摘要:

Laser writing of diffraction gratings in a liquid-crystal polymer film are studied where the optical changes take place owing to laser heating of the material above the glass transition temperature. The peak diffraction achieved is small (much less than 1%), but the evolution of the diffraction efficiency is well reproduced by theory, and it is seen that the low values obtained are due to thermal diffusion. It is shown that writing on the film with high powers or using a pulsed laser could lead to larger efficiencies.

ISSN:0950-0340    

DOI:10.1080/09500349414550411

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The formulae for the refractive indices and the reflection coefficients for a discontinuity surface between an isotropic medium and a birefringent one with dielectric and magnetic anisotropy were developed. In the case considered the symmetry axis forms an arbitrary angle with the interface. The curves obtained for the cases of dielectric, magnetic or both anisotropies are compared.

ISSN:0950-0340    

DOI:10.1080/09500349414550421

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper we discuss the non-classical and noise properties for a beam of coherent light through a nonlinear fibre with gain, and give the exact solutions of the Heisenberg-Langevin equations of motion of the operators, under the condition that the initial state is a two-mode coherent or two-mode squeezing vacuum state. Detailed numerical analysis of the results is performed and presented graphically. We find that squeezing and antibunching for the above mentioned state occur in some conditions, but no sub-Poissonian photon statistics occur. For example, when the average photon number of 1 mode is greater than the average photon number of 2 mode, the 1 mode is bunching, whereas the 2 mode is antibunching; the signal-to-noise ratio for a mode of radiation field can reach maximum values at an average photon numbern¯or at a momentt.

ISSN:0950-0340    

DOI:10.1080/09500349414550431

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Appearance of d.c. in a crystal in a purely a.c. field with asymmetric temporal profile is discussed when the frequency of the field oscillations is much larger than the inverse response time of the crystal.

ISSN:0950-0340    

DOI:10.1080/09500349414550441

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An exact solution for the problem of two two-level atoms interacting with a single-mode detuned quantized radiation field is presented. On resonance, an asymptotic result is derived for large coherent initial fields. It is shown that when the atoms are initially prepared in one of the semiclassical eigenstates, the atom-plus-field wavefunction remains almost factored into an atomic and a field part throughout the interaction. Under certain conditions, the atomic part evolves into a unique pure state at half-revival time. The effects of the cavity detuning on the dynamics of the atomic level occupation probabilities and emission spectra are studied. It is found, for non-symmetrical excitation, that far off-resonance the field acts like a virtual level by means of which the energy is transferred between the atoms. Due to non-zero detuning, nine-peaked spectra are observed and are given a clear explanation from the dressed-state viewpoint. It is established that in the case of symmetrical excitation, the intensity of the emission spectrum is two times larger than that in the case of non-symmetrical excitation.

ISSN:0950-0340    

DOI:10.1080/09500349414550451

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A multimirror device is designed for measuring vibrational temperatures in gradient ultrasonic flows by the radiation of a heated gas in the i.r. range. The movable optical system permits one to perform spatial scanning along a jet to find temperature fields and to carry out various spectrophotometric investigations including absolute measurements of energy. The high-temperature standard of black radiation is used as a reference source. The signal of a standard source is maintained along the whole scanning site with the accuracy of ± 0·5%. The expression for determining vibrational temperatures allowing for the source brightness attenuation in the spectropyrometer illumination compartment is presented.

ISSN:0950-0340    

DOI:10.1080/09500349414550461

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Arrays of equal intensity spots are usually realized by specially designed phase gratings, spatial filtering, wavefront division using holographic lenslets and the Talbot effect. In this paper, a new method of generating arrays is described where two wedge plates are used in a new configuration.

ISSN:0950-0340    

DOI:10.1080/09500349414550471

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The atomic Bloch equations driven by a quantum noise are investigated in the framework ofc-number multiplicative stochastic Rabi amplitudes. It is shown that the stochastic broad-band vacuum fluctuations can be incorporated in such a way that spontaneous absorption is removed. It is shown that the multiplicative stochastic noise with no spontaneous absorption is equivalent to the quantum vacuum noise. A stochastic model of the broad-band squeezed vacuum is introduced and investigated. From such a stochastic description the fast and the slow damping rates of the Bloch polarizations are obtained. The strong-field resonance fluorescence spectrum and the steady-state atomic inversion for the stochastic model of squeezed vacuum fluctuations are derived.

ISSN:0950-0340    

DOI:10.1080/09500349414550481

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Any initial state of the radiation field in a finite-Qcavity relaxes towards thermal equilibrium. For the case of a zero-temperature cavity, it is shown that the factorial moments of any photon distribution evolve independently, and have the same time evolution. This is applied to evaluate the transient behaviour of the photon statistics for a variety of initial states of practical interest. The coherences of the density operator obey the same equation of motion as the populations (the photon probability distribution), after a simple transformation. This is used to recover the result that a coherent state remains a pure and coherent state at all times. Also the time-dependent frequency spectrum has been evaluated, and it appeared that this spectrum is the same for any state of the radiation field. The spectral distribution is determined entirely by the cavity damping rate, the spectral width of the detector, and the observation time.

ISSN:0950-0340    

DOI:10.1080/09500349414550491

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Aq-coherent state for the quantum superalgebra U(1/1) is introduced. A path integral formalism for theq-coherent state is constructed and applied to theq-deformed Jaynes-Cummings model (q-JCM) with the Uq(1/1) dynamical supersymmetry. The complete energy spectrum of theq-JCM is obtained for both the cases when the interaction constants areC-valued and when they are Grassmann valued.

ISSN:0950-0340    

DOI:10.1080/09500349414550501

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor