Quantized Microcavity Polariton Lasing Based on InGaN Localized Excitons.

Exciton-polaritons, which are bosonic quasiparticles with an extremely low mass, play a key role in understanding macroscopic quantum effects related to Bose-Einstein condensation (BEC) in solid-state systems. The study of trapped polaritons in a potential well provides an ideal platform for manipulating polariton condensates, enabling polariton lasing with specific formation in k-space. Here, we realize quantized microcavity polariton lasing in simple harmonic oscillator (SHO) states based on spatial localized excitons in InGaN/GaN quantum wells (QWs). Benefiting from the high exciton binding energy (90 meV) and large oscillator strength of the localized exciton, room-temperature (RT) polaritons with large Rabi splitting (61 meV) are obtained in a strongly coupled microcavity. The manipulation of polariton condensates is performed through a parabolic potential well created by optical pump control. Under the confinement situation, trapped polaritons are controlled to be distributed in the selected quantized energy sublevels of the SHO state. The maximum energy spacing of 11.3 meV is observed in the SHO sublevels, indicating the robust polariton trapping of the parabolic potential well. Coherent quantized polariton lasing is achieved in the ground state of the SHO state and the coherence property of the lasing is analyzed through the measurements of spatial interference patterns and g(2)(τ). Our results offer a feasible route to explore the manipulation of macroscopic quantum coherent states and to fabricate novel polariton devices towards room-temperature operations.

Aluminum Nitride Ultraviolet Light-Emitting Device Excited via Carbon Nanotube Field-Emission Electron Beam.

With the progress of wide bandgap semiconductors, compact solid-state light-emitting devices for the ultraviolet wavelength region are of considerable technological interest as alternatives to conventional ultraviolet lamps in recent years. Here, the potential of aluminum nitride (AlN) as an ultraviolet luminescent material was studied. An ultraviolet light-emitting device, equipped with a carbon nanotube (CNT) array as the field-emission excitation source and AlN thin film as cathodoluminescent material, was fabricated. In operation, square high-voltage pulses with a 100 Hz repetition frequency and a 10% duty ratio were applied to the anode. The output spectra reveal a dominant ultraviolet emission at 330 nm with a short-wavelength shoulder at 285 nm, which increases with the anode driving voltage. This work has explored the potential of AlN thin film as a cathodoluminescent material and provides a platform for investigating other ultrawide bandgap (UWBG) semiconductors. Furthermore, while using AlN thin film and a carbon nanotube array as electrodes, this ultraviolet cathodoluminescent device can be more compact and versatile than conventional lamps. It is anticipated to be useful in a variety of applications such as photochemistry, biotechnology and optoelectronics devices.

Ultralow-threshold six-photon-excited upconversion lasing in a plasmonic microcavity.

Nonlinear multiphoton absorption (MPA) upconversion lasers have critical applications in fluorescence imaging probes and biological photonics. Here, we report the realization of ultralow-threshold six-photon-excited upconversion lasing through cavity quantum electrodynamics effects in a plasmonic microcavity. The value of the Purcell factor (Fp) in hybrid whisper-gallery mode (WGM) is enhanced five-fold relative to a bare microwire (MW), which enhances the nonlinear light-matter interactions dramatically. Compared with a MW, the threshold of six-photon upconversion WGM lasing is reduced by one order magnitude due to plasmonic enhancement effects. In addition, the temperature and polarization characteristics of upconversion lasing via a plasmonic-WGM approach show a distinct evolution, different from a bare MW. This work paves the way for extreme nonlinear optics, taking advantage of the processability and high Purcell factor of plasmonic microcavities.

Five-photon absorption upconversion lasing from on-chip whispering gallery mode.

In the progress of ultrafast optics, nonlinear interactions between light and matter are very important in scientific and technical fields. In particular, the high-order nonlinear effect induced by multi-photon absorption (MPA) upconversion lasing has injected new impetus into the research on short-wavelength laser sources. Here, we report the realization of amplified spontaneous emission (ASE) by MPA simultaneously in an epitaxy thin film. In addition, by virtue of the excellent optical confinement of cylindrical microcavities with high Q (∼4 × 103) on-chip, we demonstrated, for the first time, low-threshold upconversion lasing of five-photon absorption enhanced by a microcavity at room temperature. The resonant whispering-gallery mode (WGM) distribution in cylindrical microcavities was simulated comprehensively by the finite difference time domain (FDTD) method. We found that the high-order nonlinear optical process could be significantly enhanced in the microcavity with an increase in the lifetime of radiation photons.