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Electromagnetically induced transparency, absorption, and microwave-field sensing in a Rb vapor cell with a three-color all-infrared laser system
摘要： A comprehensive study of three-photon electromagnetically induced transparency (EIT) and absorption (EIA) on the rubidium cascade 5S1/2 → 5P3/2 (laser wavelength 780 nm), 5P3/2 → 5D5/2 (776 nm), and 5D5/2 → 28F7/2 (1260 nm) is performed. The 780-nm probe and 776-nm dressing beams are counteraligned through a Rb room-temperature vapor cell, and the 1260-nm coupler beam is co- or counteraligned with the probe beam. Several cases of EIT and EIA, measured over a range of detunings of the 776-nm beam, are studied. The observed phenomena are modeled by numerically solving the Lindblad equation, and the results are interpreted in terms of the probe-beam absorption behavior of velocity- and detuning-dependent dressed states. Interaction-time effects are discussed. To explore the utility of three-photon Rydberg EIA and EIT for microwave electric-?eld diagnostics, a sub-THz ?eld generated by a signal source and a frequency quadrupler is applied to the Rb cell. The 100.633-GHz ?eld resonantly drives the 28F7/2 ? 29D5/2 transition and causes Autler-Townes splittings in the Rydberg EIA and EIT spectra, which are measured and employed to characterize the performance of the microwave quadrupler.
关键词： Rb vapor cell,absorption,three-color all-infrared laser system,microwave-?eld sensing,electromagnetically induced transparency
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Self-Sweeping Operation of Nd-Doped Fiber Laser
摘要： The self-induced laser frequency sweeping (“self-sweeping” for short) effect in fiber lasers was observed in 2011 [1]. In this case the lasers generate self-sustained pulses and its frequency drifts slowly from pulse to pulse in one direction and jumps back after reaching a border of sweeping region. The self-sweeping operation is based on formation of long-lived dynamical phase and gain gratings. The gratings are connected to modulation of population inversion inside the active medium induced by the field of a standing wave formed in a linear cavity [2]. Dynamical gratings inscribed in the cavity by previously generated longitudinal modes are kept in the active medium for a relatively long time as compared with lifetime of a single mode and affects generation of the next spectral components. Due to broad sweeping range (more than 10 nm) and simplicity, self-sweeping fiber lasers are attractive sources for applications demanding tunable radiation. As a result, the self-sweeping laser is the simplest sort of tunable laser without any tuning elements and electrical drivers for frequency tuning. Currently the self-sweeping operation was observed in almost all common fibers: ytterbium [1-2], bismuth [3], erbium [4], holmium [5] and thulium [6]. It should be noted that the self-sweeping operation has been demonstrated up to now only in quasi-three-level laser systems. In the present paper, we demonstrate for the first time self-sweeping operation in a four-level laser system based on neodymium. The Nd-doped fiber with length of 3 meter is pumped by multi-mode laser diode with wavelength of 805 nm. The cavity is formed by highly-reflective fiber loop mirror and right-angle cleaved fiber end. Two fiber Lyot filters and a 10 nm bandpass filter were used for restriction of sweeping region. The self-induced spectral dynamics is observed in the region of 1.06 μm with range of up to 1.8 nm (Fig.1a). The laser generates periodic pulses (Fig.1b) where each of them contains single longitudinal mode radiation, which is confirmed by heterodyning with single-frequency probe radiation. The laser frequency is changed from pulse to pulse by one intermode beating frequency of the laser ~7.5 MHz. The sweeping rate is increased with pump power up to 10 nm/sec. The output power exceeds 600 mW. Self-sweeping operation for Nd-doped fiber in the new spectral range of 0.93 μm instead of standard 1.06 μm is expected.
关键词： four-level laser system,tunable radiation,fiber laser,Nd-doped,self-sweeping
更新于2025-09-11 14:15:04
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Numerical Study of Amplification of Subnanosecond Radiation Pulses in the Gas Amplifier of the THL-100 Laser System
摘要： Methods for increasing the energy characteristics of the THL-100 hybrid laser system are investigated by numerical modeling. The influence of the input laser radiation energy and system of mirrors on the energy and maximal laser radiation intensity in the amplifier is investigated. The systems of amplifier mirrors in which the number of passes of the active medium changed from Nm = 27 to 39 are considered. It is shown that at Nm =27, an increase in the pump energy of the amplifier from 270 to 400 J allows the output radiation energy to be increased by a factor of 2.6 (to 8.34 J) with a maximal radiation intensity in the amplifier no more than 7 GW?cm–2. Pulse compression to an initial duration of 50 fs will allow the average output power of the THL-100 system to be increased up to 160 TW.
关键词： amplification of subnanosecond pulses,numerical investigation,THL-100 laser system
更新于2025-09-11 14:15:04
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Optical Solitons and Stability Analysis in Ring-Cavity Fiber System with Carbon Nanotube as Saturable Absorber
摘要： This paper addresses the ring-cavity ?ber laser system. A class of gray and black soliton solutions of the model are reported by adopting an appropriate envelope ansatz. Further more, the modulation instability (MI) of the equation is studied using the linear-stability analysis (LSA) technique and the MI gain spectrum is derived. Some physical interpretations and analysis of the results obtained are also presented.
关键词： linear stability analysis,ring-cavity ?ber laser system,optical solitons,complex envelope ansatz solution
更新于2025-09-09 09:28:46
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A hydrophobic ultralow refractive-index silica coating towards double-layer broadband antireflective coating with exceptionally high vacuum stability and laser-induced damage threshold
摘要： We report the fabrication of nanoporous silica coatings with tunable refractive indices by a one-step base-catalyzed sol-gel process using tetraethoxysilane as the precursor, hexamethylisilazane as the modifier at ambient conditions. The advantages of the present method are inexpensive, etchant-free and without high temperature calcination treatment. Importantly, porosity of the coatings can be tunable by changing the monomer ratio of the starting solution, which makes them suitable for top layer of broadband AR coatings. The tri-wavelength broadband AR coating with the refractive indices of the bottom and top layers as 1.27 and 1.16 was achieved on a fused silica substrate, which possessed high transmittance of 99.6%, 98.0% and 99.3% at 351 nm, 527 nm and 1053 nm, respectively. Moreover, the double-layer coating showed significant stability, when tested with polydimethylsiloxane pollution in vacuum for a week. In addition, LIDT of the double-layer coating was up to ca. 19.0 J cm?2 at a 6.3 ns laser pulse of 351 nm wavelength. This double-layer AR coating possesses excellent broadband AR performance, high LIDT, and excellent vacuum stability, which can open a new avenue to explore applications in high-power laser systems.
关键词： Antireflective coating,Laser-induced damage threshold,High-power laser system,Sol-gel,Vacuum stability
更新于2025-09-04 15:30:14