Pump induced normal mode splittings in phase conjugation in a Kerr nonlinear waveguide

Iu. B. Milovanov, Leonid A. Chernozatonskii, В. В. Черный

Robert Shih, Harold R. Fetterman, Bradley L. Bobbs +3 more

Recent interest in degenerate four-wave mixing in artificial Kerr media to produce phase conjugate waves has concentrated on the visible and infrared spectra. Attempts to extend this technique to the millimeter wave and microwave spectral regions encounter severe difficulties arising from the requirements of medium nonlinearity and high beam intensities. The former problem may be solved by the use of artificial Kerr media and the latter by confinement in a waveguide. In a single-mode waveguide, however, wavefront perturbations cannot propagate. Phase conjugation therefore reduces in this case to a 1-D conjugation capable only of correcting for longitudinal phase error. Observation of this conjugate wave with a slow response medium is made possible by using a sequential method. The general concept is to first write the nonlinear refractive index grating using counterpropagating pump and probe waves. Subsequently, both waves are turned off, and a pump wave approaching from the opposite side reads (scatters from) the grating to produce the phase conjugate wave.

G. E. Torres-Cisneros, José Javier Sánchez Mondragón, Loric Torres

Madhav Kumar Singh, Pradip K. Jha, Aranya B. Bhattacherjee

We theoretically investigate optical bistability/multistability for all optical switching signature in a hybrid semiconductor microcavity system comprising a quantum well and a Kerr nonlinear substrate. The system is essentially two optically coupled microcavities with one of the microcavity being driven by an external amplitude-modulated pump laser. We show that the switching between bistable and multistable behaviour is influenced by the modulated pump laser, Kerr nonlinearity and the optical coupling between the two microcavities. We further investigate the intracavity spectrum of quantum fluctuations which exhibit the well-known normal mode splitting (NMS). The NMS behaviour is also found to be influenced by the system parameters. These results demonstrate that the present hybrid nonlinear system can be used in designing sensitive optical devices.

C. T. Law, A. E. Kaplan

We have shown previously that two strong laser beams (with the same frequency) counterpropagating in a Kerr nonlinear medium with linear dispersion become un stable when their intensities exceed a certain threshold.1 We demonstrate here that the system exhibits large (theoretically unlimited) amplification of a probe beam when the two pumping beams have their intensities slightly below the threshold. This is in contrast to the conventional phase conjugation due to four-wave mixing in a nondispersive Kerr nonlinear medium. The mechanism of amplification in our system can be explained in terms of positive distributed feedback from the Kerr nonlinear index grating formed by two strong pumping laser beams in the presence of dispersion giving rise to a light-induced distributed-feedback resonator. This feedback is attributed to the fact that the weak beams with both signal frequency, ω + δ, and conjugate frequency, ω − δ, propagate with phase speed different (due to dispersion) from that of a pumping wave with frequency ω, which triggers the exponentially increasing energy exchange between weak and strong beams at the nonlinear index grating (this energy exchange is prohibited in nondispersive media). When the probe frequency approaches a frequency of one of the longitudinal modes of the light-induced distributed resonator, and the pumping intensity approaches the threshold of instability, the resonant amplification increases infinitely; for presently available laser intensity stabilities, amplification as large as 104 is feasible.

David M. Pepper