Longitudinal Optical Phonon Resonant THz – Mid Infrared Radiation From Surface Metal-Semiconductor Microstructures

THz-mid infrared electric-dipole radiation resonating with longitudinal optical (LO) phonon energy is obtained from metal-semiconductor surface microstructures by heating samples for various types of semiconductors. The structures using undoped GaAs yield emission peaked at 8.5 THz. The emission properties depending on structural parameters are consistent to the electric dipole properties. The emission from n
⁺
-GaP resonates with the LO phonon, which indicates the feasibility of THz emission by optical excitation using indirect electronic transition type materials. The emission from undoped and p-type doped Ga
_0.5
In
_0.5
P presents two peaks, which indicates the feasibility of electromagnetically induced transparency at an emission energy toward optical gain.