Abstract: We have studied optical pulse propagation in a Raman fiber amplifier doped with a three-level medium and driven by a control laser pulse. We analyze the spatial-temporal dynamics of pulse propagation for different atomic initial conditions. The propagation of an optical pulse through the amplifier can be sustained by a control laser that induces transparency via quantum coherence, which is useful for extending the distance between optical repeaters. Under certain conditions, amplification is achieved without population inversion. The results could be useful for laser control of optical pulses in amplifiers and waveguides.
Abstract: Nonlinear optical processes have been used for sensitive detection of chemicals, optical imaging and spectral analysis of small particles. We have developed an exact theoretical framework to study the angular dependence of coherent anti-Stokes Raman scattering (CARS) intensity in the near field and far field for nanoparticle and microparticle. We obtain exact analytical solution for the CARS signal valid for arbitrary detection distance. Interesting angular dependence is found for nanoparticle, especially with near field detection. The study includes the erects of focused lasers and particle size on the CARS intensity distribution. We find that the detection distance and particle size do not affect the spectroscopic peaks of CARS. However, interference of reflected waves in nanoparticle can produce a dip in the backscattered spectrum.
Abstract: One dimensional photonic crystal with superconducting nanostrips and semiconductor materials can be tailored to have narrow bands, with either large transmission or large reflection. Based on the reflection and transmission coefficients, we study the temporal dynamics of the reflected and transmitted pulses from the finite photonic crystal. The output pulse dynamics show slow light effect around the narrow bands that can be useful for photonic technologies.
Abstract: It is shown that thermal energy from a heat source can be converted to useful work in the form of maser-laser light by using a combination of a Stern-Gerlach device and stimulated emissions of excited particles in a maser-laser cavity. We analyze the populations of atoms or quantum dots exiting the cavity, the photon statistics, and the internal entropy as a function of atomic transit time, using the quantum theory of masers and lasers. The power of the laser light is estimated to be sufficiently high for device applications. The thermodynamics of the heat converter is analyzed as a heat engine operating between two reservoirs of different temperature but is generalized to include the change of internal quantum states. The von Neumann entropies for the internal degree are obtained. The sum of the internal and external entropies increases after each cycle and the second law is not violated, even if the photon entropy due to finite photon number distribution is not included. An expression for efficiency relating to the Carnot efficiency is obtained. We resolve the subtle paradox on the reduction of the internal entropy with regards to the path separation after the Stern-Gerlach device.
Abstract: Quantum coherence or phaseonium medium with electromagnetic-induced transparency (EIT) may have been widely explored, but the incorporation of boundaries into finite structures like thin films and photonic crystals introduce additional resonant features. A narrow transmission peak exists in resonant medium due to multiple reflections and interference. The corresponding analytical formulas for absorptive and EIT media are derived. A double dip feature is found only for transverse magnetic polarized light, due to longitudinal electric field component in a Fabry-Perot thin film. We study these resonant features in a finite superlattice and discuss potential applications of the features. For phaseonium medium with laser-driven gain, transmission and reflection peaks beyond unity appear between the two EIT resonances. Realizations using solid-state materials such as doped crystals and quantum dots with potential applications are discussed.
Abstract: Spatial dependence of coherent anti-Stokes Raman scattering (CARS) intensity and spectra for a spherical particle are studied for different sizes, ranging from micrometers to nanometers. Effects of near field on the spectra are analyzed, showing potential application as nano-sensor in microscopy and imaging. The results can be extended to an array of nanospheres. The CARS process has been developed into a versatile real-time detection technique in spectroscopy and microscopy [1]. In particularly, backscattered ultra-violet CARS implemented on LIDAR system [2] is promising for remote detection of molecular species present in hazardous biological aerosols with microscale dimension. In practice, the aerosols could be in any dimension. Thus, we need to know study a modified the setup of the CARS technique for reliable detection of chemicals in micro- and nano-particles using near-field effects. We have developed a nonlinear semiclassical microscopic theory to describe the CARS spectra for a particle composed of a collection of arbitrarily complex molecules [3] as well as simple few levels quantum systems [2]. The theory provides useful results on the CARS spectra for any observation angle and for any form of laser pulses [3]. Here, we focus on the spectra in the near field. We wish to study how the spectra vary with the near field distance with focused laser pulses. We also analyze to what extend the dimension of the particle and the focusing laser affect the lensing effect which could enhance the backscattered light.
