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Nonlinear Optics: Materials, Fundamentals, and Applications, 1994. NLO '94 IEEE

Date 25-29 July 1994

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Displaying Results 1 - 25 of 157
  • Proceedings of 1994 Nonlinear Optics: Materials, Fundamentals and Applications

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    Freely Available from IEEE
  • Semiclassical vs. quantum behavior in fourth-order interference

    Page(s): 350 - 352
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    We explore semiclassical and quantum descriptions of fourth-order interference that are built upon classical and quantum Gaussian-state models for the signal and idler outputs from a parametric down converter. Our approach unifies the analysis of fourth-order interference with those for squeezing and photon twins. It also demonstrates that a purely-quantum fourth-order interference effect can be claimed at fringe visibilities substantially below the commonly accepted threshold of 50%. We start with a pair of models - one quantum and one classical - for the signal and idler fields produced by parametric down conversion View full abstract»

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  • Wavelength domains in bulk Kerr media

    Page(s): 341 - 343
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    Summary form only given. In this paper we consider optical phenomena in two transverse dimensions that arise from nonlinear coupling between two or more copropagating beams of different wavelengths in self defocusing, isotropic Kerr media. We find that the different wavelengths form distinct, stable domain type solitary waves bordered by sharp domain walls that are analogous to polarisation domain walls (PDWs) View full abstract»

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  • Optical and electron paramagnetic resonance investigation of the role of vanadium in photorefractive CdTe:V

    Page(s): 281 - 283
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    Cadmium telluride has been regarded as a material of choice for many envisioned photorefractive applications in the infrared because of its high electrooptic coefficient. We recently demonstrated high beam-coupling gains in CdTe:V using applied electric fields. The prospects of using this gain enhancement mechanism in self-pumped phase conjugators and the experimental demonstration of the theoretically predicted high sensitivity of the photorefractive process in CdTe:V has attracted more attention towards the development and the optimization of the photorefractive properties of this materia1. Experience has shown that vanadium is a proper dopant that results in both high resistivity and efficient photoconductive and photorefractive responses over a wide wavelength range in the infrared. Further development of this material requires an understanding of the role of V in the photorefractive process. We report on photorefractive characterization, optical absorption, photoluminescence and electron paramagnetic resonance of vanadium-doped CdTe. The results of these experiments outline the role of vanadium in the photorefractive process View full abstract»

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  • Cross-modulation distortion in subcarrier multiplexed optical systems

    Page(s): 338 - 340
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    Summary form only given. The third-order inter-modulation distortion arising from the nonlinear rate equations of a directly driven laser diode of a subcarrier multiplexed fiber-optic system has been considered by many researchers. The inter-modulation products that have been considered are the frequency distortion terms and the cross-modulation products. Cross-modulation distortion occurs when the modulation of one carrier is (unintentionally) transferred to another carrier resulting in intelligible crosstalk, as contrasted with the unintelligible crosstalk that results from inter-modulation distortion. We show in this paper that cross-modulation distortion cannot be entirely ignored View full abstract»

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  • Optical fiber nonlinear effects in lightwave communication systems

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    Advances in optical amplifier technology have reshaped the lightwave communications landscape. Erbium-doped fiber amplifiers have enabled systems engineers to begin exploiting the enormous transmission capacity of single-mode fibers. However, implementation of optical amplifiers magnify the effects of optical nonlinearities in the transmission fibers. These nonlinearities will limit the information capacity of lightwave communications. The nonlinearities can be separated into two broad classes. Stimulated scattering processes, such as Brillouin and Raman, cause wavelength conversion of signals. This gives rise to unwanted noise, crosstalk, and power depletion. The nonlinear refractive index of silica is the source of such effects as self-phase and cross-phase modulation which produce spectral broadening, and four-photon mixing which mixes signals in wavelength multiplexed systems. This talk will describe the various optical nonlinearities and discuss the limits imposed by these nonlinearities on the information capacity of lightwave communication systems. Methods for reducing the systems impact of nonlinearities will also be presented View full abstract»

