Ultra-short pulse burst laser around 1.98†µm obtained through an all-fiber nonlinear wavelength converter and Tm-doped fiber amplifier.

We report an all-fiber ultra-short pulse burst laser operating at around 1.98 µm that is obtained through a nonlinear wavelength converter and Tm-doped fiber amplifier. A mode-locked Er-doped fiber laser was first built and then amplified in subsequent amplifiers to an average power of 1.3 W. Ultra-short pulse burst output was achieved through a pulse multiplier and a fiber-pigtailed acousto-optic modulator. It was then injected into an all-fiber nonlinear wavelength converter constructed from P-doped fiber and Tm-doped fiber, obtaining an ultra-short pulse burst laser of 540 mW around 1.98 µm. Its average output power was then amplified to 4.33 W in a Tm-doped fiber amplifier with an intra-burst pulse repetition frequency of 0.9 GHz, a burst repetition frequency of 200 kHz, and a duty cycle of 2%, corresponding to about 200 pulses within each burst. This 1.98 µm pulse burst laser has enormous potential to be applied in bio-medical areas.

Coded-pulse-bunch-laser-based single-photon lidar for fast long-distance ranging.

Laser ranging based on a single-photon avalanche diode (SPAD), offering single-photon level high sensitivity, has been widely adopted in light detection and ranging (lidar) systems for long-distance ranging and imaging applications. Count detection through multiple pulses is commonly used when considering the existence of dark counting and strong background counting during the daytime, which improves the signal-to-noise ratio but at the expense of low detection speed. Here, we report a novel coded-pulse-bunch-laser-based single-photon lidar system, which aims to improve the ranging speed greatly and to expand the unambiguous distance to several kilometers. The schematic principle and construction of the lidar system, as well as the encoding method, are introduced. The time-of-flight (TOF) ranging information is extracted through real-time correlation between the transmitted pulse-bunch patterns and the received echo signals in a field-programmable gate array (FPGA). A daytime ranging experiment is demonstrated on a non-cooperative mountain target that is 5.4 km away. The method will be of great potential in fast three-dimension (3D) single-photon lidar imaging application for its relatively high data refreshing rate and large unambiguous distance.