A novel chaotic lidar (CLIDAR) system that utilizes a chaotic laser as the light source is proposed and studied. In CLIDAR, the detection and ranging are realized by correlating the signal waveform reflected back from the target with a delayed reference waveform. Benefiting from the very broad bandwidth of the chaotic waveform that can be easily generated by a semiconductor laser, a centimeter-range resolution is readily achieved. The correlation performance of CLIDAR is studied both numerically and experimentally. The power spectra, phase portraits, time series, and correlation traces of the chaotic waveforms obtained at different operating conditions are compared. The relation between the complexity of the attractor and the correlation property is examined. The correlation dimension and the largest positive Lyapunov exponent of each waveform are calculated. To compare the correlation performance of the waveforms quantitatively, peak sidelobe levels of the correlation traces with different correlation lengths and relative noise levels are investigated. Preliminary experiments show a subcentimeter accuracy in ranging with a 3-cm-range resolution, which currently is limited by the bandwidth of the oscilloscope used.

Chaotic lidar

Stable and self-starting mode-locking of a Tm:KLu(WO4)2 crystal laser is demonstrated using a transmission-type single-walled carbon nanotube (SWCNT) based saturable absorber (SA). These experiments in the 2 µm regime utilize the E11 transition of the SWCNTs for nonlinear saturable absorption. The recovery time of the SWCNT-SA is measured by pump-probe measurements as ~1.2 ps. The mode-locked laser delivers ~10-ps pulses near 1.95 µm with a maximum output power of up to 240 mW at 126 MHz repetition rate.

Passive mode-locking of a Tm-doped bulk laser near 2 microm using a carbon nanotube saturable absorber.

A compact 1.5 microm all-fiber pulsed coherent Doppler lidar system for wind sensing, which includes the functions of variable pulse width and automatic polarization control has been developed. The system configuration is introduced and key components used in the system are explained. Theoretical performances of the system in wind sensing are estimated and compared with experimental results. The measurable range corresponding to the detection probability of >80% is approximately 1 km or more in the case of 150 m range resolution under the normal atmospheric conditions.

Compact all-fiber pulsed coherent Doppler lidar system for wind sensing

Coherent Doppler lidar measurements of wind statistics in the boundary layer are presented. The effects of the spatial averaging by the lidar pulse are removed using theoretical corrections and computer simulations. This permits unbiased estimates of velocity variance, spatial velocity structure functions, energy dissipation rate, and other point statistics of the velocity field.

Coherent Doppler Lidar Measurements of Wind Field Statistics

For the first time of our knowledge, we demonstrate the graphene oxide as a saturable absorber (SA) in the passive mode-locking of a diode pumped Tm3+-doped laser. Broadly spectral region sub-10 ps mode-locking in a Tm:YAlO3 (Tm:YAP) laser near 2 μm were obtained. With a pump power of 8.64 W, the average output power of 268 mW with the maximum pulse energy of 3.7 nJ at the pulse repetition frequency (PRF) of 71.8 MHz was obtained.

https://iopscience.iop.org/article/10.1002/lapl.201110087/pdf

Graphene oxide absorber for 2 µm passive mode‐locking Tm:YAlO3 laser

The use of airborne laser radar (lidar) to measure wind velocities and to detect turbulence in front of an aircraft in real time can significantly increase fuel efficiency, flight safety, and terminal area capacity. We describe the flight-test results for two coherent lidar airborne shear sensor (CLASS) systems and discuss their agreement with our theoretical simulations. The 10.6-μm CO2 system (CLASS-10) is a flying brassboard; the 2.02-μm Tm:YAG solid-state system (CLASS-2) is configured in a rugged, lightweight, high-performance package. Both lidars have shown a wind measurement accuracy of better than 1 m/s. © 1996 Optical Society of America

Raymond S. Calloway

Papers

Coherent lidar airborne wind sensor II: flight-test results at 2 and 10 νm.