Fig. 1. Detection of weak infrared radiation via non-degenerate two-photon absorption in a Si photodiode.
a Linear absorption (blue) as a function of the pulse energy at 1030 nm, non-degenerate two-photon absorption (orange) as a function of the pump pulse energy at 1480 nm and degenerate two-photon absorption (purple) as a function of the pump pulse energy at 1480 nm. For the non-degenerate curve, the MIR pulse energy at 3388 nm was set at 0.65 nJ. Inset: proposed scheme of photon absorption in Si. b Full dynamic range for MIR detection with a detection floor of a 200 fJ picosecond pulse energy for the given detector parameters. Note that 1 V on the y-axis corresponds to 8.2 × 104 electrons/pulse