New regime of diode laser operation: 200-ps front edge of a nanosecond pulse

We report for the first time the study of a unique rangefinder based on an eye-safe diode injection laser (less than 1 μJ·cm^–2) and a single photon avalanche photodiode (single photon avalanche diode, SPAD). A new generation regime of a nanosecond laser with a 200-ps step at the front of a 4-ns pulse with a length of ∼1.2 m is implemented. It is found that the observed jump in the optical pulse amplitude is initiated by a current avalanche in a field transistor that switches the capacitance discharge in the power supply circuit of the laser diode. Registration of a 200-ps amplitude jump by a fast SPAD receiver (20 ps) increases the accuracy of the range finder by a factor of 12. The use of such rangefinders for measuring distances at a critical distance (less than the length of a laser pulse), for example, in the problems of landing or docking of spacecraft, rendezvous and mooring of underwater robots, is discussed.