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Interference Methods In The Testing And Fabrication Of NewDesign Grazing Incidence Gratings Michael C. Hettrick and Christopher Martin

Proc. Soc. Photo-Opt. Instr. Eng. vol. 503, pp. 106-113 (1984) http://dx.doi.org/10.1117/12.944820



Copyright 1984 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Testing and Fabrication the Testing in the Interference Interference Methods Methods in New-Design of NewDesign Grazing Grazing Incidence Incidence Gratings C. Hettrick and Christopher Martin Michael Michael C. Sciences Laboratory, Space Sciences California, Space University of California, Laboratory, Berkeley, Berkeley, CA CA

94720

Abstract

new identified aa new has identified soft XX-ray of soft design of the design in the Recent work in -ray and and extreme extreme UV spectrographs has incidence. To grazing incidence. at grazing increase at not increase do not aberrations do whose aberrations of reflection gratings whose class of class across aa manner across continuous manner in aa continuous varied in are varied spacings are groove spacings the groove this characteristic, achieve characteristic, the achieve this gratfan gratoriental fan the oriental grating, the groove grating, the concentric groove traces of aperture. Ray plano Ray traces of the piano grating aperture. applicalaboratory applicaand laboratory astronomy and space astronomy for space their potential for illustrate their ing and and variations variations illustrate ing and straight-groove A. Both straight AX10-1000 tions in the -1000 A. approximately20,10 of approximately range of wavelength range the wavelength tions -groove and spacings line spacings varied line concentric -groove patterns patterns have have been been successfully successfully fabricated with varied concentric-groove line-space varied line techniques. A concave varied ruling techniques. through through mechanical ruling -space grating grating has has been been measured measured method interferometric method UV. An interferometric extreme UV. the extreme in the theoretical efficiency in its theoretical to to achieve achieve 70% 70% of of its the into the scaled-up wavelengthisisscaled recording wavelength the recording which the in which discussed, in also discussed, is also of -up into of fabrication is "Type designated "Type is designated grating is spectrum. This holographic grating the spectrum. of the region of or even visible region far UV or far extreme the extreme in the aberrations in wavefront aberrations grating wavefront recording grating of recording V." Two interferometers capable of soft XX-ray and soft UV and -ray are are proposed. Introduction

the to the available to tool available powerful tool Spectroscopic study of astronomical sources most powerful the most is the sources is Spectroscopic the in the (A ^10-100 softX X-ray the soft in the important in especially important is especially This is -ray (Á'L10 -100 X) R) and in astrophysicist. responpart responin part is in extreme -1000 A), A), where where the the absence absence of of suitable suitable instrumentation is (A ^ 100-1000 extreme UV (A1,100 our This has obstructed our wavelengths. This these wavelengths. sible for for the the paucity paucity of of data data available at these sible astroenergetic astroand energetic interesting and many interesting in many occurring in the physical processes occurring understanding understanding of the dwarfs). 1 ' 2 white dwarfs).1,2 and white nomical objects (e.g., -ray binaries, binaries, cataclysmic cataclysmic variables and quasars, XX-ray (e.g., quasars, grating reflection grating of reflection design of the design for the solutions for new solutions several new Recently, we we have have proposed several Recently, geometries grating geometries unusual grating the unusual of the illustration of schematic illustration is aa schematic spectrometers.3 3 -5 " 5 Figure 11 is spectrometers. of are: (1) illumination of gratings are: these gratings features of these spectrometers. Unique features such spectrometers. in such employed in spacings the groove spacings in the 100%) variation (%(^100 light, (2) aa large variation converging light, by converging a %) in piano grating by a plano spectral of spectral incidence, of grazing incidence, at grazing minimization, at a simultaneous minimization, (3) a and (3) the aperture, and across across the in operating in to conventional In aberrations. imaging aberrations. and spatial imaging and In comparison comparison to conventional spectrometers operating performance yield performance to yield the soft soft X-ray X -ray and and extreme extreme UV UV (EUV), (EUV), these these new new systems systems are are calculated to the one approximately one and approximately resolution and spectral resolution in spectral two orders increases of of one one to to two orders of magnitude in increases efficiency. in efficiency. order of magnitude in order develpractical develthe practical in the made in been made has been which has progress which initial progress this paper, In paper, we we report on initial In this their to their relevant to is relevant which is gratings. We proposed gratings. these proposed opment of these We discuss ongoing work which spectrometer, laboratory spectrometer, and aa laboratory space-borne in aa space successful implementation -borne flight flight spectrometer spectrometer and implementation in however, we First, however, interferometry. First, employing interferometry. testing employing and testing fabrication and address methods and address and methods of fabrication of construction of and construction design and the design motivated the have motivated which have the performance capabilities which review the line-space these these varied line -space grating grating spectrometers. Spectrometers Performance Characteristics of New Spectrometers

