Showing papers on "Light field published in 1988"

Theory of coherent transients in semiconductor pump–probe spectroscopy

Abstract: Probe-transmission spectra are calculated for a semiconductor that is excited by ultrashort pulses well above its band edge. Coherent coupling of the light field to the band-to-band transitions is assumed, neglecting the mixing of different momentum states. The transmission spectra exhibit pronounced oscillatory structures caused by the interaction of the probe pulse with the medium polarization, which is driven by the pump pulse. The details of the oscillations are determined by the temporal separation between pump and probe pulses and by the total temporal width of the pump pulse. Characteristic modifications of the spectra are obtained for strong pump fields (π and 2π pulses). Possible applications of the theoretical results for the determination of intraband scattering times in semiconductors are discussed.

Auto-adjustable operating room light

Abstract: To provide for automatic adjustment of the light field of an operating room light in accordance with manual positioning of the light, an electrical servo control loop positions the respective lamps and/or deflection mirrors of circularly placed light sources (2) in the housing (1) to iluminate a given field in a given plane. The distance of the lamp from the given field is determined by an ultrasonic distance sensor (5; 5a, 5b, 5c) to provide one input to the servo loop, for comparison of the positioning of the light source to illuminate said field. If the distance of the illuminated field increases, the angular position of the light sources is automatically adjusted to provide the field at the increased distance. If the distance decreases, however, no adjustment is carried out unless an operator touches an operating handle. This is transformed into a manual readjustment signal which releases the servo system to then readjust the position of the light sources. A switch (33) is located in the control loop to interrupt the control loop and permit adjustment only upon an increase in distance. Thus, erroneous sensing of a smaller distance, for example given by the hands of a surgeon, surgical instrument, or the surgeon's head, will not affect repositioning of the lamp and the light sources therein.

Squeezing the quantum fluctuations of light

Abstract: This paper is intended to be an introduction to the field of non-classical light. Starting from a pictorial discussion of the properties of the radiation field, examples for the generation and possible applications of squeezed states of the light field are given.

The Properties of a Light Field Interacting with a Four-level Atom

Abstract: The system comprising a four-level cascade atom and a light field of single mode with frequency Ω is investigated. The mean photon number, coherence and squeezed states for the light field are discussed. 36% squeezing has been found.

Rotatory Instability of the Spatial Structure of Light Fields in Nonlinear Media with Two-Dimensional Feedback

Abstract: Optical bistability, instabilities, and chaos are usually observed as processes developing with time. (The only exception is the so-called transverse optical bistability.)

Raman Scattering Effects In Ocean Optics

Abstract: The Naval Ocean Research and Development Activity (NORDA) optical model, a Monte Carlo simulation of the radiative transfer equation, has been used for the first comprehensive optical modeling of clear ocean light fields. From this effort we propose a new optical parameterization of the clearest ocean water: the NORDA Blue Water Model. This parameterization (including molecular absorption of the water molecule, fluctuation theory scattering of the water molecule, large particle scattering, and water Raman scattering) provides the baseline for all other optical modeling of oceanic light fields. The predictions of the NORDA parameterization quantitatively account for the published data on radiant energy penetration into clear ocean water and the latest data from the state-of-the-art optics instrument of NORDA design, the POSSY (Particle Optical Sample System). The translation of the Monte Carlo output to field optical measurements is accomplished through the Three-Parameter Model of the submarine light field, which permits an exact solution of the integrated radiative transfer equation. From the Three-Parameter Model we can make quantitative estimates of both the nature of the radiance distribution field and the precise contribution of internal radiation sources to the submarine light field at any depth.© (1988) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Light diffraction by stripe domain structures in magnetic crystals

Abstract: Light diffraction by stripe domain structures (SDS) in magnetic crystals is analyzed theoretically. The applicability of the Fresnel-Kirchhoff integral for description of magneto-optical diffraction is discussed. In this connection a criterion of an optically thin layer with SDS is proposed. The effects of symmetrical and unsymmetrical domain structure realignments on the intensity and polarization parameters of the light field diffracted by a binary magnetic grating are studied. Both linear and quadratic magneto-optical effects are taken into account to specify the diffraction spectrum. Peculiarities of phase and amplitude light modulation by a magnetic grating are revealed. [Russian Text Ignored].

