The influence of the counter-rotating terms on the steady state in the Dicke model

Summary It is pointed out that the inclusion of the counter-rotating terms into the Dicke model with cavity losses prevents a total de-excitation of the atomic system and new steady states for the atomic population inversion, which could be of experimental importance, appear.     

Influence of the counter-rotating terms on the squeezing and rabi oscillations in the Jaynes-Cummings model

Summary The significant influence of the counter-rotating terms on the squeezing and collapse (revival) phenomena in the Jaynes-Cummings model is pointed out. Numerical results for the time evolution of the atomic population inversion, and atomic and field squeezing parameters for different initial fields (coherent and squeezed) are presented. The author of this paper has agreed to not receive the proofs for correction.     

Modes in the Fabry-Perot resonator with the Kerr nonlinearity

Summary The symmetric modes in the cavity of Fabry-Perot type filled by the medium with the Kerr nonlinearity are constructed. The field appears to be double periodic along the longitudinal axis.

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Riassunto Si costruiscono i modi simmetrici nella cavità del tipo di Fabry-Perot riempita dal mezzo con la non linearità di Kerr. Il campo risulta doppiamene periodico lungo l’asse longitudinale.

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Резюме Конструируются симметричные моды в резонаторе Фабри-Перо, заполненном средой с нелинейностью Керра. Оказывается, поле имеет двойную периодичность вдоль продольной оси.

     

The effect of the counter-rotating terms on the dynamical behaviour in the coherent-state jaynes-cummings model with cavity losses

Summary The effect of the counter-rotating terms in the coherent-state Jaynes-Cummings model with cavity losses is studied. Numerical results for the atomic-population inversion show a significant influence of the counter-rotating terms on the dynamical behaviour.     

The effect of the counter-rotating terms on the squeezing in the Jaynes-Cummings model for a coherent field

Summary The effect of the counter-rotating terms on the squeezing in the Jaynes-Cummings model is demonstrated. The time behaviour of the atomic population inversion, atomic and field squeezing parameters for an initially coheret field is calculated numerically.     

The effect of the cavity damping on the squeezing in the Jaynes-Cummings model within and without rotating-wave approximation for a squeezed field

Summary The squeezing is investigated in the Jaynes-Cummings model within and without rotating-wave approximation in the case of a damped cavity. The time behaviour of the atomic and field squeezing parameters for initially squeezed and coherent fields is calculated numerically.     

The counter-rotating terms in the superradiance

Summary It is pointed out that the counter-rotating terms play an important role in the superradiance of the first kind, in which the atomic system is initially in an uncorrelated state with maximal dipole moment. If the counter-rotating terms are added to the master equation for the Dicke model derived by Agarwal and Bonifacioet al., the numerical solutions for the atomic-population inversion and radiation rate show strong damped oscillations (damped recurrence effects) in their time behaviour. A new limiting relation for the cut-off frequency, which depends on the number of atoms, is also obtained for the treated model.

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Riassunto Si evidenzia che i termini controrotanti svolgono un importante ruolo nella superradianza del primo tipo, in cui il sistema atomico è inizialmente in uno stato incorrelato con impulso dipolare massimo. Se i termini controrotanti sono aggiunti all’equazione principale per il modello di Dicke derivato da Agarwal e Bonifacioet al., le soluzioni numeriche per l’inversione di popolazione atomica e il valore di radiazione mostrano forti oscillazioni smorzate (effetti di ricorrenza smorzati) nel loro comportamento nel tempo. Si ottiene anche una nuova relazione per la frequenza di taglio per il modello trattato che dipende dal numero di atomi.

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Резюме Отмечается, что члены с противоположным вращением играют важную роль в суперсветимости первого рода, где атомная система первоначально находится в некоррелированном состоянии с максимальным дипольным моментом. Если члены с противоположным вращением добавляются в ?управляющие? уравнение для модели Дикка, которое было получено Агарвалом, Ъонифачио и др., то численные решения для инверсии атомной заселенности и интенсивности излучения обнаруживают сильные затухающиее осцилляции (затухаюцие рекуррентные эффекты), в их временном поведении. Для рассматриваемой модели получено новое предельное соотношение для частоты обрезания, которая зависит от числа атомов.