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  • Giant static dipole moment and polarizability in highly oriented J-aggregates

    Page(s): 83 - 85
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    In the present paper, we report an extremely large change in a static dipole moment and polarizability observed in oriented J-aggregates of l,l'-diethyl-2,2'-quinocyanine bromide [pseudoisocyanine bromide (PIC-Br)] by electromodulation spectroscopy View full abstract»

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  • Raman-assisted UV generation in KTP frequency doublers

    Page(s): 335 - 337
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    Summary form only given. An attempt to lase a Raman line in a KTP doubler aroused our suspicions that the Raman process might be implicated in KTP damage. Although occasional flashes of directed Stokes light were observed, they were invariably self-terminating and associated with bulk crystal catastrophic damage. We therefore explored the possibility that Raman-shifted light generated in the doubling process was phase matched to produce damaging UV View full abstract»

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  • A new class of strongly photorefractive materials

    Page(s): 221 - 223
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    Certain doped compound semiconductors exhibit persistent photoconductivity (PPC) at low temperatures as a result of the optical ionization of electrons from deep, spatially localized, donor levels known as DX centers. We calculate that this release of carriers also produces a refractive index shift (through the plasma effect) which is 30 times larger than that of conventional photorefractive materials, We report the results of diffraction measurements on samples of AlGaAs which support this prediction. The induced index changes can be erased by heating above an annealing temperature determined by the material composition View full abstract»

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  • Squeezing with fiber Sagnac loop and sub-shot-noise measurement

    Page(s): 299 - 301
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    Squeezed states of light are minimum uncertainty states for which the mean square fluctuations in phase and in quadrature with respect to a reference signal are unequal. Among other interesting properties, they provide improved sensitivity of optical interferometric phase measurements. To understand this potential, one must note that quantum theory imposes measurement uncertainty only on a pair of noncommuting variables; the measurement of any one quantum observable could be done with no uncertainty View full abstract»

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  • How quickly self-Raman effects and third-order dispersion destroy squeezing

    Page(s): 373 - 375
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    We have developed a general quantum theory of nonlinear pulse propagation and a self-consistent quantum theory of self-Raman effects in optical fibers. Our approach is based on the linearization approximation, the conservation of commutator brackets, and the concept of adjoint systems. A general, self-consistent scheme is developed to quantize nonlinear optical pulse propagation problems and a general computation procedure ("the backpropagation method") is developed to calculate the quantum uncertainties of the inner product between any given function and the (perturbed) field operator. By utilizing these results, we can calculate the magnitude of squeezing when an optical pulse propagates through an optical fiber in the presence of self-Raman effects and third-order dispersion View full abstract»

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  • Photorefractive spatial solitons-theory and experiments

    Page(s): 287 - 289
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    The existence of photorefractive (PR) spatial solitons has been predicted by us some two years ago(1,2). The self-trapping effects occur when diffraction is exactly balanced by self-scattering (two-wave mixing) of the spatial (plane wave) components of the soliton beam View full abstract»

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  • Efficient resonant surface-emitting second-harmonic generators and optical power limiters based on multilayers or asymmetric quantum wells

    Page(s): 321 - 323
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    Summary form only given. Here, we propose novel type of devices that simultaneously perform two functions: frequency doubling and optical power limiting from different output ports based on resonant second-order susceptibilities in ZnSe-ZnS or AlGaAs-AlGaAs multilayer, or ZnSe-ZnMnSe or GaAs-AlGaAs asymmetric quantum well structures incorporating quarterwave stacks for resonant enhancement View full abstract»

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  • Sensitive detection of biomolecular chirality by nonlinear optical activity