Abstract: The Commutation relation for the field creation and annihilation operators is shown to be preserved explicitly if the transient operators products are evaluated from the quantum Langevin equations that contain noise operators with non-vanishing expectation (mean) values. The well-known Einstein relation, which is valid for the vanishing mean value, is inapplicable here. For a two-level atom initially in arbitrary state interacting with quantum vacuum radiation, detailed steps are provided that may be useful for calculations involving transient dynamics using the full quantum formalism, particularly in evaluating products involving the noise operators, the initial (time) field operator and initial atomic operators. The cross products of these operators contribute to the preservation of the commutation relation. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: Laser field with superintensity beyond 10(29) W/cm(2) can be generated by coherent superposition of multiple 100 fs laser pulses in circular geometry setup upon retroreflection by a ring mirror. We have found the criteria for attaining such intensities using broadband ring mirror within the practical damage threshold and paraxial focusing regime. Simple expressions for the intensity enhancement factor are obtained, providing insight for achieving unlimited laser intensity. Higher intensities can be achieved by using few-cycle laser pulses.
Abstract: We study the spatial interference pattern of two-photon correlation function for a coherently phased linear array of N emitters with a double-Raman scheme, each producing nonclassically correlated photon pairs. The N(2) dependence in the two-photon correlation serves as a coherent amplification method for producing intense nonclassical light. The spatial distribution of the correlation can be controlled by lasers, and depends on the detection configuration. For two coincident detectors, the nonclassical correlation displays the spatial Talbot pattern, but modulated by quantum interference effect. The image revival distance is found to be twice the usual Talbot length. For symmetrically located detectors (X(1) = -X(2)), the correlation displays a distorted Talbot pattern with intricate features and lack of symmetry.
Abstract: We study the transient pulse propagation in one-dimensional photonic crystal. Two new effects are identified: double reflection and slow-light ringing of transmitted and reflected pulses. We analyze these effects in superconductor-dielectric photonic crystal around the polariton resonance region of the dielectric material. Distinct double-polariton dispersions and narrow peaks in the transmission and reflection spectra are found when the plasma gap and the polariton gap of the dielectric overlap. Potential applications of these effect are discussed. (C) 2010 Optical Society of America
Abstract: A laser-cooling scheme for molecules is presented based on repeated cycle of zero-velocity selection, deceleration, and irreversible accumulation. Although this scheme also employs a single spontaneous emission as in [Raymond Ooi, Marzlin, and Audretsch, Eur. Phys. J. D 22, 259 (2003)], in order to circumvent the difficulty of maintaining closed pumping cycles in molecules, there are two distinct features which make the cooling process of this scheme faster and more practical. First, the zero-velocity selection creates a narrow velocity-width population with zero mean velocity, such that no further deceleration (with many stimulated Raman adiabatic passage (STIRAP) pulses) is required. Second, only two STIRAP processes are required to decelerate the remaining hot molecular ensemble to create a finite population around zero velocity for the next cycle. We present a setup to realize the cooling process in one dimension with trapping in the other two dimensions using a Stark barrel. Numerical estimates of the cooling parameters and simulations with density matrix equations using OH molecules show the applicability of the cooling scheme. For a gas at temperature T = 1 K, the estimated cooling time is only 2 ms, with phase-space density increased by about 30 times. The possibility of extension to three-dimensional cooling via thermalization is also discussed.
