A nonlinear converter may comprise: alternating layers of a dielectric material and a metal material; a first refractive index of the nonlinear converter for a first wavelength (i.e., input wavelength or pump wavelength) between 207 nm and 237 nm, the first refractive index being less than 0.5, the first refractive index corresponding to metal fill ratio; and a second refractive index of the nonlinear converter for a second wavelength (i.e., output wavelength or SHG wavelength), the second wavelength being approximately double the first wavelength, the second refractive index corresponding to the metal fill ratio.

An optical waveguide structure comprises a nonlinear optical waveguide, a set of tuning optical waveguides, a set of wavelength selective couplers that couples light between the nonlinear optical waveguide and one or more tuning optical waveguides in the set of tuning optical waveguide based on a wavelength of light, and a set of phase shifters located along one or more tuning optical waveguides in the set of tuning optical waveguides.

The present invention provides a far-infrared light source capable of reducing the shift in the location irradiated with far-infrared light even when the frequency of the far-infrared light changes. A far-infrared light source according to the present invention is configured so that the variation in the emission angle of far-infrared light in a nonlinear optical crystal when the frequency of the far-infrared light changes is substantially offset by the variation in the refractive angle of the far-infrared light at the interface between the nonlinear optical crystal and a prism when the frequency of the far-infrared light changes (see FIG. 8).

An optical oscillator includes a first reflection part configured to reflect light of a first wavelength, a laser medium excited by excitation light of a second wavelength different from the first wavelength and configured to emit light of the first wavelength, a second reflection part configured to form an unstable resonator together with the first reflection part, the unstable resonator being configured to output annular laser light of the first wavelength, and a saturable absorption part disposed between the laser medium and the second reflection part and of which a transmittance increases with absorption of light of the first wavelength. When a power of the excitation light is indicated by P.sub.p (kW), and an inner diameter of the annular laser light is indicated by d.sub.i, and an outer diameter is indicated by d.sub.o, and d.sub.o/d.sub.i is a magnification m, the magnification m satisfies a.sub.0+a.sub.1 Log(P.sub.p)≤m≤b.sub.0+b.sub.1P.sub.p+b.sub.2P.sub.p.sup.2.

A miniaturized PPKTP crystal-based entanglement source system using multi-mode reception is provided, which includes a pump light source, a pump light transmission module, an entanglement device, a first collection device, and a second collection device. In the entanglement source system, entangled lights are received by using multi-mode optical fibers, and an entangled light processing scheme of combining a temporal filtering technology and a spatial filtering technology is applied into a collecting device at one side of the entanglement source system, to form asymmetric device structures in the entanglement source system, to enable multi-mode reception.

A miniaturized PPKTP crystal-based entanglement source system using multi-mode reception is provided, which includes a pump light source, a pump light transmission module, an entanglement device, a first collection device, and a second collection device. In the entanglement source system, entangled lights are received by using multi-mode optical fibers, and an entangled light processing scheme of combining a temporal filtering technology and a spatial filtering technology is applied into a collecting device at one side of the entanglement source system, to form asymmetric device structures in the entanglement source system, to enable multi-mode reception.

A coherent, entangled photon source which uses a continuous wave laser to replace pulsed photon excitation sources in multiphoton nonlinear processes. In various embodiments, the device comprises a continuous wave photon laser creating electromagnetic radiation at a specific frequency and narrow linewidth. The emitted beam may be conditioned by an optical fiber to allow for efficient interaction with a nonlinear crystal. The nonlinear material is designed and fabricated in a specific manner, enabling the quantum mechanical process of a single photon with well-defined energy being converted into two or more photons which display quantum correlations. The nonlinear material and subsequent fiber-optic or free space components control the temporal, spatial, and polarization-related quantum correlations such that the entangled photons can create a signal in multi photon nonlinear processes that is the same or exceeds that of a pulsed photon source but at the average and peak powers of a continuous wave laser.

A coherent, entangled photon source which uses a continuous wave laser to replace pulsed photon excitation sources in multiphoton nonlinear processes. In various embodiments, the device comprises a continuous wave photon laser creating electromagnetic radiation at a specific frequency and narrow linewidth. The emitted beam may be conditioned by an optical fiber to allow for efficient interaction with a nonlinear crystal. The nonlinear material is designed and fabricated in a specific manner, enabling the quantum mechanical process of a single photon with well-defined energy being converted into two or more photons which display quantum correlations. The nonlinear material and subsequent fiber-optic or free space components control the temporal, spatial, and polarization-related quantum correlations such that the entangled photons can create a signal in multi photon nonlinear processes that is the same or exceeds that of a pulsed photon source but at the average and peak powers of a continuous wave laser.

An optical-resolution photoacoustic microscopy (OR-PAM) system for visualizing water content deep in biological tissue uses an all-fiber 1930-nm hybrid optical parametrically-oscillating emitter. The emitter includes a tunable laser source whose output is amplified by a first erbium-doped fiber amplifier (EDFA). The output of the first amplifier is modulated with a Mach-Zehnder amplitude modulator that receives an RF signal with a nanosecond pulse width and a multiple kilohertz repetition rate. A second EDFA further amplifies the signal and passes it to a fiber circulator that in turn delivers it to a 1950/1550 mm fiber wavelength-division-multiplexing coupler WDM. The coupler introduces the signal to a cavity that includes a spool of highly nonlinear fiber and a Thulium-doped fiber amplifier TDFA. From the TDFA the signal reaches a 50/50 fiber coupler that sends part to a second output TDFA and guides part back to the cavity through a port of the WDM.

An optical-resolution photoacoustic microscopy (OR-PAM) system for visualizing water content deep in biological tissue uses an all-fiber 1930-nm hybrid optical parametrically-oscillating emitter. The emitter includes a tunable laser source whose output is amplified by a first erbium-doped fiber amplifier (EDFA). The output of the first amplifier is modulated with a Mach-Zehnder amplitude modulator that receives an RF signal with a nanosecond pulse width and a multiple kilohertz repetition rate. A second EDFA further amplifies the signal and passes it to a fiber circulator that in turn delivers it to a 1950/1550 mm fiber wavelength-division-multiplexing coupler WDM. The coupler introduces the signal to a cavity that includes a spool of highly nonlinear fiber and a Thulium-doped fiber amplifier TDFA. From the TDFA the signal reaches a 50/50 fiber coupler that sends part to a second output TDFA and guides part back to the cavity through a port of the WDM.