Conditions for Sub-poissonian Photon Statistics and Squeezed States in Resonance Fluorescence

We study the conditions for sub-poissonian photon statistics and squeezed states in the field of resonance fluorescence of a two-state atom. These conditions as a function of the detuning from resonance, the linewidth and the Rabi frequency have some overlap, but they are largely complementary. Super-poissonian statistics arise for small linewidths and large detunings, irrespective of the Rabi frequency. Squeezed states require small linewidths and either low or moderate Rabi frequencies, or large detunings from resonance.     

Generalized Bloch-Siegert Shift in a Squeezed Vacuum

Abstract

The time evolution of the atomic dipole moment of a two-level atom damped by an off-resonance squeezed vacuum is studied. Our results are valid for arbitrary detuning between the carrier frequency of the squeezed vacuum and the atomic transition frequency and show that the atomic dipole moment can oscillate with two dominant frequencies. These frequencies are shifted from their central values by an amount which is proportional to the degree of squeezing. We show that this shift of the frequencies is the exact equivalent of the optical Bloch-Siegert shift in the case of the ordinary vacuum damping without the rotating-wave approximation.     

Three-level Atom in a Squeezed Vacuum I

Abstract

We consider a three-level atom in any of its possible configurations, ladder, lambda or vee, which interacts with two classical, resonant, monochromatic electromagnetic fields. We suppose the levels     

Cooperative Atomic Behaviour and Oscillator Formation in a Squeezed Vacuum

Abstract

Time-dependent (numerical) results are presented for super-radiant behaviour in the Dicke model of N _a = 2, 3 atoms in a broad band squeezed vacuum. This concerns the fluctuations and the intensity of the fluorescent radiation as well as the atomic population inversion of the system with atoms initially in an atomic coherent state. In the steady state, and in the N _a → ∞, we show that the ‘atomic’ Dicke model behaves like a ‘giant quantum oscillator’, in which the number of excited atoms asymptotically approaches the average number of photons in the resonant mode of the squeezed vacuum, just as in the thermally driven case.     

Effect of a Squeezed Vacuum on Coherent Population Trapping in a Three-level Lambda System

Abstract

Master equation methods are used to investigate the effects of a broad-band squeezed vacuum on a three-level atom of the lambda configuration. The two-mode squeezed vacuum is treated as a Markovian reservoir in a non-stationary phase-dependent state. In addition to the squeezed vacuum the atom is driven by two coherent laser fields each of which, depending on the polarization, can couple to one or both of the atomic transitions. We show that in general the optical Bloch equations for the atomic density matrix elements have oscillatory coefficients, thereby necessitating the use of Floquet methods. For the case of equal laser frequencies, which are also equal to the carrier frequency of the squeezed vacuum, the coefficients of the Bloch equations become time independent and stationary solutions for the populations and coherences are obtained by standard matrix methods. For the ordinary vacuum the usual coherent population trapping effect at two-photon resonance is obtained, with the upper state population being zero. An unsqueezed thermal field partially destroys the trapping effect as the upper state population is no longer zero at two-photon resonance. The squeezed vacuum has the effect of improving the trapping in that the coherence hole becomes more pronounced for some values of the relative phase between the squeezed vacuum and the driving fields. The additional effects of a coherence transfer rate between the two optical coherences, which occurs for special choices of angular momentum quantum numbers are also studied. For the case of equal laser frequencies, the inclusion of this coherence transfer process destroys population trapping and reduces the lambda system to a two-level system. However, for the case of unequal laser frequencies, the coherence transfer process in combination with the squeezed vacuum can restore to some extent the population trapping. We show that other features that do not occur for two-level atoms, such as stationary population inversions between pairs of the atomic levels, also depend on the relative phase and can be enhanced in the squeezed vacuum. In the case of unequal frequencies of the driving fields the population in the upper state depends on the relative phase only when the carrier frequency of the squeezed vacuum is equal to one of the two frequencies of the driving fields. When the carrier frequency of the squeezed vacuum is slightly detuned from both frequencies of the driving fields, the population in the upper state is insensitive to the relative phase but is dependent on the degree of squeezing. For large detunings, the population does not show any dependence on the degree of squeezing and its distribution in function of the two-photon detuning is similar to that in the thermal vacuum field.     

