Terahertz resonant emission by optically excited infrared-active shear phonons in KY(MoO4)2

TL;DR

This paper demonstrates the generation of monochromatic sub-THz radiation through coherent infrared-active shear phonons in KY(MoO4)2, offering a new approach for THz sources with long coherence times and potential laser applications.

Contribution

The study introduces a novel method of generating narrow-band sub-THz radiation using coherent optical phonons in KY(MoO4)2, a dielectric material with infrared-active shear lattice vibrations.

Findings

Emission of narrow-band sub-THz radiation at 568 and 860 GHz.

Decay time of emitted radiation is 33 picoseconds, allowing detection of over 50 oscillation periods.

Material's chemical stability suggests potential for THz laser technology.

Abstract

Generation of the monochromatic electromagnetic radiation in the terahertz (THz) range of frequencies for many decades remanes a chellenging task. Here we demonstrate the emission of monochromatic sub-THz radiation by coherent optical phonons in dielectric material KY(MoO4)2. The layered crystal structure of KY(MoO4)2 leads to infrared-active shear lattice vibrations with energies below 3.7 meV, which corresponds to the frequencies low than 900 GHz where solid-state compounds based monochromatic radiation sources are rare. Coherent infrared-active optical phonons are excited by broadband THz pulses lasting for tens of picoseconds and re-emit narrow-band subTHz radiation pulses with a decay time of 33 picoseconds, which is exceptionally long for the oscillators with frequencies below 1 THz. Such a long coherent emission allows for the detection of more than 50 periods of radiation with frequencies of 568 and 860 GHz. The remarkably long decay time together with the chemical stability of the employed materials suggest a variety of possible applications in THz laser technology.