Abstract: Extremely intense laser field that makes nonlinear quantum vacuum can be generated by coherent superposition of multiple lasers in circular configuration that incorporates optical fibers synchronization scheme and piecewise mirrors in circular array operating below typical damage threshold. Coherent amplification and large laser beams can produce intensity reaching nonlinear quantum vacuum regime. The effects of phase jitter and envelope timing of the pulses due to imperfect synchronization are simulated and analyzed for both linear and circularly polarized pulses. We obtain simple analytical expressions that well describe the envelope jitter and phase jitter. Several practical aspects are discussed, including implications of scaling the laser dimension and pulse duration, with possibility for giant laser facility.
Abstract: Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The corresponding theory is being developed to describe nonlinear scattering of a mesoscopic particle composed of complex molecules by laser pulses with arbitrary shape and spectral content. Microscopic many-body transform theory is used to compute the third order susceptibility for CARS in molecules with known absorption spectrum and vibrational modes. The theory is combined with an integral scattering formula and Mie-Lorentz formulae, giving a rigorous formalism which provides powerful numerical experimentation of CARS spectra, particularly on the variations with the laser parameters and the direction of detection.
Abstract: We examine nonclassical properties of the field states generated by applying a photon annihilation-then-creation operation (AC) and a creation-then-annihilation operation (CA) to the thermal and coherent states. Effects of repeated applications of AC and of CA are also studied. We also discuss experimental schemes to realize AC and CA with a cavity system using atom-field interactions. (C) 2009 Optical Society of America
Abstract: We investigate the directional property of photons emitted spontaneously from a partially-excited many-atom system. There exists a strong directional correlation between the emitted photons and the photons that have been absorbed by laser excitation and among all emitted photons themselves. Such a strong correlation arises from entanglement of W-type generated in the atomic system during the process of absorption and emission. (c) 2009 Elsevier B.V. All rights reserved.
Abstract: We present a microscopic theory of nonlinear scattering of mesoscopic particle that maybe composed of complex molecules. We predict that the spectrum of the scattered field depends on the angle of observation. Transform theory is used to compute the third-order susceptibility for coherent anti-Stokes Raman scattering (CARS) of molecules with known absorption spectrum and vibrational modes. By incorporating the theory into an integral scattering formula, we develop a rigorous theory which leads to powerful numerical experimentation of nonlinear optical process in mesoscopic systems composed of complex molecules and driven by laser pulses with arbitrary shape and spectral content. We obtain an expression for spectral dependent CARS field which includes multiple internal reflection and refraction of the incident fields via Mie theory. The theory is used to study the variations of the CARS spectra and intensity on laser parameters and direction of detection. High-resolution spectra computed for hybrid CARS scheme shows that the relative intensities of the characteristic peaks in the CARS spectrum depend on the direction of detection. This effect can be explained by the interference between the linear response (absorption and dispersion) and the four-wave mixing process in the mesoscopic medium. The theory is useful for nonlinear spectroscopy, microscopy and nanophotonics involving small particles. Copyright (C) 2009 John Wiley & Sons, Ltd.
Abstract: We show how two-photon correlation of a two-level amplifier in the small signal regime depends on the atomic populations and the propagation length. We predict that inverted population associated with negative temperature gives a very long correlation time even in the presence of decoherence, a useful asset for quantum communication. The correlation vanishes for very dilute atomic gas. Analytical solutions for the field operators obtained by Fourier transform and Laplace transform (with initial condition) of the time variable appear very different but yield identical numerical results except for certain parameters. The physical explanation behind the deviation is given. The presence of thermal photons is found to reduce the correlation time.