Higher Harmonics in Cooperative Resonance Fluorescence

In the Stark representation, in third-order perturbation theory with respect to fluorescence, it is shown that probability of the ω_a + 4Ω harmonic emission in the cooperative fluorescence of two two-level atoms is small and proportional to γ² / Ω², Ω² / ω² _a, contributions to this probability from non-resonant processes being of the order of γ₂ / ω₂ ^a.     

State Evolution in the Two-photon Jaynes-Cummings Model with Initial Squeezed Vacuum and Chaotic Fields

Abstract

An approximate treatment is given for the state evolution in the two-photon Jaynes-Cummings model with initial squeezed vacuum and chaotic state fields. Both initially pure and mixed atomic states are examined. Interesting features such as the evolution of the atom into unique pure states and the recurrence of the initial atomic states at certain times are found. Effects of the dynamic Stark shifts on the system state evolution are also studied.     

Squeezing and Antibunching in Phase-matched Many-atom Resonance Fluorescence

Abstract

We present two approaches to the correlation properties of the fluorescence field emitted by a many-atom source. The first approach is an extension of resonance-fluorescence theory, while the second one is based on scattering theory. Both approaches lead to an understanding of why the ‘anomalous’ correlation properties associated with squeezing and antibunching appear when some phase-matching condition is satisfied and why this condition is the four-wave-mixing one. We show that the effect of atomic motion can be taken into account in the scattering approach and that the many-atom antibunching effect cannot be considered as Doppler-free.     

真空系统中荧光屏余辉测试技术研究

像增强器荧光屏的参数测试是研制三代像增强器的前提.现建立真空测试系统.热电子面发射源在真空中发射电子,电场加速,然后轰击荧光屏,使其发亮.利用电场瞬间拒斥轰击电子,测试荧光屏的余辉;分析电场特性,设计出合理的余辉测试装备,测试出荧光屏的余辉,为其它参数测试或其它领域的研究提供了经验.     

Photon Antibunching in Resonance Fluorescence in the Presence of Atomic Number Fluctuations

An analysis of photon correlation measurements for fluorescent light from a beam of two-level atoms is given where the number of pulse pairs n(τ) with time separation τ is recorded using a time-to-digital converter. These measurements are shown to correspond precisely to a subsequently normalized second-order correlation function (i.e. the normalization is performed after time averaging).     

Squeezed Light

Abstract

In this paper we review the current state of progress in research on squeezed light. We discuss the basic theory of squeezing and the nature of quantum noise in optical fields. We examine various atomic sources of squeezed light and discuss phase-sensitive detectors of quantum noise including homodyne and heterodyne detectors. Various successful nonlinear optical methods for generating squeezed light are reviewed. We conclude with a discussion of the possible applications of squeezed light.     

Back-action-induced Squeezed Light in a Detuned Quantum Non-demolition Scheme

Abstract

We describe the experimental observation and theoretical interpretation of a squeezing effect which occurs through the coupling of two light beams in a three-level atomic system. The origin of this effect can be attributed to the transfer of the intensity fluctuations of one beam to the phase fluctuations of the other one, followed by an optical feedback onto the intensity of the initial beam. The first step of the information transfer is similar to the one which occurs in a quantum non-demolition (QND) measurement of the intensity. The feedback effect is obtained through mixing of the phase and intensity quadratures, due to the detuning of the optical cavity which contains the nonlinear medium. Therefore the information obtained by the QND measurement is used to correct the intensity fluctuations of the signal beam by a build-in mechanism, which does not require any use of external electronics.     

