametric oscillator, while below the pump power threshold, it is a bright, compact, single-mode and narrow linewidth single-photon source.

A display device including a display panel, in which a display region including a plurality of organic light emitting devices and a non-display region adjacent to the display region are defined, a protection film disposed below the display panel, a first adhesive layer contacting a bottom surface of the protection film, a supporting layer comprising a metallic material, at least overlapping the entire display region, and contacting the first adhesive layer, an input-sensing unit disposed on the display panel, an anti-reflection unit disposed on the input-sensing unit, and a window panel disposed on the input-sensing unit.