Synopsis: A More Practical Polariton Laser

A new polariton laser is electrically powered and operates at room temperatures, making it more useful for optical electronic application than previous designs.
Synopsis figure
Thomas Frost/University of Michigan

Polariton lasers are more efficient than conventional lasers because they work through spontaneous rather than stimulated emission. In a step towards making these devices more practical, researchers announce in Physical Review Letters the first electrically powered, room-temperature polariton laser. This development may eventually lead to low-power polariton lasers being used as optical switches or compact terahertz radiation sources.

A polariton is a quasiparticle that results from a coupling between a photon and an electron-hole pair (an “exciton”) in a semiconductor material. In 1996, researchers realized that—under certain conditions—polaritons will condense into a single quantum state, from which they will spontaneously emit coherent, monochromatic light (i.e., laser light). In contrast to stimulated lasing, the polariton emitters do not need to be constantly pumped up into excited states (so-called population inversion). As a consequence, polariton lasers begin lasing at a relatively low threshold power.

Experimental realizations of polariton lasers have so far required either low temperatures or a pump laser to create the initial polaritons. Pallab Bhattacharya and his colleagues at the University of Michigan, Ann Arbor, have developed a laser that works at room temperature and is powered by electricity. The device consists of a thin strip of gallium nitride (GaN) semiconductor, sandwiched between stacks of metal oxide mirrors. When electric current enters such a microcavity, it can generate polaritons. But unlike previous designs in which electricity passed through or around the high-resistance mirrors, the team injects current orthogonally to the microcavity’s emitting direction, thus avoiding overheating the device and destroying the lasing. The researchers observed laser light emission at a threshold current density of 169 amps per centimeter squared, which is almost a factor of 100 less than for conventional GaN-based lasers. – Michael Schirber


More Announcements »

Subject Areas

Semiconductor PhysicsOptoelectronics

Previous Synopsis

Biological Physics

Modeling Biodiversity

Read More »

Next Synopsis


Sorting by Sound

Read More »

Related Articles

Viewpoint: Where the Weyl Things Are

Viewpoint: Where the Weyl Things Are

Analogs to massless fermions predicted by particle physicists 80 years ago have been found in a crystalline metal and in a photonic crystal. Read More »

Synopsis: Good Vibrations
Quantum Information

Synopsis: Good Vibrations

With the assistance of lattice vibrations, quantum dots perform as single-photon emitters. Read More »

Focus: <i>Landmarks</i>—Accidental Discovery Leads to Calibration Standard
Semiconductor Physics

Focus: Landmarks—Accidental Discovery Leads to Calibration Standard

The quantum Hall effect, discovered unexpectedly 35 years ago, is now the basis for defining the unit of electrical resistance. Read More »

More Articles