Spherical cavity-mode laser with self-organized CuCl microspheres.

Area of Science:

• Condensed matter physics
• Quantum optics
• Materials science

Background:

• Exciton-polaritons are quasiparticles formed from the strong coupling of excitons and photons.
• Semiconductor microcavities offer a promising platform for observing quantum phenomena like Bose-Einstein condensation and lasing.
• Achieving lasing in microstructures requires efficient light confinement and high-gain materials.

Purpose of the Study:

• To investigate the potential of semiconductor microspheres for exciton-polariton lasing.
• To determine the lasing threshold and identify the underlying optical transition.
• To explore the use of copper chloride (CuCl) as a material for microcavity exciton-polariton devices.

Main Methods:

• Fabrication of CuCl microspheres with controlled diameters (micrometer scale) via melting bulk crystals.
• Excitation of microspheres using subpicosecond ultraviolet laser pulses at low temperatures.
• Analysis of emission spectra to identify lasing characteristics and spectral features.

Main Results:

• Successful demonstration of exciton-polariton lasing in CuCl microspheres utilizing spherical cavity modes.
• Observation of a low lasing threshold of 1 nJ/pulse, equivalent to 10^9 photons/pulse.
• Identification of the biexciton-to-longitudinal-exciton transition as the primary mechanism responsible for the observed lasing.

Conclusions:

• Semiconductor microspheres are viable microcavities for achieving exciton-polariton lasing.
• The biexciton-to-longitudinal-exciton transition provides an efficient pathway for polariton lasing in CuCl.
• These findings pave the way for developing novel optoelectronic devices based on polaritonics.