DE10227367B4 - Reflective element for free electron laser radiation, process for its preparation and its use - Google Patents

Reflective element for free electron laser radiation, process for its preparation and its use

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Publication number
DE10227367B4
DE10227367B4 DE2002127367 DE10227367A DE10227367B4 DE 10227367 B4 DE10227367 B4 DE 10227367B4 DE 2002127367 DE2002127367 DE 2002127367 DE 10227367 A DE10227367 A DE 10227367A DE 10227367 B4 DE10227367 B4 DE 10227367B4
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Germany
Prior art keywords
formed
wavelength
layer
sio
characterized
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
DE2002127367
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German (de)
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DE10227367A1 (en
Inventor
Alexandre Dipl.-Phys. Dr. Gatto
Norbert Dipl.-Phys. Dr. Kaiser
Roland Dipl.-Phys. Dr. Thielsch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Southwall Europe GmbH
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Southwall Europe GmbH
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Priority to DE2002127367 priority Critical patent/DE10227367B4/en
Publication of DE10227367A1 publication Critical patent/DE10227367A1/en
Application granted granted Critical
Publication of DE10227367B4 publication Critical patent/DE10227367B4/en
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Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/08Mirrors
    • G02B5/0891Ultraviolet [UV] mirrors
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21KTECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/06Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diffraction, refraction or reflection, e.g. monochromators
    • G21K1/062Devices having a multilayer structure
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09Processes or apparatus for excitation, e.g. pumping
    • H01S3/0903Free-electron laser

Abstract

Reflecting element for free electron laser radiation in the wavelength range between 150 and 500 nm,
in which a first alternating layer system is arranged on a substrate, whose layer pairs are made of either SiO 2 and a first refractive index or SiO 2 having first metal oxide or fluoride or
consist of two fluorides of different refractive index and whose layers are each formed as λ / 4 layers for a wavelength interval in the range around a first wavelength λ 2 ,
on the first alternating layer system a transition layer of SiO 2 or the first metal oxide or a fluoride is arranged, which is formed as λ / 4-layer for the first wavelength λ 2 ,
on the transition layer, a second alternating layer system is arranged, whose layer pairs of SiO 2 and a higher refractive index than SiO 2 having second metal oxide or fluoride or
consist of two fluorides of different refractive index and whose layers are each formed as λ / 4 layers for a wavelength interval in the range around a second wavelength λ 1 ,
where the second ...

