C. H. Raymond Ooi

Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods

Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Youngs modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems.

Polariton gap in a superconductor–dielectric superlattice

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.

Light-to-matter entanglement transfer in optomechanics

We analyze a scheme to entangle the movable mirrors of two spatially separated nanoresonators via a broadband squeezed light. We show that it is possible to transfer the Einstein–Podolsky–Rosen-type continuous-variable entanglement from the squeezed light to the mechanical motion of the movable mirrors. An optimal entanglement transfer is achieved when the nanoresonators are tuned at resonance with the vibrational frequencies of the movable mirrors and when strong optomechanical coupling is attained. Stationary entanglement of the states of the movable mirrors as strong as that of the input squeezed light can be obtained for sufficiently large optomechanical cooperativity, achievable in currently available optomechanical systems. The scheme can be used to implement long-distance quantum-state transfer provided that the squeezed light interacts with the nanoresonators.

Fluctuations in Ideal and Interacting Bose–Einstein Condensates: From the Laser Phase Transition Analogy to Squeezed States and Bogoliubov Quasiparticles ⁎

We review the phenomenon of equilibrium fluctuations in the number of condensed atoms n 0 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 ¯ 0 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 ¯ 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 steady-state probability distribution of the number of condensed atoms p n 0 ( t = ∞ ) 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. Idziaszek 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.

Nonclassicality generated by photon annihilation-then-creation and creation-then-annihilation operations

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.

Temperature dependent resonances in superconductor photonic crystal

We show that it is possible to obtain large field transmission through a periodic structure at frequencies where the field is lossy in a finite temperature superconductor. The feat is accomplished by using thin superconducting layers. This makes the superconductor photonic crystal useful for transmitting signals over larger distances at higher temperature. Narrow transmission resonances due to surface plasmon effect are damped more quickly with increasing temperature than broader transmission bands. The temperature dependence is useful, particularly for developing optothermal sensors in terahertz and far infrared regimes.

High-performance dye-sensitized solar cells based on morphology-controllable synthesis of ZnO-ZnS heterostructure nanocone photoanodes.

High-density and well-aligned ZnO–ZnS core–shell nanocone arrays were synthesized on fluorine-doped tin oxide glass substrate using a facile and cost-effective two-step approach. In this synthetic process, the ZnO nanocones act as the template and provide Zn2+ ions for the ZnS shell formation. The photoluminescence spectrum indicates remarkably enhanced luminescence intensity and a small redshift in the UV region, which can be associated with the strain caused by the lattice mismatch between ZnO and ZnS. The obtained diffuse reflectance spectra show that the nanocone-based heterostructure reduces the light reflection in a broad spectral range and is much more effective than the bare ZnO nanocone and nanorod structures. Dye-sensitized solar cells based on the heterostructure ZnO–ZnS nanocones are assembled, and high conversion efficiency (η) of approximately 4.07% is obtained. The η improvement can be attributed primarily to the morphology effect of ZnO nanocones on light-trapping and effectively passivating the interface surface recombination sites of ZnO nanocones by coating with a ZnS shell layer.

Single-mode and intermodal higher-order nonclassicalities in two-mode Bose-Einstein condensates

Biswajit Sen , Sandip Kumar Giri, Swapan Mandal, C. H. Raymond Ooi, Anirban Pathak Department of Physics, Vidyasagar Teachers’ Training College, Midnapore-721101, India Department of Physics, Panskura Banamali College, Panskura-721152, India Department of Physics, Visva-Bharati, Santiniketan, India Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia Jaypee Institute of Information Technology, A-10, Sector-62, Noida, UP-201307, India RCPTM, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Science of the Czech Republic, Faculty of Science, Palacky University, 17. listopadu 12, 771 46 Olomouc, Czech RepublicSandip Kumar Giri, Biswajit Sen, C H Raymond Ooi4† and Anirban Pathak Department of Physics, Panskura Banamali College, Panskura-721152, India Department of Physics, Vidyasagar University, Midnapore 721102, India Department of Physics, Vidyasagar Teachers’ Training College, Midnapore-721101, India Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia Jaypee Institute of Information Technology, A-10, Sector-62, Noida, UP-201307, India RCPTM, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Science of the Czech Republic, Faculty of Science, Palacky University, 17. listopadu 12, 771 46 Olomouc, Czech Republic

Beam splitter entangler for nonlinear bosonic fields

Some years ago Katriel and Solomon [1] described applications to the characterization of the photon statistics of nonideal lasers, nonclassical light, and deformed photon states using f-deformed coherent states. In this letter, we study the effect of a beam splitter on these nonlinear coherent states. We find that these states are useful for generating quantum entanglement as the deformation parameter gets farther form the unity and for strong input field regimes. The results are confirmed through the Werhl entropy.

Improving quantum microscopy and lithography via Raman photon pairs: II. Analysis*

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).