,

three terms of three in terms summarized in largely summarized be largely can be spectrometer can grating spectrometer The performance of aa grating The section, this section, In this light. In (3) stray light. (2) (2) efficiency, efficiency, and and (3) criteria: (1) principal (1) resolution, principal criteria: three all three in all designs in grating designs the proposed grating by the realized by the advantages realized briefly discuss we we briefly discuss the areas. Resolution do not not worsen aberrations do grating aberrations the grating that the is that class is this grating class striking property of this A striking limit the limit in the achieved in In incidence. In fact, fact, minimum minimum grating grating aberrations are achieved grazing incidence. towards grazing towards the precede the However, given given aberrations which inevitably inevitably precede angle. However, graze angle. small graze of of aa vanishingly vanishingly small of reflection angle of graze angle larger graze optics, aa larger collecting optics, the collecting in the those inherent in such as grating, grating, such as those are angles are graze angles these graze However, these power. However, dispersive power. increased dispersive the increased basis of the the basis is is favored favored on on the conventional gratings for conventional incidence mountings for normal incidence required normal the required in comparison to the small small in grating). circle grating). (e.g., aa concave Rowland circle similar resolution (e.g., having having similar

extreme from extreme suffer from will suffer grating will piano grating light, a conventional plano in converging light, If situated If situated in proposed the proposed of the spacings of aberrations. 6 The smoothly varying groove spacings astigmatic astigmatic and comatic aberrations.6 Two distinct levels of aberrationeffect. Two this effect. completely, overcomes this or completely, largely, or designs designs largely, Periodic Structures of Periodic Fabrication of and Fabrication Theory, and Application, Theory, 503 Application, Vol. 503 SPIE Vol. 106 //SPIE Structures (1984)

