Transmitted Light Beam Research Articles

Correction of systematic errors in the determination of X-ray diffraction intensities by integrating microdensitometers

Correction of errors in measurement of X-ray diffraction intensities by integrating microdensitometers which arise from nonlinear characteristics response curves and a finite size of the cross section of the transmitted light beam is discussed.

Optical Probing of Acoustic Surface Waves

Light diffraction by acoustic surface waves is used as a probe to study the propagation characteristics of Rayleigh waves on y-cut z-oriented LiNbO3. Both the surface deformation and the periodic variation of the index of refraction in the medium, which diffracts the transmitted light beam, are related to the particle displacements of the propagating Rayleigh waves. For the reflected beam, only the surface deformation contributes to the diffracted light. Experimental demonstrations of using the optical probe to observe the Fresnel diffraction of a rectangular interdigital transducer to measure the transmission and reflection coefficients of a transducer and to determine the propagation characteristics, such as velocity, attenuation of Rayleigh waves on a LiNbO3 substrate and on a metalized LiNbO3 substrate, will be discussed.

Errors in extinction measurements as due to scattering of light by solutions of relatively small particles

Extinctions measured on macromolecular solutions will generally be too low owing to the addition of scattered light to the transmitted light beam. Even in solutions with predominantly Rayleigh scattering the values are affected by a relative systematic error of 2% or more. The relative error is independent of the molecular weight for limitingly small particles. At infinite dilution it is maximal and solely determined by geometrical characteristics of the spectrophotometer used.

Magneto-Optical Variable Memory Based Upon the Properties of a Transparent Ferrimagnetic Garnet at Its Compensation Temperature

The requirements to be met by a changeable memory medium for flying spot variable memory system are discussed. Although simple reversible photochromic materials satisfy most of these requirements, their lack of a writing threshold limits their applicability. The application of a transparent ferrimagnetic garnet near its compensation temperature is discussed. At the compensation temperature the net magnetization of the garnet is zero so that the remanent magnetization of the sublattices normal to the surface of a thin crystal is not subject to demagnetization fields. The magnetization of the iron sublattice of the garnet produces a large magneto-optical rotation of the polarization of a transmitted light beam in opposite senses for the two directions of the remanent magnetization, which can, therefore, be interrogated non-destructively. In passing through the compensation temperature, the coercive field for a magnetization reversal passes through a sharp maximum. Thus, the direction of remanent magnetization can be changed by applying a magnetic field in coincidence with a high-intensity pulsed light beam which produces a transient temperature excursion of ∼3°C from the compensation temperature. This provides a writing-threshold making it possible to change the remanent magnetization of a selected crystal in an array without disturbing the magnetization of the remainder. Practical aspects of this approach are discussed.