Longitudinal computer-generated holograms for digital frequency control in electronically tunable terahertz lasers

摘要

Longitudinal computer-generated holograms (LCGHs) can be used for the inverse design of aperiodic photonic lattices for customizable frequency control of light propagation. A one-dimensional binary LCGH, designed to harness the coarse gain tuning of a terahertz (THz) quantum cascade laser (QCL) operating at around 2.9 THz, is patterned directly by ion milling into the surface plasmon-based waveguides of pre-characterized QCLs. The initial multi-mode emission is suppressed in favour of electronically controlled, discretely tunable single-mode lasing spanning over 160 GHz. Side-mode suppression ratios of over 20 dB are also demonstrated in these tunable THz LCGH-QCLs.