Design and optimization of diamond mid-infrared phase shifter

Abstract

Herein, the mid-infrared (7.7–13.7 μm) diamond-based phase shifter was designed and optimized by finite-element analysis. The ridge-shaped diamond waveguide is designed and doped to form the internal p–n structure, and the internal carrier distribution is changed by applying forward and reverse voltages to change the effective refractive index to achieve the effect of π-phase shift. The results show that when p-doping concentration is 4 × 1017 cm−3 and n doping concentration is 1 × 1018 cm−3, upon the reverse voltage (8 V) is applied, the change of the real part of effective refractive index (ΔR) is 1.6 × 10−5, and the length of the phase shifter (L) required to realize the π-phase shift is 241 mm; upon the forward voltage (–8 V) is applied, ΔR increases to 3.2 × 10−4, and the length of the phase shifter required is shortened to 12.03 mm. Such a short length is relatively easy in industrial production. In order to make the refractive index distribution more uniform, the carrier concentration has been optimized as 1 × 1017 cm−3 for p-type and 4 × 1017 cm−3 for n-type, respectively.