A method of manufacturing photonic band gap structures operable in the optical spectrum has been presented. The method comprises the steps of creating a patterned template for an elastomeric mold, fabricating an elastomeric mold from poly-dimethylsiloxane (PDMS) or other suitable polymer, filling the elastomeric mold with a second polymer such as epoxy or other suitable polymer, stamping the second polymer by making contact with a substrate or multilayer structure, removing the elastomeric mold, infiltrating the multilayer structure with ceramic or metal, and heating the multilayer structure to remove the second polymer to form a photonic band gap structure

Cann, David

Constant, Kristen

Ho, Kai-Ming

Kang, Henry

Kim, Chang-Hwan

Lee, Jae Hwang

Leung, Wai

Sigalas, Mihail

English

Leung, Wai Y.

Constant, Kristen P.

Cann, David P.

Iowa State University Computer Science Technical Reports

Fabrication of photonic band gap materials using microtransfer molded templates

A method of manufacturing photonic band gap structures operable in the optical spectrum has been presented. The method comprises the steps of creating a patterned template for an elastomeric mold, fabricating an elastomeric mold from poly-dimethylsiloxane (PDMS) or other suitable polymer, filling the elastomeric mold with a second polymer such as epoxy or other suitable polymer, stamping the second polymer by making contact with a substrate or multilayer structure, removing the elastomeric mold, infiltrating the multilayer structure with ceramic or metal, and heating the multilayer structure to remove the second polymer to form a photonic band gap structure.</p

Digital Repository @ Iowa State University (ISU)

