The July special issue on x-ray/EUV optics begins with a consideration of the application of multilayer mirror technology to astronomy, microscopy, and spectroscopy. The Ultra-High Resolution XUV Spectroheliograph (a com¬plex array of multilayer x-ray telescopes that has been selected for flight on the U.S. space station Freedom) is described. This paper is followed by an overview of advances in multilayer x-ray/EUV optics by one of the pioneers of the field. Normal incidence multilayer x-ray mirrors have applications as optical components for Schwarzschild x-ray microscopes as well as telescopes.

We describe a space-borne solar observatory, the Ultra High Resolution XUV Spectroheliograph (UHRXS), which has been selected by NASA for flight among the initial scientific instruments to be placed on the space station Freedom. The principal UHRXS instruments are nine XUV multilayer Ritchey-Chrétien telescopes covering the spectral range from ~70 to ~350 Å; each telescope is able to isolate line multiplets, within a narrow wavelength interval, excited over a narrow temperature range, providing full disk images of diagnostic quality covering structures in the solar atmosphere ranging in temperature from T ~ 50,000 K (He II, ? ~ 304 Å) to 20,000,000 K (Fe XXIV, ? ~ 192 Å). The XUV images will be recorded on high resolution 70 mm format film, allowing resolutions as high as 0.1 arcsec to be achieved for a 1.0° field. The XUV images will be supplemented by (i) full disk high resolution (~0.1 arcsec) far ultraviolet images in H I Ly ? (? - 1216 Å) and C IV (? ~ 1548/1550 Å), (ii) full disk soft x-ray images in four bands in the interval ?? ~ 6 to 70 Å, and (iii) electronically recorded high resolution (?/?? > 10,000) spectrohelio-grams in 2 XUV, 1 EUV (~450 to 1100 Å) and 2 FUV (~1100 to 1600 Å) bands. The electronically recorded images will use the multi-anode multichannel array detector. We propose to utilize the resulting data sets to address fundamental problems related to the following solar phenomena: (i)the fine structure of the solar chromosphere/corona interface, (ii) the structure, energetics, and evolution of high temperature coronal loops, (iii) the large scale structure and dynamics of the corona, including the solar wind interface, the magnetic field, and coronal mass ejections, and (iv) solar flares, especially the preflare state, the impulsive release of energy, and the evolution of postflare loops.

The field of multilayer optics for the x-ray, soft x-ray and extreme ultraviolet wavelengths is maturing at a rapid pace. There are more than forty groups worldwide actively working in this area. A large part of these efforts is directed to improving the quality of multilayer structures by developing a better understanding of the synthesis-structure-property relationship. Although the quality of multilayer structures may be substantially improved, there are now significant instrumental applications for these reflecting optics. In this paper the current status of this field is discussed.

Normal incidence multilayer x-ray mirror technology has now advanced to the point that high resolution x-ray microscopes with relatively large fields of view are feasible. High resolution aplanatic imaging x-ray microscopes configured from low x-ray scatter normal incidence multilayer optics should be ideal for laser fusion research, biological investigations, and astronomical studies when used in conjunction with grazing incidence or multilayer x-ray telescope systems. We have designed several Schwarzschild x-ray microscope optics. Diffraction analysis indicates that better than 600 Å spatial resolution in the object plane up to a 0.7 mm field of view can be achieved with 100 Å radiation. We are currently fabricating a 20 x normal incidence multilayer x-ray microscope of 1.35 m overall length. We have also analyzed and designed other microscope systems for use in conjunction with x-ray telescopes. This paper reports on the results of these studies and the x-ray microscope fabrication effort.

This paper describes a fabrication method for making multilayer coated phase reflection gratings and arbitrary phase patterned reflection optics suitable for soft x-ray imaging. This represents an improvement over previous fabrication methods using anisotropic or ion-beam etching, which were limited to amplitude structures by the induced roughness on the etched portions of the substrate. Included also is a scalar model for multilayer phase grating reflectivity.

Recent advances in multilayer structures for the extreme ultraviolet now make it possible to construct diffraction gratings in the wavelength range below 350 Å, which can be used for precision measurements using normal incidence spectrometers. We report results from two such gratings, one with conventionally ruled blazed facets and the other with a holographically ruled sinusoidal surface. Both gratings are 1 m in radius, 1200 lines/mm coated with a molybdenum-silicon multilayer for use in the 150 Å wavelength region. A 1 m normal incidence spectrometer with a Garton flash tube source and a film detector was used to test the spectral resolution. Relative efficiency measurements were obtained by comparison to spectra produced by an osmium coated grating. Emission lines in the wavelength region of interest (characteristic of the source) are easily detected and well resolved with both multilayer coated gratings. Quantitative efficiency measurements were obtained using a Penning source coupled to a 1 m grazing incidence monochromator and an imaging photon counting detector.