     

The influence of the counter-rotating terms on the single-atom spontaneous emission inside a low-Q cavity

Summary Taking into account the counter-rotating terms, an exact equation of motion for the atomic population inversion is derived in the case of the single-atom spontaneous emission inside a damped cavity, by applying a modified Robertson projection-operator method developed previously by the authors. For strongly damped (low-Q) cavities an analytic solution showing the significance of the effect of the counter-rotating terms is obtained. Experimental verification with Rydberg atoms may be feasible.     

A comparison of the iterative Fourier transform method and evolutionary algorithms for the design of diffractive optical elements

Three methods of designing diffractive optical elements (DOE) are compared. The iterative Fourier transform algorithm (IFTA) is compared to an evolutionary strategy (ES) approach and a combination of both methods. It is shown that the combination of both methods produces a better solution than the iterative method and is faster than using the evolutionary strategy only.     

Retina imaging system with adaptive optics for the eye with or without myopia

An adaptive optics system for the retina imaging is introduced in the paper. It can be applied to the eye with myopia from 0 to 6 diopters without any adjustment of the system. A high-resolution liquid crystal on silicon (LCOS) device is used as the wave-front corrector. The aberration is detected by a Shack-Harmann wave-front sensor (HASO) that has a Root Mean Square (RMS) measurement accuracy of λ/100 (λ = 0.633 μm). And an equivalent scale model eye is constructed with a short focal length lens (∼18 mm) and a diffuse reflection object (paper screen) as the retina. By changing the distance between the paper screen and the lens, we simulate the eye with larger diopters than 5 and the depth of field. The RMS value both before and after correction is obtained by the wave-front sensor. After correction, the system reaches the diffraction-limited resolution approximately 230 cycles/mm at the object space. It is proved that if the myopia is smaller than 6 diopters and the depth of field is between −40 and +50 mm, the system can correct the aberration very well.     

Nonlinear liquid-crystal interfaces: Determination of the local director orientation

Summary We present a new computational method which allows to work out the director orientation in each location of a nematic liquid-crystal cell from a measurement of its reflectivity. We show how it is possible to extract this information from the fringe pattern due to the onset of total internal reflection inside the sample. The very good agreement with the expected results makes the method suitable to study several kinds of deformations occurring in liquid crystals. Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988.     

Recursive differential equations of the raman-nath type: A general review

Summary In this paper we discuss the differential recursive equations of the Raman-Nath type and introduce a very general technique of analysis, valid for both exact and perturbed solutions.

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Riassunto In questo lavoro si studiano equazioni differenziali alle ricorrenze di tipo Raman-Nath e s’introduce una tecnica di analisi valida per la ricerca di soluzioni esatte e perturbate.

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Резюме В этой статье мы обсуждаем дифференциальные уравнения Рамана-Ната и вводим очень общую технику анализа, справедливую для точных и пертурбационных решений.

     

Single-atom radiation effects in the presence of a damped fock-state field

Summary In this paper an exact analytic solution for the Jaynes-Cummings model in the presence of a damped Fock-state field is derived. In addition simpler approximate solutions are given for large and small cavity damping. Moreover, numerical results for atomic population inversion, atomic radiation rate and atom-field correlation are presented for different cavity dampings and initial photon numbers. In the case of small cavity damping damped periodic revivals as well as the existence of a new quasistationary state are pointed out.

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Riassunto In questo lavoro si deriva una soluzione analitica esatta per il modello di Jaynes-Cummings in presenza di un campo smorzato dello stato di Fock. Si danno anche soluzioni approssimate piú semplici per smorzamento a piccole e grandi cavità. Inoltre, si presentano risultati numerici dell'inversione della popolazione atomica, della quantità di radiazione atomica e della correlazione atomo-campo per diversi smorzamenti di cavità e numeri fotonici iniziali. Nel caso di smorzamento a piccola cavità, si mettono in evidenza riprese periodiche smorzate così come l'esistenza di un nuovo stato quasi stazionario.

