Grating Element Research Articles

Simultaneous Measurement of Transverse Load and TemperatureUsing a Single Long-Period Fibre Grating Element

A single long-period fibre grating (LPFG) element written by focusedhigh-frequency CO2 laser pulses is demonstrated for simultaneousmeasurement of transverse load and temperature. Temperature andtransverse load can be directly measured by detecting the resonantwavelength shift and the resonant peak amplitude change of the LPFG,respectively, as there are two special circular orientations along thefibre axis where the resonant peak amplitude change of the LPFG has alinear relationship with the load applied and is insensitive to theresonant wavelength shift. Such a sensor could solve thecross-sensitivity problem between transverse load and temperature dueto the unique feature of this type of LPFG, i.e. thewavelength-load-sensitivity of the LPFG strongly depends on loadingorientations due to the non-uniform distribution of the refractiveindex on the cross-section of the LPFG caused by the thermal shockeffect and other effects of the high-frequency CO2 laser pulsesexposure method used.

Ultraprecision Micro-Grinding of Germanium Immersion Grating Element for Mid-Infrared Super Dispersion Spectrograph

The design of a mid-infrared high dispersion spectrograph with a resolution of 200,000 at 10μm employing germanium immersion grating elements is required for the ‘SUBARU’ large space telescope. The authors applied an ultraprecision micro-grinding technique using fine-diamond grinding tools whose edges have been sharpened by electrical and mechanical processes to fabricate the element, and successfully obtained the required element with a sharp and smooth V-faced grating structure using germanium. The successful fabrication of this element is expected to contribute to the production of a compact and efficient high dispersion spectrograph in the development of the most advanced image analyzer.

Compact and dynamic optical bypass-exchange switch

A novel, compact and dynamic optical bypass-exchange switch is presented. It is based on a planar optics configuration with polarization-sensitive linear grating holographic optical element, and a polarization rotator light modulator. Representative switches were designed, fabricated and experimentally evaluated. The results indicate that relatively low crosstalk level can be reached to make such switches suitable for practical optical interconnect networks.

Influence of substrate thickness on plasma resonance in a semiconductor heterostructure with a two-dimensional electron gas

A strict electrodynamic approach is used to analyze the excitation of oscillations of a two-dimensional electron plasma by an external plane electromagnetic wave in a semiconductor heterostructure with a grating coupling element. An analysis is made of the influence of the substrate thickness on the resonance magnitude and the profile of the resonance curve.

Reconstruction of the refractive index profile in diffused waveguides

A simple method is proposed for measuring the refractive index n(x) at the surface of a diffused waveguide whereby the profile n(x) can be reconstructed uniquely from the mode spectrum of the waveguide. A description is given of a method of measuring effective refractive indices of the waveguide modes using a grating element for coupling radiation into the waveguide. The profile n(x) in single-mode waveguides is discussed.

Role of retinal image motion in evoking the McCollough effect.

MCCOLLOUGH1 has described a phenomenon whereby after repeated, successive and alternate inspections of a black and orange straight line grating orientated vertically, the vertical white elements in an achromatic grating appeared pink and the horizontal white elements appeared greenish. This phenomenon has been termed the “McCollough effect”. The effect has been reported to persist for several days and to be orientation specific, both with respect to head inclination and grating element orientation. Typically, in inducing the McCollough effect, subjects alternately view, for about 10 s each, a black and white grating and a homogeneously coloured field over a period of approximately 10 min (termed the inspection period). After this the subjects view two black and white straight line gratings, the elements of one being at right angles to those of the other. One of the gratings occupies the same orientation as that observed during the inspection period. Subjects report the presence (or absence) of colour in these two gratings. This is termed the test period.

Polarization interferometer for 2800 MHz solar noise studies with a 0.5? fan beam

The construction and operation of a high resolution interferometer for solar noise observations at 10.7 cm for the Algonquin Radio Observatory is described. One element is the existig 32 element array of 3 m reflectors while the second is a grating element of 4 reflectors symmetrically placed on the same E-W line. The aperture of 665 m produces a fan beam of 0.5′ E.W. by 2° N.S. Four Faraday rotators in the antenna feeds of the newly commissioned grating enable three Stoke's parameters to be observed. The expected antenna pattern is confirmed by making observations on the brighter radio sources. Observations of the Sun on 1972, January 6 show the range of phenomena to be observed and a detailed study of the association of eight radio emissive regions with all centers of solar activity is presented.

Asymptotic behaviour of the solutions of problems of the diffraction of long plane waves at periodic gratings and corrugated surfaces

THE problem of the diffraction of a plane wave at a densely periodic grating is reduced to two problems of the diffraction of the same wave at densely periodic corrugated surfaces, with Dirichlet's condition and with the mixed boundary condition at them, respectively. Each of these two problems is reduced by the method of Malyuzhinets to two recurrent sequences of boundary value problems for the Laplace and Poisson equations. It is shown that the reflection coefficients of the corrugated surfaces are defined in terms of the grating form factors. The first of these coefficients have the physical sense of mass and associated mass of a grating element, and determine the asymptotic behaviour of the solutions of the problems named above, of diffraction far from the surface and grating, with an accuracy up to O( k 2) as k → 0.