    Page(s): 80 - 82
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    We have studied nonlinear optical activity in second-harmonic generation from Langmuir-Blodgett monolayers of a synthetic chiral polymers. All observed effects are explained by a model that includes the contributions of both electric and magnetic dipole transitions to the second-order nonlinearity of the chiral surface. In this paper, we use samples of bacteriorhodopsin as an example to show that such nonlinear optical activity can be used as a sensitive probe of chiral environment of biological material View full abstract»

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  • A new twist on light: applications of the optical vortex soliton

    Page(s): 27 - 29
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    An optical vortex appears as a black circular spot surrounded by bright illumination in the transverse cross-section of a light beam. This phenomenon is attributed to the phase of the beam, which twists like a spiral stair-case, along the optical axis. In fact, this field is a well known mode in both waveguide and scattering theory, and is given in cylindrical coordinates. As will be shown, there are simple methods of producing such linear waves. In self-defocusing nonlinear refractive media, the refractive index is greatest where the intensity is zero, e. g., in the center of an optical vortex View full abstract»

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  • Quasi-phase matched second-harmonic generation from asymmetric coupled quantum wells

    Page(s): 157 - 159
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    Quasi-phase matched (QPM) second-harmonic (SH) generation in both insulator and semiconductor waveguides has applications ranging from the generation of coherent visible light to optical signal processing. QPM compensates the wavevector mismatch between the fundamental and SH light by periodically varying the SH susceptibility, χ(2), and refractive index, along the SH light propagation direction. It would be very useful if quantum wells could be used to engineer materials with a large χ(2) which can be easily varied. Large asymmetric quantum well SH susceptibilities have been measured for far infrared wavelengths, where the nonlinear response is dominated by intra-subband transitions. Although there have been several theoretical studies predicting a quantum well χ(2) comparable to that of LiNbO3 or larger in the near infrared and visible wavelength range, there have been no experimental measurements of χ(2) . The authors use reflection geometry QPM to selectively enhance the SH signal from an asymmetric coupled quantum well (ACQW) superlattice. In addition they present the first measurement, to the best of their knowledge, of χ(2) in the visible wavelength range for an ACQW View full abstract»

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  • Frequency conversion by four-wave mixing in single-mode fibers

    Page(s): 332 - 334
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    Summary form only given. Four-wave mixing in optical fibers is an important nonlinear process which has a profound effect on optical communications. The mixing may cause some cross-talk problems in a wavelength-division-multiplexing system. On the other hand, the mixing process is useful for frequency conversion. In this paper, we calculate the frequency conversion efficiency and discuss some related issues View full abstract»

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  • Nonlinear optical properties of thin film composite materials

    Page(s): 459 - 461
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    Several groups have proposed the use of composite materials as a means of achieving large values of the third-order susceptibility χ(3). One proposal involves forming a composite of alternating layers of two different materials with layer thicknesses much smaller than an optical wavelength. The angular dependence of the nonlinear optical response of this material can offer a means to determine quantitatively the extent to which the χ((3)) susceptibility is enhanced. In the present paper, we report the results of our experimental study of this angular dependence. We find that the angular dependence is in good qualitative agreement with theoretical predictions View full abstract»

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  • Photorefractive properties of rhodium doped barium titanate

    Page(s): 278 - 280
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    Summary form only given. We have measured the effective trap density, the number of active trap levels, the sign of the dominant charge carrier, and the photorefractive two-beam coupling gain of four rhodium-doped crystals of BaTiO3, all grown at Hughes Research Laboratories View full abstract»

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  • Polarization patterns in a passive ring-cavity

    Page(s): 63 - 65
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    A ring-cavity system, filled with an isotropic nonlinear medium and driven by a linearly polarized coherent input field, has been the subject of intense study over the last decade. This system can show a number of non-equilibrium phase transitions, including optical bistability (OB), and transverse pattern formation. The instability responsible for pattern formation then simply serves to drive the system from the unstable lower branch to the stable upper branch. This conclusion, however, is based on the assumption that the internal field in the nonlinear ring-cavity preserves its polarization state as that of the input field. Here we extend the mean field model to include polarization effects View full abstract»

