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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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[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) - Spectral Luminescence Properties of Ho <sup>3+</sup> Ions in Active Media Codoped with Tb <sup>3+</sup> , Pr <sup>3+</sup> and Yb <sup>3+</sup> for Mid-Infrared Laser Development
摘要： Lasers operating in mid-infrared spectral region specifically with 3 m wavelength attract a lot of attention due to their various applications in atmospheric monitoring, medical surgery, remote sensing and scientific research. Such laser can be used as an efficient and high-quality radiation source for optical parametric oscillators and converters to longer IR wavelengths. Laser active media doped with Ho3+ ions are of interest for obtaining the radiation in this spectral range. However the realization of the laser radiation at 5I6 → 5I7 optical transition in Ho3+ ions is a complicated task due to the lack of commercially available laser diodes for efficient pumping of Ho3+ ions. Yb3+ ion is known as an efficient sensitizer for Ho3+ ions in various laser active crystals. The scheme with the excitation transfer from Yb3+ to Ho3+ was realized in Cr:Yb:Ho:YSGG and Cr:Yb:Ho:Eu:YAP lasers with flash lamp pumping [1, 2] and Ho:Yb:GGG and Ho:Yb:YSGG lasers with diode pumping [3]. In addition 5I6 → 5I7 optical transition is known as a “self-terminating” one because the fluorescence lifetime of the lower laser level 5I7 is considerably larger than that of the upper laser level 5I6. Codoping of Ho3+ active media with Tb3+ or Pr3+ ions can accelerate the deactivation process of the lower laser level. The concentration set of CaF2 crystal doped with Ho3+, Yb3+, Tb3+, Pr3+ ions was grown using the Bridgman technique. The number of Gd2O3, Y2O3 single crystal fibers doped with the same ions was successfully obtained by laser-heated pedestal growth method. Absorption spectra of Yb:Ho:Gd2O3 and Yb:Ho:Pr:Gd2O3 crystals showed that Yb3+ doping increased the absorption coefficient within 850-1050nm spectral region and make Yb doped media suitable for efficient pumping by commercially available laser diodes. The fluorescence lifetime of 5I6 and 5I7 manifolds of Ho3+ ions was investigated in CaF2 crystals codoped with Tb3+ and Pr3+ ions. It was found that this codoping resulted in the depopulation of the lower laser level 5I7 in Ho3+ ions and at the same time had little influence on the upper laser level 5I6 (Table 1). The lifetime of the lower laser level reduced from 17.5 ms for Yb:Ho:CaF2 crystal to 0.75 ms for Yb:Ho:Tb:CaF2. Deactivation effect of lower laser level 5I7 in Ho3+ was also observed in Yb3+:Ho3+:Pr3+:Gd2O3 and Yb3+:Ho3+:Tb3+:Gd2O3 single crystal fibers. The lifetime of the lower laser level 5I7 decreased from 8.25 ms to 1.04 ms and to 0.67 ms with a codoping of 0.5 at.% Pr3+ and 0.5 at.% Tb3+ ions, respectively. The use of Yb3+, Tb3+ or Pr3+ codoping with Ho3+ to enhance the laser properties of Ho3+ ions at 5I6→5I7 optical transition at the wavelength of ~2.8-3 μm were investigated in the Gd2O3, Y2O3 single crystal fiber for the first time. Obtained results indicate that single crystal fiber Yb3+:Ho3+:Tb3+:Gd2O3 and CaF2 :Yb3+:Ho3+:Tb3+ crystal is a promising laser medium for developing compact LD-pumped lasers operating at the wavelength of 2.8-3 μm.
关键词： Pr3+ ions,Tb3+ ions,mid-infrared laser,fluorescence lifetime,laser active media,Ho3+ ions,Yb3+ ions
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Wave Processes in Moderately and Strongly Nonlinear and Active Hyperbolic Metamaterials and Potential Applications
摘要： Two approaches to the moderately and strongly nonlinear active planar hyperbolic metamaterials, with and without an averaging over a unit cell are applied. For the proper sign of the nonlinearity of the layers included into the elementary cell of the metamaterial, the hotspots can be formed in IR range. Hypothetically, the hot spot formation is a rather common feature of the strongly nonlinear media with the interfaces between linear and nonlinear layers. The new evolution equations for the envelope amplitude of the nonlinear wave packets propagating in active hyperbolic media under an arbitrary angle to the optical axis are derived in the parabolic approximation. The mixed derivative in the evolution equation disappears and the equations reduce to the Nonlinear Schrodinger Equation (NSE) form for the waves propagating along an optical axis. The nonlinear quantum optics approach to the waves in hyperbolic active metamaterials is outlined.
关键词： stabilization,active media,nonlinearity,metamaterials,hyperbolic
更新于2025-09-10 09:29:36