OPTICAL-PROPERTIES OF ALGAAS/GAAS NIPI SUPERLATTICES AND THEIR APPLICATION IN ASYMMETRIC CAVITY SPATIAL LIGHT MODULATORS

Homo-nipi and hetero-nipi superlattices incorporated into asymmetric Fabry-Perot cavity structures are compared and evaluated for possible use as bit plane optical memory elements in terms of the magnitude of their optical nonlinearities, on-off contrast ratio, insertion loss, carrier lifetimes, and power required to change the state of the structure. Changes in superlattice absorption coefficient as high as 1500 cm-1 and 1300 cm-1 have been achieved in type I and type II AlGaAs/GaAs hetero-nipi structures, respectively. When normalized to the GaAs quantum well layer thicknesses, the change in absorption coefficient in the Type I superlattice was as high as 12000 cm-1. In asymmetric cavity modulator structures, on-off reflection contrast ratios as high as 60 : 1, carrier lifetimes as long as 4 ms, and on-state reflectivities as high as 0.62 have been observed. A 54 : 1 contrast ratio and an insertion loss of 8.5 dB were achieved simultaneously in a planar Fabry-Perot cavity structure excited with a pump beam power of 3.8 mW. The effective carrier lifetime in this case was 25 mus.