テラへルッ帯量子力スケードレーザーの現状と将来

摘要

Terahertz (THz) imaging and sensing are powerful techniques that exploit a nonionizing (i.e., safe) portion of the electromagnetic spectrum located between microwaves and infra-red. Because of their nondestructive nature, THz imaging and sensing are applicable to many areas. For example, they have advantages over x-rays for the diagnosis of skin cancer and can detect sketches under paintings. However, in the THz frequencies, the fundamental device technology, which includes the semiconductor emitter, amplifier, modulator, focal plane array detector, and optical thin film, has not yet been fully established. Therefore, a measurement system in the THz range remains a costly alternative. Among several emitter technologies, THz quantum cascade laser (THz-QCL) technology is considered the most promising candidate for a compact and powerful emitter working from 1.5 to 5.0 THz. In this review paper, we report the recent developments of THz-QCLs in both device technology and theoretical simulations.