Remote Sensing Applications of a Free-electron Laser Lidar

This paper 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 midinfrared. Peak power in the picosecond long micropulses of the FEL will reach 10s 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.