Remote sensing applications of a free-electron laser lidar

A high average power and high spectral brightness free-electron laser (FEL) being developed at the University of Hawaii as a lidar transmitter for atmospheric and oceanic research. The FEL will be tunable from the UV to the mid-infrared. Peak power in the picosecond long micropulses of the FEL will reach 10 s of MW, and these will average to the order of 100 kW over the 5 microsecond long macropulses. The repetition rate of the micropulses will be in the range 1 to 3 GHz during one macropulse, and the macropulses will repeat at 180 Hz. The unique pulse structure of the FEL output with high pulse power will allow exploitation of non-linear optical spectroscopic techniques for identifying various types of aerosols and pollutants in the atmosphere. The wide tunable range in the mid-IR region will allow sensitive detection of chemical species by operating the FEL transmitter in the differential absorption lidar (DIAL) mode, and the high spectral brightness will allow unprecedented signal-to-noise ratio.