Description

  • The Invention relates to a reflective element for free electron laser radiation, a method for producing such a reflective element and its use for adjusting a resonator of a free Electron laser beam source in the wavelength range between 150 to to 500 nm and possibly above also possible.
  • The Since about 1977 known free electron laser sources can in a wide wavelength range, from infrared to ultraviolet and even to Vacuum ultraviolet wavelengths be exploited. Unlike the other conventional ones Laser beam sources become a relativistic medium as an active medium Electron beam is used, which under appropriate conditions a reinforcement caused by stored within a resonator light. Thereby can with the free electron laser sources monochromatic and coherent Radiation with high peak and continuous power can be generated, the additionally also tunable. Accordingly, such a free electron laser beam source specifically set to a specific selected wavelength become.
  • Should Such free electron laser radiation in the lower wavelength range, For example, in the field of ultraviolet or vacuum ultraviolet radiation, used in an optical resonator of such a laser beam source are due to the low gain in this wavelength range Layer systems formed from alternating layers required, the a high reflectivity exhibit and opposite are resistant to synchrotron radiation. Because of the high performance needs the absorption of the substrates used, on which the corresponding reflective alternating-layer systems are formed, very small be held to destruction through increased warming to avoid. In particular, the small wavelengths are critical here.
  • at Use of such a reflective element as a front Mirror of an optical resonator of a free electron laser beam source acts not just the first harmonic of this radiation, but the whole radiation emitted by the undulator. It follows that the corresponding radiation a very broad wavelength band includes and also into the wavelength range of the X-ray radiation enough.
  • For applications with free electron laser radiation, corresponding reflective elements on which an alternating-layer system for a certain wavelength is formed are known. Usually, SiO 2 is used as a material for a layer of such a layer-change system as a low-refractive index component, since this oxide is transparent to radiation up to a wavelength of approximately 150 nm. Other higher refractive index oxidic compounds usually have higher wavelength lower bounds, which lose their transparency. Accordingly, conventional reflective elements are used with alternating layer systems, which have their reflection maxima in the range of about 300 nm. However, this relatively high upper limit, which must be met because of the correspondingly high absorption, limits the use of the free electron laser radiation down to this lower limit. For many applications but working wavelengths are desired, which are smaller than 300 nm.
  • Such, to only one wavelength designed in the ultraviolet and vacuum-ultraviolet spectral range reflective elements cause problems when adjusting one free electron laser beam source to a certain operating wavelength, the so-called tuning. This problem is compounding towards shorter wavelengths because of the corresponding increase in absorption and the associated lower reinforcement. Furthermore affect the small signal to noise ratio and the corresponding Sensitivity decrease of a photodetector to be used.
  • Thus, in EC Contract ERBFMGECT980102. "Development of a Combined Synchrontron Radiation and VUV Free-Electron Laser Facility" Minutes of the 7 th Project Meeting, Trieste, Italy on March 10, 2001 Notes for the training of mirrors in connection with Such mirrors are to be provided with two different metal oxide / silicon oxide layer systems, which have been selected for different wavelength ranges, namely 350 to 400 nm and 220 to 230 nm For both spectral ranges, reflectivities above 94 % can be achieved.
  • Out DE 31 02 301 A1 It is generally known that in interference filters between two different alternating-layer systems for different wavelengths transition layers should be arranged. In particular, it can be seen there that one or more coupling layers should be arranged between alternating-layer systems / alternating-layer groups whose optical thickness, as well as the alternating-layer systems / alternating-layer groups, are tuned to a single measuring wavelength λ 0 .
  • It is therefore an object of the invention, for free electron laser radiation reflective elements available to provide, even at working wavelengths below 300 nm with a free electron laser beam source can be used, a simple Adjusting the optical elements in the beam path and a simple and allow fast tuning of the resonator to a working wavelength.
  • According to the invention this Task with a reflective element that has the characteristics of the claim 1, solved. The reflective according to the invention Elements can with a method according to claim 11 are made and use is made with the claim 13 defined.
  • The subordinate claims contain characteristics for advantageous embodiments and refinements of the invention.
  • The reflective according to the invention Elements for free electron laser radiation in the wavelength range between 150 and preferably up to 500 nm have two superimposed different Alternating layer systems, each aligned to specific wavelengths for increased reflectivity are, so that one can also speak of a two-wavelength mirror.
  • In this case, on the surface of a substrate, a first alternating layer system, which is formed from layer pairs of SiO 2 and a first metal oxide or fluoride. This metal oxide or fluoride has a higher refractive index than the SiO 2 . In this case, the individual layer thicknesses of the SiO 2 and metal oxide or fluoride layers are formed as λ / 4 layer thicknesses for a wavelength interval in the range around a first wavelength λ 2 .
  • In an alternative of the invention can the first alternating layer system also made of two fluorides, respectively be formed of different refractive index.
  • On this alternating layer system, only a transition layer is present, which consists of SiO 2 or the first metal oxide or fluoride and which is formed as λ / 4-layer for the first wavelength λ 2 .
  • In turn, a second alternating layer system is formed on this transition layer whose layer pairs comprise SiO 2 and a second metal oxide or fluoride, which likewise has a higher refractive index than SiO 2 .
  • Also the second alternating layer system can be used in an alternative according to the invention formed from two fluorides, each with different refractive index be.
  • The individual layers are formed as λ / 4 layers for a wavelength interval in the range around a second wavelength λ 1 .
