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Monte-Carlo simulations of superradiant lasing
摘要： We simulate the superradiant dynamics of ensembles of atoms in the presence of collective and individual atomic decay processes. We apply the Monte-Carlo wave-function method and identify quantum jumps in a reduced Dicke state basis, which reflects the permutation symmetry of the system. While the number of density matrix elements in the Dicke representation increases polynomially with atom number, the quantum jump dynamics populates only a single Dicke state at the time and thus efficient simulations can be carried out for tens of thousands of atoms. The superradiant pulses from initially excited atoms agree quantitatively with recent experimental results of strontium atoms but rapid atom loss in these experiments does not permit steady-state superradiance. By introducing an incident flux of new atoms to maintain a large average atom number, our theoretical calculations predict lasing with a millihertz linewidth despite rapid atom number fluctuations.
关键词： quantum jumps,lasing,superradiance
更新于2025-09-09 09:28:46
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Applied Nanophotonics || Stimulated emission and lasing
摘要： Stimulated transitions in quantum systems represent the principal background for laser operation. Lasers play important roles in daily life and form a valuable part of photonics. Though the first lasers were supposed to have an impact on material processing owing to extreme energy concentration, currently the main applications of lasers are not based on high-energy abilities, but essentially on their compactness, cheapness, and efficiency. Optical communication, laser printers, and DVD players are the most common laser applications, and here semiconductor lasers are definitely unsurpassed. In this chapter we provide a brief introduction to the principles of laser operation and laser device engineering to emphasize where nanostructures can be useful and which components of lasers can be improved by means of nanophotonic solutions. Because of the scope of this book, a brief explanatory style is used which may confuse laser experts but at the same time may still appear complicated for newcomers. This chapter may appear complicated for readers not at all familiar with lasers, and in this case appropriate textbooks are suggested for further reading.
关键词： quantum systems,lasing,stimulated emission,optical gain,semiconductor lasers
更新于2025-09-09 09:28:46
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UV Luminescence and Lasing in Ensembles of Zinc-Oxide Microcrystals with Copper
摘要： Microrod arrays of zinc oxide with copper have been grown by chemical vapor deposition on single-crystal sapphire substrates preliminarily covered with a nanoscale copper layer. The presence of copper (about 0.3%) in zinc-oxide microrods has been experimentally shown to increase the photoluminescence intensity of the ZnO microcrystal arrays, reduce the lasing threshold, and lead to a small (by ~2.5 nm) blue shift of the radiation intensity peak of the ZnO microcrystals. It is shown that the laser-radiation character depends on the morphology of the ZnO microrod arrays.
关键词： lasing,zinc-oxide microcrystals,UV luminescence,copper doping,chemical vapor deposition
更新于2025-09-09 09:28:46
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Lasing in optimized two-dimensional iron-nail-shaped rod photonic crystals
摘要： We demonstrated lasing at the Γ-point band-edge (BE) modes in optimized two-dimensional iron-nail-shaped rod photonic crystals by optical pulse pumping at room temperature. As the radius of the rod increased quadratically toward the edge of the pattern, the quality factor of the Γ-point BE mode increased up to three times, and the modal volume decreased to 56% compared with the values of the original Γ-point BE mode because of the reduction of the optical loss in the horizontal direction. Single-mode lasing from an optimized iron-nail-shaped rod array with an InGaAsP multiple quantum well embedded in the nail heads was observed at a low threshold pump power of 160 μW. Real-image-based numerical simulations showed that the lasing actions originated from the optimized Γ-point BE mode and agreed well with the measurement results, including the lasing polarization, wavelength, and near-field image.
关键词： optical pulse pumping,photonic crystals,iron-nail-shaped rod,lasing,band-edge modes
更新于2025-09-04 15:30:14
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Dynamic regulating of single-mode lasing in ZnO microcavity by piezoelectric effect
摘要： Realizing single-mode-lasing output while being able to dynamically select and regulate a specified resonant mode could bring revolutionary impact for laser technology, on-chip data communication, and optical sensing/switches. Here, we demonstrate a single-mode lasing achieved by the piezoresistive and piezoelectric polarization synergistic effect on an epoxy-encapsulated ZnO microresonator. Based on relative shifts of gain spectrum and the resonant wavelength, the lasing mode in a hexagonal ZnO rod can be selected and regulated dynamically within a certain range. The relationship between the corresponding applied strain and the tunable refractive index is analyzed in depth and discussed systematically. Our studies open up exciting avenues for constructing optical mode-phase modulator, high-sensitive optical switches and color-perceived optical sensing.
关键词： optical sensing,ZnO microresonator,single-mode lasing,piezoelectric effect,dynamic regulation
更新于2025-09-04 15:30:14