Sub-Terahertz Monochromatic Transduction with Semiconductor Acoustic Nanodevices

TL;DR

This paper demonstrates that semiconductor superlattices and nanocavities can serve as narrow-band, monochromatic acoustic transducers in the sub-terahertz range, enabling spectrally selective generation and detection of coherent phonons.

Contribution

It introduces semiconductor nanostructures as effective narrow-band acoustic transducers and detectors in the sub-terahertz range, with fully decoupled generation and detection processes.

Findings

Spectrally narrow wavepackets of coherent phonons generated near zone center.

Nanostructured semiconductor devices act as sensitive, spectrally selective detectors.

Generation and detection processes are fully decoupled in the experimental setup.

Abstract

We demonstrate semiconductor superlattices or nanocavities as narrow band acoustic transducers in the sub-terahertz range. Using picosecond ultrasonics experiments in the transmission geometry with pump and probe incident on opposite sides of the thick substrate, phonon generation and detection processes are fully decoupled. Generating with the semiconductor device and probing on the metal, we show that both superlattices and nanocavities generate spectrally narrow wavepackets of coherent phonons with frequencies in the vicinity of the zone center and time durations in the nanosecond range, qualitatively different from picosecond broadband pulses usually involved in picosecond acoustics with metal generators. Generating in the metal and probing on the nanoacoustic device, we furthermore evidence that both nanostructured semiconductor devices may be used as very sensitive and spectrally selective detectors.