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Single-mode large-mode-area Er–Yb fibers with core based on phosphorosilicate glass highly doped with fluorine
摘要： Single-mode Er–Yb fibers with the core based on a phosphorosilicate glass matrix (up to 6.5 mol.% P2O5) highly doped with fluorine (up to 0.9 wt.%) were fabricated using an all-gas-phase modified chemical vapor deposition method. The core numerical aperture was in the range of 0.07–0.08 relative to the pure silica, which allowed us to increase the single-mode core diameter up to 20 μm. The slope efficiency in lasers based on the fabricated fibers reached 34% relative to the launched pump power.
关键词： fiber lasers,optical fibers,erbium–ytterbium fibers,erbium-doped fiber amplifiers
更新于2025-09-23 15:22:29
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Aperiodic order induced enhancement of weak nonlocality in multilayered dielectric metamaterials
摘要： Recent studies on fully dielectric multilayered metamaterials have shown that the negligibly small nonlocal effects (spatial dispersion) typically observed in the limit of deeply subwavelength layers may be significantly enhanced by peculiar boundary effects occurring in certain critical parameter regimes. These phenomena, observed so far in periodic and randomly disordered geometries, are manifested as strong differences between the exact optical response of finite-size metamaterial samples and the prediction from conventional effective-theory-medium models based on mixing formulas. Here, with specific focus on the Thue-Morse geometry, we make a first step toward extending the studies above to the middle ground of aperiodically ordered multilayers, lying in between perfect periodicity and disorder. We show that, also for these geometries, there exist critical parameter ranges that favor the buildup of boundary effects leading to strong enhancement of the (otherwise negligibly weak) nonlocality. However, the underlying mechanisms are fundamentally different from those observed in the periodic case and exhibit typical footprints (e.g., fractal gaps, quasilocalized states) that are distinctive of aperiodic order. The outcomes of our study indicate that aperiodic order plays a key role in the buildup of the aforementioned boundary effects and may also find potential applications to optical sensors, absorbers, and lasers.
关键词： absorbers,optical sensors,lasers,Thue-Morse geometry,aperiodic order,multilayered dielectric metamaterials,nonlocality
更新于2025-09-23 15:21:21
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Picosecond-Range Avalanche Switching of Bulk Semiconductors Triggered by Steep High-Voltage Pulses
摘要： Experimental observation and numerical simulations of sub-nanosecond avalanche switching of Si and ZnSe bulk semiconductor structures initiated by high-voltage pulses with steep (dU/dt > 10 kV/ns) ramp are reported. The measured switching time is ～100 ps. The switching is sustainable and repetitive and has negligible jitter. Comparison of the experimental and numerical results suggests that after switching, the whole volume of the structure is uniformly ?lled with nonequilibrium electron–hole plasma.
关键词： semiconductor lasers,Power electronics,pulse-power system switches
更新于2025-09-23 15:21:21
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Frequency shift of an optical frequency standard as a function of probe modulation of the radiation frequency, pressure, and gas temperature in an absorbing cell
摘要： Frequency shifts of an optical Nd : YAG/I2-standard are measured in a pressure range of molecular iodine 5 – 22 mTorr and deviation of probe modulation frequency 480 kHz – 4 MHz for the hyperfine structure component a1 of the molecular iodine absorption line R(56) 32 – 0. The frequency shift of the optical standard is estimated under varied temperatures of a cell and cell finger, which determines the pressure of the molecular iodine vapour. The requirements are defined to temperature stability of the cell and its finger for obtaining high long-term frequency stability of the optical frequency standard.
关键词： molecular iodine,optical frequency standards,saturation absorption spectroscopy,acousto-optical modulator,lasers,luminescence
更新于2025-09-23 15:21:21
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High Speed Directly Modulated Fabry-Perot Lasers with an Ultra-Short Cavity Length
摘要： In this study, Fabry-Perot quantum well lasers with shortened cavity designs (25 and 50 μm) were fabricated. The devices had dry-etched and cleaved facets that exhibited an output power of up to 2.36 mW for a cavity length of 25 μm; good spectral performance was achieved. Single-optical-mode operation with better than 25dB of side mode suppression ratio can be achieved for the fabricated devices with 25- and 50-μm cavities. The short-cavity devices also exhibited high-speed modulation at elevated temperatures. Moreover, 25 Gb/s eye diagrams could be obtained at 65oC for the 25 μm device and 55oC for the 50 μm device. Due to their small area, ultra-short-cavity Fabry-Perot laser can be suitably used in next-generation light sources for optical communication.
关键词： Optical device fabrication,Semiconductor lasers,Laser cavity resonators,Amplitude modulation,Diode lasers,Quantum well lasers,Laser modes
更新于2025-09-23 15:21:01
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Optimization of Transmitter-Side Signal Rotations in the Presence of Laser Phase Noise
摘要： In this paper, we present a 1050-nm electrically pumped microelectromechanically tunable vertical cavity surface-emitting laser (MEMS-VCSEL) with a record dynamic tuning bandwidth of 63.8 nm, suitable for swept-source optical coherence tomography (SS-OCT) imaging. These devices provide reduced cost and complexity relative to previously demonstrated optically pumped devices by obviating the need for a pump laser and associated hardware. We demonstrate ophthalmic SS-OCT imaging with the electrically-pumped MEMS-VCSEL at a 400 kHz axial scan rate for wide-field imaging of the in vivo human retina over a 12 mm × 12 mm field and for OCT angiography of the macula over 6 mm × 6 mm and 3 mm × 3 mm fields to show retinal vasculature and capillary structure near the fovea. These results demonstrate the feasibility of electrically pumped MEMS-VCSELs in ophthalmic instrumentation, the largest clinical application of OCT. In addition, we estimate that the 3 dB coherence length in air is 225 ± 51 m, far greater than required for ophthalmic SS-OCT and suggestive of other distance ranging applications.
