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The photorefractive effect (optically induced index change) has been extensively studied in electrooptic insulators because of its potential for all-optical processing, i.e., convolution and correlation image amplification, phase conjugate resonators, holographic interferometry, and matrix algebra. All the materials to date have exhibited slow response because of the low carrier mobilities and are only sensitive in the visible spectrum. We report for the first time the observation of the photorefractive effect in semi-insulating GaAs:Cr and lnP:Fe by four-wave mixing. In both of these materials the dopants give rise to optical absorption and photoconduction at photon energies below the band edge, to ~1.3 μm In lnP:Fe (~1017 cm−3), and to 1.8 μm in GaAs:Cr (~1016 cm−3). The observed material response times are ~10−4 sec, determined by the dielectric relaxation time, and can be decreased to subnanosecond time scales by increasing the crystal conductivity (i.e., by decreasing the dopant concentration). This lower limit is determined by the drift velocity of photoexcited carriers during space charge separation and relaxation. Thus the material response time can be varied to suit the application. Despite the small electrooptic coefficients of InP and GaAs the photorefractive recording sensitivities (the index change per absorbed photon) are comparable to the best nonlinear recording media, ~1 pJ/bit. Diffraction efficiencies of 10−3 have been achieved with only 50 mW/cm2 of cw YAG:Nd laser irradiation at 1.06 μm. Large high-optical-quality crystals are now available which allow the long interaction length (~10 cm) necessary to obtain diffraction efficiencies close to unity. The electrical and optical properties of the crystals can be tailored to optimize the material parameters for specific applications.1

Doping of CdTe with Ti impurities results in improved photorefractive sensitivity and enhanced gain in the 0.9 to 1.3-um spectral region.

Measurement of the molecular correlation length of the ferroelectric liquid crystal $S\ensuremath{-}2\mathrm{m}\mathrm{e}\mathrm{t}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{b}\mathrm{u}\mathrm{t}\mathrm{y}\mathrm{l}\ensuremath{-}4\ensuremath{-}n\ensuremath{-}\mathrm{d}\mathrm{e}\mathrm{c}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{y}\mathrm{l}\mathrm{o}\mathrm{x}\mathrm{y}\mathrm{b}\mathrm{i}\mathrm{p}\mathrm{h}\mathrm{e}\mathrm{n}\mathrm{y}\mathrm{l}\ensuremath{-}{4}^{\ensuremath{'}}\ensuremath{-}\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{x}\mathrm{y}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{e}$ (2M4DBC) has been obtained from field-dependent pyroelectric studies. The liquid-crystal behavior can be described in terms of a dynamically fluctuating mixture of two conformers having polarizations of opposite sense. The relative density of these species can be altered with an electric field, thereby allowing measurement of the effective dipole moment and correlation volume of the molecular clusters.

The use of titanium diffused optical waveguides in ferroelectric LiNbO3 crystals has led to efficient high speed electro-optical directional coupler switches and modulators as well as several other devices for optical processing.1 For many applications an optical power of 0.1 to 1mW in the waveguide is desirable which requires intensities of about 1kW/cm in single mode structures. However, visible light of this intensity changes the refractive index of the waveguides. This effect is called the photorefractive (PR) effect or optical damage. While the effect can be used to advantage for certain devices (for instance using two-photon absorption2) it is a problem for most integrated optical devices. For instance it has recently been shown to be the origin of optical crosstalk drift in Δβ reversal couplers.3 Little effort has been devoted to understanding or eliminating or even characterizing the effect in Ti in-diffused guides, despite the remarkable success in reducing the effect in out-diffused layers.4