(12) United States Patent Leung et al. US006555406B1 (10) Patent N0.: (45) Date of Patent: US 6,555,406 B1 Apr. 29, 2003 (54) FABRICATION OF PHOTONIC BAND GAP MATERIALS USING MICROTRANSFER MOLDED TEMPLATES (75) Inventors: Wai Leung, Ames, IA (US); Kristen Constant, Ames, IA (US); Kai-Ming Ho, Ames, IA (US); Mihail Sigalas, Santa Clara, CA (US); Henry Kang, Miami, FL (US); Chang HWan Kim, Ames, IA (US); David Cann, Ames, IA (US); Jae Hwang Lee, Ames, IA (US) (73) Assignee: Iowa State University Research Foundation, Ames, IA (US) ( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days. (21) Appl. No.: 10/081,729 (22) Filed: Feb. 22, 2002 Related US. Application Data (60) Provisional application No. 60/271,345, ?led on Feb. 23, 2001. (51) Int. Cl.7 .............................................. .. H01L 21/00 (52) US. Cl. .......................................... .. 438/22; 438/42 (58) Field of Search ............................ .. 438/22, 25, 26, 438/31, 35, 36, 42, 51, 55, 64 (56) References Cited U.S. PATENT DOCUMENTS 6,469,682 B1 * 10/2002 de Maagt et al. OTHER PUBLICATIONS Yablonovitch, E., “Photonic Band—Gap Structures”, J. Opt. Soc. Am. B, vol. 10 (2), p. 283—295, Feb. 1993. OZbay, E., “Layer—by Layer photonic crystals from micro Wave to far—infrared frequencies”, J. Opt. Soc. Am. B, vol. 13 (9), p. 1945—1955, Sep. 1996. Wanke, M.C., Stuke, M., “Laser Rapid Prototyping of Paper Photonic—Band—Gap Microstructures”, Science (1996). X.M Zhao, Y. Xia, G.M Whitesides, “Fabrication of Three—Dimensional Micro—Structures: Microtransfer Mold ing”, Advanced Materials Communications 8 (10), p. 837—840, 1996. A. Kumar, H.A. Biebuyck, G.M. Whitesides, “Patterning Self—Assembled Monolayers: Applications in Materials Sci ence”, Langmuir, 10, p. 1498—1511, 1994. P. Yang, T. Deng, D. Zhao, P. Feng, D. Pine, B.R. Chmelka, G.M. Whitesides, G.D. Stucky, “Hierarchically Ordered Oxides”, Science V 282, p. 2244—2246, Dec. 18, 1998. A. Feigel, Z. Kotler, B. SfeZ, A. Arsh, M. Klebanov, V. Lyubin, “Chalcogenide glass—based three—dimensional pho tonic crystals”, American Institute of Physics, Applied Phys ics Letters, vol. 77 No. 20, p. 3221—3223, 0003—6951/2000/ 77(20)/3221/3, 2000. M. MiitZel, S. Tandler, D. Haubrich, D. Meschede, K. Peithmann, M. Flaspohler, K. Buse, “Atom Lithography With a Holographic Light Mask”, The American Physical Society, Physical RevieW Letters, vol. 88, No. 8, Feb. 25, 2002. Brian T. Holland, Christopher F. Blanford, Andreas Stein, “Synthesis of Macroporous Minerals With Highly Ordered Three—Dimensional Arrays of Spheroidal Voids”, Science, vol. 281, p. 38—40, Jul. 24, 1998. * cited by examiner Primary Examiner—David Nelms Assistant Examiner—Phuc T. Dang (74) Attorney, Agent, or Firm—Leydig, Voit & Mayer, Ltd. (57) ABSTRACT A method of manufacturing photonic band gap structures operable in the optical spectrum has been presented. The method comprises the steps of creating a patterned template for an elastomeric mold, fabricating an elastomeric mold from poly-dimethylsiloxane (PDMS) or other suitable polymer, ?lling the elastomeric mold With a second polymer such as epoxy or other suitable polymer, stamping the second polymer by making contact With a substrate or multilayer structure, removing the elastomeric mold, in?l trating the multilayer structure With ceramic or metal, and heating the multilayer structure to remove the second poly mer to form a photonic band gap structure. 18 Claims, 17 Drawing Sheets U.S. Patent Apr. 29, 2003 Sheet 1 0f 17 US 6,555,406 B1 /22 /22 U.S. Patent Apr. 29, 2003 Sheet 2 0f 17 US 6,555,406 B1 new“ FIG. 2 f ,oALl? ; Create patterned ] ‘ template ‘ ls. ,#___l e 32 V f Fabricate elastomeric mold l ‘ l / Fill elastomeric mold with epoxy material (___-__wiw> 77;» / 36 e34 / / V | Fill ela§tomeric Place the epoxy material mold With epoxy in contact with substrate material at required or multilayer structure places ' —~—;~?:~ l (/38 Remove the elastomeric mold lntroduce\ \ __i //)/All layers\> detect? /// No \ created’i/ // i T Yes ’/ 46 l infiltrate layers with ceramic; remove epoxy from layers U.S. Patent Apr. 29, 2003 Sheet 4 0f 17 US 6,555,406 B1 ,‘d /22 // 22 5 /22 22 22 /,/i( // VA 22 24 r 24f kR-+ VA 24 22 f\ »/”\22 24 r 24 \/ ¢ R~+ 0A 24 W “A 22 FIG. 4 U.S. Patent Apr. 29, 2003 Sheet 5 0f 17 US 6,555,406 B1 57 FIG. 5a 59 58 //" 104 102 I 100 I V Dd///’A\\ 110 FIG. 5b 0 $> 59 FIG. 5C 100 110 57 U.S. Patent Apr. 29, 2003 Sheet 6 6f 17 US 6,555,406 B1 FIG. 6 U.S. Patent Apr. 29, 2003 Sheet 7 0f 17 US 6,555,406 B1 FIG. 7 U.S. Patent Apr. 29, 2003 Sheet 8 0f 17 US 6,555,406 B1 FIG. 8 U S Patent Apr. 29, 2003 Sheet 9 0f 17 US 6,555,406 B1 U.S. Patent Apr. 29, 2003 Sheet 10 0f 17 US 6,555,406 B1 U.S. Patent Apr. 29, 2003 Sheet 11 0f 17 US 6,555,406 B1 U S Patent Apr. 29, 2003 Sheet 12 0f 17 US 6,555,406 B1 U.S. Patent Apr. 29, 2003 Sheet 13 0f 17 US 6,555,406 B1 US 6,555,406 B1 Sheet 14 0f 17 Apr. 29, 2003 a...