HK1123610A - Assembly of quasicrystalline photonic heterostructures - Google Patents

Description

Assembly of quasicrystalline photonic heterostructures

This work was supported by national science foundation (funding numbers DMR0451589, DMR021306, and DMR0243001) and the U.S. department of energy (funding number DE-FG02-91ER 40671).

Cross reference to related patent applications

This patent application claims priority from U.S. provisional application No. 60/697,872 filed on 8/7/2005 and is incorporated herein by reference in its entirety.

Technical Field

The present invention relates generally to the field of quasicrystalline heterostructures. More particularly, the present invention relates to the assembly of quasicrystalline photonic heterostructures with specific orientation symmetry in two dimensions or along any two of three-dimensional structures, or with any specific three-dimensional quasicrystalline symmetry, and to the use of Holographic Optical Traps (HOTS) to perform the assembly and the use of these HOTS assembled structures in a variety of applications.

Background

Crystalline materials have long been developed for use in many optical and electronic applications due to their physical properties resulting from their crystal symmetry. Although these crystalline materials enable many technological applications, there are limitations to this crystal symmetry. For example, ordered arrangements (alignments) of dielectric materials with alternating domains (domains) of high and low refractive index are known to exhibit light transmission properties known as photonic bandgaps. The optical properties of photonic band gap materials are characterized by the inability of light within a certain frequency range to propagate and be absorbed. This behavior is similar to the electronic bandgap produced in semiconductors for transporting electrons and should lead to a similarly broad range of applications. The photonic band gap limit (extend) of a material depends not only on the dielectric properties of the constituent dielectric material but also on the symmetry of its three-dimensional arrangement. The limited set of different symmetries available for crystal arrangements requires a very large contrast in dielectric constants to achieve a complete (full) photonic bandgap, and these symmetries result in optical materials whose optical properties are very sensitive to structural and chemical defects. In contrast, quasicrystals are known to have much higher rotational symmetry than crystals. Therefore, a quasicrystal should exhibit a photonic band gap that is larger and more uniform than any crystal arrangement of the same material, and should have optical properties that are more resistant to defects and disorder. Thus, two-dimensional and three-dimensional quasicrystalline arrangements of materials should have a wide range of technological applications based on their optical and other physical properties.

Summary of The Invention

It is therefore an object of the present invention to provide an improved system and method for fabricating quasicrystalline structures.

It is another object of the present invention to provide improved systems and methods for fabricating quasicrystalline photonic heterostructures using holographic optical traps.

It is yet another object of the present invention to provide an improved article of manufacture of a three-dimensional quasicrystalline photonic heterostructure.

It is a further object of the present invention to provide improved systems and methods for constructing materials having photonic bandgaps that are forbidden in crystalline materials.

It is another object of the present invention to provide improved systems and methods for constructing rotationally symmetric heterostructures having optical, mechanical, chemical, biological, electrical and magnetic properties not attainable with crystalline materials.

It is a further object of the present invention to provide improved quasicrystalline heterostructures with programmable optical, mechanical, biological, electrical, magnetic and chemical properties.

It is a further object of the present invention to provide improved systems and methods for constructing a quasicrystalline structure having a particular brillouin zone for a selected technological application.

It is another object of the present invention to provide improved systems and methods for constructing a quasicrystalline material having a substantially spherical brillouin zone.

It is yet another object of the present invention to provide an improved system and method for constructing a quasicrystalline material having long-range orientational order without transitional periodicity and constructed to operate in a predetermined manner in response to at least one of an electric field, a magnetic field and electromagnetic radiation.

It is another object of the present invention to provide improved systems and methods for constructing quasicrystalline heterostructures that can be changed in their physical, biological and chemical properties by repositioning particles to change the quasicrystalline heterostructure from one structural state to another.

It is another object of the present invention to provide an improved system and method of constructing quasicrystalline heterostructures by using holographic optical traps to dynamically change chemical and physical properties in accordance with time sensitivity requirements.

It is another object of the present invention to provide an improved system and method for constructing a quasicrystalline heterostructure with holographic optical traps to form design elements (engineered features) capable of producing narrow band waveguides and frequency selective filters of electromagnetic radiation.

It is yet another object of the present invention to provide an improved system and method for organizing different elements using holographic optical traps to place optional elements in a quasicrystalline heterostructure to establish chemical, biological and physical properties for desired technological applications.

It is a further object of the present invention to provide improved systems, methods of manufacture and articles of manufacture having intentionally introduced defects to programmably achieve a variety of electrical, optical, magnetic, mechanical, biological and chemical properties and applications.

It is a further object of the present invention to provide an improved method and article of manufacture for a quasicrystal having alternating spheres or other elements of different sizes or shapes to alter the local photonic properties of the quasicrystal.

