Two-wave mixing via reflection population gratings

Lin Lou, Jia Sun, Weikang Feng +3 more

George C. Valley

K. Kuroda

Abstract Dynamic population gratings formed by two‐wave mixing in an erbium‐doped fiber amplifier are reported. One of the counter‐propagating fields is intensity‐modulated to distinguish reflection from the grating from amplified transmission fields. The modulation‐frequency dependence of the reflection is studied under single‐wavelength and two‐wavelength input conditions to separate reflection from transient gain. The results are analyzed by measuring the gain saturation and recovery times using self‐probe and pump–probe techniques.

K. S. Syed, Graham J. Crofts, Michael J. Damzen

We model transient copolarized degenerate four-wave mixing in a saturable gain medium, using pulses of duration much shorter than the population lifetime with a finite probe beam. Initially we describe a model to include the simultaneous existence of both the reflection and transmission gratings for arbitrary field strengths. Then we develop a model to include all four possible gratings, including standing-wave gratings between counterpropagating pump beams and the probe and conjugate beams. By use of two expansion methods for the higher-order grating terms it is possible to model regimes in which either one grating is arbitrarily strong or all four gratings are strong. Comparisons are made among models including one, two, and four gratings. Good agreement is found between the theoretical four-grating case and pulsed copolarized degenerate four-wave mixing experiments in laser-pumped Ti:sapphire for a finite probe beam.

A. A. Sevenyuk, А. В. Сухов

Yi Ding, Hans Joachim Eichler

The optimal grating shift for four-wave mixing differs from that of two-wave mixing. With temperature control of this shift, the phase-conjugate reflectivity is increased to 400% in negative readout geometry. In the range of strong coupling the phase-shift control leads to bistable behavior of the four-wave mixing reflectivity.