“ y. ..  U S Patent U.S. Patent US 6,555,406 B1 E Sheet 15 0f 17 1... 22 Apr. 29, 2003 U S Patent Apr. 29, 2003 Sheet 16 0f 17 US 6,555,406 B1 m U S Patent Apr. 29, 2003 Sheet 17 0f 17 US 6,555,406 B1 US 6,555,406 B1 1 FABRICATION OF PHOTONIC BAND GAP MATERIALS USING MICROTRANSFER MOLDED TEMPLATES CROSS-REFERENCE TO RELATED PATENT APPLICATIONS This patent application claims the bene?t of US. provi sional patent application No. 60/271,345, ?led Feb. 23, 2001. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention Was made in part With Government support under DOE Contract No. W-7405-Eng-82 and DOC Con tract No. ITA87-02. The government may have certain rights in this invention. FIELD OF THE INVENTION The present invention relates generally to photonic band gap devices and methods of manufacturing same, and more particularly to a photonic band gap structure suitable for ?ltering in the optical Wavelength region and a method of manufacturing same. BACKGROUND OF THE INVENTION Photonic band gap (PBG) structures are periodic dielec tric or metallic structures that exhibit frequency regions in Which electromagnetic Waves cannot propagate. The interest in PBGs arises from the fact that photon behavior in a dielectric structure is similar to the behavior of electrons in a semiconductor. The periodic arrangement of atoms in a semiconductor lattice opens up forbidden gaps in the energy band diagram for the electrons. Similarly in all-dielectric PBG structures, the periodic placement of dielectric “atoms” opens up forbidden gaps in the photon energy bands. The idea of PBGs has led to the proposal of many novel applications at optical Wavelengths, such as thresholdless lasers, single-mode light-emitting-diodes and optical Wave guides. In addition, PBGs are already being used in the millimeter and microWave regimes, Where the applications include ef?cient re?ectors, antennas, ?lters, sources and Wave guides. They have also found possible applications as infrared ?lters. The PBG structures behave as ideal re?ectors in the band gap region. Depending on the directional periodicity of these dielectric structures, the band gap may exist in 1-D, 2-D or all the three directions. Various lattice geometries Were studied to ?nd a periodic structure that Would exhibit a photonic band gap in all the directions. After several unsuc cessful attempts in ?nding the right lattice geometry using “trial-and-error” techniques, researchers at IoWa State Uni versity Were ?rst to predict the existence of a complete band gap in a periodic dielectric structure arranged in diamond lattice geometry. Diamond lattice ran structures Were calcu lated to have large gaps for a refractive index ratio betWeen the tWo at dielectrics as loW as tWo. Further research indicated that, similar to the impurity doping in a semiconductor, localiZed electromagnetic modes can be created in the band gap region of PBG structures by introducing defects that disturb the periodicity of the struc ture. This defect can be achieved by removing a part of the PBG structure, thus creating states similar to the semicon ductor behavior With acceptor atoms. The defect can also be achieved by adding extra material to the crystal, Which acts like a donor atom of a semiconductor. The defect gives rise 10 15 25 35 45 55 65 2 to donor modes Which have their origin at the bottom of the conduction band. Experiments have shoWn that the acceptor modes, acting like cavities, are of greater importance With their highly localiZed and single-mode cavity characteristics. In photonic crystals With defects, the transmission spectrum is changed by the presence of a narroW transmission peak Within the band gap. Defect peaks With quality factors in the range of 1000—2000 have been experimentally demon strated. After the initial research into the existence of photonic band gap, there Was an increased effort to ?nd neW structures that could be more easily fabricated. These fabrication techniques include creating the PBG structure through emulsions, With carbon structures, and by creating crystals by a liquid-phase chemical reaction to in?ltrate a polysty rene template. These manufacturing techniques alloW the defect to be introduced by adding extra material to the crystal or by removing material after the photonic band gap structure