correction are are possible: possible: (1) in an classical in in-plane in aa (coni(coni(1) Straight Straight grooves grooves in an otherwise classical -plane geometry geometry (Figure (Figure la) la) or or in cal) off off-plane the dominant dominant term term cal) -plane fan fan geometry geometry (Figure (Figure Ib) lb) completely completely remove remove astigmatism and the in coma. In In typical typical astronomical mountings, mountings, using using light light converging converging at -f10, at aa speed speed of of f5f5-flO, in spectral resolutions resolutions of of XA/AX few xx 10 2 are Figure 2a is is the the result result of of ray ray trace trace /AX %tifew 102 are attained. Figure calculations 4 for that such calculations`` for an an in-plan in -planstraight straightgroove groove solution solution using using an an f6 f6 beam, beam, reveals that such resolution over aa wide wide instantaneous instantaneous band. band. In instrument, where In aa laboratory instrument, where slower slower resolution extends extends over beams (e.g., f30) resolutions near near 104 10 4 are are attainable with these these designs. designs. beams (e.g., f30) are are more more common, common, resolutions (2) in the the groove spacings spacings permit permit higher higher-order (2) Additional Additional spatial spatial variations variations in -order corrections corrections to to be For imaging is is provided by the the curved curved (e.g., (e.g., concentric) concentric) For example, example, stigmatic imaging be applied. grooves in Figure lc. Ic. Figures 2b and and 2d 2d confirm this, this, and reveal excellent imaging imaging grooves shown shown in Figures 2b over a finite finite spectral spectral band band near near the the stigmaticallystigmatically-corrected at X304 X304 A. A. Further, over corrected wavelength at quasi-stigmatism quasi- stigmatism isis available available through through use use of of aa fan fan groove groove pattern pattern whose whose angular angular spacings spacings inincrease towards the the edges of of the the fan.4 fan. 4 Thus, both in in-plane off-plane crease at at towards Thus, both -plane and and off -plane gratings gratings are found the ability ability to to attain attain XX/AX 4 over found to exhibit the /AX =several = several xx 10 104 over useable useable bandpasses. bandpasses. The varied varied-angle an echelle fed The -angle fan fan grating grating is is the the ideal ideal candidate candidate for for use use as as an fed by by aa conconcentric groove groove prepre-disperser. 3 is is an an illustration illustration of aa promising instrument instrument design design disperser. Figure Figure 3 for space a new class class of of collecting collecting mirror telescope.' telescope. 5 Ray traces traces of for space astronomy, astronomy, utilizing utilizing a of the grating of 30,000 the grating system system reveal reveal aa resolution resolution of 30,000 over over a 30% 30% range in in wavelength, as as shown shown in in Figure 4. 4. This to approximately approximately X100 X100 AA at This grazing grazing incidence design can extend to at this this resoluresoluDetailed calculations which elaborate elaborate upon upon this this result result will will be tion. Detailed be reported reported in in future future publications. Efficiency In to conventional high high-resolution In contrast contrast to -resolution spectrometers, spectrometers, the the proposed proposed designs operate without (e.g., collimators, or camera mirrors). mirrors). A minimum without additional additional optics optics (e.g., collimators, relay optics or number is thereby achieved, achieved, all all at grazing incidence. incidence. The effinumber of of reflections reflections is The resulting efficiencies are therefore therefore extremely high. high. For ciencies which which can can be be attained attained are For example, example, a single grating grating at (approximately 40% 40% absolute efficiency in in the the EUV) EUV) results results in in aa at aa 10° 10° graze graze angle angle (approximately telescope/grating/detector 5% relative to to telescope /grating /detectorinstrument instrumentwhich whichoperates operates at at aa net net efficiency efficiency of of 5% the geometric aperture. In (Figure 3), 3), a a net efficiency of the geometric telescope aperture. In an an echelle echelle mode mode (Figure approximately 1.5% is is expected.' expected. 