Abstract: We study the effects of arbitrary laser pulse excitations on quantum correlation, entanglement, and the role of quantum noise. The transient quantities are computed exactly using a method that provides exact solutions of the Langevin field operators for photon pairs produced by a double Raman atom driven by laser pulses. Short pulses with appropriate chirping, delay, and/or detuning can generate broadband photon pairs and yield results that provide insights on how to generate very large nonclassical correlation. We find that short pulses are not favorable for entanglement. Photon correlation and entanglement are favored by exclusively two different initial conditions. We find rapid variations of entanglement with pulse width and strength. Explanation is given based on the pulse area concept and the phase-sensitive nature of entanglement. Analysis of results reinforces our understanding of the two nonclassical concepts and the nature of quantum noise.
Abstract: The Doppler effect of moving atoms can create irreversibility of light. We show that the laser field in an electromagnetic induced transparency (EIT) scheme with atomic motion can control the directional propagation of two counter-propagating output probe fields in an atomic gas. Quantum coherence and the Doppler effect enable the system to function like an optical transistor with two outputs that can generate states analogous to the Bell basis. Interference of the two output fields from the gas provides useful features for determining the mean atomic velocity and can be used as a sensitive quantum velocimeter. Some subtle physics of EIT is also discussed. In particular, the sign of the dispersive phase in EIT is found to have a unique property, which helps to explain certain features in the interference.
Abstract: We obtain an analytical expression for two-photon correlation G((2)) from two atoms driven in a double-Raman (or Lambda) configuration where collective effects such as superradiant, subradiant, and dipole-dipole interaction are included. It is found that the collective effects on the G((2)) can be quenched to some extent by a resonant control laser field. The collective effects provide features via G((2)) that enable the two atoms to be resolved at subwavelength separation. We also identify an effect in the double Raman scheme due to the collective effects and the control field, i.e., the Stokes and anti-Stokes frequencies are increased by fourfold.
Abstract: An extended medium driven in a double Raman configuration generates Stokes and anti-Stokes fields that are described by coupled parametric oscillator equations with solutions that depend on input boundary operators and quantum noise operators. We identify the conditions where the boundary operators can be the substitute to the noise operators for describing two-photon cross correlation in forward and backward geometries. These conditions include short sample and small decoherence between ground states gamma(bc), and they are fulfilled by the spontaneous Raman electromagnetic induced transparency scheme (weak pump with large detuning). We verify the correspondence between the results from boundary and noise operators analytically and show that the correlation due to the boundary operators is typically smaller than that due to the noise operators. In general the noise operators are required to obtain the correct correlation, especially when the control laser field is weak and gamma(bc) is finite. Explanations for the findings are given based on the physics represented by the boundary operators and noise operators. Similar conclusions are obtained for the Stokes and anti-Stokes intensities.
Abstract: We present a largely analytical theory for two-photon correlations G((2)) between Stokes (s) and anti-Stokes (a) photon pairs from an extended medium (amplifier) composed of double-Lambda atoms in counterpropagating geometry. We generalize the parametric coupled equations with quantum Langevin noise given in a beautiful experimental paper of Balic et al. [Phys. Rev. Lett. 94, 183601 (2005)] beyond adiabatic approximation and valid for arbitrary strength and detuning of laser fields. We derive an analytical formula for cross correlation G(as)((2)) = < E-s(dagger)(L)E-a(dagger)(0,tau)E-a(0,tau)E-s(L)> and use it to obtain results that are in good quantitative agreement with the experimental data. Results for G(as)((2)) obtained using our coupled equations are in good quantitative agreement with the results using the equations of Balic et al., while perfect agreement is obtained for sufficiently large detuning. We also compute the reverse correlation G(sa)((2)) which turns out to be negligibly small and remains classical while the cross correlation violates the Cauchy-Schwartz inequality by a factor of more than a hundred.
Abstract: We study the effect of spontaneously generated coherence (SGC) on two-photon correlation in a double-cascade scheme. An analytical expression for two-photon correlation is obtained and analyzed. The SGC and asymmetry in the two cascade channels provide a "sinelike" interference term that distorts the profile of the correlation. We show that the SGC term contains nonclassical features that are identical to the spontaneous Raman electromagnetic-induced transparency scheme which shows antibunching. Yet the correlation shows bunching instead of antibunching, and this is explained. We consider all possible transitions and find that photon antibunching is not possible in the double-cascade scheme.