has been built. This increases the manufacturing time and cost of the photonic band gap structures. What is needed is a Way to manufacture a photonic band gap structure that provides the capability to introduce defects Without adding extra material or removing material after the photonic band gap structure is built. BRIEF SUMMARY OF THE INVENTION It is an object of the instant invention to overcome at least some of the aforementioned and other knoWn problems existing in the art. More particularly, it is an object of the instant invention to provide a neW and improved method of manufacturing a photonic band gap structure alloWing operation in the optical region. It is a further object of the instant invention to provide a neW and improved method of manufacturing PBGs having a three-dimensional photonic band gap structure. It is also an object of the instant invention to provide a neW and improved method of manu facturing photonic band gap structures having adjustable process steps resulting in varying photonic band gap struc tures Whose performance characteristics are adjusted to meet speci?c performance requirements. Furthermore, it is an object of the instant invention to provide a neW and improved method of manufacturing photonic band gap structures utiliZing micro-transfer molded structures. In vieW of the above objects, it is a feature of the instant invention to provide a method of manufacturing photonic band gap structures Which utiliZe simple cost effective micro-transfer based construction techniques. It is an addi tional feature of the instant invention that the photonic band gap structures resulting from the method of manufacturing of the instant invention have characteristics of simple high pass ?lters, band stop ?lters, or ?lters having more complex transmission characteristics in the optical region depending upon the periodic pattern of the grids. Furthermore, it is a feature of the instant invention that the photonic band gap structures resulting from the method of the instant invention are lightWeight and compact. In accordance With an embodiment of the instant invention, a method of manufacturing a photonic band gap structure operable in the optical region comprises the steps of: a) creating a patterned template for an elastomeric mold; b) fabricating an elastomeric mold from poly dimethylsiloxane (PDMS) or other suitable polymer; c) ?lling the elastomeric mold With a second polymer; d) stamping the second polymer (epoxy) by making contact With a substrate or multilayer structure; e) introducing a ceramic bearing material (e.g., a sol or slurry) into the US 6,555,406 B1 3 second polymer to form a ceramic and epoxy structure; f) heating the ceramic-epoxy structure to remove the epoxy. The method of the instant invention may be repeated to produce multi-layer structures of 1, 2, 3, 4, 5, etc. layers. These method steps may be performed so that the thickness of dielectric layers separating the patterns are approximately equal, or are unequal. These steps include, in the step of forming a second or middle pattern in a three layer structure, the step of introducing a defect in the pattern. This defect may be adjusted to control a parameter of a ?lter charac teristic. The second polymer may be made With a slurry or sol gel in?ltration and may also be made With metal in?l tration. The second polymer may also be an epoxy or other suitable polymers of appropriate viscosity and With physical and chemical properties that alloW the building of a layered structure and removal via pyrolysis. Additionally, each step of forming a pattern may include the step of introducing a defect in the pattern. In one embodiment, the photonic band gap structure is formed With layers of rods stacked on top of each other, each layer having its axes oriented at 90° With respect to adjacent layers, alternate layers having their axes parallel to each other With the rods of one layer in offset betWeen the rods of the other layer forming a three-dimensional structure of stacked layers having a four-layer periodicity, the dielectric rods arranged With parallel axes at a given spacing to form a planar layer and arranged in a material having a different and contrasting refractive index, the dimensions of the rods, the spacing betWeen the rods and the refractive contrast of the materials selected to produce a photonic band gap operable in the optical region made by the method of the instant invention. Other objectives and advantages of the invention Will become more apparent from the folloWing detailed descrip tion When taken in conjunction With the accompanying