Application of multilayer dispersion elements in the x-ray, soft x-ray, and extreme ultraviolet has been defined by their intrinsic properties, including large normal incidence reflectivities at wavelengths greater than 40 Å, low to moderate spectral resolution, and the ability to engineer unique capabilities into these optics as a result of their synthetic nature. In this paper the potential for extension of multilayers to high resolution applications is considered. A qualitative discussion of the characteristics of simple uniform multilayers required for high resolution is given first. Multilayer diffraction gratings are then considered and a simple analysis of their properties is presented. Application of such gratings in a multilayer-multilayer grating bending magnet synchrotron beamline monochromator is described, and the potential for efficient high resolution performance is discussed.

We present x-ray measurements of total reflectivity and scattering from gold-coated foils. The foils are two sorts of 0.3 mm thick dip-lacquered aluminum, 0.125 mm thick plastic (Upilex) and 0.5 mm thick dip-lacquered nickel. The analysis of the data shows a high reflectivity for all but the plastic foil, and only small microroughness (~15 Å at length scales below ~0.1 µm), evidenced by low resolution scattering measurements.

The Extreme Ultraviolet Explorer (EUVE) is a NASA-funded astronomy mission that will operate in the 70 to 760 Å band. The science payload# which has been designed and built by the Space Sciences Laboratory at the University of California, Berkeley, consists of three grazing incidence scanning telescopes and an EUV spectrometer/deep survey instrument. We give details of the planned mission profile and an overview of the instrumentation that the science payload comprises. Topics such as the thermal design, contamination control, and details of the electronics system are discussed. Finally, we review the results of the calibration of the various subsystems that make up the EUVE instrumentation and discuss the calibration plan for the integrated EUVE instruments, which began in June 1989 at the Berkeley EUV Calibration Facility.

A Bragg crystal oriented at 45° to an incoming beam of x rays acts as a polarization analyzer. This crystal geometry preferentially reflects those x rays that satisfy the Bragg condition and whose electric vectors are perpendicular to the plane defined by the incident and reflected photons. X rays with electric vectors parallel to this plane of incidence are photoelectrical^ absorbed. The energy bandwidth of nearly perfect crystals is extremely small, which makes them very inefficient x-ray polarimeters. This limitation is particularly acute for observations of the relatively weak x-ray continuum of stellar sources. The bandwidth can be greatly increased by employing mosaic or ideally imperfect crystals. Mosaic crystals possess a high integrated reflectivity, which results in a large increase in the reflection of continuum radiation. A review of the theory and performance characteristics of crystal polarimeters designed for observations of cosmic x-ray sources is presented.

Scattering from bound electrons in a suitable material placed at the focus of an x-ray telescope can be exploited to measure the linear polarization of radiation emitted from cosmic x-ray sources. Among the factors that affect the performance of such an instrument is a spurious polarization signal from unpolarized sources that lie within the field of view but are offset from the telescope pointing direction. In this paper we present the results of analytical and Monte Carlo studies of this effect and provide means of evaluating its impact on realistic polarimeters for x-ray astronomy.

n this paper we describe an x-ray polarimeter that will be flown on the Spectrum X-Gamma mission. The instrument exploits three distinct physical processes to measure polarization: Bragg reflection from a graphite crystal, Thomson scattering from a metallic lithium target, and pho-toemission from a cesium iodide photocathode. These three methods allow polarization measurements over an energy band from 0.3 to 12 keV. The polarimeter will make possible sensitive measurements of several hundred known x-ray sources, an increase of two orders of magnitude over the x-ray polarimeters flown to date. X-ray polarization measurements will allow us to constrain the geometry of gas flow in x-ray binaries, identify nonthermal emission in supernova remnants, test current models for x-ray emission in radio pulsars, determine the radiation mechanisms in active galactic nuclei, and search for inertial frame dragging (Lense-Thirring effect) around the putative black hole in Cygnus X-1.

Averaging line noise standard deviations and averaging line noise variances are two commonly used techniques for determining frame noise or noise equivalent temperature difference (NETD). The two techniques are equivalent if all lines in the frame have the same noise statistics, that is, if the noise process is ergodic. However, if a few lines contain a larger amount of noise, the process is not ergodic and the two techniques yield different results. A simple theoretical relationship for the difference between the two is developed and compared to a computer simulation under a variety of conditions. Results of the simulation closely matched the theoretical relationship. We recommend the use of the variance average as a description for noise in an NETD calculation, since it is more sensitive to lines that exhibit excess noise.

A 160x244 element PtSi IRCCD imaging array is characterized using a conventional approach commonly reported for visible imagers, introducing, as needed, issues specific to the IR. Mean-variance data are used to extract two CCD charge transfer efficiencies; one efficiency corresponds to the charge partitioning in a transfer (0.9987), and the other efficiency corresponds to the charge lost to charge pumping in a transfer (0.9994). The array is shown to be background limited for pixels near the output node. A 2-point correction is shown to substantially reduce fixed pattern noise of linear PtSi photodetectors at backgrounds offset from the points of correction, but it can introduce additional noise at the point of compensation if adequate precision is not used when calculating the 2nd-point coefficients. The measured D* (detectivity) and NE?T (noise equivalent temperature difference) are 6.5x1010 cm. ?Hz W-1 and 0.1°C, respectively. The horizontal and vertical MRT (minimum resolvable temperature) of the array is measured to be 0.02°C at a spatial frequency of 1//6 cycle/mrad. Pixel 1/f noise was below shot noise to 2x 10_5 Hz.