  • In this case, the second wavelength λ 1 is smaller than the first wavelength λ 2 .
  • Fluoride change layer systems are to be preferred if the second smaller wavelength λ 1 is to be less than 190 nm.
  • Accordingly can with a certain bandwidth corresponding to the wavelength interval the two wavelengths high reflectivities of the reflective according to the invention Elementes are secured.
  • For the alternating layer systems, various metal oxides can be used. Thus, the corresponding layers of HfO 2 , Al 2 O 3 , ZrO 3 , Sc 2 O 3 , Y 2 O 3 , La 2 O 3 , Ta 2 O 5 or Nb 2 O 5 are formed. Of course, the metal oxide chosen in each case also has a corresponding influence on the design of the layer system and the respective reflected wavelengths.
  • The fluorides may be selected from MgF 2 , LaF 3 , GdF 3 , BaF 2 , CaF 2 and AlF 3 .
  • For the alternating layer systems should each be at least five Layer pairs selected become.
  • As substrate materials, for example quartz glass, sapphire BK7, crystalline quartz, CaF 2 , MgF 2 , BaF 2 or silicon can be used.
  • The metal oxides used for the alternating-layer systems should be selected such that the greatest possible distance between the two selected wavelengths λ 1 and λ 2 is recorded.
  • The respective higher wavelength λ 2 should preferably be selected above 300 nm. It is favorable to choose a wavelength in the visible spectral range.
  • As a result, the adjustment to specific wavelengths can be significantly simplified because of the good tunability present in the case of free electron laser beam sources. Thus, the optical resonator of the free electron laser beam source in this higher wavelength range due to the correspondingly larger gain, the higher signal / noise ratio, the higher sensitivity of Photonendetekto ren in the corresponding wavelength range very precisely to the first Wavelength λ 2 are set. The larger bandwidth, ie the larger wavelength interval around this first wavelength λ 2 , in which an increased reflectivity is present, also has a favorable effect for the fine tuning of the optical resonator to this wavelength λ 2 .
  • If the optical resonator has been set to this wavelength, the free electron laser beam source can be changed to the second wavelength λ 1 , as operating wavelength, by simply switching the undulator, without adjusting the optical resonator to this wavelength λ 1, which is more complex for correspondingly smaller wavelengths is required.
  • Thus, for example, a reflective element on which a first alternating layer system, which is formed from HfO 2 and SiO 2 individual layers, with corresponding λ / 4 layer thicknesses for the first wavelength λ 2 equal to 380 nm and subsequent to the formed on this alternating layer system SiO 2 transition layer, the second alternating layer system of Al 2 O 3 - and Sio 2 layers are formed with corresponding λ / 4 layer thicknesses for the second wavelength λ 1 equal to 220 nm.
  • As already mentioned, then the Einjustierung the optical resonator to the wavelength λ 2 equal 380 nm and after adjustment to this wavelength, the operating wavelength λ 1 equal to 220 nm is turned on by appropriate switching of the undulator.
  • There the reflective element according to the invention in the critical wavelength ranges, at where the free electron laser beam source is to be operated, has a low absorption, is also a continuous operation with high performance readily possible. With other metal oxides already mentioned above, alternating layer systems can be used for others wavelength be formed.
  • For example, an alternating layer system SiO 2 -Ta 2 O 5 for a wavelength of 500 nm, an alternating layer system SiO 2 - HfO 2 for a wavelength of 300 nm, a alternating layer system Y 2 O 3 -SiO 2 for a wavelength of 250 nm, a Alternating layer system SiO 2 - Al 2 O 3 for a wavelength of 190 nm and an alternating layer system MgF 2 - LaF 3 for a wavelength of 150 nm.
  • Thereby can different combinations, considering the corresponding wavelengths reflective elements are obtained.
  • The reflective according to the invention Elements can advantageously prepared in vacuum by means of ion-assisted plasma evaporation become.
  • there should be preferred to the formation of the respective individual layers within a vacuum chamber by appropriate known evaporation of the respective oxides are formed.
  • there Argon is used as working gas and oxygen as reactive gas fed.
  • By appropriate adjustment of the respective oxygen partial pressure can influence the stoichiometry the respective oxide layer are taken.
  • The individual layers thereby achieve an amorphous structure a high packing density of the atoms or molecules. This allows the optical Properties are further improved, which in particular one further reduced absorption and increased reflectivity concerns.
  • following the invention should be further exemplified.
  • there shows:
  • 1 a diagram of the reflectivity and transmission of an example of a reflective element according to the invention with increased reflectivity at the wavelengths 220 and 380 nm.
  • For the production of the corresponding reflective element, a silicon substrate with a layer design / (HS) 11 H (SA) 24 / air was formed. H stands for hafnium oxide, S for silicon dioxide and A for aluminum oxide.
  • The layer thicknesses of the first alternating layer system consisting of silicon and hafnium oxide layers are formed at a first wavelength λ 2 of 380 nm and for the second alternating layer system as λ / 4 layer thicknesses for 220 nm from SiO 2 and Al 2 O 3 .
  • It is with the in 1 shown clearly that in the thus produced reflective element in certain bandwidths increased reflectivities could be achieved with about 98% at 220 nm and 99.1% at 380 nm.
  • The single layers of the alternating layer systems of this example one reflective according to the invention Elementes were treated with a commercially available plasma source Advanced Plasma Source produced in a high vacuum coating system.
  • It was worked within the vacuum chamber at a base pressure of 3.10 -4 Pa, with a bias voltage between 150 to 200 V. The average coating rate was 0.2 nm / s.
  • In addition, as already mentioned in the general part of the description, argon was fed as the working gas and oxygen as the reactive gas, while the partial pressure of the oxygen was deliberately adjusted in accordance with the respective oxide layer to be formed. Thus, for the formation of HfO 2 and Al 2 O 3 layers, an oxygen partial pressure in the range of 3 × 10 -4 mbar and for SiO 2 layers an oxygen partial pressure in the range of 1 × 10 -4 mbar are set. The substrate was heated to 100 to 150 ° C.