5 approximately 1.5% Varied spacings on a concave grating have have been been mechanically mechanically ruled ruled and Varied groove groove spacings and used used in in aa laboratory incidence spectrometer spectrometer by Kita et al.7 al. 7 Measurements of laboratory grazing grazing incidence of its its efficiency efficiency in in the EUV have have recovered 65 65-70% values. 8 Thus, be the -70% of of the the theoretical values.8 Thus, varied spacings can be ruled as conventional gratings. gratings. ruled with with aa high high groove groove efficiency as Stray Light We found a a low level level of stray stray or scattered scattered light light in in the the EUV EUV for for the the concave concave grating grating We have have found discussed above.8 above. 8 A continuum continuum level level of of only only 10 10~~-5 5 /&/Awas wasmeasured measured in in first first order order at at aa wavewavelength from the the parent parent line line at length pixel pixel 50 50 XA away from at X304 X304 A. A. The profile of this this scattered scattered light light The profile was similar similar to to that that of of the zero zero order distribution, was distribution, suggesting suggesting that that groove groove location location errors errors were not the the dominant contribution. contribution. This initial measurement is in in agreement with the the were not This initial measurement is theoretical be small when ruled ruled with with an theoretical expectation expectation that that groove groove misplacements misplacements must be an engine engine which to permit accurate accurate and which has has been been upgraded upgraded to and independent independent positioning positioning of of grooves. grooves. In In addition, ruling errors errors should not give rise rise to to Rowland Rowland ghosts ghosts (as tion, light light scattered scattered from from periodic periodic ruling (as in the ratio ratio of of the the periodic error error to to the the (varied) (varied) groove in aa conventional conventional grating), grating), since since the groove spacings is is not in in resonance. resonance. Thus, spacings Thus, there there are are several several straightforward reasons reasons to to expect expect the the level of light to to be be consistently consistently low low for for aa varied varied line line-space level of stray light -space grating. grating. Proto-type Proto -type Grating Grating Fabrication Fabrication and and Testing A straight straight-groove ruled -groove varied varied line-space line -spacepiano plano grating grating (Figure (Figure la) la) has has been been mechanically ruled by Inc. as as part part of of the the prepre-flight the Extreme by Hitachi Hitachi Instruments Inc. flight effort effort in in support support of the satellite. 9 Electron the Hitachi grating appear appear in in Ultraviolet Explorer satellite.9 Electron micrographs micrographs of the Figure 5. 5. This This grating is is currently currently being being tested tested in in the the EUV, EUV, using using the the apparatus apparatus illustraillustrated in Figure 6. 6. The is situated in in aa converging beam beam representative representative of of that that proproThe grating grating is vided in the the actual actual flight flight instrument. instrument. The functional imaging imaging properties of the the grating are are The functional vided in therefore manifested in the the spot spot sizes sizes produced at the the detector. detector. Such an optical system system therefore manifested in therefore also a laboratory spectrometer, spectrometer, which can be be used used to to study study the the properpropertherefore also constitutes constitutes a ties of in the the EUV. EUV. At wavelengths wavelengths above approximately X304 X304 A, A, the the small ties of sources sources emitting in small normal normal incidence incidence optic optic can can be be coated coated in a conventional conventional manner manner (e.g., (e.g., with Osmium). Osmium). Such aa is also also being being coated coated with with Mo Mo/Si multi-layers mirror is /Si multilayers to to permit permit coverage coverage to to wavelengths as as short at at 130 130 A. &. Near-normal at Near -normal incidence incidence reflectances reflectances of of Mo/Si Mo /Si mirrors mirrors have have been been measured measured at greater than than 5050%. 10 This apparatus apparatus should should provide provide an an efficient efficient means %.10 means of of measuring measuring grating grating resolution light profile. profile. resolution and and stray light SPIE SP /EVol. Vol503 503Application, Application, Theory, Theory,and andFabrication FabricationofofPeriodic PeriodicStructures Structures(1984) (1984)/ / 107

