Room Temperature Bistability, Logic Gate Operation, Incoherent Switching and High Signal Gain with InSb Devices

Abstract

We present details of the performance of several devices utilising the giant nonlinear refractive index of InSb (n₂ = 0.1 cm²/kW at 77 K and 5.5 µm; n₂ = 10^-4 cm²/kW at 300 K and 10.6 µm). Optical bistability was observed at 300 K using a CO₂ laser with intensities of order 100 kW/cm² and switching times 5–30 ns. At 77 K and 5.5 µm devices could be operated with cw holding beams combined with time-varying switching or signal pulses. The ^Tall-optical circuit elements¹ demonstrated are: (i) AND, OR, NAND or NOR gates in which ‘switch on’ of the function is inferred to be on a picosecond timescale and ‘switch off’ of the order of carrier recombination time; (ii) the switching of one optical logic gate by another; (iii) switching of a bistable device in both directions with an incoherent beam; (iv) two beam signal amplification in a transphasor of order 1.3 × 10⁴.