Claims (13)

  1. Reflective element for free electron laser radiation in the wavelength range between 150 and 500 nm, in which a first alternating layer system is arranged on a substrate whose layer pairs either of SiO 2 and a higher refractive index than SiO 2 having first metal oxide or fluoride or two fluorides of different Refractive index and whose layers are each formed as λ / 4 layers for a wavelength interval in the range around a first wavelength λ 2 , on the first alternating layer system, a transition layer of SiO 2 or the first metal oxide or a fluoride is arranged as λ / 4 Layer is formed for the first wavelength λ 2 , on the transition layer, a second alternating layer system is arranged, whose layer pairs of SiO 2 and a higher refractive index than SiO 2 having second metal oxide or fluoride or two fluorides of different refractive index and whose layers each al s λ / 4 layers are formed for a wavelength interval in the range around a second wavelength λ 1 , wherein the second wavelength λ 1 is smaller than the first wavelength λ 2 .
  2. Element according to claim 1, characterized in that the metal oxides are selected from HfO 2 , Al 2 O 3 , ZrO 2 , Sc 2 O 3 , Y 2 O 3 , La 2 O 3 , Ta 2 O 5 and Nb 2 O 5 .
  3. Element according to claim 1 or 2, characterized in that the fluorides are selected from MgF 2 , LaF 3 , GdF 3 , BaF 2 , CaF 2 and AlF 3 .
  4. Element according to at least one of the preceding claims 1 to 3, characterized in that the alternating layer systems at least five each Layer pairs are formed.
  5. Element according to at least one of the preceding claims, characterized in that a first alternating layer system formed from SiO 2 and HfO 2 has at least eleven layer pairs and a second alternating layer system formed from SiO 2 and Al 2 O 3 has at least twenty layer pairs.
  6. Element according to at least one of the preceding claims, characterized in that the substrate consists of quartz glass, sapphire, BaF 2 , CaF 2 , MgF 2 , BK7, crystalline quartz or silicon.
  7. Element according to at least one of the preceding Claims, characterized in that the layers are formed in amorphous form are.
  8. Element according to at least one of the preceding claims, characterized in that the first wavelength λ 2 is greater than 300 nm.
  9. Element according to at least one of the preceding claims, characterized in that the first alternating layer system for a first wavelength λ 2 of 380 nm and the second alternating layer system for a second wavelength λ 1 of 220 nm is formed.
  10. Element according to at least one of the preceding claims, characterized in that the wavelength interval is formed by the first wavelength λ 2 greater than the wavelength interval around the second wavelength λ 1 of 220 nm.
  11. Process for making a reflective Element according to one of the claims 1 to 9, characterized in that, the two alternating layer systems and the transition layer forming individual layers in vacuo by ion-assisted plasma evaporation formed of the respective oxides with the supply of argon and oxygen become.
  12. Method according to claim 10, characterized in that that the oxygen partial pressure within a vacuum chamber in dependence the respective oxide layer to be formed is adjusted.
  13. Use of a reflective element after one of the claims 1 to 9 for adjusting an optical resonator of a free electron laser beam source.
DE2002127367 2002-06-13 2002-06-13 Reflective element for free electron laser radiation, process for its preparation and its use Expired - Fee Related DE10227367B4 (en)

