Method and apparatus for nonlinear frequency generation using a

Abstract

Efficient nonlinear processes in a nonlinear optical medium are achieved by combining the concept of electromagnetically induced transparency (EIT) and a strongly-driven atomic local oscillator. The present method uses a nonlinear optical medium having elementary entities, such as atoms or molecules, in which a ground state .vertline.1> and a second state .vertline.2> are selected such that the transition between the ground state .vertline.1> and the second state .vertline.2> is a dipole forbidden transition. An upper state .vertline.3> selected from among the energy states .vertline.i> above the ground state .vertline.1> such that a two-photon transition between the ground state .vertline.1> and the second state .vertline.2> via the upper state .vertline.3> is allowed. A strongly-driven coherent superposition state which gives rise to the strongly-driven local oscillator is produced by applying two pumping beams, P1 and P2, at frequencies corresponding to transitions between states .vertline.2> and .vertline.3> and between states .vertline.1> and .vertline.3>. The nonlinear optical medium prepared in this way is used for efficient sum-and-difference and parametric generation in .LAMBDA. and ladder systems.