A Self-Assembled Plasmonic Substrate for Enhanced Fluorescence Resonance Energy Transfer

Fluorescence resonance energy transfer (FRET) has found widespread uses in biosensing, molecular imaging, and light harvesting. Plasmonic metal nanostructures offer the possibility of engineering photonic environment of specific fluorophores to enhance the FRET efficiency. However, the potential of plasmonic nanostructures to enable tailored FRET enhancement on planar substrates remains largely unrealized, which are of considerable interest for high-performance on-surface bioassays and photovoltaics. The main challenge lies in the necessitated concurrent control over the spectral properties of plasmonic substrates to match that of fluorophores and the fluorophore–substrate spacing. Here, a self-assembled plasmonic substrate based on polydopamine (PDA)-coated plasmonic nanocrystals is developed to effectively address this challenge. The PDA coating not only drives interfacial self-assembly of the nanocrystals to form closely packed arrays with customized optical properties, but also can serve as a tailored nanoscale spacer between the fluorophores and plasmonic nanocrystals, which collectively lead to optimized fluorescence enhancement. The biocompatible plasmonic substrate that allows convenient bioconjugation imparted by PDA has afforded improved FRET efficiency in DNA microarray assay and FRET imaging of live cells. It is envisioned that the self-assembled plasmonic substrates can be readily integrated into fluorescence-based platforms for diverse biomedical and photoconversion applications.     

Two-mode Squeezed Gaussons

Abstract

Two-mode squeezed Gaussons are non-classical states of light which are intermediate between single-mode and two-mode squeezed states. They may be prepared by coherently mixing two single-mode squeezed states at a beam-splitter or via a frequency converter. When equally squeezed single-mode squeezed states are incident on a 50/50 beam-splitter the output will range between a two-mode squeezed state and two single-mode squeezed states as the phase of the input squeezed light is varied. This behaviour is reflected when the properties of such states are investigated.     

Properties of Squeezed Binomial States and Squeezed Negative Binomial States

Abstract

The effect of squeezing on binomial states and on negative binomial states is studied in terms of second-order correlation functions and quasi-probabilities of Wigner and Q-functions. The photon number distribution of these states is also discussed. The results presented for squeezed binomial (negative binomial) states may be useful for studying a transition from squeezed coherent states to squeezed number (quasi-thermal) states.     

Statistical Properties of a New Squeezed Operator Model

Abstract

We introduce a new squeezed operator which is a combination of the two-mode squeezed operator and the two single photon squeezed operator. Here we study the effects of this operator on the photon number sum and difference. The squeezing in the frequency converter model has been examined, and statistical investigations are carried out for the quasi-probability distribution functions (Wigner function and Q-function). An application to the parametric amplifier is given.     

Interaction of a Two-level Atom with Squeezed Light

The dynamic response of the inversion in a two-level atom to single-mode squeezed states of the radiation field is examined. Depending on the direction of squeezing, an increase or decrease in the collapse time is demonstrated. A number of additional departures from the response of the atom to a coherent field are noted. In particular, for certain squeezed states the response of the atom is similar to that expected for chaotic radiation.     

Propagation of Squeezed Light in Dielectrics

Abstract

We model the propagation of squeezed light through a dielectric medium. Frequency-dependent absorption reduces the level of squeezing and may decrease the squeezing bandwidth. Dispersion dephases the squeezing at different frequencies within the spectrum.     

Generalized Two-mode Squeezed States

Abstract

A new generalized two-mode squeezed state which has less fluctuation in one quadrature phase then the usual two-mode squeezed state at the expense of increased fluctuation in the other quadrature is proposed. The coordinate representations and normally ordered expansions of the generalized two-mode squeeze operators and are given. The wavefunction of the generalized two-mode squeezed coherent state is obtained. The non-classical properties of the state such as squeezing and sub-Poissionian statistics are discussed.