Anti-Stokes conversion of Nd-laser radiation on the basis of cooperative processes

B. Arad, S. Eliezer, Y. Paiss

В. Емелянов, Nikolai V Kravtsov, Nikolai I Naumkin

N. A. Enaki

The paper proposes to unify the two-photon laser and induced cooperative scattering Raman lasing in which the flying ensemble of two-level excited radiators are coupled with the bimodal cavity field in nonlinear two-photon and scattering interactions. It discusses the situation in which the induced two-quantum lasing takes place together with the cooperative scattering conversion of photons between the pump, Stokes, and anti-Stokes cavity modes. The proposed master equation describes cooperative energy exchanges between Raman and two-photon lasing processes by portions of energies multiple to the energy of the entangled photon pair. The generators of such emission and absorption processes belonging to the symmetries of Raman conversion and two-photon cooperative generation are unified. The first symmetry belongs to su(2) algebra connected to the scattering conversion in the Stokes, pump, and anti-Stokes modes of cavity (Opt. Commun.,285(5) (2012) 686–692). The second one belongs to multi-mode su(1,1) symmetry which quantifies the cooperative process belonging to two-photon emission in cavity/fiber mode components of field (see Opt. Commun. 247(4–6) (2005) 381–392). The bimodal collective photon operators are introduced describing the emission or absorption acts of the fixed portion of energy from the cavity equal to the transition energy between the states of each excited atom. A key impact of the study focuses on the statistical properties of the bimodal field and their detection possibilities are proposed for the description of the time evolution of quantum correlations between the field components of Raman conversion and two-photon emission.

Wayne T. Whitney, Nicholas Djeu

N. I. Shamrov

B. Wellegehausen, Klaus Ludewigt, H. Welling

The anti-Stokes Raman laser process is an interesting method for frequency upconversion and generation of tunable UV radiation. This method requires no index matching and allows high-conversion efficiencies and output energies and large frequency shifts in a single step. A basic requirement is a population inversion between a metastable level and a suitable lower-lying level. So far anti- Stokes laser emission has been demonstrated using the metastable TI (6P3/2). l(5P1/2). and Br (4P1/2) levels, where a population inversion with respect to the corresponding atomic ground states has been generated by photodissociation of suitable compounds.1-3 For the Tl system efficiencies of 10 % and output energies of ~1 mJ (at 377 nm) have been reported,1 and with Br a shortest wavelength of 149 nm was possible by upconversion of 157.5-nm radiation of a F2 laser.3