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- 摘要
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On loss compensation, amplification and lasing in metallic metamaterials
摘要： The design of metamaterials, which are artificial materials that can offer unique electromagnetic properties, is based on the excitation of strong resonant modes. Unfortunately, material absorption—mainly due to their metallic parts—can damp their resonances and hinder their operation. Incorporating a gain material can balance these losses, but this must be performed properly, as a reduced or even eliminated absorption does not guarantee loss compensation. Here we examine the possible regimes of interaction of a gain material with a passive metamaterial and show that background amplification and loss compensation are two extreme opposites, both of which can lead to lasing.
关键词： loss compensation,split-ring resonator,active media,lasing,nanophotonics,Metamaterials
更新于2025-09-23 15:22:29
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Photonics of boron(III) and zinc(II) dipyrromethenates as active media for modern optical devices
摘要： Photonics of complexes of p- and d-elements with dipyrromethenates is investigated. The role of substituents (their type and localization in the ligand) and of the medium in which dipyrromethenates are placed (solvents, gas mixtures, or solid matrices) is discussed as well as the effect of complexing agents on photonics of the examined complexes. The possibilities for dipyrromethenates application as liquid and solid state laser active media, sensor media for determining the oxygen concentration in a gas mixture, and photosensitizers for singlet oxygen generation in optical devices are presented.
关键词： Photochemistry,Dipyrromethenates,Sensorics,Photophysics,Lasing,Photosensitization
更新于2025-09-23 15:22:29
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Observation of stimulated emission from Rhodamine 6G-polymer aggregate adsorbed at foam interfaces
摘要： This paper reports for the first time the observation of stimulated emissions from the gas–liquid interface between two adjacent bubbles in highly ordered foams containing Rhodamine 6 G and surfactant. Stimulated emissions centred at 595 nm were observed when a monolayer of foam (～liquid fraction 0.11), placed on a highly reflective surface, was pumped with a 532 nm continuous wave laser directed along ～45° from the direction perpendicular to the substrate. Additionally, using confocal microscopy and micro-photoluminescence, it was found that the liquid fraction of the foam, the gap between two adjacent bubbles and the incidence angle of the laser are important parameters in guiding the light and promoting stimulated emissions at the interface. The adsorption of the polymer and dye increased the local concentration at the narrowest gaps between pairs of bubbles, which led to the formation of hemispherical micelles-dye agglomerates. The presence of the micelles aggregation caused random scattering induced stimulated emission. These results could have a significant impact on a number of applications, such as photocatalytic conversion at bubble interfaces, where TiO2 can scatter light and hence reaction rates may be increased.
关键词： photocatalysis,Stimulated emission,interface,lasing,microbubbles,foam
更新于2025-09-23 15:22:29
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2nd-order random lasing in a multimode diode-pumped graded-index fiber
摘要： Raman lasing in a graded-index fiber (GIF) attracts now great deal of attention due to the opportunity to convert high-power multimode laser diode radiation into the Stokes wave with beam quality improvement based on the Raman clean-up effect. Here we report on the cascaded Raman generation of the 2nd Stokes order in the 1.1-km long GIF with 100-μm core directly pumped by 915-nm diodes. In the studied all-fiber scheme, the 1st Stokes order is generated at 950–954 nm in a linear cavity formed at GIF ends by two fiber Bragg gratings (FBGs) securing beam quality improvement from M2 ≈ 30 to M2 ≈ 2.3 due to special transverse structure of FBGs. The 2nd Stokes wave is generated either in linear (two FBGs) or half-open (one FBG) cavity with random distributed feedback via Rayleigh backscattering. Their comparison shows that the random lasing provides better beam quality and higher slope efficiency. Nearly diffraction limited beam (M2 ≈ 1.6) with power up to 27 W at maximum gain (996 nm), and 17 W at the detuned wavelength of 978 nm has been obtained, thus demonstrating that the 2nd-order random lasing in diode-pumped GIF with FBGs provides high-efficiency high-quality beam generation in a broad wavelength range within the Raman gain spectral profile.
关键词： laser diode,fiber Bragg gratings,beam quality,graded-index fiber,Raman lasing,random distributed feedback
更新于2025-09-23 15:21:21
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Plasma effects on lasing of a uniform ultralight axion condensate
摘要： Lasing of an ultralight axion condensate into photons can be sensitive to the presence of a background plasma owing to its coupling to electromagnetism. Such a scenario is particularly relevant for a superradiant axion condensate around stellar mass black holes since the axion mass can be within a few orders of magnitude of the plasma frequency of the surrounding medium. In this paper, I discuss the properties of the plasma around a black hole and analyze its effects on the lasing of a uniform axion condensate of mass of the order of the plasma frequency.
关键词： superradiance,lasing,black holes,axion condensate,plasma effects
更新于2025-09-23 15:21:21
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Switchable Multi-Color Solution-Processed QD-laser
摘要： In this paper, for the first time, the switchable two-color quantum dot laser has been realized considering solution process technology, which has both simultaneous and lonely lasing capability exploiting selective energy contacts. furthermore, both channels can be modulated independently, which is a significant feature in high-speed data transmission. To this end, utilizing superimposed quantum dots with various radii in the active layer provides the different emission wavelengths. In order to achieve the different sizes of QDs, solution process technology has been used as a cost-effectiveness and fabrication ease method. Moreover, at the introduced structure to accomplish the idea, the quantum wells are used as separate selective energy contacts to control the lasing channels at the desired wavelength. It makes the prominent device have simultaneous lasing at different emission wavelengths or be able to lase just at one wavelength. the performance of the proposed device has been modeled based on developed rate equation by assuming inhomogeneous broadening of energy levels as a consequence of the size distribution of quantum dots and considering tunnel injection of carriers into the quantum dots via selective energy contacts. Based on simulation results, the simultaneous lasing in both or at one of two wavelengths 1.31 μm and 1.55 μm has been realized by the superimposition of two different sizes of InGaAs quantum dots in a single cavity and accomplishment of selective energy contacts. Besides, controlling the quantum dot coverage leads to managing the output power and modulation response at the desired wavelengths. By offering this idea, one more step is actually taken to approach the switchable QD-laser by the simple solution process method.
