The chirped steady state pulse in an amplifier with loss

J.A. Hermann

Sien Chi, Tsun-Yee Wang

James P. Wittke, Peter J. Warter

Pulse propagation in maser-type traveling-wave amplifiers with a homogeneously broadened transition is treated by a formalism analogous to the Bloch equations. Phenomenological dephasing (T2) and recovery (T1) times are defined, and a linear (nonsaturable) loss mechanism is included. In the numerical calculations, only the case of negligible excitation during the time it takes a pulse to pass is considered. When pulses are allowed to grow until the amplifier is ``saturated,'' steady-state pulses having a unique shape and intensity independent of the initial pulse are found. The parameters of these steady-state pulses depend only on the ratio of the linear loss and gain coefficients. Steady-state pulses have a peak intensity that decreases monotonically from infinity to zero as the linear loss coefficient varies from zero to the gain coefficient, while the pulse width correspondingly varies from zero to infinity, and the pulse energy varies from a finite value to zero. Steady-state pulses propogate at a velocity less than that of the small signal velocity in the medium.

Mark D. Rotter, Roger A. Haas

Valentin P. Petrov

The steady state solitary solution in a two-level homogeneously broadened amplifier with host nonlinearity and dispersion is perturbatively studied by consideration of gain saturation up to second-order energy terms normalized to the saturation energy of the transition. Carrier frequency shift occurs as a result of the saturation. The chirped solitary pulses derived exist in the anomalous group velocity dispersion region only.

Joachım Herrmann, A. Nazarkin

Taking into account the nonlinear loss and nonlinear refraction-index change due to medium ionization, high-power pulse amplification is studied under coherent conditions. An exact self-phase-modulated steady-state pulse solution is found for the coupled Maxwell-Bloch equations with a nonlinear loss and refraction-index change caused by the medium ionization, representing a generalization of the known \ensuremath{\pi}-pulse solution. The ultimate parameters of an amplifier as maximum pulse energy or minimum pulse duration are estimated and compared with experimental data.