Gallium arsenide electron-beam-pumped laser with a distributed feedback

Abstract

The statistical multistep compound (SMC) theory of Feshbach, Kerman and Koonin (FKK) is used to analyse the energy and angular distributions of 14 MeV neutrons inelastically scattered by 59C0 and 93Nb. An acceptable fit is obtained to the whole energy spectrum provided the contributions from the (n, 2n) and (n, pn) reactions, also calculated with the SMC formalism, are added at low energies. The theory also accounts well for the (n, p) cross sections. The sensitivity of the results to the level density parameters is investigated.

Resonant radiationless excitation transfer in pores of porous silicon

“…A simple model iodine molecule was chosen as a sorbate. First, one can expect that the absorption spectrum of the iodine sorbed on the surface of nanoporous silicon strongly overlaps with the luminescence spectrum of porous silicon in the range from ~400 to ~650 nm [6][7][8][9][10]. Second, I 2 does not absorb near λ = 266 nm (fourth harmonic of a neodymium laser) [7,8].…”

“…First, one can expect that the absorption spectrum of the iodine sorbed on the surface of nanoporous silicon strongly overlaps with the luminescence spectrum of porous silicon in the range from ~400 to ~650 nm [6][7][8][9][10]. Second, I 2 does not absorb near λ = 266 nm (fourth harmonic of a neodymium laser) [7,8]. Based on the results of studies [6][7][8][9][10], one can assume that the spectrum of iodine submonolayers physisorbed on the nanoporous surface cannot be shifted and broadened to the extent that it occurs in the range of 266 nm.…”

“…Second, I 2 does not absorb near λ = 266 nm (fourth harmonic of a neodymium laser) [7,8]. Based on the results of studies [6][7][8][9][10], one can assume that the spectrum of iodine submonolayers physisorbed on the nanoporous surface cannot be shifted and broadened to the extent that it occurs in the range of 266 nm. At the same time, the absorption coefficient of nanoporous silicon is high at this wavelength.…”

“…And, finally, the intrinsic dipole moment of the iodine molecule is zero, which must minimize the influence of iodine sorbed in the pores of nanoporous silicon on the PL of the latter [3]. Moreover, the studies of electronic relaxation of the iodine molecules sorbed on various surfaces have shown that, owing to the enhanced role of radiationless recombination, the luminescence quantum yield of the sorbed iodine layers decreases and can be as low as 10 -4 -10 -5 [7,8], which is three orders of magnitude lower than the quantum yield of porous silicon [2]. Because of this, the luminescence of excited iodine can be ignored in the background of the luminescence of porous silicon.…”

“…2 Experimental techniques and samples preparation The experimental methods included laserinduced luminescence [6,10] and laser desorption mass spectrometry [7][8][9]. To excite porous silicon, the fourth harmonic (λ = 266 nm) of a YAG:Nd 3+ laser was used in both methods.…”