Current tuned slotted Y‐branch laser for wafer thickness measurements with THz radiation

Abstract

A slotted Y-branch laser diode that emits two spectral modes at a difference frequency of about 1 THz is investigated in the context of photonic based cw-THz measurements. The beating frequency of the emitted laser light can be tuned by ±10.5 GHz around 1 THz by changing the applied laser current, which allows for potentially fast measurements. A second spectral window of ±6.5 GHz was found at 850 GHz. Pointwise scanning of the difference frequency is demonstrated with thickness determination of HRFZ-Si wafer samples as a possible application scenario.