A 1024 x 8, 700-ps Time-Gated SPAD Line Sensor for Planetary Surface Exploration With Laser Raman Spectroscopy and LIBS

A 1024 x 8 time-gated, single-photon avalanche diode line sensor is presented for time-resolved laser Raman spectroscopy and laser-induced breakdown spectroscopy. Two different chip geometries were implemented and characterized. A type-I sensor has a maximum photon detection efficiency of 0.3% and median dark count rate of 80 Hz at 3 V of excess bias. A type-II sensor offers a maximum photon detection efficiency of 19.3% and a median dark count rate of 5.7 kHz at 3 V of excess bias. Both chips have 250-ps temporal resolution and fast gating capability, with a minimum gate width of 1.8 ns for type I and 0.7 ns for type II. Raman spectra were successfully observed from natural minerals, such as calcite and willemite. With the use of subnanosecond gating, background fluorescence was significantly reduced.