Abstract: Is the directional property of radiation emitted from atoms characteristically different depending on whether the atoms are entangled or not? We investigate this question by analyzing and comparing directional properties of radiation emitted from two and three atoms prepared in an entangled state and in a separable state.
Abstract: Sub- and superradiant dynamics of spontaneously decaying atoms are manifestations of collective many-body systems. We study the internal dynamics and the radiation properties of two atoms in free space. Interesting results are obtained when the atoms are separated by less than half a wavelength of the atomic transition, where the dipole-dipole interaction gives rise to new coherent effects, such as (a) coherence between two intermediate collective states, (b) oscillations in the two-photon correlation G((2)), (c) emission of two photons by one atom, and (d) the loss of directional correlation. We compare the population dynamics during the two-photon emission process with the dynamics of single-photon emission in the cases of a Lambda and a V scheme. We compute the temporal correlation and angular correlation of two successively emitted photons using the G((2)) for different values of atomic separation. We find antibunching when the atomic separation is a quarter wavelength lambda/4. Oscillations in the temporal correlation provide a useful feature for measuring subwavelength atomic separation. Strong directional correlation between two emitted photons is found for atomic separation larger than a wavelength. We also compare the directionality of a photon spontaneously emitted by the two atoms prepared in phased-symmetric and phased-antisymmetric entangled states parallel to +/->(k0)=e(0)(ik)center dot r(1)parallel to a(1),b(2)>+/- e(0)(ik)center dot r(2)parallel to b(1),a(2)> by a laser pulse with wave vector k(0). Photon emission is directionally suppressed along k(0) for the phased-antisymmetric state. The directionality ceases for interatomic distances less than lambda/2.
Abstract: We show that an absolute coherent phase of a laser can be used to manipulate the entanglement of photon pairs in two-photon laser. We present simple physics behind a general master equation for two-photon laser. Our focus is on the generation of a continuous source of macroscopically entangled photon pairs in the double Lambda (or Raman) scheme. We show how the steady-state photon numbers and entanglement depend on the laser parameters, especially the phase. We obtain a relationship between entanglement and two-photon correlation. We derive conditions that give steady-state entanglement for the spontaneous Raman-electromagnetic-induced transparency scheme and use it to identify the region with macroscopic entanglement. No entanglement is found for the double resonant Raman scheme.
Abstract: A radiative interaction in a collective two-atom system forms subradiant and superradiant states when the distance between neighboring atoms is less than half a wavelength of resonant radiation. We calculate the G((2)) function depending on the atomic separation and detection angle and show that it oscillates with a time delay between two successively emitted photons. These oscillations are the signature of coherent effects due to the periodic emission and absorption of photons by each atom.
Abstract: We study several aspects of two-photon correlation of an optically driven extended medium (amplifier) with parametric down-conversion (PDC) scheme and three-level cascade scheme. The correlation for the PDC scheme is modeled by coupled parametric equations with constant self-coupling and cross coupling coefficients. This provides simple physical insights to how the correlation profile depends on the sign and magnitude of the coefficients in the presence of propagation group delay between signal and idler photons. The results with constant coefficients are related to the results of the driven three-level cascade scheme obtained from quantum Langevin-Maxwell's equations. The correlation transforms from bunching to antibunching as the pump field increases. Cauchy-Schwartz inequality is violated for all time delay in the case of off-resonant pump, showing nonclassical correlation. We verify that the correlation obtained without noise operators is qualitatively correct regardless of the optical density, especially for large detuning. We also discuss the interesting physics behind antibunching and oscillations found in the reverse correlation.