Various surface passivations of p-type Hg1_xCdx Te were studied to understand their interface properties and their potential for device technology. Anodic oxide forms an inverted layer near the interface. This n-type skin layer exhibits extremely good n-type properties, which equal and even surpass bulk properties. The high electron mobility may be explained by quantization of the electron levels in the space-charge region and the formation of a two-dimensional electron gas near the interface. Thick (~500 Å) anodic sulfide generates a similar inversion layer. The charge density is proportional to the sulfide thickness. Carefully prepared thin (~100 Å) anodic sulfide films as well as ZnS coating on freshly etched surfaces form nearly flatband conditions that are suitable for n+ on p diode technology. The surface recombination velocity, determined for these two passivations using the photoelectromagnetic effect, is shown to be similar at low temperatures, increasing with decreasing temperatures. The dominant trapping mechanism at the surface is similar to that in the bulk and is probably mostly due to vacancies.

Experimental results show that the contribution of the graded n region to the current of Hg1 _xCdx Te diodes is not negligible, as compared to that of the p type bulk. The theoretical analysis reveals the influence of the electric field present outside the depletion region on the current generated by the graded region. This field not only produces a drift component, which drives the minority carriers into the junction; it also greatly modifies the excess carrier distribution, thereby changing the diffusion part of the current. The analysis shows the importance of the lifetime profile in the graded region, which is a function of the specific recombination mechanism and its dependence on the local dopant concentration. The effect of parameters such as substrate concentration, surface concentration, and junction depth on this current is discussed.

A recursive optical notching filter (RONF) [U.S. Patent No. 4,522,466 (1985)] was developed to eliminate narrowband interference (NBI) expe-rienced by rf receiver systems such as those used in radar and commu-nications. Electromagnetic interference (EMI) can drastically reduce the effective range of radars and cause intermodulation products in the re-ceiver and subsequent demodulation. The RONF functions to identify the interferers and their numbers and locations as well as to adaptively construct a notch filter structure that uniquely excises the NBI from the rf signal spectrum. Further, by the use of a novel recursive architecture, it is possible to develop notch depths approaching the signal dynamic range. The RONF operations are accomplished by impressing the unprocessed rf signal onto a laser carrier by means of an acousto-optic modulator (Bragg cell). The modulated laser beam is then optically Fourier transformed to produce a real-time frequency spectrum. At the carrier optical wavelength, the frequency-translated rf signal with NBI appears in spatial coordinates for parallel processing with spatial intercepts of the EMI provided by programmed amplitude, and phase "blockers" constructed by the programmable spatial filter (PSF). It is at the PSF that optical recursion is used to obtain superior notching depth [U.S. Patent No. 4,645,300 (1987)]. With the NBI removed, the optical signal is then inverse Fourier transformed and the original radio frequency signal is recovered by optical heterodyne conversion. Laboratory tests with radar systems as well as various related stimuli have been conducted under field and on-site conditions. The RONF test systems have demonstrated notch depths greater than 40 dB using the recursive architecture.

An electronic speckle pattern interferometry system has been developed for in situ measurements of microdeformations on buildings or monuments. Design of the optomechanical setup received special attention to allow firm and steady contact between object and optical head. Features are the miniaturization of the light source (laser diode) and pickup (CCD camera). Image processing was carried out with a personal computer. Deformation monitoring was demonstrated successfully over periods of several weeks in the study of decay mechanisms of walls in an historic church.

A high speed pulsed light generator system has been developed for the optical analysis and imaging of fast processes in fluid dynamics. As a light source, one or more high power LEDs are used. The maximum light power generated by one diode is 1 W. The pulse repetition rate is up to 2 MHz and the pulse width can be adjusted in the range 50 ns to 10 µs. The light emitted from the diodes has a wavelength of 660 nm. Due to its pronounced coherence, it is especially suited for the observation of light-phase-shifting objects by interferometric methods. Examples of the application of the generator are presented.

A lithographic alignment vernier based on low-magnification imaging of line-space patterns has been developed. Its resolution is limited only by the lithographic process used; a vernier that can be interpolated to 1/16 µm is demonstrated, using step-and-repeat optical lithography. This vernier can be read quickly and easily because it is read at low magnification, where there are no problems with depth of focus, even for multilevel resists. The vernier is tolerant to variations in linewidth, resist thickness, and edge profile. A machine-readable version of this vernier is also described.

This PDF file contains the editorial “Book Rvw: Optical Computing, Digital and Symbolic," edited by Raymond Arrathoon for OE Vol. 29 Issue 07

This PDF file contains the editorial “Book Rvw: Handbook of Microwave and Optical Components: Volume 3, Optical Components," edited by Kai Chang for OE Vol. 29 Issue 07

This PDF file contains the editorial “Editorial: Of Astronomy and Tamiasciurus hudsonicus grahamensis” for OE Vol. 29 Issue 07