draWings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying draWings incorporated in and forming a part of the speci?cation illustrate several aspects of the present invention, and together With the description serve to explain the principles of the invention. In the draWings: FIG. 1 is a simpli?ed isometric illustration of a layer-by layer photonic band gap structure manufactured in accor dance With the teachings of the present invention; FIG. 2 is a How chart illustrating the manufacturing process utiliZed in accordance With the teachings of the present invention; FIGS. 3a—3f are an isometric illustration of a portion of the steps of the manufacturing process of FIG. 2; FIG. 4 is a schematic illustration of tWo layers of a photonic structure With one layer having defects introduced therein; FIGS. 5a—5c are illustrations of a technique to apply epoxy into an elastomeric mold in accordance With the teachings of the present invention; FIG. 6 is a top vieW illustration of a four layer aligned photonic structure; FIG. 7 is a tWo dimensional top vieW of a four layer photonic structure With the top tWo layers 4 degrees out of alignment With the bottom tWo layers; FIG. 8 is a tWo dimensional top vieW of a four layer photonic structure With the top tWo layers 7 degrees out of alignment With the bottom tWo layers; FIG. 9a is an image of a resulting light pattern of a light shined through a misaligned four layer photonic structure at a magni?cation of 400x; 15 25 35 45 55 65 4 FIG. 9b is an image of a resulting light pattern of a light shined through a misaligned four layer photonic structure at a magni?cation of 200x; FIG. 9c is an image of a resulting light pattern of a light shined through a misaligned four layer photonic structure at a magni?cation of 50x; FIG. 10a is an image of a side-vieW of a tWo-layer photonic structure having a 2.5 pm periodicity manufactured using a slurry in?ltration in accordance With the teachings of the present invention; FIG. 10b is an enlarged image of the photonic structure of FIG. 10a; FIG. 11 is an image of the top vieW of the photonic structure of FIG. 10a; FIG. 12a is an image of a side vieW of a tWo-layer photonic structure having a 2.5 pm periodicity manufactured using a sol-gel in?ltration in accordance With the teachings of the present invention; FIG. 12b is an enlarged image of the photonic structure of FIG. 12a; FIG. 13a is an image of a side vieW of a four-layer photonic structure having a 2.5 pm periodicity manufactured using a sol-gel in?ltration in accordance With the teachings of the present invention; FIG. 13b is an enlarged image of the photonic structure of FIG. 13a; FIG. 14a is an image of a tWo-layer epoxy mold having a 1 pm periodicity made in accordance With the teachings of the present invention; FIG. 14b is an enlarged image of the epoxy mold of FIG. 14a; FIG. 15 is an image of a tWo layer ceramic photonic structure having a 1 pm periodicity made from the mold of FIGS. 14a and 14b; and FIG. 16 is an image of a four layer ceramic photonic structure having a 1 pm periodicity made from a four layer epoxy mold. While the invention Will be described in connection With certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modi?cations and equivalents as included Within the spirit and scope of the invention as de?ned by the appended claims. DETAILED DESCRIPTION OF THE INVENTION Turning noW to FIG. 1, theoretical band calculations in conjunction With experimental measurements have ?rmly established that the structure 20 has a fundamental full photonic band gap. This occurs betWeen the loWest set of bands (i.e., bands 2 and 3). The structure 20 has a layer of rods stacked on top of each other. Each layer of rods consists of an ordered array of parallel rods 22, With a spacing d betWeen rods 22. The axes of each layer are oriented at 90° With respect to adjacent layers. Alternate layers have their axes parallel to each other With the rods 22 of one layer in offset betWeen the rods 22 of the other layer forming a three-dimensional structure of stacked layers having a four layer periodicity The offset betWeen alternate layers in one embodiment is half the spacing d (i.e., d/2). The rods 22 can be fabricated With dielectric or non-linear materials. In the description that folloWs, epoxy Will be used to describe the building of a photonic band gap. Other suitable polymers of appropriate viscosity and With physical and 

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Fabrication of photonic band gap materials using microtransfer molded templates

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