Intensity-dependent Coupling Research Articles

AMPLITUDE-SQUARED SQUEEZING IN THE m-PHOTON JAYNES-CUMMINGS MODEL WITH SQUEEZED FIELD INPUT

Amplitude-squared (AS) squeezing has been investigated for the m-photon Jaynes-Cummings model assuming the field to be initially in the squeezed states. The role played by intensity-dependent coupling has also been discussed. It has been shown that for the large initial average photon number [Formula: see text] with odd values of m, AS squeezing revokes permanently whereas with even values it recurs periodically. As m increases the revocation is hastened and the duration of occurrence decreases. Higher values of m for the initial field in a squeezed vacuum state can make one of the quadrature permanently squeezed. The AS squeezing behavior for two initial states of the atom, i.e., ground state versus excited state is also compared.

Quantum properties of field modes in trilinear optical processes.

We consider a trilinear Hamiltonian in boson operators describing various physical processes such as frequency conversion, Raman or Brillouin scattering, or the interaction of N two-level atoms with a single-mode radiation field. Due to the fact that two independent integrals of motion can be found, the solution of the dynamics of the system is reduced to the diagonalization of a finite matrix (as was already shown by Walls and Barakat [Phys. Rev. A 1, 446 (1970)]). Performing a numerical diagonalization, we analyze the statistical properties of the field modes (sub-Poissonian statistics, anticorrelation, squeezing). We also pay attention to the appearance of collapses and revivals in the mean photon number of the modes. The relation of this model to the model of two coupled modes with an intensity-dependent coupling constant is pointed out.

The time evolution operator of an atom in a deformed intense field

We explicitly calculate the time evolution operator of an atom in a deformed electromagnetic field which is dependent on deformation parameter and possesses quantum group symmetry. The density operator and the time variation of photon distribution are also given, both with and without intensity-dependent coupling.

SU(1, 1) and SU(2) Squeezing in Trilinear Optical Processes

Abstract The squeezing properties in terms of SU(1, 1) and SU(2) operators for the case of trilinear processes are studied. The initial state of the system is supposed to be a coherent state in one of the modes and number states in the remaining modes. It is pointed out that in several cases a considerable amount of squeezing can be achieved. Due to the common mathematical structure the case of a two-mode coupler with intensity dependent coupling is also analysed.

Berry phases and Rabi oscillations

The Berry phases for a spherically symmetric atom in a circularly polarized semiclassical radiation field are calculated using an operator decomposition scheme. The author then takes the two-level atomic limit and recovers the Berry phases already calculated by other means. His attention is then focused on the two-level atom. He shows that in the semiclassical problem the Rabi oscillations do not arise from cyclic wavefunctions. Hence any comparison of the phases of the initial and final states must use the Pancharatnam connection. In the quantum model he no longer gets perfect Rabi oscillations as there are partial collapses and revivals. These collapses and revivals are exploited in alternative quantum optical models, the Raman coupling model and intensity-dependent coupling model, for which they are exactly cyclic. Again he finds that he must invoke the Pancharatnam connection.

Amplitude-squared squeezing of radiation in some lossless models.

An analysis of the amplitude-squared squeezing is presented for the lossless anharmonic-oscillator, Jaynes-Cummings, and intensity-dependent coupling Jaynes-Cummings models using coherent and squeezed inputs. Periodic revivals of the amplitude-squared squeezing are shown to exist in the anharmonic-oscillator and intensity-dependent coupling Jaynes-Cummings models for any value of the initial average photon number n\ifmmode\bar\else\textasciimacron\fi{}. The Jaynes-Cummings model, on the other hand, displays this characteristic for small n\ifmmode\bar\else\textasciimacron\fi{} only. The effect of the squeezing angle on the amplitude-squared squeezing is studied. A comparison with the normal-order squeezing is presented.

On the Squeezing of Coherent States by the Multiphoton Jaynes-Cummings Hamiltonian with an Intensity-dependent Coupling

Abstract The squeezing properties of the multiphoton Hamiltonian with intensity-dependent coupling are evaluated for the [xcirc] and [pcirc] x quadratures, for the initial state of a coherent electromagnetic field and an atom in the ground state. Two measures of squeezing: the percentage of total squeezing and the squeezing time-period percentage, are introduced. Interesting squeezing properties with respect to [xcirc] are observed for real coherent states when the time evolution of the above measures and of the time-averaged squeezing are analysed. The multiphoton intensity-dependent coupling Hamiltonian is found to be almost independent of the specific powers of the annihilation and creation operators, as long as the sum of the powers is kept constant.

N-level Atom Interacting with Single-mode Radiation Field: An Exactly Solvable Model with Multiphoton Transitions and Intensity-dependent Coupling

Abstract We study the dynamics of an N-level atom coupled in a lossless cavity to a single-mode near-resonant quantized field. The atomic levels are coupled by the multiphoton transitions and the coupling constants between the field and the atomic levels are supposed to be intensity dependent. We find the exact solution for the state vector describing the dynamics of the atom-plus-field system. As an illustration we use the model for studying (i) the time evolution of the atomic occupation probability with the initially coherent field and (ii) the light squeezing, when the cavity field is initially in the vacuum state and the atom is prepared in the atomic ‘coherent state’ (a superposition of atomic states).