an through an ruled through Concentric -groove gratings gratings with with varied varied spacings spacings have have been been mechanically ruled Concentric-groove be can be technology can such technology that such 11 We expect that in -house effort effort at at the the Perking-Elmer Perking -Elmer Corporation. Corporation." in-house is interuse. It incidence use. to grazing incidence design geometries relevant to the design include the extended extended to to include It is gratconcave gratgroove concave concentric groove ruled aa concentric Sakayanagi 12 both designed and ruled that Sakayanagi12 esting to to recall recall that esting uniform ruled with uniform is was ruled thirty years years ago, ago, although although is grating") groove grating "circular groove (the "circular ing ") thirty ing (the light. lin- spacings and and admittedly admittedly suffered suffered from from severe severe levels levels of of stray stray light. lin-spacings Gratings Type V Holographic Gratings groove generate groove to generate light to visible light utilize visible exist which utilize Holographic recording geometries exist Holographic the to the tailored to geometry, tailored wavelengths. Such shorter wavelengths. at shorter aberrations at patterns which correct aberrations Such a geometry, patterns which 4. We mention varied-space proposed varied -space piano plano gratings, gratings, is is discussed discussed at at length length in reference 4. results: the main results: here only the here (1) (1) ing ing the the

gratthe grata circle centered at the (visible wavelength) Two real real point point sources sources (visible wavelength) are are placed placed on on a Two of side of same side the same on the placed on be placed flat, both sources may be is flat, grating is the grating As the to be to be recorded. As below). or below). (e.g., above or grating grating (e.g.,

tuned to be tuned the corrected (2) AA small small change change in in the the radius radius of of this this circle circle allows allows the corrected wavelength to (2) range. large range. over a large over (3) This This wavelength-scaling wavelength- scaling procedure procedure results results in in aa finite finite aberration aberration at at the the corrected corrected wave(3) Multi-partite size. Multi grating size. the grating of the square of length, which increases as the -partite recordings recordings must the square length, which softX X-ray. EUVororsoft the EUV resolutions inin the high resolutions obtain high to obtain therefore be -ray. be used to therefore

was wavelength was recording wavelength the recording where the example, where for one example, Figure 2c the ray trace results for shows the 2c shows Figure A. Five 304 A. at XX == 304 chosen at 3637 AA and and maximum aberration -correction was chosen Five reaberration-correction be AX = 3637 to be assumed to aberrations that aberrations result that the result with the mm, with 180 mm, of 180 aperture of the grating aperture cordings were were used across the used across cordings 2a. straight-groove mechanically-ruled the mechanically to the were comparable to -ruled straight -groove design design of of Figure Figure 2a. were distinguishbeing distinguishvariety, being V" variety, "Type V" as aa "Type designated as is designated grating is This type of holographic grating This type converging in converging use in intended use its intended and its surface and plane surface able its plane by its varieties by holographic varieties able from other holographic light. of fabrication of potential fabrication the potential in the is in holography is visible holography of visible An interesting application of interesting other application recording wavelength the recording this case, order. In in high order. a -space echelle echelle operating operating in In this case, the line-space a varied line mainused, mainis used, grating is the grating which the in which order in echelle order the echelle scales naturally by the magnitude of the by the scales naturally order spectral order in spectral 100 AA in near 100 to operate near is to Thus, if echelle is if an echelle stigmatism. Thus, taining complete stigmatism. taining the patterns. However, However, the 60,visible visible holography holography will will directly directly record record the the stigmatic stigmatic groove groove patterns. ^A,60, techspecial techthat special requiring that angles, requiring blaze angles, large blaze at large triangles at required groove profiles profiles are triangles required groove photoresist. the photoresist. the processing of the in the niques niques be be used used in SoftX X-ray andSoft EUVand the EUV in the Interferometry in -ray, Interferometry Extreme Extreme Ultraviolet aberrawavefront aberrameasure wavefront to measure used to be used can be which can system which optical system new optical Figure illustrates aa new 8 illustrates Figure 8 stigthe stigline-space varied line tions for for the -space piano plano gratings. gratings. It It takes takes advantage of the the proposed varied tions the grating matic zero -order image image off off of of aa plane plane grating grating in in converging converging light. light. In In essence, essence, the zero-order matic correcthe correcto the stigmatic points corresponding to two stigmatic is illuminated illuminated in in reverse, reverse, starting starting with with two is aberration-free image. Thus, order image. Thus, an aberration -free grating grating will will yield zero order the zero to the tion and to tion wavelength and parabooff-axis surface byby ananoff film surface flat film upon aa flat imaged upon is imaged which is wave, which -axis paraboaa perfectly spherical wave, will pinhold. This will exit pinhold. an exit of an absence of the absence is the unique feature interferometer is this interferometer feature to this AA unique loid. sizes pinhole sizes required pinhole the required where the region, where greatly increase this wavelength region, in this its sensitivity in increase its greatly aberrations the aberrations that the weak. Note that inherently weak. the light sources are inherently are very very small small and and where where the are was interferometer. This was this interferometer. of this limit of of the grating determine the resolution limit the resolution toroidal grating the toroidal of either on either points on quasi-stigmatic the quasiat the lie at to lie points to source points two source the two choosing the minimized by stigmatic points by choosing normal. the toroidal normal. side side of of the of made of were made simulations were interferometer, simulations this interferometer, of this capabilites of the diagnostic capabilites To illustrate the To illustrate of contributions of aberration contributions (the aberration specified conditions (the under specified fringe patterns the fringe the patterns generated under results. these results. shows these Figure 88 shows of Figure inset of The inset included). The been included). not been have not the toroidal grating have the toroidal like grating like VLS grating groove VLS straight groove by aa straight 304 A by The top panel shows shows aa fringe fringe pattern produced at 304 top panel The in plane the in the stigmatism from the illustrates the It illustrates spectromter. It the EUVE spectromter. for the that that designed designed for grating groove grating perfect concentric groove plane. AA perfect off plane. aberration off in aberration increase in rays, and increase grating grating rays, that errors that ruling errors with ruling grating with imperfect grating an imperfect from an interferogram from image; an interferogram produces a perfect image; a perfect produces the sensitivity of the the sensitivity illustrate the the bottom panel) (in the increase off off plane plane has has been been shown shown (in panel) to illustrate increase would that would Thus errors that 10 1*. Thus of A,% 104. resolution of in aa resolution result in shown result interferometer. The errors shown method. this method. using this detectable using easily detectable be easily 30,000 would be than 30,000 less than resolution to less degrade the the resolution degrade Soft XX-ray -ray Periodic Structures (1984) of Periodic and Fabrication of Theory, and Application, Theory, 503 Application, Vol. 503 SPIE 108 //SP /E Vol