Recently, the 1.06-μm photorefractive response of semi-insulating GaAs and InP has been measured.1,2 Preliminary experiments have now been performed using the photorefractive effect in GaAs:Cr as a sensitive nonlinearity for simple low-power picosecond pulse diagnostics at IR wavelengths. In these beam coupling or two-wave mixing2 experiments, a photorefractive index grating is formed by the interference of two 4-ps duration 1.06-μm beams in a 1,5-mm thick GaAs:Cr crystal. The optical pulses were obtained from a fiber-grating compressed cw mode-locked Nd:YAG laser. The temporal profile of these pulses was obtained by detecting the fraction of chopped pump beam scattered by the index grating into the probe beam as a function of delay between the two beams, using an InGaAs PIN photodiode and lock-in amplifier. The measured temporal profile was identical to that obtained by standard noncollinear background-free correlation using second harmonic generation in a 1-mm LilO3 crystal and photomultiplier tube (PMT). With only 2 μW of average power per beam, photorefractive autocorrelation measurements were made with SNRs greater than 5:1 in this nonoptimized experiment. The beam coupling efficiency can be improved by several orders of magnitude by using a longer crystal, antireflection coatings, and an applied electric field. Beam coupling in GaAstCr is linear in intensity and photosensitive beyond 1.6-μm,1 while the harmonic process is quadratic in intensity and the quantum efficiency of typical PMTs is poor at 0.8-μm and beyond. Therefore, photorefractive auto-correlation may prove to be very attractive for real-time measurement of the temporal diagnostics of low-power long-wavelength mode-locked semiconductor lasers.

Improvements in the quantum efficiency of both metal-oxide-metal (MOM) tunnel junction detectors and metal-insulator-metal (MIM) photoconductive detectors have been achieved by periodic microstructuring of their electrodes. E hancement in sensitivity are due to plasmon coupling, reduced reflection and coupling into a guided wave resonance.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Prevention de l'usure des moteurs avec les huiles SAE 5W 30 (Society of automotive engineers)

The photorefractive effect (‘‘optical damage’’) severely limits the application of LiNbO3 in visible wavelengths. We have found that proton exchanged LiNbO3, in which up to 70% of the Li ions are replaced by protons, exhibit no measurable index change with average intensities of visible light up to 5 kW/cm2 or peak pulse intensities of ∼5×108 W/cm2 in the guide. These experiments demonstrate that the photorefractive sensitivity of proton exchanged waveguides is at least four orders of magnitude lower than that of conventional titanium diffused guides. Similar results are obtained with titanium diffused waveguides which are subsequently proton exchanged.

We report measurements of the zero field photorefractive sensitivity (optical damage) of waveguides fabricated by silver ion exchange in both LiNbO3 and LiTaO3 and of LiNbO3 :Ti guides diffused in the presence of H20. Marked differences in the photorefractive sensitivity are found for the different fabrication proceseses. In particular, LiNbO3 :Ti guides diffused in the presence of H20 were significantly less susceptible to optical damage than those diffused in a dry atmosphere, and no index changes were observed in LiTaO3 :Ag waveguides for exposures up to 105 J/cm2 at 4579 A.

THIS communication reports the initial results of our investigation of the crystal chemistry of the rare earth faujasite system. In this investigation a single crystal of faujasite was placed in contact with concentrated cerium nitrate, Ce(NO3)3, at room temperature for 6 months. The exchange data of Ames1 on the cerium exchange of Linde X and our own data (H. S. Sherry, personal communication) suggest that the cerium exchange in the crystal will be approximately 60 per cent, which corresponds to a unit cell composition, (Ce2O3)6 (CaO)7.6(Na2O)3.9·29.5 Al2O3·133 SiO2·270 H2O.

