Cascaded Injection Locked Diode Laser Transmitter For Lidar Measurements

A lidar laser transmitter useful for profiling of clouds, aerosols, and differential absorption measurements of atmospheric trace constituents such as carbon dioxide, water vapor, and ozone is proposed. The proposed laser transmitter is based on a master tunable external cavity diode laser (ECDL) used to injection lock a series of free running laser diodes (FRLD's). The FRDL's amplify the injected optical signal from the master ECDL so that the output of the laser transmitter maintains the tunability and narrow linewidth of the master ECDL. The amplified output signal of the laser transmitter is easily pulsed by modulating the drive current to the FRDL's. The innovative laser transmitter maintains the tunability and narrow linewidth of the master ECDL important for differential absorption lidar (DIAL) measurements while providing a pulsed amplified output. Cascading four injection locked FRDL's to a master ECDL can produce a peak power of 1W. An order of magnitude improvement in the signal to noise performance of a lidar system can be obtained using the cascaded injection locked laser transmitter compared to the state of the art pulsed flared amplifiers.