Ram Krishna Sarkar

All-optical passive transistor

We show the possibility of developing an all-optical passive transistor in a simple and novel way. This could be done by copropagating two coaxial beams through a modified optical power filter. We show NOT logic and intensity modulation of the strong beam by the weak beam obtained with the analog.

Coupled spatial-soliton pairs in saturable nonlinear media

We present a simple and straightforward approach to investigate coupled spatial-soliton pairs of two copropagating mutually incoherent (i.e., both beams are fully spatially and temporally coherent, but are incoherent with respect to one another) light beams in saturable nonlinear media. The approach provides a deeper understanding of coupled spatial-soliton pairs and reveals many interesting features, including the entire existence curve of such solitons.

Spatial solitons of desired intensity and width and their self-tapering/uptapering in cubic quintic nonlinear medium

In this paper, we have investigated the propagation behavior of a Gaussian beam in cubic quintic nonlinear medium with and without absorption or gain. A governing differential equation for the evolution of beam width with the distance of propagation has been derived using the standard parabolic equation approach. By solving the governing equation numerically for different sets of parameters, we have shown that spatial solitons of fixed width and desired intensity and of fixed intensity and desired width are possible. Such liberty does not exist in other saturable media. We have also investigated self-tapering and self-uptapering of spatial solitons in the presence of absorption or gain and showed that the rate of self-tapering/uptapering is not only controlled by the magnitude of absorption or gain but also by the values of cubic and quintic terms. It is revealed that by self-tapering, the smallest achievable soliton width decreases/increases by increasing the magnitude of the cubic/quintic term. It is also revealed that the smallest achievable soliton width by self-tapering, is smaller for a larger initial width.

Spatial Soliton Pairing of Two Cylindrical Beams in Saturable Nonlinear Media

In this paper, we have extended the recently introduced theory of coupled propagation of two coaxially co-propagating and mutually incoherent bright 1-D beams to coupled propagation of two 2-D (cylindrical) bright beams and investigated the propagation behavior and spatial soliton pair formation of such beams by a recently introduced simple approach. We have considered saturable form of the nonlinear medium in this paper as 2-D spatial solitons are unstable in Kerr type media. We found that many of the propagation features of two 2-D beams in saturable media are same that of 1-D beams in Kerr type media. However, many features are difierent and to the best of our knowledge, reported in this paper for the flrst time. The present version of the theory is applicable in all possible physical situations and parameters.