Transfer of momentum and torque from a light beam to a liquid

Refraction or absorption of light results in the force and torque, i.e., transfer of momentum and angular momentum from light to the medium. In transversely inhomogeneous beams, the force per unit volume f may have curlf not equal 0 leading to flow or to nonthermal and nongravitational convection in liquids. The force and the torque in scattering systems are as strong as in absorbing materials and may allow one to carry out experiments avoiding thermal effects. Nonlinear optical response of liquid crystals due to this convection is discussed

Overview of optical phase conjugation

Magnificent short courses on optical phase conjugation and its application have been given. In this communication, additional issues about phase conjugation are presented. These include, among others, time reversibility (TR) of optical wave propagation, mathematical description of TR in terms of complex amplitudes and complex-conjugated amplitudes, etc. The order is for tutorial purposes

Overview of optical phase conjugation

Magnificent short courses on optical phase conjugation and its application have been given. In this communication, additional issues about phase conjugation are presented. These include, among others, time reversibility (TR) of optical wave propagation, mathematical description of TR in terms of complex amplitudes and complex-conjugated amplitudes, etc. The order is for tutorial purposes

Azimuthal solitons/FWM instability for tubular waveguides and whispering gallery modes

The nonlinear optical processes, such as four-wave mixing and transverse solitons in waveguides of specific configuration are discussed. It is assumed that only one radial transverse mode is bound by the bump of refractive index in the radial direction. The remaining transverse coordinate y = Rφ may be considered as defined at length L = 2πR of circumference, such that 0≤y≤L. The eigenmodes in terms of y-dependence are simply Fourier-components ex-p(imφ) = exp(2πimy/L). The main dimensionless factor is the ratio d/2πR of the radial thickness of the mode of tubular waveguide to the circumference. Tubular propagation of light in a round flattop fiber may be mimicked by the whispering gallery modes

Momentum and torque transfer from light to liquid crystal

Orientational nonlinearity such as momentum and torque transfer is demonstrated in dye-doped absorbing liquid crystals (LC) as a function of the light field. The light is considered as a flux of photons carrying momentum hk/2π and energy hv moving along the Poynting vector. The momentum is balanced when the energy in and out is exactly balanced for the transparent medium. However, the directions of the input and output photons make an angle with the perpendicular to the input/output facets. Therefore, a momentum arm a appears, resulting a torque T transferred from light to LC

Talbot effect for whispering gallery modes and modes of tubular waveguides

The self-reproduction effect, or Talbot effect, is usually observed for the light-wave incident at a normal to a rectangular grating with the same transverse periods. A natural example of a one-index set of modes for which the Talbot effect must be quite pronounced is a tubular waveguide. This effect of azimuthal self-reproduction may be an important component of nonlinear azimuthal interactions of optical waves in multimode fibers. The self-reproduction effect is sensitive to the wavelength of radiation and therefore may be used for an inexpensive device for azimuthal scrambling and unscrambling of analog data

Change Of Partial Polarization Of A Beam Under Phase Conjugation

Possible change of the polarization state in the process of propagation is considered theoretically. We were able to suggest a mechanism that allows for a very unusual behavior of the Stokes parameters of the beam. Specially arranged phase conjugation procedure yields the decrease of only one (e.g. |ζ3| ∝ |(|Ex|2 - |Ey|2)|) Stokes component, while the degrees of 45°- and circular polarization, ζ1 and ζ2, are not changing at all

Wave Propagation In A Guiding Structure: One Step Beyond The Paraxial Approximation

Propagation of electromagnetic waves is considered for a medium with (x, y)-dependent locally isotropic dielectric and magnetic susceptibilities ∈ik = ∈(x, y)δik and μik = μ(x, y)δik, i.e., for a waveguide. In the paraxial approximation the polarization is disconnected from the propagation. We have developed a self-consistent theory of the postparaxial corrections. It allows, in particular, for the description of intrafiber geometrical rotation of polarization and its inverse phenomenon, the optical Magnus effect, which are both determined by the profile of refractive index n = √∈μ only and constitute spin-orbit interaction of a photon. The birefringence splitting of linearly polarized modes or meridional rays on the other hand, turns out to be dependent on the gradients of impedance ρ = √μ/∈, the quadrupole part of spin-orbit interaction. An important point of the theory is a transformation of field variables such that the z-propagation operator becomes Hermitian, in analogy with the transitions from a full relativistic Dirac equation to the Schrödinger-Pauli equation with spin-orbital corrections. A theoretical explanation is given for the phenomenon previously observed in experiment: preservation of circular polarization by an axially symmetric step-profile multimode fiber and depolarization of an input linearly polarized wave by the same fiber. @ 1996 Optical Society of America

Relaxation Of A Two-Level System: Non-Negativity Of Density Matrix And Possibility For Anomalously Long T2

Density matrix equations for the relaxation of a two-level system are studied. Standard dogma, Γik ≥ (γi + γk)/2, about the relaxation constant for the off-diagonal (Γik) and diagonal (γi) matrix elements is verified for the case of up- and down-transitions with high rates w21 and w12. Non-negativity of the density matrix imposes much weaker limitation, Γ21 ≥ (1/2)[(w21)1/2 -(w12)1/2]2. An almost \u27physical\u27 system is suggested, which describes to a certain approximation such decrease of transverse relaxation constant Γ