It is another object of the present invention to provide an improved method and article of manufacture for selectively replacing one or more spheres on other molecular element geometries of different chemical composition or at different positions from a given quasicrystalline location to produce new properties, or breaking the quasicrystalline symmetry to produce new properties, for various applications.

It is another object of the present invention to provide improved methods and articles of manufacture for quasicrystals having certain domains with topological defects, such as phase slip, similar to grain boundaries in common crystal molecules, thereby creating new useful properties.

It is another object of the present invention to provide an improved method and article of manufacture for producing two or more quasicrystalline domains by holographic trapping operations to produce a more ordered structure and the resulting assembly having optical properties selected from each of the component domains.

It is yet another object of the present invention to provide an improved method and article for creating a combination of one or more quasicrystalline domains and one or more crystalline domains to create useful higher order structures.

It is another object of the present invention to provide an improved method and article of manufacture, including the use of optical tweezers and/or other particle force assembly methods, including self-assembly, electrophoresis (electrophoresesis), and optical gradient fields to assemble crystalline and quasicrystalline domains to produce useful composite structures.

These and other objects, advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.

Brief Description of Drawings

FIG. 1(a) shows a view of silica spheres organized into planar pentagonal quasicrystals by holographic optical tweezers (scale bar represents 5 microns); FIG. 1(b) shows heptagonal quasicrystalline domains; FIG. 1(c) shows the arrangement of octagonal quasicrystalline domains; and FIG. 1(d) shows an octagonal quasicrystalline domain with embedded waveguides;

FIG. 2(a) shows the first of four views of an icosahedron assembled from a dielectric colloidal sphere using holographic optical traps; FIG. 2(b) shows a second view with a 2-fold axis of symmetry; FIG. 2(c) shows a third view with a 5-fold axis of symmetry; and figure 2(d) shows a fourth view mid-plane (midplane); FIG. 2(e) shows the stepwise assembly of the colloidal quasicrystal shown in FIGS. 2(a) - (d); and

FIG. 3(a) shows a holographic assembly of a three-dimensional colloidal quasicrystal with particles trapped in a two-dimensional projection of a three-dimensional icosahedral quasicrystal lattice; FIG. 3(b) shows the particles being displaced into a full three-dimensional structure, the shaded region being an embedded icosahedron; FIG. 3(c) shows the reduction of the lattice constant to produce a compact three-dimensional quasicrystal; and fig. 3(d) shows the measured optical diffraction pattern showing the 10-fold symmetric peaks of the structured quasicrystal; and figure 3(e) shows the stepwise assembly of the colloidal quasicrystal shown in figures 3(a) - (d).

Detailed description of the preferred embodiments

A system and method have been developed to construct quasicrystalline heterostructures for various technological applications. Various articles and compositions of matter may be prepared. In a most preferred embodiment, holographic optical traps are used as a starting tool to position selected particles at a given location. Thus, in the preferred embodiment, the method is based on the well-known holographic optical trapping technique, in which a large three-dimensional array of optical traps is created by projecting a computer-generated hologram through a high numerical aperture microscope objective. In our implementation, 532nm light produced by a frequency doubling diode pumped solid state laser (CoherentVerdi) was imprinted with a liquid crystal Spatial Light Modulator (SLM) (Hamamatsu X8267 PPM) to produce a pure phase hologram. The modified laser beam was delivered to the input pupil of a 100-fold Splan Apo oil immersion objective lens with NA of 1.4, mounted in an inverted optical microscope (Nikon TE2000U), which focused it into an optical trap. The same objective lens can be used to form an image of the captured object by using the conventional imaging group system (train) of the microscope. As a soft fabrication technique, holographic assembly requires significantly less processing than conventional methods such as electron beam lithography and is applicable to a wider range of materials. Holographic optical trap assembly is suitable for creating non-uniform structures (e.g., microstructure arrangements, compositions of articles and substances) with specific design elements, such as channels embedded in octagonal domains in fig. 1 (d). These structures can act as, for example, a narrow band waveguide and frequency selective filter for visible light.

The ability of holographic trapping to assemble free-form heterostructures also extends to three dimensions. The image sequences of the rotating icosahedron in fig. 2(a) - (d) show how the appearance of a colloidal sphere varies with distance from the focal plane. This sequence demonstrates that holographic trapping using a single laser beam can successfully organize spheres into longitudinal stacks along the optical axis while maintaining one sphere in each well.

