Search results for "Stimulated emission"
showing 10 items of 69 documents
Strong optical nonlinearities in gallium and indium selenides related to inter-valence-band transitions induced by light pulses
1997
A nonlinear optical effect is shown to occur in gallium and indium selenides at photon energies of the order of 1.5 eV. It corresponds to transitions from a lower-energy valence band to the uppermost one when a nonequilibrium degenerate hole gas is created in the latter by a laser pulse. This inter-valence-band transition is allowed by crystal symmetry. Its oscillator strength is estimated through the $f$-sum rule and turns out to be about two orders of magnitude higher than that of the fundamental transition. The intensity of this effect is stronger when the pump pulse photon energy is close to that of the inter-valence-band transition; a condition that can be fulfilled only in indium sele…
Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer
2018
We systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic Fe layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially at for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of of up to two in field.
Some Advantages of the Gyrotrons with Width Emitters
2020
The main trends in gyrotron development are escalation of the radiated power and increasing the frequency of coherent radiation. For both trends it is beneficial to develop gyrotrons with wide emitters because this allows one to use cryomagnets with smaller inner bore sizes. For analyzing and optimizing the operation of gyrotrons with wide emitters it is proposed to represent such emitters as a superposition of thin rings and analyze the properties of electron beams emitted by each of these rings. The analysis of electron beam properties, for electron optical systems with different emitters is presented. The possibility to reduce velocity spread by anode profiling is discussed. The dynamics…
Continuous-wave spontaneous lasing in mercury pumped by resonant two-photon absorption
2010
The first continuous-wave two-photon absorption laser-induced stimulated emission (CTALISE) is demonstrated. The 7^1S-6^1P transition in mercury at 1014nm wavelength is used and selective lasing of different isotopes is observed.
Polymer-metal plasmonic waveguide : passive and active components for integrated photonics
2009
Dielectric loaded surface plasmon polariton waveguides (DLSPPWs) enable transmission at a sub-wavelength scale of both electrical and plasmonic (optical waves at the interface between a metal and a dielectric) signals in the same circuitry. Moreover, the use of a polymer as the dielectric load enables the functionalization of DLSPPWs. Therefore, this configuration is of great interest for integrated photonic applications. However, DLSPPWs suffer strong losses due to dissipation into the metal film. We address here the possibility of compensating the losses using a configuration analogous to an optical amplifier. We first set theoretical (effective index model), numerical (differential metho…
Measurements of the 90,91,92,94,96 Zr n, gamma cross-sections at n_TOF
2005
Neutron capture cross sections of the 90,91,92,94,96Zr have been measured over the energy range from 1 eV to 1 MeV at the spallation neutron facility n TOF at CERN in 2003. The innovative features of the neutron beam, in particular the high instantaneous flux, the high energy resolution and low background, together with improvements of the neutron sensitivity of the capture detectors make this facility unique for neutron-induced reaction cross section measurements with much improved accuracy. The preliminary results of the Zr measurements show capture resonance strengths generally smaller than in previous measurements. Peer Reviewed
Characterization of a neutron-beta counting system with beta-delayed neutron emitters
2016
Abstract A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a self-triggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β–neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on …
Oxygen-related defects and energy accumulation in aluminum nitride ceramics
2001
Abstract Features of oxygen-related defects in the AlN crystalline lattice were studied. Spectral characteristics of photoluminescence and photostimulated luminescence under the UV light irradiation of AlN ceramics were examined. The results obtained allow us to propose the mechanisms of luminescence and radiation-induced energy accumulation in AlN.
Luminescence mechanisms of oxygen-related defects in AlN
2002
Spectral characteristics of native oxygen-related defects existing in the crystalline lattice of AlN were studied. Features of photoluminescence observed under exposure to ultraviolet light together with those of the photostimulated luminescence testify the recombination character of luminescence. The mechanism of luminescence of oxygen-related defects is proposed.
Recent Developments in Cladding-Pumped Doped Fiber Amplifiers for Telecommunications Systems
2020
This paper aims to review recent developments in the field of doped fiber-based optical amplifiers and serve as a reference for promising optical signal amplification techniques that may be useful for practical implementation in high-capacity and cost-efficient telecommunications systems. The main focus is put on different rare-earth dopant elements, double-clad fibers, and optical couplers for cladding-pumping technique. It is found that codoped double-clad fiber-based amplifiers currently have attained the main research interest and show possible application also in multichannel fiber optical transmission systems. Additionally, we have compared different free space and waveguide construct…