Quantum-optical Phase and Canonical Conjugation

Abstract

We use a new limiting procedure, developed to study quantum-optical phase, to examine canonically conjugate operators in general. We find that Dirac's assumption that photon number and phase should be canonically conjugate variables, similar to momentum and position, is essentially correct. The difficulties with Dirac's approach are shown to arise through use of a form of the canonical commutator which, although the only possible form in the usual infinite Hilbert space approach, is not sufficiently general to be used as a model for a number-phase commutator. The approach in this paper unifies the theory of conjugate operators, which include photon number and phase, angular momentum and angle, and momentum and position as particular cases. The usual position-momentum commutator is regained from a more generally applicable expression by means of a domain restriction which cannot be used for the phase-number commutator.     

Picosecond Phase Conjugation in Sodium Vapour

Abstract

Phase conjugation by degenerate four-wave mixing in sodium vapour was demonstrated using 80 ps transform-limited pulses. Values of the phase-conjugated reflectivity were measured as a function of the temperature of the vapour and the delay of the probe beam.     

Atomic Phase Conjugation From a Bose Condensate

We discuss the possibility of observing atomic phase conjugation from Bose condensates, and using it as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that since phase conjugation results from the scattering of a partial matter wave off the spatial grating produced by two other waves, it offers a natural way to directly measure such properties, and as such provides an attractive alternative to the optical methods proposed in the past.     

被动相位共轭处理在水声通信中的应用

由于海洋信道的复杂性,要实现可靠的水下声通信,必须进行有效的信道匹配.本文描述了一种能利用信道特性的信道匹配技术-被动相位共轭处理.仿真计算结果表明该技术在水下声通信中有很好的应用前景.     

Phase Conjugation in Degenerate Four-wave Mixing with Finite Apertures

The phase-conjugate field fidelity in backward-going four-wave mixing, based on the diffraction model solvable analytically, is investigated. The method assumes interaction of the non-depleted infinite plane pump waves with the spatially limited probe and signal waves inside the nonlinear medium. Solutions are obtained applying the Fourier transformation and the Green function technique under various boundary conditions for coupled wave equations. The probe and its phase-conjugate waves are defined by using a complex phase formulation including both the phase variation and amplitude modulation. It is shown that the analysed approach can involve assumptions leading to the ideal or distorted phase conjugation.     

Picosecond Phase Conjugation and Two-wave Coupling in Strontium Barium Niobate

Abstract

Picosecond phase conjugation and two-wave coupling in cerium-doped strontium barium niobate at 778 nm were studied. The phase conjugation reflectivity at 778 nm was measured to be R _pc = 58%. It is close to that pumped by a continuous-wave pump source. The temporal width t _pc and spectral width δγ_pc of the phase conjugate pulse were measured to be the same as that of the pump pulse. The intensity coupling gain of two-wave coupling as a function of time delay τ_D between two beams was also studied.     

Phase Conjugation by Degenerate Four-wave Mixing in Inverted Dye Solutions

Abstract

Phase conjugation has been observed in an amplifying medium of rhodamine 6G dye molecules in solution, excited either by flashlamps or by a laser. It is found that the mechanism involved in phase conjugation is degenerate four-wave mixing through gain saturation, and reasonable agreement obtained with the theory of saturable amplifiers. A phase-conjugate signal was observed over the tuning range of the dye system (580–605 nm) and a reflectivity up to a maximum of 25% was obtained.     

High-intensity Effects in Self-pumped Photorefractive Phase Conjugation Using Nanosecond Pulses

Abstract

This paper reports on self-pumped photorefractive phase conjugation using repetitively pulsed high intensity (MW cm^?2) pulses of nanosecond duration. An intensity-dependent phase conjugate reflectivity is measured experimentally. In the corner self-pumped geometry the direction of beam fanning and corner self-pumping is observed to reverse above a critical intensity. Formation of a higher order spatial mode is reported for the external loop self-pumped geometry.     

Multipass Amplification Using Optical Phase Conjugation by Stimulated Brillouin Scattering

Abstract

We built up a multipass amplifier for multiplication of infrared nanosecond pulses based on stimulated Brillouin scattering in acetone. Starting with a Q-switched Nd-doped yttrium aluminium garnet oscillator emitting pulses with less than 5 ns duration, we were able to generate a train of up to five pulses with a pulse shortening. Because only phase-conjugating mirrors have been used, we expect the pulses to have a high transverse homogeneity.     

Phase Conjugation of a Plane Electromagnetic Wave at an Interface

Boundary conditions for electromagnetic waves which undergo phase conjugation at an interface between two media of different refractive index are considered. Appropriate laws of reflection and refraction are derived, showing a certain symmetry with ordinary interaction at a boundary, and affecting the Fresnel equations accordingly.     

Polarization Characteristics of Phase Conjugation at Four-wave Mixing in Uniaxial Crystals

The phenomenon is considered of degenerate phase conjugation at four-wave mixing in uniaxial crystals. Polarization characteristics are calculated. The cases of complete and incomplete phase conjugation are analysed.     

