Towards simultaneous coherent radiation in the visible and microwave bands with doped molecular crystals

TL;DR

This paper demonstrates a novel solid-state method for simultaneous coherent radiation in visible and microwave bands using doped molecular crystals, enabling multiband lasing and masing at ambient conditions.

Contribution

It introduces a mechanism for concurrent stimulated emission in visible and microwave frequencies using pentacene-doped p-terphenyl, validated by experimental ASE and masing observations.

Findings

Observed amplified spontaneous emission at 645 nm with narrow linewidth

Achieved masing at 1.45 GHz with lower ASE threshold

Potential for optimizing multiband coherent sources through polarization control

Abstract

Coherent sources exploiting the stimulated emission of non-equilibrium quantum systems, i.e. gain media, have proven indispensable for advancing fundamental research and engineering. The operating electromagnetic bands of such coherent sources have been continuously enriched for increasing demands.Nevertheless, for a single bench top coherent source, simultaneous generation of radiation in multiple bands, especially when the bands are widely separated, present formidable challenges with a single gain medium. Here, we propose a mechanism of simultaneously realizing the stimulated emission of radiation in the visible and microwave bands, i.e. lasing and masing actions, at ambient conditions by utilizing photoexcited singlet and triplet states of the pentacene molecules that are doped in p-terphenyl. The possibility is validated by the observed amplified spontaneous emission (ASE) at 645 nm with a narrow linewidth around 1 nm from the pentacene-doped p-terphenyl crystal used for masing at 1.45 GHz and consolidated by a 20 fold lower threshold of ASE compared to the reported masing threshold. The overall threshold of the pentacene-based multiband coherent source can be optimized by appropriate alignment of the pump-light polarization with the pentacene's transition dipole moment. Our work not only shows a great promise on immediate realization of multiband coherent sources but also establishes an intriguing solid-state platform for fundamental research of quantum optics in multiple frequency domains.