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Register a new userWhispering-gallery-mode based CH3NH3PbBr3 perovskite microrod lasers with high quality factors
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Lead halide perovskite based micro- and nano- lasers have been widely studied in past two years. Due to their long carrier diffusion length and high external quantum efficiency, lead halide perovskites have been considered to have bright future in optoelectronic devices, especially in the green gap wavelength region. However, the quality (Q) factors of perovskite lasers are unspectacular compared to conventional microdisk lasers. The record value of full width at half maximum (FWHM) at threshold is still around 0.22 nm. Herein we synthesized solution-processed, single-crystalline CH3NH3PbBr3 perovskite microrods and studied their lasing actions. In contrast to entirely pumping a microrod on substrate, we partially excited the microrods that were hanging in the air. Consequently, single-mode or few-mode laser emissions have been successfully obtained from the whispering-gallery like diamond modes, which are confined by total internal reflection within the transverse plane. Owning to the better light confinement and high crystal quality, the FWHM at threshold have been significantly improved. The smallest FWHM at threshold is around 0.1 nm, giving a Q factor over 5000.
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Whispering gallery mode biosensors allow selective unlabelled detection of single proteins and, combined with quantum limited sensitivity, the possibility for noninvasive realtime observation of motor molecule motion. However, to date technical noise sources, most particularly low frequency laser noise, have constrained such applications. Here we introduce a new technique for whispering gallery mode sensing based on direct detection of back-scattered light. This experimentally straightforward technique is immune to frequency noise in principle, and further, acts to suppress thermorefractive noise. We demonstrate 27 dB of frequency noise suppression, eliminating frequency noise as a source of sensitivity degradation and allowing an absolute frequency shift sensitivity of 76 kHz. Our results open a new pathway towards single molecule biophysics experiments and ultrasensitive biosensors.
Whispering gallery mode (WGM) resonators are compelling optical devices, however they are nearly unexplored in the terahertz (THz) domain. In this letter, we report on THz WGMs in quartz glass bubble resonators with sub-wavelength wall thickness. An unprecedented study of both the amplitude and phase of THz WGMs is presented. The coherent THz frequency domain measurements are in excellent agreement with a simple analytical model and results from numerical simulations. A high finesse of 9 and a quality (Q) factor exceeding 440 at 0.47 THz are observed. Due to the large evanescent field the high Q-factor THz WGM bubble resonators can be used as a compact, highly sensitive sensor in the intriguing THz frequency range.
Whispering gallery mode (WGM) microresonators, benefitting from the ultrahigh quality (Q) factors and small mode volumes, could considerably enhance the light-matter interaction, making it an ideal platform for studying a broad range of nonlinear optical effects. In this review, the progress of optical nonlinear effects in WGM microresonators is comprehensively summarized. First, several basic nonlinear effects in WGM microresonator are reviewed, including not only Pockels effect and Kerr effect, but also harmonic generations, four-wave mixing and stimulated optical scattering effects. Apart from that, nonlinearity induced by thermal effect and in PT-symmetric systems are also discussed. Furthermore, multistep nonlinear optical effects by cascading several nonlinear effects are reviewed, including frequency comb generations. Several selected applications of optical nonlinearity in WGM resonators are finally introduced, such as narrow-linewidth microlasers, nonlinearity induced non-reciprocity and frequency combs.
Highly prolate-shaped whispering-gallery-mode bottle microresonators have recently attracted considerable attention due to their advantageous properties. We experimentally show that such resonators offer ultra-high quality factors, microscopic mode volumes, and near lossless in- and out-coupling of light using ultra-thin optical fibers. Additionally, bottle microresonators have a simple and customizable mode structure. This enables full tunability using mechanical strain and simultaneous coupling of two ultra-thin coupling fibers in an add-drop configuration. We present two applications based on these characteristics: In a cavity quantum electrodynamics experiment, we actively stabilize the frequency of the bottle microresonator to an atomic transition and operate it in an ultra-high vacuum environment in order to couple single laser-cooled atoms to the resonator mode. In a second experiment, we show that the bottle microresonator can be used as a low-loss, narrow-band add-drop filter. Using the Kerr effect of the silica resonator material, we furthermore demonstrate that this device can be used for single-wavelength all-optical signal processing.
Ultrahigh repetition rate lasers will become vital light sources for many future technologies; however, their realization is challenging because the cavity size must be minimized. Whispering-gallery-mode (WGM) microresonators are attractive for this purpose since they allow the strong light-matter interaction usually needed to enable mode-locking. However, the optimum parameter ranges are entirely unknown since no experiments have yet been conducted. Here, we numerically investigate pulsed operation in a toroidal WGM microresonator with gain and saturable absorption (SA) to study the experimental feasibility. We show that dispersion is the key parameter for achieving passive mode-locking in this system. Moreover, the design guideline provided in this work can apply to any small resonators with gain and SA and is not limited to a specific cavity system.
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