Abstract
We demonstrate the strong modulation of the long wave infrared transmission of GaInSb/InAsSb/AlInAsSb heterostructures under carrier injection. This results in the population of states in the conduction band of the narrow-gap layer and changes the absorption and refractive index over a broad wavelength range. At λ = 8.6-μm, a single-pass intensity modulation depth up to 9% was demonstrated at T = 77 K for a 1-μm–thick InAs0.58Sb0.42 absorber. By modeling the structure, we show that this corresponds to the electron quasi-Fermi level rising up to 30 meV above the conduction band edge. Due to the strong band-to-band absorption, the change in the quasi-Fermi level is accompanied by a modulation of the refractive index by up to 0.06 in the spectral range below the energy gap of the alloy. This change is orders of magnitude greater than what is achievable in conventional electro-optic materials and allows, for example, the external intensity modulation of long-wave infrared laser sources with a high extinction ratio and a nanosecond-scale time response. Low power requirements make it possible to develop arrays of integrated devices for optical beam steering and shaping.
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