Emission spectra for the Jaynes-Cummings model with intensity-dependent coupling

The authors have investigated the spectrum of the emitted light by a single atom interacting with a single mode of the radiation in an ideal cavity via the intensity-dependent coupling (the Jaynes-Cummings model with intensity-dependent coupling see B. Buck, Phys. Lett., vol.A81, p.132 (1981)). From the authors' results it follows that in the resonant case the two-peaked structure of the spectrum associated with the vacuum-field Rabi splitting is preserved for any initial state of the radiation field (e.g. number state, thermal state, coherent state and the squeezed vacuum) with an arbitrary average number of photons.

An analysis of a planar optical directional coupler with a lossless Kerr-like coupling medium

The nonlinear all-optically controlled coupling characteristics are studied analytically and numerically for two planar optical waveguides coupled through a lossless Kerr-like slab. The exact dispersion equation for this waveguiding structure is derived in terms of Jacobian elliptic functions. The optical intensity-dependent coupling length is described as a combination of symmetriclike and antisymmetriclike modes of propagation, derived from the nonlinear combination of the independent modes of the structure. A simple analytical formula is derived for the critical power, defined as the power above which the antisymmetric mode disappears and complete energy transfer between the two waveguides is no longer possible. The analysis provides insight into the complicated nature of the waveguiding structure behavior, and it shows one possible approach to solving difficult propagation problems in nonlinear optical waveguides of this or similar configuration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Heisenberg picture operator solution for the Jaynes-Cummings model with intensity-dependent coupling

The author has found solutions in the Heisenberg representation for the basic operators of the Jaynes-Cummings model with intensity-dependent coupling. The dipole-dipole correlation function has been evaluated for the most general initial state of the atom-field system. The atomic inversion for various initial states of the cavity field has been obtained in a closed form for the resonant case.

Light Squeezing in the Jaynes-Cummings Model with Intensity-dependent Coupling

Abstract We have found that in the intensity-dependent-coupling Jaynes-Cummings model with the coherent radiation field light squeezing exhibits periodical revivals. The influence of the initial states of the atom on the squeezing of light is investigated in detail.

Jaynes-Cummings model with intensity-dependent coupling interacting with squeezed vacuum

We have investigated the time evolution of the squeezing and the atomic population inversion in the Jaynes-Cummings model with intensity-dependent coupling with a radiation field initially prepared in the squeezed vacuum state. We have shown that in contrast with the results obtained in one-photon (by Gea-Banacloche et al.) well as two-photon (by Gerry) modifications of the model the above physical quantities may exhibit exact periodicity.

Jaynes-Cummings model with intensity-dependent coupling interacting with Holstein-Primakoff SU(1,1) coherent state.

We show that in the Jaynes-Cummings model with the intensity-dependent coupling interacting with the Holstein-Primakoff SU(1,1) coherent state the revivals of the radiation squeezing are strictly periodical for any value of initial squeezing. The expression for the atomic population inversion exhibiting the exact periodicity of the population revivals is obtained.

Nonlinear optical processes in a polymer waveguide: Grating coupler measurements of electronic and thermal nonlinearities

We report here the first clear demonstration of intensity-dependent phase shift due to electronic nonlinearity in a nonlinear polymer waveguide in which propagation distances over 5 cm have been achieved with total attenuation of ∼1.2 cm−1 . Intensity-dependent coupling angle, intensity-dependent coupling efficiency, and limiter action behavior have been observed in the polyamic acid waveguide using grating excitation with 400 fs, 80 ps, and 10 ns pulses. A nonlinear grating coupler analysis identifies the subpicosecond and picosecond processes with electronic nonlinearity, but the dominant effect in the nanosecond experiment is due to thermal nonlinearity derived from weak absorptions. The magnitude and sign of n2 of electronic nonlinearity are measured.

Organic nonlinear optical waveguides formed by solvent-assisted indiffusion

A technique is described for producing robust, low-loss waveguides from a wide range of organic nonlinear optical materials. The linear and nonlinear properties of waveguides produced by this solvent-assisted indiffusion process have been evaluated and intensity-dependent prism coupling demonstrated.

Nonlinear single-mode fiber coupler using liquid crystals

The operation of a new nonlinear optical waveguide coupler, fabricated in single-mode fibers and using a liquid crystal as the nonlinear medium, is described. Strongly intensity-dependent coupling and associated bistability are observed to occur in the intensities of the light in the uncoupled and coupled fibers, plotted as a function of the intensity in the input fiber. The effects of applying a dc electric field are also reported. Criteria for the development of liquid crystals suitable for the construction of various types of nonlinear optical devices in single-mode optical fibers are proposed.

Nonlinear mode coupling in birefringent fiber: Application to optical pulse reshaping

It is theoretically shown that intensity dependent mode coupling is induced by nonlinear birefringence between two orthogonally polarized modes in optical fibers in such way that the weak light field polarized along the slow axis of the birefringent fiber couples more strongly to the other mode having the perpendicular polarization than to the strong light field. By utilizing the mode coupling property it is possible in a birefringent single-mode fiber to isolate the optical pulse launched, say, in the LPx01 mode from the precursor and tailing edges or weak background by coupling them to the LPy01 mode. This will readily lead to the application of birefringent fibers to optical pulse compression. In this scheme of pulse reshaping, the loss of the LPy01 mode is required to be much larger than that of the LPx01 mode in order to avoid the unnecessary coupling back to the main mode.