The present invention provides a method for fabricating KTP nonlinear racetrack micro-ring resonator, composed of six steps: KTP wafer processing, ion implantation, electron beam exposure, subsequent processing, reactive ion etching and final processing. A thin-film waveguide structure similar to the on-insulator lithium niobate thin-film can be achieved through only one process of ion implantation, which enables significantly simplified procedure, shortened time, and reduced cost. Meanwhile, the KTP micro-ring resonator produced according to the present invention has an optical damage threshold several times higher than the existing lithium niobate micro-ring resonator. It can output nonlinear frequency converted light to the power of milliwatts, and suitable for the case where both the input and output optical signals are pulsed lasers. Since Ion implantation, electron beam exposure, metal evaporation deposition, and reactive ion etching are all relatively developed micro-nano machining technologies, the present invention has wonderful operability and repeatability.

It discloses a system and a method for generating heralded single photons, wherein the system comprises a high-quality optical ring cavity, a PPKTP nonlinear crystal, a polarization beam splitter, a dichroic mirror, a light filtering device, a reflector module, an atomic vapor cell and a single photon detector, wherein: the high-quality optical ring cavity is formed by a first plano-concave reflector, a second plano-concave reflector, a third plano-concave reflector and a fourth plano-concave reflector; the PPKTP nonlinear crystal and the polarization beam splitter are positioned in an optical path between the first plano-concave reflector and the second plano-concave reflector; the dichroic mirror is positioned in an optical path behind a reflecting end of the polarization beam splitter.

Disclosed is an apparatus for single-pixel imaging using quantum light, the apparatus including: a light source which generates a photon pair through spontaneously parametric down conversion of a non-linear crystal and splits the photon pair into an idler photon of first polarized light and a signal photon of second polarized light; a signal processing unit which aligns the signal photon with the first polarized light and modulates the signal photon with a pattern of a spatial light modulator, and sends the modulated signal photon to a target; and a signal detecting unit which simultaneously measures signal photons collected after an interaction of the idler photon and the target to obtain an image.

It discloses a system and a method for generating heralded single photons, wherein the system comprises a high-quality optical ring cavity, a PPKTP nonlinear crystal, a polarization beam splitter, a dichroic mirror, a light filtering device, a reflector module, an atomic vapor cell and a single photon detector, wherein: the high-quality optical ring cavity is formed by a first plano-concave reflector, a second plano-concave reflector, a third plano-concave reflector and a fourth plano-concave reflector; the PPKTP nonlinear crystal and the polarization beam splitter are positioned in an optical path between the first plano-concave reflector and the second plano-concave reflector; the dichroic mirror is positioned in an optical path behind a reflecting end of the polarization beam splitter.

A laser adjustment method includes a first adjustment step and a second adjustment step. In the first adjustment step, using a light detector detecting a second harmonic light, optical intensity and wavelength of the second harmonic light is detected and a first temperature adjuster is adjusted to adjust temperatures of a Nd:YVO.sub.4 crystal and a KTP crystal such that the detected wavelength of the second harmonic light approaches a desired wavelength and such that the optical intensity of the second harmonic light reaches at least a predetermined value. In the second adjustment step, after the first adjustment step, a temperature of an etalon is adjusted by a second temperature adjuster such that the detected wavelength of the second harmonic light approaches the desired wavelength and such that the optical intensity of the second harmonic light reaches at least a predetermined value.

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.

The present invention provides a method for fabricating KTP nonlinear racetrack micro-ring resonator, composed of six steps: KTP wafer processing, ion implantation, electron beam exposure, subsequent processing, reactive ion etching and final processing. A thin-film waveguide structure similar to the on-insulator lithium niobate thin-film can be achieved through only one process of ion implantation, which enables significantly simplified procedure, shortened time, and reduced cost. Meanwhile, the KTP micro-ring resonator produced according to the present invention has an optical damage threshold several times higher than the existing lithium niobate micro-ring resonator. It can output nonlinear frequency converted light to the power of milliwatts, and suitable for the case where both the input and output optical signals are pulsed lasers. Since Ion implantation, electron beam exposure, metal evaporation deposition, and reactive ion etching are all relatively developed micro-nano machining technologies, the present invention has wonderful operability and repeatability.

Systems and embodiments for an integrated photonics mode splitter and converter are provided herein. In certain embodiments, a system includes a substrate having a first index of refraction. Additionally, the system includes a waveguide layer on the substrate, wherein the waveguide has a second index of refraction different from the first index of refraction. Also, the waveguide layer includes one or more mode splitters that receive at least one of a first photon in a first mode and a second photon in a second mode through an input port and provide one of the first photon through a first output port and the second photon through a second output port. The waveguide layer also includes a mode converter coupled to the second output of a mode splitter, wherein the mode converter receives the second photon through a port and outputs the second photon in the first mode through the port.

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 wavelength conversion system comprising a transport system for a laser beam comprising: a circular polarization laser beam; an articulated arm comprising a mirror at each of its joints, arranged at 45° with respect to said laser beam; each of said mirrors having a phase shift between the reflected components of less than 10°; means for converting said laser beam from circular polarization to linear polarization and providing a linear polarization output laser beam; a non-linear converter for converting the wavelength of said output laser beam to linear polarization.