tailieunhanh - EIT enhanced self-kerr nonlinearity in the three level lambda system under doppler broadening

Using density-matrix theory, an analytical expression of the self-Kerr nonlinear coefficient of a three-level lambda EIT medium for a weak probe light is derived. Influences of the coupling light and Doppler broadening on the self-Kerr coefficient are investigated and compared to experimental observation with a good agreement. The selfKerr nonlinearity of the medium is modified and greatly enhanced in the spectral region of EIT window. Furthermore, sign, slope, and magnitude of the self-Kerr coefficient can be controlled with frequency and intensity of the coupling light and temperature of the medium. | Communications in Physics, Vol. 24, No. 3 (2014), pp. 217-224 DOI: EIT ENHANCED SELF-KERR NONLINEARITY IN THE THREE-LEVEL LAMBDA SYSTEM UNDER DOPPLER BROADENING DINH XUAN KHOA, LE VAN DOAI, PHAM VAN TRONG, TRAN MANH CUONG, VU NGOC SAU, AND NGUYEN HUY BANG Vinh University, 182 Le Duan Street, Vinh City, Nghe An, Vietnam LE NGUYEN MAI ANH Nong Lam University - Thu Duc district - Ho Chi Minh City - Vietnam E-mail: bangvinhuni@ Received 17 April 2014 Accepted for publication 30 August 2014 Abstract. Using density-matrix theory, an analytical expression of the self-Kerr nonlinear coefficient of a three-level lambda EIT medium for a weak probe light is derived. Influences of the coupling light and Doppler broadening on the self-Kerr coefficient are investigated and compared to experimental observation with a good agreement. The selfKerr nonlinearity of the medium is modified and greatly enhanced in the spectral region of EIT window. Furthermore, sign, slope, and magnitude of the self-Kerr coefficient can be controlled with frequency and intensity of the coupling light and temperature of the medium. Specially, for a given set of fixed values of the parameters of coupling and probe lights, it could be able to choose an optimized temperature to have largest magnitude of the self-Kerr coefficient. Such controllable Kerr nonlinearity can find interesting applications in optoelectronic devices working with low-light intensity at various temperature conditions. Keywords: Kerr nonlinearity; atomic coherence; electromagnetically induced transparency. I. INTRODUCTION The Kerr nonlinear materials are used widely in photonic devices and multi-wave mixing converters. In most cases, a strong nonlinear response is often needed to gain conversion efficiency. However, due to weakness of Kerr nonlinearity of traditional optical materials, several theoretical proposals have not yet been experimentally observed. Finding materials having large Kerr .