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The chapter is concerned with the design of planar dielectric layer diffraction gratings, which exhibit sharp resonances due to the coupling of exterior evanescent diffractive fields to the leaky modes of dielectric waveguides.
Several designs that are based on the Offner concentric spectrometer form, with the grating formed on the convex secondary mirror.
A multiple-write electron beam lithography techniques is described as linear filter on the grating spatial frequency spectrum.
High-performance blazed gratings have been fabricated on convex surfaces by electron beam lithography, for use in an instrument to be flown on NASA's NM-EO1 spacecraft.
Arcus will be proposed to the NASA Explorer program as a free-flying satellite mission that will enable high-resolution soft X-ray spectroscopy (8-50 Angstroms) with unprecedented sensitivity-effective areas of greater than 500 sq cm and spectral resolution greater than 2500. The Arcus key science goals are (1) to determine how baryons cycle in and out of galaxies by measuring the effects of structure formation imprinted upon the hot gas that is predicted to lie in extended halos around galaxies, groups, and clusters, (2) to determine how black holes influence their surroundings by tracing the propagation of out-flowing mass, energy and momentum from the vicinity of the black hole out to large scales and (3) to understand how accretion forms and evolves stars and circumstellar disks by observing hot infalling and outflowing gas in these systems. Arcus relies upon grazing incidence silicon pore X-ray optics with the same 12m focal length (achieved using an extendable optical bench) that will be used for the ESA Athena mission. The focused X-rays from these optics will then be diffracted by high-efficiency off-plane reflection gratings that have already been demonstrated on sub-orbital rocked flights, imaging the results with flight-proven CCD detectors and electronics. The power and telemetry requirements on the spacecraft are modest. The majority of mission operations will not be complex, as most observations will be long (~100 ksec), uninterrupted, and pre-planned, although there will be limited capabilities to observe targets of opportunity, such as tidal disruption events or supernovae with a 3-5 day turnaround. After the end of prime science, we plan to allow guest observations to maximize the science return of Arcus to the community.
Optical frequency domain reflectometer (OFDR) systems provide for the interrogation of hundreds of fiber Bragg gratings (FBGs) within a single optical fiber. The coupling of FBG sensors to an OFDR interrogator results in a highly distributed measurement system utilizing sensors that are lightweight, immune to electromagnetic interference, and low-profile. This paper presents and explores a basic derivation of OFDR-FBG signals, the processing of those signals, the assembly of a basic OFDR system, an example measurement scenario, and the effects of specific component and configuration changes on interrogator speed, resolution, and accuracy.
Simple scanning arrangement for the concave grating spectrometer
Collimation of concave gratings at glancing incidence
Thermal-vacuum stressing of replica diffraction gratings
Space environment simulation experiments on possible electron impact damage to gold replica gratings
Response of replica gratings to thermal vacuum stressing and electron irradiation
Michelson interferometer to detect grating table rotation in infrared spectrometer
Electron bombardment effects on performance characteristics of UV gratings
Optical modulation through Doppler frequency shift obtained by rotating radial diffraction grating
Concave grating spectrometer for use in near and vacuum ultraviolet regions
Particle irradiation tests on concave and Pyrex gratings
Optical modulation using rotating diffraction grating to obtain frequency shifts
Large diffraction gratings by interferometrically controlled commercial measuring machine