Parallel Polarization Processor

Abstract: PARALLEL POLARIZATION PROCESSORJOSEPH M. GEARY *ABSTRACTA possible method for measuring the polarization of high power laser fields(for example, industrial lasers, gas dynamic lasers, etc.) via a device withno moving parts is presented.INTRODUCTIONMeasuring the polarization of high power laser fields (HPLF) has always beenan extremely difficult task. Such fields are ill- behaved. They experiencelarge random temporal and spatial amplitude and phase variations. Theyoperate over several discrete wavelengths and the relative power in eachline is subject to significant fluctuation. It would not be all thatsurprising, therefore, to find that polarization also varies temporally andspatially across the beam, and that it may vary with wavelength (dependingon the local kinetics of the gain media). Complicating things a bit furtheris the fact that some HPLF typically operate over short periods of time,i.e. runs are measured in seconds or fractions thereof. Finally, most HPLFhave operated in the infrared. Polarization metrology on such systems haveusually consisted of a pair of power measurements along orthogonal axesusing wire grid polarizers.Polarization behavior of HPLF is important in the context of its interactionwith the beam train, which consists mainly of mirrors. Phase shifts areintroduced upon each reflection. The amount of shift depends on the localpolarization of the incoming field, and the nature of the coating. Therecould be a dozen or more mirrors in the beam control system, and, in someHPLF, there is at least one grating (for beam sampling). If in the exitpupil of a beam propagation telescope the light field has uniform phase,amplitude, and polarization, the far field will consist of a classic Airypattern, with a Strehl ratio of unity. However, should the polarization varysubstantially across the pupil, then the diffraction pattern will degradeand so too the Strehl. In other words, system performance suffers.Consequently, it is very important to know the polarization behavior of theHPLF not only to predict system performance, but also to correct, as far aspossible, factors hindering optimum behavior.POLARIZATION ELLIPSE MEASUREMENTSThe polarization state of any light field is determined via intensitymeasurements. Use is made of a high quality, linear polarizer which isrotated through a full cycle to find the shape and intensity of the* United Technologies Optic91 Systems

An improved technique for aligning the light field with the radiation fields on radiotherapy accelerators.

Abstract: An improved scheme has been developed for measuring the coincidence of the light field and radiation fields of a radiotherapy accelerator. Scans of the light and radiation fields are made sequentially using a photodiode on standard field plotting apparatus. By superimposing the two plots, differences between the two fields’ boundaries can be accurately determined. The technique is simple and avoids uncertainties inherent in common techniques employing film.

Effective interactions in non-linear optics

Abstract: A new theoretical approach to the problem of non-linear polarisation of matter is suggested The density matrix equation for a low-density gas in a strong light field has been solved without using the phenomenological relaxation constants Use is made of the general Hamiltonian that explicitly involves, besides the interaction of atoms with the external field, also their interactions with each other and with the vacuum electromagnetic field The equation is solved by the canonical transformation method (a variant of the Bogolyubov-Mitropolski method of averages) It is generalised and used in the more complicated case of interacting multilevel atoms (molecules) in a strong light field An expression for the cubic susceptibility is obtained, enabling analysis of the resonant saturation in both stationary and non-stationary cases The proposed method provides correct expressions for the dynamic Stark shifts, amplitudes of multiphoton transitions and of radiational collisions, as well as for effective interatomic interactions caused by photon exchange The proposed theoretical approach can also be used in studying non-linear optical processes in dense gases, liquids and solids

The Physical Simulation Of Marine Light Fields For Underwater Vision Research

Abstract: An apparatus has been constructed that allows the underwater marine light field to be physically simulated using artificial light sources and optical components. The arrangement of components allows downwelling, sidewelling, and upwelling marine light to be recreated in its measured or theoretically determined spectral and polarized structure. The design of an apparatus of this type takes into account a generalized set of simulation categories called simulation regimes. The visual parameters of the animal to be studied, the optical nature of the water to be simulated, and the depth in the water column selected, define a particular simulation regime categgry through the underwater contrast-visual range equation of Duntley and the geometrical criteria defined in this paper. This work seeks to provide researchers with a means of investigating marine animal behaviors that utilize specific aspects of the spectral and polarized structure of marine light. Initial results of experiments performed with the apparatus, involving a marine crustacean, are given to demonstrate the use and range of application of the apparatus.