Inversionless amplification with standing-wave drive

We study amplification without inversion in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field. Our results are compared to those of the well-known case of a traveling-wave drive. A distinguishing feature of the SW case is the contribution to probe the gain of multiphoton processes involving one probe photon and several pump photons, with alternating absorption and emission from the two counterpropagating pump components. These processes are only weakly affected by Doppler broadening for probe to drive frequency ratios R equal to integer numbers. Examples of inversionless amplification with frequency up-conversion ratios R = 3 and R = 4 are presented. Copyright © 1999 by MANK "Hayκa/Interperiodica".