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  • Control of photocurrent directionality via interference of single and two photon absorption in a semiconductor

    Page(s): 239 - 241
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    Summary form only given. In quantum mechanics, if two or more perturbations induce a transition between the same initial and final states of system, the overall transition probability is determined by the modulus squared of the sum of the transition amplitudes for each perturbation. It is therefore possible for interference effects to determine the outcome as it does in the classical Young's double slit experiment. If two coherent beams with frequencies ω and 2ω are applied to a system, the interference between the quantum mechanical pathways associated with single and two photon absorption events can lead to final states on the system whose properties are dependent on the relative phase of the beams View full abstract»

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  • Coherent phonon-polaritons as a probe of anharmonic lattice vibrations

    Page(s): 394 - 396
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    We investigate the dielectric properties of LiTaO3 and LiNbO3 in the THz regime by measuring the dynamics of coherently generated phonon-polaritons. The dielectric response of these ferroelectric crystals is dominated by the lowest-energy lattice vibration of A1 symmetry. This so-called ferroelectric mode is associated with a strong absorption peak at 6 THz (200 cm-1) in LiTaO3 and at 7.5 THz (250 cm-1) in LiNbO 3. The properties of these vibrations are strongly affected by the displacement of ions which occurs when the lattice temperature approaches the ferroelectric phase transition temperature. The dielectric properties of LiTaO3 and LiNbO3 can be described by modelling these modes with a microscopic vibrational potential within one unit cell. The structure of this potential determines critically the polariton response. Therefore, the experimental determination of the phonon-polariton dispersion and damping provides information about the microscopic properties of LiTaO 3 and LiNbO3 View full abstract»

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  • Grating response time of photorefractive KNbO3:Rb+

    Page(s): 284 - 286
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    Photorefractive crystals play an increasingly important role in optical information processing. Some of these crystals have been used in a variety of optical computing applications. The photorefractive response time is a critical issue because it directly determines the processing speed of the devices. Crystals that are widely used at present, such as BaTiO3, LiNbO3, and SBN, etc., are relatively slow when the light intensity is 1 W/cm2. Semiconductor crystals such as GaAs and GaP have a higher speed but suffer from small coupling constants. For high processing speed, KNbO 3 has the best promise because it has the highest figure of merit among the oxide photorefractive crystals. Volt et. al studied the photorefractive response time of KNbO3:Fe. They found that reduction of the crystal could decrease the response time by several orders of magnitude. However, such KNbO3 crystals often become optically inhomogeneous after reduction. In this paper, we report our investigation of the transient photorefractive response of KNbO3:Rb+ crystals, which exhibit a fast response time while maintaining a significant gain and good optical homogeneity for information processing applications View full abstract»

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  • Spontaneous pattern formation in an absorptive system

    Page(s): 75 - 76
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    We present analytical and numerical results indicating pattern formation in a purely absorptive medium, namely a resonantly-excited two-level system in a ring cavity. Pattern formation occurs when the cavity is mistuned such that the optical wavelength exceeds that of the nearby cavity mode. But then off-axis or "tilted" waves can exactly fit the cavity, and this determines the dominant transverse wave vector of the pattern View full abstract»

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  • Compensation for distortions and depolarization of a multi-mode fiber using a Brillouin phase-conjugate mirror

    Page(s): 415 - 417
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    We have used Brillouin phase conjugation to demonstrate compensation of phase aberrations and depolarization induced by a multi-mode fiber, and we have achieved a high degree of fidelity. Although the relatively weak signal-beam power led to our selection of a PCM based on Brillouin enhanced four-wave mixing (BEFWM), with its associated complexities, simple SBS PCMs are capable of thresholds much less than those of the present device. For example, the use of longer capillaries (lengths of several meters) with smaller cross sections (100 μm) has been shown to yield SBS threshold powers as low as ~ 100 W View full abstract»

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