Abstract: A collection of N static atoms is fixed in a crystal at a low temperature and prepared by a pulse of incident radiation of wave vector k ->(0). The N atoms are well described by an entangled Dicke-like state, in which each atom carries a characteristic phase factor exp(ik ->(0)center dot r ->(j)), where r ->(j) is the atomic position in the crystal. It is shown that a single photon absorbed by the N atoms will be followed by spontaneous emission in the same direction. Furthermore, phase matched emission is found when one photon is absorbed by N atoms followed by two-photon down-conversion.
Abstract: We review the phenomenon of equilibrium fluctuations in the number of condensed atoms no in a trap containing N atoms total. We start with a history of the Bose-Einstein distribution, a similar grand canonical problem with an indefinite total number of particles, the Einstein-Uhlenbeck debate concerning the rounding of the mean number of condensed atoms (n) over baro near a critical temperature T(C), and a discussion of the relations between statistics of BEC fluctuations in the grand canonical, canonical, and microcanonical ensembles. First, we study BEC fluctuations in the ideal Bose gas in a trap and explain why the grand canonical description goes very wrong for all moments <(n(0) - (n) over bar (0))(m)>, except of the mean value. We discuss different approaches capable of providing approximate analytical results and physical insight into this very complicated problem. In particular, we describe at length the master equation and canonical-ensemble quasiparticle approaches which give the most accurate and physically transparent picture of the BEC fluctuations. The master equation approach, that perfectly describes even the mesoscopic effects due to the finite number N of the atoms in the trap, is quite similar to the quantum theory of the laser. That is, we calculate a steadystate probability distribution of the number of condensed atoms pn(0)(t = infinity) from a dynamical master equation and thus get the moments of fluctuations. We present analytical formulas for the moments of the ground-state occupation fluctuations in the ideal Bose gas in the harmonic trap and arbitrary power-law traps. In the last part of the review, we include particle interaction via a generalized Bogoliubov formalism and describe condensate fluctuations in the interacting Bose gas. In particular, we show that the canonical-ensemble quasiparticle approach works very well for the interacting gases and find analytical formulas for the characteristic function and all cumulants, i.e., all moments, of the condensate fluctuations. The surprising conclusion is that in most cases the ground-state occupation fluctuations are anomalously large and are not Gaussian even in the thermodynamic limit. We also resolve the Giorgini, Pitaevskii and Stringari (GPS) vs. ldziaszek et al. debate on the variance of the condensate fluctuations in the interacting gas in the thermodynamic limit in favor of GPS. Furthermore, we clarify a crossover between the ideal-gas and weakly-interacting-gas statistics which is governed by a pair-correlation, squeezing mechanism and show how, with an increase of the interaction strength, the fluctuations can now be understood as being essentially 1/2 that of an ideal Bose gas. We also explain the crucial fact that the condensate fluctuations are governed by a singular contribution of the lowest energy quasiparticles. This is a sort of infrared anomaly which is universal for constrained systems below the critical temperature of a second-order phase transition.
Abstract: For many applications of slow or stopped light, the delay-time-bandwidth product is a fundamental issue. So far, however, slow-light demonstrations do not show a large delay-time-bandwidth product, especially in room temperature solids. Here we demonstrate that the use of artificial inhomogeneous broadening has the potential to solve this problem. A proof-of-principle experiment is done using slow light produced by two-beam coupling in a photorefractive crystal CeBaTiO3 where Bragg selection is used to provide the artificial inhomogeneity. Examples of how to generalize this concept for use with other room temperature slow-light solids are also given.
