Quantum laser turns energy loss into gain?

Date:
July 7, 2021
Source:
The Korea Advanced Institute of Science and Technology (KAIST)
Summary:
Scientists have fabricated a laser system that generates highly
interactive quantum particles at room temperature. Their findings
could lead to a single microcavity laser system that requires
lower threshold energy as its energy loss increases.



FULL STORY ========================================================================== Scientists at KAIST have fabricated a laser system that generates highly interactive quantum particles at room temperature. Their findings,
published in the journal Nature Photonics, could lead to a single
microcavity laser system that requires lower threshold energy as its
energy loss increases.


==========================================================================
The system, developed by KAIST physicist Yong-Hoon Cho and colleagues,
involves shining light through a single hexagonal-shaped microcavity
treated with a loss-modulated silicon nitride substrate. The system
design leads to the generation of a polariton laser at room temperature,
which is exciting because this usually requires cryogenic temperatures.

The researchers found another unique and counter-intuitive feature of
this design. Normally, energy is lost during laser operation. But in
this system, as energy loss increased, the amount of energy needed to
induce lasing decreased.

Exploiting this phenomenon could lead to the development of high
efficiency, low threshold lasers for future quantum optical devices.

"This system applies a concept of quantum physics known as parity-time
reversal symmetry," explains Professor Cho. "This is an important
platform that allows energy loss to be used as gain. It can be used to
reduce laser threshold energy for classical optical devices and sensors,
as well as quantum devices and controlling the direction of light."
The key is the design and materials. The hexagonal microcavity divides
light particles into two different modes: one that passes through the upward-facing triangle of the hexagon and another that passes through
its downward-facing triangle. Both modes of light particles have the
same energy and path but don't interact with each other.

However, the light particles do interact with other particles called
excitons, provided by the hexagonal microcavity, which is made
of semiconductors. This interaction leads to the generation of new
quantum particles called polaritons that then interact with each other
to generate the polariton laser. By controlling the degree of loss
between the microcavity and the semiconductor substrate, an intriguing phenomenon arises, with the threshold energy becoming smaller as energy
loss increases.

This research was supported by the Samsung Science and Technology
Foundation and Korea's National Research Foundation.

========================================================================== Story Source: Materials provided by The_Korea_Advanced_Institute_of_Science_and_Technology_ (KAIST). Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hyun Gyu Song, Minho Choi, Kie Young Woo, Chung Hyun Park,
Yong-Hoon Cho.

Room-temperature polaritonic non-Hermitian system with single
microcavity. Nature Photonics, 2021; DOI: 10.1038/s41566-021-00820-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210707112456.htm

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