<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

We present the quantum theory of a two-photon nonlinear laser when the lasing medium consists of long-lived atoms. There is no population inversion in this laser, but the system exhibits gain arising from the four-wave-mixing process in an active nonlinear medium. The strong phase correlation between the photons generated in four-wave mixing leads to a narrower than usual linewidth of the two-photon laser far above threshold. The laser output is also squeezed. Systems with a higher lifetime have the advantage of requiring a lower pump to reach the threshold of laser oscillation. We give explicit solutions for the noise spectrum of the intensity difference of the two output modes in the steady state and show that it is highly squeezed even for non-Markov systems. © 1994 The American Physical Society.

World University root node

SNU Management

Physical Review A

Two-photon squeezed laser with long-lived atoms

The theory of magneto-optic Kerr effects is formulated on the basis of classical interaction of light and matter in a coordinate system attached to the light wave. Induced polarization of the magnetic medium along the propagation axis of the electromagnetic wave is described in terms of an equivalent electric field and the effects are incorporated in the boundary conditions and Fresnel equations for the reflectivity tensor are modified accordingly. The results are given up to second order in the magnetic field. © 1994 The American Physical Society.

Physical Review B

Theory of magneto-optic Kerr effects

It is shown that the intensity correlation function is central to the understanding of various aspects of nonclassicality of the electromagnetic field, e.g. quantum interference, antibunching, nonclassical statistics, squeezing and nonlocality. Particular emphasis is given on correlations of twin signals generated in nonlinear mixing interactions. © 1994 Indian Academy of Sciences.

Current Science

Quantum correlations in nonlinear optical signals

The coupling of light waves travelling clockwise and counterclockwise along an optical ring due to a back-scattering element is studied. An asymmetric mode splitting occurs as a consequence of the discontinuity suffered by the waves at the scattering point. The mode splitting shows up in an interference pattern and lends itself to an experimental verification. © 1993 the Indian Academy of Sciences.

Pramana

Optical mode-coupling in a ring due to a back-scatterer

The effects of phase-interrupting and velocity-changing collisions between active and perturber atoms on the spectral profile of a gas laser are studied. Exact analytical results for the density matrix are presented for the case of strong collisions in a unidirectional ring laser, and the laser intensity is then evaluated in the Doppler limit under the condition of self-consistency. The washout of the hole burning in the steady-state population difference and the broadening of the laser line shape are discussed. The results of the third-order perturbation theory are compared with the exact calculations valid for an arbitrarily intense pump. © 1993 The American Physical Society.

Collisional effects in gas lasers

Fields generated in a large number of nonlinear-optical processes (including those with losses) have a Wigner distribution that is Gaussian centered around the mean value of the field. We show that the Bell inequality for an optical-correlation experiment with two coupled modes generated in a nonlinear process can be expressed as an inequality relating to the parameters of the underlying Wigner distribution function. We consider examples of parametric down-conversion and a two-mode squeezed laser, which can be used in experiments to demonstrate quantum nonlocality. © 1991 The American Physical Society.

Wigner-function description of quantum-mechanical nonlocality

Erratum: Theory of a two-photon squeezed laserlike oscillator (Physical Review A (1990) 42, 1 (665))

It is theoretically shown how a two-photon laserlike oscillator with strongly squeezed output can be constructed. The physical mechanism leading to squeezed laserlike oscillator is the strong competition among the nonlinear gain due to resonant four-wave mixing process, nonlinear losses due to the absorption of generated photons, and linear losses from the cavity. In the balanced case, the photon correlations result in a linewidth that is narrower than the Schawlow-Townes limit. © 1989 The American Physical Society.

Theory of a two-photon squeezed laserlike oscillator

By measuring the joint probability for the detection of two photons at two points as a function of the separation between the points, we have demonstrated the existence of nonclassical effects in the interference of signal and idler photons in parametric down-conversion. In principle, the detection of one photon at one point rules out certain positions where the other photon can appear. © 1987 The American Physical Society.

Physical Review Letters

Observation of nonclassical effects in the interference of two photons

Experimental results are presented that demonstrate that the light intensity of a good-cavity single-mode standingwave dye laser can exhibit chaotic behavior. The governing attractor is of dimensionality 6.5 and entropy 50 kbits/sec. An examination of the pump-laser beam before and after its interaction with the dye indicates that the chaos is probably due to the turbulent flow of dye within the dye cell. This interpretation is confirmed by the absence of chaos in two similar dye lasers that use a dye jet rather than a dye cell. © 1987 Optical Society of America.

Optics Letters

Chaos in a good-cavity single-mode dye laser due to turbulent dye flow

A theoretical treatment is given of the process in which the two photons produced simultaneously in the parametric frequency splitting of light are allowed to interfere. It is shown that, while there is no interference in the usual sense involving quantities that are of the second order in the field, fourth-order interference effects are present. These may be revealed by measuring the joint probability of detecting two photons at two points x,x in the interference plane with photoelectric detectors as a function of the separation x-x. The probability exhibits a cosine modulation with x-x, with visibility that can approach 100%, even though the integration time in the experiment may greatly exceed the reciprocal bandwidth of the photons. The interference effect has a nonclassical origin and implies a violation of local realism in the highly correlated two-photon state. © 1986 The American Physical Society.

Interference of two photons in parametric down conversion

It is pointed out that a method recently described by Hillery and Zubairy can be generalized to yield the multitime correlation function in any order for an interacting quantum field in the form of a phase-space average. The correlations are expressible as c-number integrals with the help of the coherent-state propagator, but the associated phase-space density is complex. © 1984 The American Physical Society.