Showing papers on "Light field published in 1977"

Attenuation of light in natural waters

Abstract: A general account, aimed at the practising limnologist, is given of the attenuation of light in natural waters. The most relevant characteristics of the incident light field-its intensity, spectral composition and angular distribution are outlined. The inherent optical properties of the water absorption coefficient, scattering coefficient and volume scattering function are defined, and the contributions of different components of the aquatic system to these are discussed. Taking the properties of the light field and the properties of the water together, the diminution of intensity and the change in spectral quality of the light with increasing depth, in different types of water, are considered. Finally, the characteristic pattern of attenuation of total photosynthetically active radiation, as measured with a quanta meter, in inland and coastal waters is discussed.

Two photon absorption with coherent and partially coherent driving fields

Abstract: A model of two photon absorption in a cavity with an external driving field is presented. Phase and amplitude fluctuations in the driving field are taken into account to model a partially coherent multimode source. The photon statistics of the light in the cavity are investigated through a calculation of the second-order correlation function of the light field in the steady state. For a coherent driving field the field inside the cavity will exhibit photon antibunching for low intensities. As the fluctuations in the driving field are increased the photon antibunching is lost. For a particular coherent field, g(2)(0) is reduced with increasing laser intensity. This reduction with laser intensity is slower with increasing laser amplitude fluctuations. This could provide a possible explanation for the recent experimental observations of Kransinski and Dinev (1976).

Cooling and capture of atoms and molecules by a resonant light field

Abstract: Spectroscopy Institute, USSR Academy of Sciences and Physics Institute, Ukrainian Academy of Sciences (Submitted September 22, 1976) Zh Eksp Teor Fiz 72, 1328-1341 (April 1977) A detailed classical analysis is presented of the method of cooling and capturing atoms and molecules by a resonant light field The light-pressure forces acting on a particle in a three-dimensional standing light wave are determined It is shown that these forces can be used for effective cooling and spatial capture of cold particles in the nodes or antinodes of a light field The use of the method for the observation of narrow spectral lines in optical spectra or atoms or molecules, and for spectroscopic investigations for exceedii~gly small numbers of atoms, is considered PACS numbers: 0765Eh

The light ray (contribution to the theory of the light field)

Abstract: The electrodynamic aspects of the concept of the light ray, of the principal concepts and laws of photometry, polarimetry, and ray optics as a unified approximation of actual optics are explained. The apparatus-related origin of these concepts is demonstrated and the structure of the general theory of the light field is explained, including algebraic optics and the theory of radiative transfer. The principal premise of the photometric or ray approximation is the concept of the wavelet or the wave packet, the energy and the dynamic parameters of which are defined essentially in frequency-momentum rather than coordinate-time representation. The ray (photometric) approximation operates exclusively with observable quantities that are connected with the finite character of the dimensions and characteristic times of the square-law receivers used in optics. The generalization of photometric, polarimetric, and ray concepts to include a radiation field of arbitrary structure follows from the fact that the action of such a field on an optical receiver is equivalent to the action on this receiver of a beam of incoherent wavelets, the region of coherence of which is determined by the parameters of the receiver. This makes it possible to regard the field as an aggregate of light rays, each of which is described in a photometric approximation generalized with allowance for the polarization effects (Stokes parameters), which leads to formulation of the principal laws of photometry and polarimetry, and also to the photometric formulation of the conservation laws, and makes it possible to establish a direct relation between photopolarimetry and general theory of coherence. The limited nature of the region of coherence of the wavelet train leads to the problem of its transformation in time and in space, the description of which is effected by methods of algebraic optics by introducing the operators of differential and local transformations of the ray, and this leads directly to formulation of the radiative-transfer equation and to a delineation of the limits of its applicability. It is shown that the Stokes parameters are insufficient for a complete physical and mathematical description of the light ray, and it is necessary to introduce the three-dimensional distribution function of the wavelet trains over the polarization states; the problem of spin spectroscopy, i.e., of spatial selection of incoherent trains in accordance with the state of their polarization, is discussed.

Method and apparatus for measuring the distribution of a light field about the optical axis of a light source

Abstract: A video signal produced by picking up the light image of light projected upon a screen is quantized by a plurality of voltage comparators grouped in pairs and applied with different reference voltage levels. One of the outputs of comparators of respective pairs is inverted in an orderly manner and then synthesized with the rest of the outputs to produce a dark and bright stripe signal which is displayed on a video display device to form a radially discrete annular pattern representative of equibrightness curves.

Downward illumination device for bright field and dark field illumination

Abstract: Direct illumination apparatus for microscopes for generating illumination of light fields, phase contrasts, interference contrast and dark fields. A deflecting mirror is located in the observation beam, which is partly specular at its center region and fully specular in an annular zone, and an annular condensor is associated with the illumination system. The apparatus is provided with an adjustable stop or diaphragm for the purpose of suppressing the light field beam and with optical components for illuminating an objective pupil for the light field and the annular condensor with collimated light for the dark field. An aperture stop is located in the path of the light field beam nearly or approximately limiting the illumination of the object field in the path of the dark field beam. An annular lens (17) is mounted centrally to the optical axis (15) in the at least approximately collimated dark field beam, this annular lens imaging the diaphragm or aperture stop plane (7) in a plane (18) located near the threaded portion (3') of microscope objective (3).

Laser-Induced Line Shifts and Double-Quantum Lamb Dips

Abstract: There has been recently considerable interest in light-induced resonance frequency shifts of atoms and molecules, since they can give rise to systematic errors in high-resolution spectroscopy Light shifts occur when atomic or molecular oscillators interact with off-resonant light fields It is useful to think of these shifts as being generated by the exchange of virtual quanta between the light field and the oscillator [1J From this point of view one may acknowledge that they constitute a class of fundamental phenomena of intrinsic importance rather than a mere experimental nuisance