Measurement of far-infrared waveguide loss using a multisection single-pass technique

Waveguide loss measurements based on a multisection single-pass technique have been performed for both mid-infrared and far-infrared quantum cascade structures. The far-infrared quantum cascade structures are based on a vertical transition active region emitting at $\text{λ≈76\hspace{0.05em}μ}\mathrm{m},$ embedded in a double-plasmon waveguide. The measured waveguide loss of $\text{42±20\hspace{0.05em}}{\mathrm{cm}}^{\mathrm{-1}}$ agrees well with the calculated one based on free carrier absorption.