Laser Remote Sensing With 1.5?M Single Photon Detectors

Single-photon detector is the most precision measurement instrument, which can detect the smallest unit of light, i.e. a single photon. It has been widely used in the field of lidar, distributed fiber sensor, biological fluorescence detection, quantum information, and optical imaging. Currently the main techniques for single-photon detection at 1.5?m include superconducting nanowire single-photon detectors,up-conversion single-photon detectors and InGaAs/InP single-photon avalanche diodes. 1.5 ?m aerosol lidars offer several advantages, including higher maximum permissible exposure to human eyes, lower atmospheric attenuation, minor disturbance from Rayleigh scattering, and weaker sky radiance. In this dissertation,the laser remote sensors are developed with those three kinds of single photon detectors.This dissertation proceeds as follows.1. A micro-pulse lidar at eye-safe wavelength is constructed based on an upconversion single-photon detector. The ultralow-noise detector enables using integration technique to improve the signal-to-noise ratio of the atmospheric backscattering even at daytime. With pulse energy of 110 ?J, pulse repetition rate of 15 kHz, optical antenna diameter of 100 mm and integration time of 5 min, a horizontal detection range of 7 km is realized. In the demonstration experiment,atmospheric visibility over 24 h is monitored continuously, with results in accordance with the weather forecasts.2. An all-fiber, micro-pulse and eye-safe high spectral resolution wind lidar(HSRWL) at 1.5 ?m is proposed and demonstrated by using a pair of upconversion single-photon detectors and a fiber Fabry-Perot scanning interferometer (FFP-SI). In order to improve the optical detection efficiency, both the transmission spectrum and the reflection spectrum of the FFP-SI are used for spectral analyses of the aerosol backscatter and the reference laser pulse. Taking advantages of high signal-to-noise ratio of the detectors and high spectral resolution of the FFP-SI, the center frequencies and the bandwidths of spectra of the aerosol backscatter are obtained simultaneously. Continuous LOS wind observations are carried out on two days at Hefei (31.843°N, 117.265°E), China.The horizontal detection range of 4 km is realized with temporal resolution of 1 minute. The spatial resolution is switched from 30 m to 60 m at distance of 1.8 km. In a comparison experiment, LOS wind measurements from the HSRWL show good agreement with the results from an ultrasonic wind sensor Vaisala wind-cap WMT52). An empirical method is adopted to evaluate the precision of the measurements. The standard deviation of the wind speed is 0.76 m/s at 1.8 km.The standard deviation of bandwidth variation is 2.07 MHz at 1.8 km.3. For the first time, to the best of our knowledge, a compact, eye-safe, and versatile direct detection Doppler lidar is developed using an upconversion single-photon detection method at 1.5 ?m. An all-fiber and polarization maintaining architecture is realized to guarantee the high optical coupling efficiency and the robust stability. Using integrated-optic components, the conservation of etendue of the optical receiver is achieved by manufacturing a fiber-coupled periodically poled lithium niobate waveguide and an all-fiber Fabry-Perot interferometer (FPI). The double-edge technique is implemented by using a convert single-channel FPI and a single upconversion detector, incorporating a time-division multiplexing method. The backscatter photons at 1548.1 nm are converted into 863 nm via mixing with a pump laser at 1950 nm. The relative error of the system is less than 0.1% over nine weeks. In experiments, atmospheric wind and visibility over 48 h are detected in the boundary layer. The lidar shows good agreement with the ultrasonic wind sensor, with a standard deviation of 1.04 m/s in speed and 12.3°in direction.4. We present a fully integrated InGaAs/InP negative feedback avalanche diode(NFAD) based free-running single-photon detector (SPD) designed for accurate lidar applications. A free-piston Stirling cooler is used to cool down the NFAD with a large temperature range, and an active hold-off circuit implemented in a field programmable gate array is applied to further suppress the afterpulsing contribution. The key parameters of the free-running SPD including photon detection efficiency (PDE), dark count rate (DCR), afterpulse probability, and maximum count rate (MCR) are dedicatedly optimized for lidar application in practice. We then perform a field experiment using a Mie lidar system with 20 kHz pulse repetition frequency to compare the performance between the free-running InGaAs/InP SPD and a commercial superconducting nanowire single-photon detector (SNSPD). Our detector exhibits good performance with 1.6 Mcps MCR (0.6 ?s hold-off time), 10% PDE, 950 cps DCR, and 18%afterpulse probability over 50 ?s period. Such performance is worse than the SNSPD with 60% PDE and 300 cps DCR. However, after performing a specific algorithm that we have developed for afterpulse and count rate corrections, the lidar system performance in terms of range-corrected signal (Pr2) distribution using our SPD agrees very well with the result using the SNSPD, with only a relative error of -2%. Due to the advantages of low-cost and small size of InGaAs/InP NFADs, such detector provides a practical solution for accurate lidar applications.5. A dual-frequency direct detection Doppler lidar is demonstrated using a superconducting nanowire single-photon detector (SNSPD) at 1.5 ?m. The so-called double-edge technique is implemented by using a dual-frequency laser pulse, rather than using a double-channel Fabry-Perot interferometer. Such a modification to the reported lidars enhances the frequency stability in the system level. Using the time-division multiplexing method, only one piece of SNSPD is used in the optical receiver, making the system simplified and robust. The SNSPD is adopted to enhance the temporal resolution since it offers merits of high quantum efficiency, low dark count noise, no after-pulsing probability, and a high maximum count rate. Two telescopes that point westward and northward at a zenith angle of 30° are used to detect the line-of-sight wind components, which are used to synthesize the horizontal wind profile. Horizontal wind profiles up to an altitude of about 2.7 km are calculated with vertical spatial/temporal resolution of 10 m/10 s. Wind dynamic evolution and vertical wind shears are observed clearly.6. A direct-detection Brillouin optical time-domain reflectometry (BOTDR) using an up-conversion photon-counting detector and an all-fiber structure Fabry-Perot scanning interferometer is proposed and demonstrated with shot-noise limited performance. Taking advantage of ultra-low noise equivalent power of the up-conversion photon-counting detector and high spectral resolution of the interferometer, the Brillouin spectra along a polarization maintaining fiber (PMF)are analyzed in the optical frequency domain directly. In contrast with heterodyne BOTDR, photon-counting BOTDR has better EM compatibility and faster speed in data processing. In experiments, using peak input power of 20dBm,temperature profile along a 9km PMF is retrieved according to the Brillouin shifts,with spatial/temporal resolution of 2m/15s.The minimum/maximum standard deviation is 0.66/1.47?.