Method and apparatus for wavelength locking free optical frequency comb based differential absorption Lidar

A differential absorption Lidar comprising:

• a mode-locked fiber laser, wherein the mode-locked fiber laser generates an electromagnetic radiation, wherein the electromagnetic radiation comprises an optical frequency comb with a frequency comb spacing of a pulsed repetition rate of the mode-locked fiber laser;
• an acousto-optic modulator comprising an input and an output, wherein the electromagnetic radiation is coupled to the input of the acousto-optic modulator and wherein the acousto-optic modulator is configured to down select the pulse repetition rate of the electromagnetic radiation;
• a power amplifier comprising an input and an output, wherein the input of the power amplifier is coupled to the output of the acousto-optic modulator and wherein the power amplifier is configured to amplify the down selected pulse repetition rate electromagnetic radiation;
• a collimator comprising an input and an output, wherein the input of the collimator is coupled to the output of the power amplifier and wherein the collimator is configured to collimate the amplified down selected pulse repetition rate electromagnetic radiation;
• an azimuth and elevation scanner comprising an input and an output, wherein the input of the azimuth and elevation scanner is coupled to the output of the collimator and wherein the azimuth and elevation scanner is configured to steer the collimated amplified down selected pulse repetition rate electromagnetic radiation onto a target;
• a telescope comprising an input and an output, wherein the input of the telescope is configured to collect electromagnetic radiation backscattered from the target;
• a DWDM comprising an input and an output, wherein the input of the DWDM is coupled to the output of the telescope;
• a photon counting receiver, wherein the photon counting receiver is coupled to the output of the DWDM;
• a signal processing and control unit, wherein the signal processing and control unit is coupled to the photon counting receiver and wherein the signal processing and control unit is configured to synchronize and gate the mode-locked fiber laser, the acousto-optic modulator, and the photon counting receiver;
• and
• a computer coupled to the signal processing and control unit, wherein the computer is configured to compare an on-resonant band intensity of the backscattered electromagnetic radiation with an off-resonant band intensity of the backscattered electromagnetic radiation.