Figure 9 illustrates illustrates aa second second interferometer interferometer which which can can extend extend into into the the soft softX X-ray, and is is Figure 9 -ray, and based upon upon similar similar principles as as the the above above design. design. A monochromatic light light source source is is placed placed based behind a pinhole which which provides provides diffraction diffraction-limited at an an intersection intersection of of behind -limited waves waves emanating at two correspond to to two two multimulti-layered These Rowland circles correspond layered spherical spherical two Rowland circles. These mirrors, focus the the incident incident beam. beam. The The spatial separation separation of of the the two two respecrespecmirrors, which which split and focus tive (A and be selected by choosing the the correct separation separation of of the the Rowland Rowland tive images images (A and B) B) can can be circle centers centers (A (A and B); B); the the light light source source remains remains fixed fixed in in position position during during this this motion. motion. A circle small the image image A is is again again employed employed as as with the the previous previous interferometer. interferometer. small flat flat mirror mirror near near the In In the theabsence absenceof of grating grating aberrations, aberrations, aa perfectly perfectly spherical spherical wavefront should emerge. emerge. The aberrant is therefore therefore recorded recorded by by using using aa spherical spherical detector detector (e.g., (e.g., film). film). aberrant fringe fringe pattern pattern is Alternately, an an off off-axis in combination with aa flat flat detecting detecting Alternately, -axis camera camera mirror mirror may may be be used used in surface. Lengths Coherence Lengths The coherence length length required required for for the the light light source source is is small, small, being being equal equaltotothe thepath pathThe length the grating sample (the length retardation retardation across across the (the aberrant aberrant fringe fringe contribution contribution is is neglinegligible) For using aa wavelength wavelength of of 304 304 AA and and aa 100 gible).. 100 mm mm grating grating with with a anominal nominalline For example, example, using linedensity of 2000 the total total path -length difference difference is only 66 mm. 2000 mm mm"-1, 1 , the path-length mm. This corresponds corresponds to to aa decay time decay time of of only only ti% 22 xx 1010"" 11 seconds for for the the emission emission-line -11 -line of of the the light light source, source, or or a a line line width of of 33 mA. m&. Conventional laboratory laboratory sources, sources, such such as as the the Penning Penning discharge discharge source,l3 source, 13 should this line line width when operated at should be be able able to to achieve achieve this at low low pressures. pressures.

SPIE Vol. 109 SPIE Vol.503 503 Application, Application, Theory, Theory,and andFabrication Fabricationof ofPeriodic PeriodicStructures Structures(1984) (1984)// 109

References 1.

