Research And Application Based On Single-Photon Upconversion System With Synchronized Pump

Single-photon frequency upconversion based on the nonlinear optical effect of sum frequency generation provided a new method for the sensitive detection of near/mid-infrared photons with high efficiency and low noise. According to the quansi-phase matching requirement in the frequency upconversion processing, a spectral resolved infrared single-photon detection is possible, paving a way to a sensitive infrared spectrometer. Infrared spectroscopy plays a significant role in applied science as well as in fundamental science. Lots of research works have been focused on the infrared spectrum measurement over the last few decades. However, the sensitivity of infrared spectrometers still requires improvement. We built a sensitive infrared spectrometer based on a wavelength tunable single-photon frequency upconversion system with synchronous pulsed pump-signal system. A high conversion efficiency was achieved with an ultralow low noise probability per pulse of. The highly sensitive infrared spectrometer was successfully demonstrated in the infrared absorption spectrum detection of hydrogen sulfide gas, showing its potential as a gas monitor for remote spectrum analysis at eye-safe wavelengths, where the returning light intensity is very weak.Moreover, since the nonlinear bulk crystal has been widely adopted as the spatial and phase information could be well preserved when the infrared image is transferred to visible regime by frequency upconversion, a quantum information interface based on the frequency upconversion for photons carrying OAM states from telecom wavelength to visible regime could be realized by sum-frequency generation with high quantum conversion efficiency. Recently, light with helical phase structures has been widely used in quantum communication since the orbital angular momentum (OAM) of light was first found by Allen in 1992. However, OAM qubits at optical fiber telecommunication wavelengths around 1550 nm could not match the quantum information storage and processing devices based on atoms, ions or NV color centers that absorb and emit photons at visible wavelengths around 600-700 nm. A kind of interface is urgent for those OAM carried qubits. Based on our synchronous pulsed pump-signal single-photon frequency upconversion system, we demonstrate the high efficiency frequency upconversion of photons carrying orbital angular momentum for a quantum information interface. Photons carrying OAM of 1h were converted from telecom wavelength to the visible regime with 68% quantum conversion efficiency, which could be potential applied in quantum information techniques using OAM encoding of the photons. With the OAM value of 0 1h, the overlap was 94.3% due to the beam size mismatch of the pump and the signal in the PPLN crystal. The noise of the system was only 3.8 x 103 cps and the SNR was still as high as about 50:1.