We report an eye-safe aerosol and cloud lidar with an Erbium-doped fiber laser (EDFL) and a free-space intracavity upconversion detector as the transmitter and receiver, respectively. The EDFL was home-made, which could produce linearly-polarized pulses at a repetition rate of 15 kHz with pulse energies of ~70 μJ and pulse durations of ~7 ns centered at 1550 nm. The echo photons were upconverted to ~631 nm via the sum frequency generation process in a bow-tie cavity, where a Nd:YVO₄ and a PPLN crystal served as the pump and nonlinear frequency conversion devices, respectively. The upconverted visible photons were recorded by a photomultiplier tube and their timestamps were registered by a customized time-to-digital converter for distance-resolved measurement. Reflected signals peaked at ~6.8 km from a hard target were measured with a distance resolution of 0.6 m for an integral duration of 10 s. Atmospheric backscattered signals, with a range of ~6 km, were also detectable for longer integral durations. The evolution of aerosols and clouds were recorded by this lidar in a preliminary experiment with a continuous measuring time of over 18 h. Clear boundary and fine structures of clouds were identified with a spatial resolution of 9.6 m during the measurement, showing its great potential for practical aerosol and cloud monitoring.

We have demonstrated a spectral and repetition rate programmable Yb-doped fiber laser (YDFL) employing an acousto-optic tunable filter (AOTF) as both the intra-cavity spectral filter and temporal modulator. The AOTF was driven with specially programmed sequences of wave packets enabling different pulsed operation modes including tunable single-wavelength, simultaneous dual-wavelength, and alternative dual-wavelength lasing at different repetition rates in one configuration. The maximal wavelength tuning range of 88 nm covering 1024 to 1112 nm was achieved for this YDFL by properly adjusting the waveform of each drive wave packet. Stable pulse trains with repetition rate from 10 to 130 kHz could be obtained within most of the wavelength tuning range for all available operation modes by changing the time interval between adjacent drive wave packets. It is believed that the combination of both spectral and temporal control without moving elements has paved a promising approach towards the development of a simple yet versatile fiber laser for a wide range of applications including spectroscopy, telecommunication, and Lidar.