PART ONE: FAMILY HEALTH AND MEDICINE Family Medicine and Family Therapy - Lucy Candib and Michael Glenn Comparative Development, Methods and Roles When Is It Helpful to Convene the Family? - David D Schmidt Family Therapy, Family Somatics and Family Medicine - F J A Huygen and A J A Smits Children of Parents with Major Affective Disorders - William R Beardslee et al The Family and the Child with Epilepsy - Michael Ferrari, Wendy S Matthews, and Gabor Barabas Effect of Spouse Support and Health Beliefs on Medication Adherence - William Doherty et al PART TWO: FAMILY THERAPY From Family Symptom to Family System - Candyce S Russell et al Review of Family Therapy Research Process, Structure and World Views - Carlos E Sluzki Toward an Integrated View of Systemic Models in Family Therapy Contrasting Strategic and Milan Therapies - Laurie Mackinnon The EPPI Family Therapy Outcome Study - Guillermo Bernal, Elizabeth Deegan, and Christina Konjevich Family Therapy Research and the New Epistemology - Alan S Gurman PART THREE: MARITAL THERAPY Beyond Empiricism - Neil S Jacobson The Politics of Marital Therapy The Influence of Marital Therapy on Sexual Satisfaction - K Daniel O'Leary and Ileana Arias Spouse-Aided Versus Individual Therapy in Persisting Psychiatric Disorders - R Julian Hafner et al A Systematic Comparison Short and Long-Term Effectiveness of Two Communication Training Modalities with Distressed Couples - Ludwig Schindler, Kurt Hahlweg, and Dirk Revenstorf Divorce Therapy Outcome Research - Douglas H Sprenkle and Cheryl Storm A Substantive and Methodological Review Couples Long-Term Evaluations of Their Marriage Encounter Experience - Mary Ellen Lester and William J Doherty PART FOUR: SEXUALITY AND THE FAMILY Sex Education - Peter R Kilmann et al A Review of Its Effects Changes in Sexual Attitudes and Behavior of College Students from 1965 to 1980 - Ira E Robinson and Davor Jedlicka A Research Note Parent and Peer Influence on Sexual Behavior, Contraceptive Use, and Pregnancy Experience of Young Women - Farida Shah and Melvin Zelniek The Salience of Sexuality in the Early Years of Marriage - Cathy Stein Greenblat Extramarital Sex - Anthony P Thompson A Review of the Research Literature PART FIVE: WORK AND FAMILY LIFE Sources of Conflict Between Work and Family Roles - Jeffrey H Greenhaus and Nicholas J Beutell A Model of Work, Family, and Interole Conflict - Richard E Kopelman, Jeffrey H Greenhaus, and Thomas F Connolly A Construct Validation Study Dividing Work, Sharing Work, and In-Between - Catherine E Ross, John Mirowsky, and Joan Huber Marriage Patterns and Depression Factors Influencing the Quality of Life in Dual-Career Families - Uma Sekaran Parental Work Patterns in Alternative Families - Irla Lee Zimmerman and Maurine Bernstein Influence on Child Development PART SIX: ADULTHOOD AND AGING IN FAMILIES The Elderly as Network Members - Ann Stueve Family Ties of the Aged in Cross-Cultural Perspective - Corinne N Nydegger Adult Children's Attachment and Helping Behavior to Elderly Parents - Victor G Cicirelli A Path Model Women's Changing Roles and Elderly Parents - Elaine M Brody et al Attitudes of Three Generations of Women Impact of Work on Women at Midlife - Lerita M Coleman and Toni C Antonucci PART SEVEN: KINSHIP The Dispersion of Kinship Ties in Modern Society - Claude S Fischer Contemporary Data and Historical Speculation Christmas Gifts and Kin Networks - Theodore Caplow Kinship Interaction Over the Family Life Span - Geoffrey K Leigh When Out of Town Relatives Visit - Paul C Rosenblatt, Patricia A Johnson, and Roxanne M Anderson Intergenerational Family Transfers - David J Cheal PART EIGHT: COMPARATIVE AND CROSS-CULTURAL STUDIES Comparative Marriage and the Family - Marie Witheres Osmond A Cross-Cultural Test of Collins' Theory of Sexual Stratification - G David Johnson and Lewellyn Hendrix Conjugal Egalitarianism and Violence Across Cultures - V Tellis-Nayak and Gearoid O Donoghue Father Absence and Reproductive Strategy - Patricia Draper and Henry Harpending An Evolutionary Perspective A Cross-Cultural Comparison of Sibling Violence - Suzanne K Steinmetz Cohabitation in the Nordic Countries - Jan Trost

The steady-state and dynamic behavior of absorption and phase gratings in semi-insulating GaAs and InP have been studied by four-wave mixing. These measurements permit independent study of the space-charge-field screening kinetics and free-carrier recombination kinetics in these materials. The study is important both for the design of optimized materials for photorefractive applications and for the characterization of the defect electronic structure in these materials.

By using an evaporated silver film that has a continuously varying thickness, we have demonstrated the dependence of surface-enhanced Raman scattering (SERS) on the dielectric properties of the film. These results support local field models that are based on metal-particle resonances for SERS.

Injection mechanisms responsible for the electroluminescence in GaAs diffused diodes are studied by examining the behavior of the emission peaks as a function of injection level, doping level, temperature, and depletion-layer widths. Three different injection mechanisms seem to be operative in providing radiation at near-band-gap energies. Models for two of these are proposed and tested. The nature of the third emission remains an open question.