关键词： Medical imaging,tunable lasers,optical coherence tomography,micro and nano opto-electromechanical systems (MOEMS),semiconductor lasers
更新于2025-09-23 15:21:01
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Vertically coupled InP/InGaAsP microring lasers using a single epitaxial growth and single-side lithography
摘要： The experimental demonstration of vertical microring lasers requiring only one single epitaxial growth and two single-side lithographic steps is presented, in what is the simplest fabrication scheme for such devices published to date. The fabricated lasers show series resistance of around 20 Ω at forward bias, threshold currents at room temperature between 35 and 58 mA, and single-mode emission with a side-lobe suppression ratio higher than 30 dB. The measured optic output power level is of tens of microwatts. The approach allows the improvement of the optical features maintaining the simplicity of the manufacturing procedure.
关键词： semiconductor lasers,semiconductor waveguides,Integrated optics,ring lasers
更新于2025-09-23 15:21:01
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Explosion induced rogue waves and chaotic multi-pulsing in a passively mode-locked all-normal dispersion fiber laser
摘要： In this work, an experimental study of non-stationary pulse dynamics consisting of explosion events and chaotic multi-pulsing from an all-normal dispersion Yb-fiber laser operating in noise-like pulse (NLP) state have been reported. During explosion in NLP state, which resembled soliton explosion, dispersive Fourier transform measurements revealed large, intermittent amplitude fluctuations in the real-time spectrum indicative of rogue waves. The fluctuations either appeared randomly at the lasing wavelength within the Yb-gain spectra or at the frequency downshifted Raman Stokes wavelength. It was also observed that such fluctuation at the Raman wavelength could even exceed the amplitude of the spectral components at the main lasing wavelength. With suitable adjustments, the laser operation could be switched to chaotic multi-pulsing state where the acquisition of a large number of consecutive roundtrips revealed inter-pulse motion with unique trajectories occurring over millisecond time scales.
关键词： optical rogue waves,multi-pulsing,non-stationary pulse dynamics,noise-like pulse,fiber lasers,mode-locked fiber lasers,non-linear dynamics
更新于2025-09-23 15:21:01
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The laser beamline in SULF facility
摘要： In this paper, we report the recent progress on the 1 PW/0.1 Hz laser beamline of Shanghai Superintense Ultrafast Laser Facility (SULF). The SULF-1 PW laser beamline is based on the double chirped pulse ampli?cation (CPA) scheme, which can generate laser pulses of 50.8 J at 0.1 Hz after the ?nal ampli?er; the shot-to-shot energy ?uctuation of the ampli?ed pulse is as low as 1.2% (std). After compression, the pulse duration of 29.6 fs is achieved, which can support a maximal peak power of 1 PW. The contrast ratio at ?80 ps before main pulse is measured to be 2.5 × 10?11. The focused peak intensity is improved by optimizing the angular dispersion in the grating compressor. The maximal focused peak intensity can reach 2.7 × 1019 W/cm2 even with an f /26.5 off-axis parabolic mirror. The horizontal and vertical angular pointing ?uctuations in 1 h are measured to be 1.89 and 2.45 μrad, respectively. The moderate repetition rate and the good stability are desirable characteristics for laser–matter interactions. The SULF-1 PW laser beamline is now in the phase of commissioning, and preliminary experiments of particle acceleration and secondary radiation under 300–400 TW/0.1 Hz laser condition have been implemented. The progress on the experiments and the daily stable operation of the laser demonstrate the availability of the SULF-1 PW beamline.
关键词： lasers,ultrafast lasers,titanium,laser ampli?ers
更新于2025-09-23 15:21:01
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Advances in Mid-Infrared Spectroscopy-Based Sensing Techniques for Exhaled Breath Diagnostics
摘要： Human exhaled breath consists of more than 3000 volatile organic compounds, many of which are relevant biomarkers for various diseases. Although gas chromatography has been the gold standard for volatile organic compound (VOC) detection in exhaled breath, recent developments in mid-infrared (MIR) laser spectroscopy have led to the promise of compact point-of-care (POC) optical instruments enabling even single breath diagnostics. In this review, we discuss the evolution of MIR sensing technologies with a special focus on photoacoustic spectroscopy, and its application in exhaled breath biomarker detection. While mid-infrared point-of-care instrumentation promises high sensitivity and inherent molecular selectivity, the lack of standardization of the various techniques has to be overcome for translating these techniques into more widespread real-time clinical use.
关键词： point-of-care (POC),infrared lasers,MIR,photoacoustic spectroscopy,biomarkers,exhaled breath analysis,non-invasive diagnostics,QCL,quantum cascade lasers,mid-infrared
更新于2025-09-23 15:21:01