On the Scattering Matrix of Multimode Fibres for Polarization Recovery by Phase Conjugation

Abstract

A phenomenological model for the scattering matrix of a long mode-scrambling optical fibre is derived, predicting incomplete polarization information recovery using a single-polarization phase-conjugating mirror at the fibre output, in agreement with some recent experimental findings.     

高斯光束强度共轭的数值模拟

本文从傍轴波动方程出发,在线性化假设下,导出了任意振幅分布的发射场相位与接收场振幅分布之间的解析关系式,并对高斯光束进行了数值模拟。模拟结果表明,衍射场强度与要求场强度之间符合较好。最后对数值模拟结果进行了讨论。     

Conjugation of active iron superoxide dismutase to nanopatterned surfaces

Superoxide dismutase enzymes (SODs) are an essential part of the first line of cellular defense system against free radicals species. They catalyze the dismutation of superoxide radicals into oxygen and hydrogen peroxide. Although several studies have examined the attachment of superoxide dismutases to nanoparticles and nanostructures, never has been used a member of the Fe/MnSOD family. In this study, the behavior of plant origin FeSOD enzyme on three different nanopatterned surfaces was investigated as a function of covalent and electrostatic binding. Fluorescence microscopy was used to demonstrate that the protein is attached only to the gold layer. We also examined the activity of SOD by a colorimetric assay, and we have shown that the enzyme remains active after attachment to the three different surfaces under both kind of binding (electrostatic and covalent). This methodology could be useful for those who want to functionalize nanostructures with a SOD enzyme and test the activity. This process could be of great interest for the development of peroxynitrite and superoxide biosensors.     

Conjugation of gold nanoparticles to polypropylene mesh for enhanced biocompatibility

Polypropylene mesh materials have been utilized in hernia surgery for over 40 years. However, they are prone to degradation due to the body's aggressive foreign body reaction, which may cause pain or complications, forcing mesh removal from the patient. To mitigate these complications, gold nanomaterials were attached to polypropylene mesh in order to improve cellular response. Pristine samples of polypropylene mesh were exposed to hydrogen peroxide/cobalt chloride solutions to induce formation of surface carboxyl functional groups. Gold nanoparticles were covalently linked to the mesh. Scanning electron microscopy confirmed the presence of gold nanoparticles. Differential scanning calorimetry and mechanical testing confirmed that the polypropylene did not undergo any significantly detrimental changes in physicochemical properties. A WST-1 cell culture study showed an increase in cellularity on the gold nanoparticle-polypropylene mesh as compared to pristine mesh. This study showed that biocompatibility of polypropylene mesh may be improved via the conjugation of gold nanoparticles.     

Conjugation of biomolecules with luminophore-doped silica nanoparticles for photostable biomarkers.

A new molecular conjugation method has been developed to label biomolecules with optically stable metalorganic luminophores, such as tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), which are otherwise not possible for direct linking with the biomolecules. Unique biochemical properties of the biomolecule can, thus, be associated with photostable luminophores. This opens a general way to conjugate desired biomolecules using a sensitive signal transduction method. It also promotes the application of excellent luminescent materials, especially those based on photostable metalorganic luminophores, in biochemical analysis and biomolecular interaction studies. The conjugation method is based on uniform luminophore-doped silica (LDS) nanoparticles (63 +/- 4 nm). These nanoparticles have been prepared using a water-in-oil (W/O) microemulsion method. The controlled hydrolysis of tetraethyl orthosilicate (TEOS) in W/O microemulsion leads to the formation of monodisperse LDS nanoparticles. The luminophores are doped inside the nanoparticles, and the particle's silica surfaces can be used to covalently bind with biomolecules. The luminophores are well-protected from the environmental oxygen when they are doped inside the silica network. As an example, we used an antibody for leukemia cell recognition. The antibody was first immobilized onto the luminophore-doped nanoparticle through silica chemistry and then was used for leukemia cell identification by an optical microscopy imaging technique. The leukemia cells were identified easily, clearly, and with high efficiency using these antibody-coated nanoparticles. The advantages of using small, uniform luminophore-doped nanoparticles are discussed.     

Conjugation of curcumin with PVP capped gold nanoparticles for improving bioavailability

Curcumin, a natural polyphenolic compound, has astounding therapeutic applications but lacks in bioavailability mainly due to its poor solubility in water. Polyvinyl pyrrolidone (PVP) which is a proven drug carrier has been used to facilitate the conjugation of curcumin with gold nanoparticles and to improve the solubility of curcumin in water. In this conjugate diaryl heptanoid chromophore group of curcumin which is a much needed group in biomedical applications remains intact as observed from FTIR and UV–vis spectroscopy analysis. The work shows good promise for such conjugates as therapeutic-cum-imaging materials in biomedical field.