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DE10227367B4 true DE10227367B4 (en) 2007-01-11

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Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009033511A1 (en) 2009-07-15 2011-01-20 Carl Zeiss Smt Ag Micro mirror arrangement for forming pupil in lighting system utilized for microlithography, has anti-reflex coating with absorbing layer made of non-metallic material whose absorption coefficient and wavelength are set as specific value
WO2011006685A1 (en) * 2009-07-15 2011-01-20 Carl Zeiss Smt Gmbh Micromirror arrangement having a coating and method for the production thereof
DE102010048088A1 (en) 2010-10-01 2012-04-05 Carl Zeiss Vision Gmbh Optical lens with scratch-resistant anti-reflection coating
JP6389896B2 (en) 2013-09-23 2018-09-12 カール・ツァイス・エスエムティー・ゲーエムベーハー Multilayer mirror

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3102301A1 (en) * 1980-02-01 1982-01-21 Jenoptik Jena Gmbh "Interference mirror with a high reflection for several spectral bands"
DE4430363A1 (en) * 1994-08-26 1996-02-29 Leybold Ag An optical lens made of a clear-sighted plastic

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3102301A1 (en) * 1980-02-01 1982-01-21 Jenoptik Jena Gmbh "Interference mirror with a high reflection for several spectral bands"
DE4430363A1 (en) * 1994-08-26 1996-02-29 Leybold Ag An optical lens made of a clear-sighted plastic

Non-Patent Citations (8)

* Cited by examiner, † Cited by third party
Title
European UV/VUV Storage Ring FEL at ELETTRA. Proc,22nd Int. FEL Conference, Durham, USA, Au- gust 2000
EC Contract ERBFMGECT980102: Developement of a Combined Synchrotron Radiation and VUV Free-Elec- tron Laser Facility. Minutes of the 7th Project Meeting, Trieste, Italy, 10th march 2000 *
G.P. Callahan: Charakteristics of Deep UV Optics at 193 & 157 nm. SPIE, 1998 *
H. Lauth et al: 193/157 nm UV Coatings for Next Generation Photolithographie-All Aspects. Optical Interference Coatings, Banff, July 15-20, 2001 *
R. Thielsch et al.: Absorption Limited Performance of SiO¶2¶/AIO¶3¶ Multi-layer Coatings at 193 nm-A Systematic Study. Optical Society of America, OIC 2001 Postshow Presentations. Last updated October 4, 2001 *
R. Thielsch et al.: Absorption Limited Performance of SiO2/AIO3 Multi-layer Coatings at 193 nm-A Systematic Study. Optical Society of America, OIC 2001 Postshow Presentations. Last updated October 4, 2001
R.P Walker et al.: First Lasing and Initial Per- formance of the *
R.P. Walker et al.: The European UV/VUV Storage Ring FEL Project at Elletra. Proceedings of EPAF 2000, Vienna *

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