Kahn, S. S. M., Seward, S. S. P., P., and Kahn, M., Seward, and Chlebowski, Chlebowski, F. F. T., T. , Ap. Ap. J., J., in in press press (1984). (1984).

2. Dupree, Dupree, A. A. K., K., "The "The astrophysical astrophysical interest interest of of EUV EUV observations observations of of extra extra-solar -solar objects," Harvard-Smithsonian preprint no. no. 1452. 1452. objects," Harvard -Smithsonian Center Center for for Astrophysics, Astrophysics, preprint 3. 3.

Hettrick, C., and and Bowyer, Bowyer, S., S., Appl. Appl. Opt., Opt., Vol. Vol. 22, 22, p. p. 3921. 3921. Hettrick, M. M. C.,

4. 4.

Hettrick, M. M. C., C., Appl. Appl. Opt. Hettrick, Opt.

1983.

Sept. 15, 1984. 1984. Sept. 15,

5. Hettrick, M. C., and and Bowyer, Bowyer, S., S., "A "A new new class class of of grazing grazing incidence incidence telescopes telescopes for for 5. Hettrick, M. C., soft X X-ray -rayand andEUV EUVspectroscopy," spectroscopy," accepted accepted in in Appl. Appl. Opt. Opt. (1984). (1984). 6. 6.

Murty, R. K., K., J. J. Opt. Opt. Soc. Soc. Am., Am., Vol. Vol. 52, 52, p. p. 768. 768. Murty, M. M. V. V. R.

7. 7.

Kita, T., Nakano, Nakano, N., N., and and Kuroda, Kuroda, H., H., Appl. Appl. Opt., Opt., Vol. Vol. 22, 22, p. Kita, T., T., Harada, Harada, T., p. 512. 512.

1962. 1983.

8. Edelstein, J., Hettrick, Hettrick, M. M. C., C., Mrowka, Mrowka, S., S., Jelinsky, Jelinsky, P., P., and and Martin, Martin, C., C., Appl. Appl. Opt. Opt. Edelstein, J., 8. Oct. 1, 1984. 1984. Oct. 1, 9. Bowyer, 9. R., Lampton, Lampton, M., M., Finley, Finley, D., D., Paresce, Paresce, F., F., and and Penegor, Penegor, G., Bowyer, S., S., Malina, Malina, R., G., Proc. Proc. Soc. Photo Photo-Opt. 279, p. p. 176. 176. 1981. Soc. -Opt. Instrum. Instrum. Eng., Eng., Vol. Vol. 279, 10. Barbee, S., and Hettrick, Hettrick, M. M. C., C., "Extreme "Extreme Ultraviolet 10. Barbee, T. T. W., W., Mrowka, Mrowka, S., Ultraviolet Measurements Measurements of of Molybdenum Appl. Opt. Opt. (August, (August, 1984). 1984). Molybdenum and and Silicon," Silicon," submitted Appl. 11. Bunner, A., Perkin Perkin-Elmer communication (1984). (1984). 11. Bunner, A., -Elmer Corporation, Corporation, private communication 12. Sakayanagi, Y., Sci. Sci. Light, Light, Vol. Vol. 3, 3, p. p. 1. 1. 12. Sakayanagi, Y.,

(Tokyo). 1954 (Tokyo).

13. Finley, S., Paresce, Paresce, F., F., and Malina, R. F., F., 13. Finley, D. D. S., S., Bowyer, Bowyer, S., Malina, R. p. 649. 1979. p. 649.

