Low driving voltage spatial light modulator fabricated by ultrahigh-purity GaAs

Highly efficient surface normal spatial light modulators (SLMs) using ultrahigh purity GaAs layers (30 μm thick) grown on (100) - oriented n⁺ - GaAs substrate by liquid phase epitaxy (LPE) method have been realized. The extinction ratio of 25 dB has been demonstrated with a low - driving voltage (32 V) at 895 nm, based on electroabsorption (EA) effect. Very large depletion length over 150 μm is confirmed by analyzing the extinction ratio and capacitance- voltage (C-V) measurements. The calculated value of impurity concentration is low (≈10¹² cm^-3) and indicates donor and accepter in the device are highly compensated.