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Резюме В этой статье выводится точное аналитическое решение для модели Джейнса-Камингса в присутствии поля затухающих фоковских состояний. Кроме того, приводятся более простые приближенные решения для больших и малых затуханий. Для различных затуханий и начальных чисел фотонов приводятся численные результаты для инверсии атомной заселенноси, интенсивности излучения атома и атом-полевой корреляции. В случае малого затухания отмечаются затухающие периодические восстановления, а также существование нового квази-стационарного состояния.

     

Silicon Photonics Rectangular Universal Interferometer

Universal multiport photonic interferometers that can implement any arbitrary unitary transformation between input and output optical modes are essential to support advanced optical functions. Integrated versions of these components can be implemented by means of either a fixed triangular or a fixed rectangular arrangement of the same components. We propose the implementation of a fixed rectangular universal interferometer using a reconfigurable hexagonal waveguide mesh circuit. A suitable adaptation synthesis algorithm tailored to this mesh configuration is provided and the experimental demonstration of a rectangular multiport interferometer by means of a fabricated silicon photonics chip is reported. The 7‐hexagonal cell chip can implement 2 × 2, 3 × 3 and 4 × 4 arbitrary unitary transformations. The proposed hexagonal waveguide mesh operates in a similar way as a Field Programmable Gate Array (FPGA) in electronics. We believe that this work represents an important step‐forward towards fully programmable and integrable multiport interferometers.     

Is there any need for the born approximation in spontaneous emission by a single two-level atom?

Summary In the case of spontaneous emission, up to date, it was believed that the Born approximation in the projection-operator method as well as in the Heisenberg equations of motion is inevitable. Therefore, no consistent comparison between these methods and that of Weisskopf-Wigner (where no such approximation has been used) was possible. This inconsistency is removed in the present paper.     

Wigner optics in the metaxial regime

A consistent methodology is developed, using the Wigner matrix associated with the Helmholtz equation, to treat metaxial optical systems. The propagation equation of this matrix is derived and its relationship with the corresponding paraxial propagation equation is clarified.     

高功率激光系统中近轴鬼像点的寻找

考虑了空间滤波小孔隔离鬼像点的作用后，提出了寻找大型高功率激光装置中近轴鬼像点的矩阵光学方法，并根据实际系统提出了判断鬼像点虚实的可行方法。所编制出的程序可用于寻找激光放大系统中的任意高阶鬼像点。     

What is wrong with the projection operator method? removal of inconsistencies and a new self-consistent method for non-Markovian treatment of atom-field interactions

Summary In this paper it is pointed out, for the first time to the author's knowledge, that the application of the projection-operator method leads to the violation of a consistency condition if the so-called Born approximation is employed. Namely, the violation of this consistency condition causes the appearence of negative probabilities in the non-Markovian master equation and thus makes the applicability of the projection-operator method questionable. Further, it is shown that an additional Markov approximation re-establishes the applicability of the method. Moreover, a new self-consistent projection-operator method for treating non-Markovian time evolution in the case of interactions between atoms and field (reservoir) is developed. Finally, in the appendix it is shown that, if the usual non-self-consistent projection-operator method in the Born approximation is applied to the case of spontaneous emission from a two-level hydrogen atom, a negative probability for finding the atom in the excited state emerges. The author of this paper has agreed to not receive the proofs for correction.     

Focal waveforms with tunable carrier frequency using dispersive aperturing

We introduce the concept of dispersive aperturing involving a beam truncation by hard-edge apertures where diameter of the processed beam changes upon frequency. Applied to focused waves, this procedure transforms power spectra at the focal point (and the surroundings). Waveforms at focus conserve pulse duration but carrier frequency may be altered substantially. In principle, some degrees of freedom allow carrier-frequency tuning at convenience.