110 //SPIE SPIE Vol Vol.503 503Application, Application,Theory, Theory,and andFabrication Fabricationof ofPeriodic Periodic Structures Structures (1984) (1984) 110

Appl. Appl. Opt., Opt., Vol. Vol. 18, 18,

h-

I.OmT -2-I (a) (a) STRAIGHT STRAIGHT GROOVES GROOVES

COLLECTING MIRROR

DETECTOR TECTOR

(b) ))) HYPERBOLIC HYPERBOLIC GROOVES, GROOVES, PfLANE

X Rq =304& =3040

°

REFLECTION GRATING I40±0.35& 140TO EA

200 +_ ± 0.5 & 200 0.54

260 ± 0.65 & 26020.654

304 ± 0.75 & 30420.754

380±0.95& 36020.954

(c) (C)

(a)

HYPERBOLIC HYPERBOLIC GROOVES , GROOVES, X R =363]4 =3637& T2

I C( ONCENTRIC

STRAIGHT B PARALLEL

(d) (d)

CONCENTRIC CONCENTRIC

(b) (b)

GROOVES GROOVES

(d) VARIED-AN GLE FAN FAN (d) VARIED-ANGLE

FAN FAN

Figure 1. 1. Plane reflection gratings gratings Plane reflection in conve rging light. light. Sever in converging al Solutions Solutions Several for e spacings spacings are shown. for the the groov groove shown.

Figure 2. 2. Raytr Figure ace spot diagrams diagrams for Raytrace for (a) ght grooves, grooves, (b) (a) strai straight (b) stigm atic stigmatic hyper bolas, (c) hyperbolas, -stig matic hyper (c) quasi quasistigmatic hyperbolas bolas gener ated by visible visible holography, holography, and generated (d) conce ntric grooves. In all cases, (d) concentric grooves. the ntial focal surfaces have the tange tangential focal surfaces have been employed, and each wavelength wavelength in the employed, tripl ets is is separated separated by by AXAX/A triplets /A = = 1/400. 1/400.

ECHELLO GRAM RAY RAY TRACES TRACES ECHELLOGRAM ABERRATIONS --GRATING GRATING ABERRATIONS90aa ±0.09A

916 A t 0.09

\\°

CONCENTRIC X- DISPERSER

-30mm 980 Ax ± o.Ia O.I 990E

FAN ECHELLE

--a

PINHOLE TELESCOPE FOCUS

ELLIPSOID

C,A

PARABOLOID

1

ViA

DETECTOR

1000420.14

1o2oAto.1A

1200A20.12A

1171 A 2 0.12 A

Figur e 3. 3. Raytr Figure ace results results for for aa two Raytrace two-eleme nt echel le spectrometer. spectrometer. A grating element echelle grating resol ving power resolving power of of 40,000 40,000 is achieved achieved across the 900 900-1 200 AA bandp across the -1200 bandpass. ass.

Figur e 4. Figure 4. A grazing incidence incidence telescope A grazing telescope-spect rometer instr ument, consisting consisting of spectrometer instrument, of only four grazing grazing reflections. only reflections. The echel le is is a conical conical diffraction echelle diffraction fan gratin g, and and the the cross cross-disp grating, -disperser erser is is a conce ntric groove groove grating. grating. concentric

SPIE SP /EVol. Vol.503 503Applicat Application, ion, Theory, Theory, and Fabrication Fabrication of of Periodic es (1984) Periodic Structur Structures 11984)// 111 111

Hitachi of Hitachi 5. Electron micrographs of Figure 5. piano line-space straight -groove varied line -space plano straight-groove and I/mm and 1400 1/mm is 1400 line density is grating; line 1600 1I/mm. /mm.

SPHERICAL SPHERICAL MULT!MULTI- LAYERED LAYERED MIRROR MIRROR

ñc WAVELENGTH » CORRECTION WAVELENGTH X c CORRECTION

ZERO ORDER

IMAGE FOCUS

ROWLAND CIRCLE

MCP DETECTOR IMAGING DETECTOR MCP IMAGING

for 6. Laboratory apparatus for Figure 6. measuring imaging imaging and and scattering performance measuring for of piano plano VLS VLS gratings, gratings, to be used for of preflight testing testing of of Extreme Ultraviolet preflight gratings. Spherical Explorer Spectrometer gratings. A) 300 A) > 300 (A > mirror may may be be coated coated with Osmium (A mirror A). or multilayers (A (A