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Two schemes of four-wave mixing oscillators with nondegenerate pumps are proposed for above-threehold generation of squeezed light with nonzero mean-field amplitudes. Noise and correlation properties and optical spectra of squeezed-light beams generated in these schemes are discussed.
This paper presents a theory for quantum light propagation in a single-mode fiber which includes the effects of the Kerr nonlinearity, group-velocity dispersion, and linear loss. The theory reproduces the results of classical self-phase modulation, quantum four-wave mixing, and classical solution physics, within their respective regions of validity. It demonstrates the crucial role played by the Kerr-effect material time constant, in limiting the quantum phase shifts caused by the broadband zero-point fluctuations that accompany any quantized input field. Operator moment equations - approximated, numerically, via a terminated cumulant expansion - are used to obtain results for homodyne-measurement noise spectra when dispersion is negligible. More complicated forms of these equations can be used to incorporate dispersion into the noise calculations.
Solid-state device developed for high-speed acquisition, dynamic storage, and amplification of three-dimensional holographic images. Holograms generated via four-wave mixing in two or more photorefractive crystals (or subelements of single crystal) to create single-crystal or multicrystal oscillator. Apparatus provides dynamic storage of holographic image of object after electronic shutter closed to turn off object beam. Provides capability to store, amplify, process, and transmit time-varying, two-dimensional, spatial information. Developments include sensors, actuators, and optical computers operating at speeds on order of speed of light. Potential in applications in which need for high-speed acquisition and storage of three-dimensional holographic images.
Ultrafast relaxation kinetics of the third order nonlinear susceptibility of polythiophene and polycondensed thiophene-based polymer was determined by the forward degenerate four-wave mixing technique. Deep into the absorption band the nonlinear response shows only a fast component (less than 900 fs at 587 nm) while at the edge of the absorption band at 642 nm a much slower and complex decay was measured.
Polydiacetylenes are a very promising class of polymers for both photonic and electronic applications because of their highly conjugated structures. For these applications, high-quality thin polydiacetylene films are required. We have discovered a novel technique for obtaining such films of a polydiacetylene derivative of 2-methyl-4-nitroaniline using photodeposition from monomer solutions onto UV transparent substrates. This heretofore unreported process yields amorphous polydiacetylene films with thicknesses on the order of I micron that have optical quality superior to that of films grown by standard crystal growth techniques. Furthermore, these films exhibit good third-order nonlinear optical susceptibilities; degenerate four-wave mixing experiments give x(3) values on the order of 10(exp -8) - 10(exp -7) esu. We have conducted masking experiments which demonstrate that photodeposition occurs only where the substrate is directly irradiated, clearly indicating that the reaction occurs at the surface. Additionally, we have also been able to carry out photodeposition using lasers to form thin polymer circuits. In this work, we discuss the photodeposition of polydiacetylene thin films from solution, perform chemical characterization of these films, investigate the role of the substrate, speculate on the mechanism of the reaction, and make a preliminary determination of the third-order optical nonlinearity of the films. This simple, straightforward technique may ultimately make feasible the production of polydiacetylene thin films for technological applications.
The nonlinear optical properties of metal-free phthalocyanine (MFPC) thin films were examined using the second harmonic at 532 nm from a pulsed Nd:YAG laser, and the cw He-Ne , and Ar+ lasers. The He-Ne laser transmission at fixed input intensity was found to increase temporally within a time scale of twelve hours. The origin of this temporal change of transmission is discussed. The third order nonlinear susceptibilities (chi (exp(3))) by four-wave mixing were measured for films of different thickness. The saturation intensity of MFPC, and its absorption cross section, at 633 nm from a He-Ne laser, are reported. An optical bistability was recorded using a He-Ne laser. An AND logic gate was also demonstrated in the system. These phenomena in the system are attributed to refractive index modulation by thermal excitations.
A variety of niobate crystals have found their places in nonlinear optical applications as well as in laser devices. In recent years much attention has been paid to study the ultrafast optical response in a variety of photorefractive crystals such as KTa(1-x)Nb(x)O3 and KNbO3 crystals, glasses, semiconductors and polymers for applications in optical switching, information processing, optical computing, and all-optical device systems. Third-order optical nonlinearity is the most important property for realization of all-optical switching. Therefore experiments have been performed on the third order susceptibility using a variety of techniques such as the third-order harmonic generation, EFISH and degenerate four-wave mixing(DFWM). The latter has been conducted with a variety of pump wavelengths and with nanosecond, picosecond and femtosecond pulses. Niobate crystals, such as potassium niobate KNbO3, potassium tantalate niobate KTN family (KTa(1-x)Nb(x)O3), strontium barium niobate SBN (Sr(x)Ba(1-x)Nb2O6) and potassium-sodium niobate SBN (KNSBN) are attractive due to their photorefractive properties for application in optical storage and processing. The pulsed probe experiments performed on theses materials have suggested two types of time responses. These responses have been associated with an coherent response due to Chi(sup 3), and a long lived component due to excited state population. Recent study of DFWM on KNbO3 and KTN family reveals that the long lived component of those crystals depends on the crystal orientation. A slowly decaying signal is observable when the grating vector K(sub g) is not perpendicular to the C-axis of those photorefractive crystals', otherwise the optical response signal would be only a narrow coherent peak with FWHM equal to the cross-correlation width of the write beam pulses. Based on this understanding, we study the photodynamical process of a variety of niobate crystals using DFWM in a Kg perpindicular to C geometry with a ps-YAG: Nd laser operating at 532nm. However, the discrepancies in numerical estimations of Chi(sup 3) in these materials and other nonlinear optical media have resulted in a number of discussions. In order to better understand the photodynamical process of niobate crystals after an short pulse excitation we analyze the factors governing the coherent signal and present the DFWM spectra of niobate crystals.
The competition effects among the processes of atomic ionization, optical pumped stimulated radiation (OPSR), four-wave frequency mixing (FWFM) and molecular stimulated diffuse band radiation at the atomic two-photon resonance of 3S approaches 4D in Na2 - Na mixture were observed. The dip at the two-photon resonance in the excitation spectrum for the diffuse-band radiation was interpreted as suppression of population in 4D state.
A Raman-scattering-suppressing input/ output coupling scheme has been devised for a whispering-gallery-mode optical resonator that is used as a four-wave-mixing device to effect an all-optical parametric oscillator. Raman scattering is undesired in such a device because (1) it is a nonlinear process that competes with the desired nonlinear four-wave conversion process involved in optical parametric oscillation and (2) as such, it reduces the power of the desired oscillation and contributes to output noise. The essence of the present input/output coupling scheme is to reduce output loading of the desired resonator modes while increasing output loading of the undesired ones.