关键词： solution process technology,high-speed data transmission,multi-wavelength lasing,quantum dot laser,selective energy contacts
更新于2025-09-23 15:21:01
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Planar multifrequency mid-IR microwave-pumped lasers
摘要： The characteristics of planar repetitively pulsed diffusion-cooled HF, DF, HF – DF, Xe, and HF – DF – Xe(Kr) lasers pumped by a microwave discharge (2.45 GHz) are studied depending on the pump pulse duration (10 – 40 ms) and repletion rate (50 – 400 Hz), as well as on the composition and pressure of the working gas mixture (30 – 200 Torr) at low (to 0.6 L s–1) gas flow rates. It is demonstrated for the first time that a HF – DF – Xe gas-discharge laser may simultaneously operate as a HF – DF chemical molecular laser and a recombination laser based on xenon atom transitions and generate broadband (octave) radiation in the range 2.0 – 4.2 mm with an average output power of 43 mW and an efficiency of 0.9 %. With substitution of xenon for krypton, lasing in a HF – DF – Kr laser is obtained at wavelengths of 2.52 – 4.15 mm. Lasing in a HF – DF laser was achieved simultaneously in two spectral regions (2.7 – 2.9 and 3.6 – 4.2 mm) with an output power of ~50 mW. It is found that a decrease in the pump pulse duration with a simultaneous increase in the pulse repletion rate for retaining the average energy deposition leads to an increase in the average output power and efficiency of the laser. At low pulse repetition rates (50 – 100 Hz) and a low gas mixture flow rate, helium buffer gas can be effectively substituted for neon. Operation of the Xe laser was achieved in the spectral range 2.03 – 3.65 mm with an average output power of 580 Mw at a pump pulse duration of 20 ms, a pulse repetition rate to 10 kHz, and a maximum efficiency of 55 %. The obtained experimental results demonstrate the possibility of creating broadband HF – DF – Xe lasers emitting in the frequency range 2 – 4 mm with a desired ratio of intensities in different spectral ranges.
关键词： gas discharge,spectral characteristics,planar HF – DF – Xe laser,multifrequency lasing
更新于2025-09-23 15:21:01
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Robust Wavelength-Converting and Lasing Media from Wafer-Scale Inorganic Perovskites Enabled by a Protective Surface Layer
摘要： Despite that the inorganic halide perovskites show great promise in wavelength-conversion and lasing applications, the stability and scalability remain as the obstruction toward practical applications. Herein, we, for the first time, employ the wafer-scale inorganic perovskite single crystals to address the above issue. Our spectroscopic analysis reveals that the carrier trapping on the crystal surface is the most probable culprit to hinder the optical amplification for the weak-penetrating one-photon pumping, whilst, the interior of the crystal preserves intact and show low-threshold stimulated emission by two-photon absorption in the near infrared regime. Thanks to the effective protection from the surface layer, the stimulated emission maintains 90% of the initial intensity upon uninterrupted pumping of 4 hours and shows nearly constant threshold upon long-term storage without any encapsulation (> one year). By exploiting a parallel-mirror cavity, an optically pumped wavelength-converting and laser device featuring a spatially coherent output beam is constructed. Our finding greatly advances the development of practical coherent light sources based on halide perovskites.
关键词： wavelength-conversion,lasing,scalability,two-photon absorption,inorganic halide perovskites,stability,coherent light sources,stimulated emission
更新于2025-09-23 15:21:01
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exposed to an intense laser pulse
摘要： We investigate the role of the rotational excitation in the coherent and unidirectional B 2Σ+u emission of N2+ at 391 nm called air lasing generated when N2 is irradiated with intense femtosecond near-infrared laser pulses at 800 nm. We simulate the time-dependent population transfer process of N2+, which is assumed to be generated suddenly in an intense ultrashort laser pulse, by including vibrational and rotational degrees of freedom, and reveal that, when the light field intensity is below ≈ 4 × 1014 W cm?2, the population inversion can be achieved in N2+ only between rotationally highly excited levels in the vibrational ground (v' = 0) state of the B 2Σ+u state and those in the vibrational ground (v'' = 0) state of the electronic ground X 2Σ+g state, so that the lasing at 391 nm is realized even when the total population in the v' = 0 state of the electronically excited B 2Σ+u state is not inverted with respect to the total population in the v'' = 0 state of the electronic ground X 2Σ+g state.
关键词： air lasing,N2+,rotational excitation,population inversion,femtosecond laser pulses
更新于2025-09-23 15:21:01
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High Circular Polarized Nanolaser with Chiral Gammadion Metal Cavity
摘要： We demonstrate a circularly polarized laser with the metal-gallium-nitride gammadion nanocavities. The ultraviolet lasing signal was observed with the high circular dichroism at room temperature under pulsed optical pump conditions. Without external magnetism which breaks the time-reversal symmetry to favor optical transitions of a chosen handedness, the coherent outputs of these chiral nanolasers show a dissymmetry factor as high as 1.1. The small footprint of these lasers are advantageous for applications related to circularly polarized photons in future integrated systems, in contrast to the bulky setup of linearly-polarized lasers and quarter-wave plates.
关键词： ultraviolet lasing,gammadion nanocavities,circular dichroism,chiral nanolasers,circularly polarized laser
更新于2025-09-23 15:21:01