Abstract: The atom fluctuation statistics of an ideal, mesoscopic, Bose-Einstein condensate are investigated from several different perspectives. By generalizing the grand canonical analysis (applied to the canonical ensemble problem), we obtain a self-consistent equation for the mean condensate particle number that coincides with the microscopic result calculated from the laser master equation approach. For the case of a harmonic trap, we obtain an analytic expression for the condensate particle number that is very accurate at all temperatures, when compared with numerical canonical ensemble results. Applying a similar generalized grand canonical treatment to the variance, we obtain an accurate result only below the critical temperature. Analytic results are found for all higher moments of the fluctuation distribution by employing the stochastic path integral formalism, with excellent accuracy. We further discuss a hybrid treatment, which combines the master equation and stochastic path integral analysis with results obtained based on the canonical ensemble quasiparticle formalism [Kocharovsky , Phys. Rev. A 61, 053606 (2000)], producing essentially perfect agreement with numerical simulation at all temperatures.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: A critical limitation of slow light schemes is the limited time-bandwidth product. Recently we showed that this limitation can be overcome by making use of inhomogeneities. Here we analyze the effects of crosstalk noise that can be induced by these inhomogeneities in certain situations, and how to minimize such noise. The proof of principle experiment was done using three-wave mixing in a photorefractive crystal Ce:BaTiO3 where Bragg selection is used to provide the inhomogeneity.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: Backscattered signal of coherent anti-Stokes Raman spectroscopy can be an extremely useful tool for remote identification of airborne particles, provided the signal is sufficiently large. We formulate a semiclassical theory of nonlinear scattering to estimate the number of detectable photons from a bacterial spore at a distance. For the first time, the theory incorporates enhanced quantum coherence via femtosecond pulses and a nonlinear process into the classical scattering problem. Our result shows a large backscattered signal in the far field, using typical parameters of an anthrax spore with maximally prepared vibrational coherence. Using train pulses of 1 kHz of repetition rate each with energy of 10 mJ, we estimate that about 10(7) photons can be detected by a 1 m diameter detector placed 1 km away from the spore in the backward scattering direction. The result shows the feasibility of developing a real time remote detection of hazardous microparticles in the atmosphere, particularly biopathogenic spores.
Abstract: The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.
Abstract: The quantum correlation between a pair of Stokes and anti-Stokes photons, involving a Raman emission process is calculated. All realistic radiative and nonradiative decays are included in the calculation and the photon correlation between the pair for arbitrarily strong excitation fields and detunings are calculated. The correlation function shows photon antibunching, and a damped sinusoidal behavior with respect to the time delay between the measurement of the two photons. The current system can also produce four photon entanglement.
Abstract: We present ail analytical calculation to determine the atomic injection time effects on lasing Without inversion (LWI) in a three level lambda system with its ground state driven by ail arbitrarily strong classical microwave field. We systematically take into account Subtle effects associated with the injection times. We derive an expression for the optical coherences and show that one gets amplification of the field without Population inversion which is governed by a temporal phase, in addition to the initial (random) phases of the ground state coherence. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: We show that by using the strongly correlated photon pairs generated in a Raman quantum erasure scheme (Scully M and Druhl K 1982 Phys. Rev. A 25 2208), it is possible to exceed the Rayleigh resolution limit of classical microscopy. The complete analysis of the underlying physics is given here. Further discussion of the physics and potential applications are presented in a companion paper (Scully M O 2004 Improving quantum microscopy and lithography via Raman photon pairs: I. Biological applications, submitted).
Abstract: A general scheme for rotational cooling of diatomic heteronuclear molecules is proposed. It uses a superconducting microwave cavity to enhance the spontaneous decay via Purcell effect. Rotational cooling can be induced by sequentially tuning each rotational transition to cavity resonance, starting from the highest transition level to the lowest one using an electric field. Electrostatic multipoles can be used to provide large confinement volume with essentially homogeneous background electric field.
Abstract: A general scheme for reducing the center-of-mass entropy is proposed. It is based on the. repetition of a cycle, composed of three concepts: velocity selection, deceleration and irreversible accumulation. Well-known laser techniques are used to represent these concepts: Raman pi-pulse for velocity selection, STIRAP for deceleration, and a single spontaneous emission for irreversible accumulation. No closed pumping cycle nor repeated spontaneous emissions are required, so the scheme is applicable to cool a molecular gas. The quantum dynamics are analytically modelled using the density matrix. It is shown that during the coherent processes the gas is translationally cooled. The internal states serve as an entropy sink, in addition to spontaneous emission. This scheme provides new possibilities to translationally laser-cool molecules for high precision molecular spectroscopy and interferometry.
