Continuous resonant four-wave mixing in double-Lambda level configurations of Na-2

Efficient continuous resonant frequency mixing omega(4) = omega(1) - omega(2) + omega(3) in Na-2 has been realized. A bichromatic field (lambda(1) = 488 nm, lambda(2) = 525 nm), generated by an Ar+-laser-pumped Na-2 Raman laser, and radiation at lambda(3) = 655 nm from a dye laser interact resonantly with corresponding transitions X(1) Sigma(g)(+)(v = 3, J = 43) --> B-1 Pi(u)(6, 43) --> X(1) Sigma(g)(+)(13, 43) --> A(1) Sigma(g)(+)(24, 44) in a test Na-2 heat pipe. For input powers of 200, 25, and 400 mW an output beam of as much as 0.2 mW at lambda(4) = 599 nm has been observed. Measured parameter dependences indicate an influence of interference effects. This is directly related to the discussion of lasing without inversion. (C) 1996 Optical Society of America