Multilayer mirror

Fig. 12. Schematic of surface-emitting laser diodes where U represents the active region (a) planar cavity surface-emitting laser diode (PCSEL) with 45° etched reflectors and (b) vertical cavity surface-emitting laser diode (VCSEL) with semiconductor-based multilayer mirror stacks grown into the stmcture.

The state-of-the-art mirror system now in use is a glass second-surface silver mirror backed with copper and paint, as shown in Fig. 2. For this system, the characterization and study of the glass/silver, silver/copper, and copper/paint interfaces before and after various stages of use are clearly required to understand the multilayer mirror stack. The methods of characterization outlined in Sec. 2.4 of Ref. 3, especially those of ISS, XPS, AES, and SIMS, are clearly applicable to this problem. In ter facial degradation reactions may begin at the silver/glass interface... 

Curved mirrors can be used to collimate or focus a divergent X-ray beam. Still rather rare on laboratory instruments, graded-multilayer mirrors may be used to produce a near-parallel incident beam, which may be advantageous when working with non-flat or irregular samples or with samples under non-ambient conditions. 

Fischer, D.A., Colbert, J., and Gland, J.L., Ultrasoft (C,N,0) x-ray-fluorescence detection — Proportional counters, focusing multilayer mirrors, and scattered-light systematics, Rev. Sci. Instruments 60, 1596-1602, 1989. 

At 13.5-nm wavelength, silieon and molybdenum make an excellent pair of materials for an EUV multilayer mirror. The real part of their refractive indices is quite different in the EUV spectral region in addition, molybdenum has the lowest absorption at EUV relative to other alternative metals with reasonable single interface reflectivity. ... 

Figure 14.5 Calculated normal Incidence reflectivity curve for a molybdenum-silicon multilayer mirror with number of bIlayers 50. The molybdenum thickness Is 2.7 nm and the silicon thickness Is 4.2 nm. (Reprinted with permission from Ref. 44. 2009 McGraw-Hill.)...

Figure 14.11 EUV spectrum for a Sn droplet obtained with a CO2 drive laser of an LPP system during high-repetition-rate operation in comparison with a high-temperature stable multilayer mirror reflectance curve. (After D.C. Brandt et al. )...

S.B. Hill, N.S. Faradzhev, C. Tarrio, T.B. Lucatorto, T.E. Madey, B.V. Yakshinskiy, E. Loginova, and S. Yulin, Accelerated lifetime metrology of EUV multilayer mirrors in hydrocarbon environ ments, Proc. SPIE 6911, 692117 (2008). 

K. Boiler, R.P. Haelbich, H. Hogrefe, W. Jerk, and C. Kunz, Investigation of carbon contamination of mirror surfaces exposed to synchrotron radiation, Nucl. Instrum. Method. 208, 273 279 (1983). M.E. Malinowski, C. Steinhaus, W.M. Clift, L.E. Klebanoff, S. Mrowka, and R. Soufli, ControlUng contamination in Mo/Si multilayer mirrors by Si surface capping modifications, Proc. SPIE 4688, 442 (2002). 

Figure 14.14 Reflectivity and photoelectron current as a function of the photon dose (which is proportional to the thickness of the carbon contamination on the surface of the multilayer mirror). ...

Under EUV photon irradiation in the presence of oxygen or oxidizing agents, the surfaces of EUV optics and reticles are easily oxidized, leading to reflectivity loss of such surfaces. Oxides strongly absorb EUV radiation, and a small increase in oxide film thickness ( 1.5 nm) can decrease EUV multilayer mirror reflectivity by up to 1.6% (absolute). Because oxidation is difficult to remove, even small amounts of oxidation can negatively affect the EUV optics lifetime. The oxidation of silicon-capped EUV multilayer reflectors has been reported to show similar trends as those observed for carbon deposition. In particular, the rate of reflectivity loss due to oxidation of EUV mirrors has been observed to increase with the partial pressure of water in the optics environment, as well as with the EUV radiation intensity (see Eig. 14.16). " ... 

Bajt, H.N. Chapman, N. Nguygen, J. Alameda, J.C. Rohinson, M. Malinowski, E. Gullikson, A. Aquila, C. Tarrio, and S. Grantham, Design and performance of capping layers for extreme ultraviolet multilayer mirrors, Appl. Opt. 42(28), 5750 5758 (2003). 

M. Niihe, Y. Kakutani, S. Terashima, H. Takase, Y. Gomei, S. Matsunari, T. Aoki, K. Murakami, and Y. Eukuda, New contamination experimental equipment in the new SUBARU and evaluation of Si capped multilayer mirrors using it, Proc. SPIE 6151, 615134 (2006). 

Hill, C. Tamo, S.E. Grantham, T.B. Lucatorto, T. Madey, I. Ermanoski, S. Bajt, M. Chandhok, P. Yan, O.R. Wood II, S. Wurm, and N.V. Edwards, EUV testing of multilayer mirrors critical issues, Proc. SPIE 6151, 61510F (2006). 

Mizutani, U., Yamaguchi, T., Ikuta, H. et al. 2008. Eabrication of Mo/Si multilayer mirrors for extreme ultraviolet lithography by means of superconducting bulk magnet magnetron sputtering. Physica C Superconductivity 468 1456-1460. 

The joint use of a Whiter I concentrator based on multilayers to focus low energy (<40 keV) X-rays and a Bragg concentrator like HAXTEL to focus higher energy X-rays appears a possible telescope configuration that efficiently focuses X-rays in a broad energy band (from 1 keV to about 200 keV). A replication technique to fabricate multilayer mirrors is currently investigated, that would render feasible a Wolter I multilayer concentrator... 

The effective area of an EBB coated two reflection conical mirror is shown in Figure 2 in comparison with that of a uniform period multilayer mirror. Aside from the coatings two mirror systems are identical four modules, each with 24cm diameter and 10m focal length and reflectors that are 80 cm long. 

In order to overcome the mentioned problems in the fabrication of an (approximated or not) Wolter I multilayer mirror, we intend to investigate new techniques. They are an extension of the replication technology by electroforming successfully employed for the SAX and JETX missions (Citterio et al., 1989)... 

By assuming to be capable to build a multilayer mirror with Wolter I (approximated or not) geometry, we have investigated a hard X-ray telescope configuration with bandwidth from 2 to 60-70 keV. We assumed a multilayer coating with the features given in Table 1. 

Initial wavelength selection is done by a mechanical (rotating) velocity selector, since energy resolution is not an important issue here. Polarized neutrons may be produced by reflection by a magnetic multilayer mirror. Essential parts are the so-called flippers. These devices, consisting of flat coils, can change the direction of the neutron spin (which is extremely sensitive to external magnetic fields). 

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