Abstract: We study the quantum dynamics of the center-of-mass momentum distribution for the populations of a cold gas with two-level system undergoing spontaneous decay and coupled to a Markovian thermal reservoir at arbitrary temperature. We derive the momentum-convolutionless coupled equations for momentum Fourier transform of the populations which can be easily solved numerically and analytically for a specific internal scheme and for zero-temperature cases. The time and momentum evolutions of the populations are obtained by inverse Fourier transform. The momentum spread and the center-of-mass entropy across one momentum dimension are computed and compared for different internal schemes, between zero-temperature and finite-temperature cases and between pi and sigma(+/-) transitions. For initial subrecoil momentum width, the sigma(+/-) transition displays a two-peak feature. Our results well describe the momentum spread dynamics of cold gas in thermal radiation at early: time and complement the results based on Fokker-Planck equation.
Abstract: We foresee applications and interesting possibilities of incorporating the photonic crystals concept into superconducting electronics. In this paper, we present interesting features of the computed lower band structure of a nondissipative superconductor-dielectric superlattice using the two-fluid model and the transcendental equation [Pochi Yeh, Optical Waves in Layered Media, Wiley Series in Purl and Applied Optics (Wiley, New York, 1988)]. The necessary conditions for approximating the complex conductivity by an imaginary conductivity is derived and the feasibility of achieving the conditions are discussed. The superlattice dispersion obtained is similar to that of the phonon-polariton dispersion in ionic crystal. We found a nonlinear temperature-dependent "polariton gap" and a low-frequency (plasma) gap, and suggested the existence of a photon-superelectron hybrid around the polariton gap. The polariton gap may be observed in an infrared-microwave regime using a high-T-c, superconductor with sufficiently low normal-fluid relaxation time (approximate to 10(-15) s), and in an optical regime using lower penetration depth (approximate to 50 nm) and extremely low relaxation time (approximate to 10(-17) s).
Abstract: In this paper, we present more general, exact, and concise expressions for calculating the electromagnetic density of modes (EDOM) in one dimension photonic crystal (superlattice) for E and H polarizations. The expression is used for numerical computation of the EDOM in the lower-index (dielectric constant) layer. We discuss the difference between the EDOM in high- and low-index layers as due to the presence of waveguiding modes and evanescent-excited Bloch modes in the higher-index layer. Two methods of computation are presented to compute the EDOM in the lower-index layer. We suggest the possibility of using the EDOM to establish population inversion, which may be useful for higher-frequency lasers (e.g., x rays) and control any radiative processes. We also elaborate on the limitations of the results of Alvarado Rodriguez ct al. as due to the approximation used in the evaluation of partial derivative omega/partial derivativek(y,z) for del (k)omega and comment on the Limitations of the one-dimensional EDOM expression of Bendickson et al.
Abstract: Photonic band structures explored in the past 12 years were mainly fabricated from dielectric materials, typically used in the semiconductor technology. However, we foresee novel applications and interesting possibilities by incorporating the photonic crystals concept into superconducting devices. In this paper, we study the band structure of a non-dissipative superconductor-dielectric superlattice using the two-fluid model. We apply the dispersion relations in both layers of the superlattice to the transcendental equation for a double-layer superlattice, from which we compute the bandgap structure for the dielectric-superconducting superlattice. Computation results show the existence of dispersion-curve splitting similar to the phonon-polariton case in addition to the low-frequency gap similar to the plasma-frequency gap. The polariton gap size is characterized by polarization and the penetration depth, and highly dependent on temperature at the vicinity of superconducting transition temperature. Our analysis shows that the properties of this material structure may have application in optical region if extremely low relaxation time superconductor is used. This may be an asset for superconducting electronics-photonics integration. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