The icosahedron itself is the basic building block of a class of three-dimensional quasicrystals, such as the examples in fig. 3(a) - (d). Based on our previous work on holographic assembly, we constructed by assembling three-dimensional quasicrystalline domains by first generating a two-dimensional arrangement of spheres corresponding to a planar projection of the planned quasicrystalline domains (see fig. 3 (a)). We then convert the spheres along the optical axis to their final three-dimensional coordinates in the quasicrystalline domain, as shown in fig. 3 (b). An icosahedron unit is highlighted in FIGS. 3(a) and (b) to illustrate this approach. Finally, in fig. 3(c), the spacing between wells is reduced to produce an optically dense structure. This particular domain consists of 173 spheres in 7 layers with a typical interparticle spacing of 3 μm.

The completed quasicrystal was gelled and its optical diffraction pattern at 632nm wavelength was recorded as follows: the sample was illuminated with a collimated beam from a HeNe laser, the diffracted light was collected with the objective lens of a microscope and projected onto a Charge Coupled Device (CCD) camera with a Bertrand lens. The well-defined diffraction points clearly reflect the five-fold rotational symmetry of the quasicrystal on the projection plane.

Holographic assembly of colloidal silica quasicrystals in water can be readily generalized to other materials with alternative optical, electrical, magnetic, chemical and mechanical properties for various types of technological applications. Deterministic organization of different elements under holographic control can be used to embed gain media in Photonic Band Gap (PBG) cavities, mount materials with nonlinear optical properties within waveguides to form switches, and create domains with different chemical functions. The relatively small domains we make can be combined into larger heterostructures by sequential assembly and spatially localized photopolymerization. In all cases, this soft manufacturing method results in a mechanically and environmentally stable material that can be easily incorporated into a larger system.

In addition to holographic trapping to make quasicrystalline materials, the ability to create and continually optimize these various articles and compositions of matter has given us the opportunity to obtain products that were previously unavailable and perform processes that were previously not possible. Many other functionalities may be performed, such as evaluating the dynamics and statistical mechanics of colloidal quasicrystals. The optically generated quasi-periodic potential energy map (landscapes) described herein also provides a flexible model system for experimental studies of transmission through non-periodic modulation environments.

In other embodiments, the methods of making and manipulating quasicrystalline structures described above can also be used to manipulate compositions of matter to introduce various specific defects, which can establish useful electrical, optical, biological, mechanical, magnetic, and chemical properties. Due to the many degrees of freedom available through the ability to establish these quasicrystalline structures and associated defects, one can obtain many different physical, mechanical and chemical properties, many of which are not obtainable with crystalline and amorphous structures. These properties can be used in a variety of commercial fields, across electronics, computers, biology, chemistry, optics, mechanical properties, and magnetic fields.

The technique also allows for the fabrication of quasicrystals with replacement of balls or other elements with balls of different sizes or shapes or elements of different sizes or shapes, which can alter properties, such as photonic characteristics. This concept can also be used to replace spheres or other size and shape groups of elements at selected locations with compositions of different chemical, mechanical, electrical, magnetic or optical properties, allowing for controlled design of quasicrystalline arrangements with different selectable properties useful in many commercial fields.

In other embodiments, the domains of quasicrystals can be selectively altered to introduce phase slip boundaries (similar to grain boundaries in crystalline materials) to exploit properties of interest for commercial exploitation. In addition to this, two or more quasicrystalline domains may be created by optical trapping of the particles in order to create a more ordered structuring element with physical and/or chemical property characteristics characteristic of each constituent domain. In addition, these combinations may be combined with crystalline domains to create higher order structures for alternative commercial applications.

The assembly of all these structures can be achieved not only by using optical tweezers but also by other particle force moving force sources. These other force movement sources may be used alone or in combination with optical tweezers, and these other particle movement sources may include self-assembly, other photonic methods, and at least one of controllable electric and magnetic fields. These methods allow the controlled construction of virtually any desired structure exhibiting a wide range of engineered physical, biological or chemical properties.

The following non-limiting example describes a method of assembling colloidal particles into a quasi-crystal.

Examples

Colloidal silica microspheres (Duke scientific Lot 5238) with a 1.53 μm diameter can be organized by first dispersing them in an aqueous solution of acrylamide, N-methylenebisacrylamide and diethoxyacetophenone (all Aldrich electrophoretic grades) at 180: 12: 1 (wt/wt). The solution is rapidly photopolymerizable to a clear polyacrylamide hydrogel under UV irradiation, while otherwise being stable. The fluid dispersion was allowed to penetrate into the 30 μm thick slit aperture formed by bonding the edge of the #1 cover slip to the surface of the microscope slide. The sealed sample is then mounted on the stage of a microscope for processing and analysis.

The silica spheres are approximately twice as dense as water to deposit rapidly as a monolayer over the cover glass. The thin spherical layer can be easily organized into any two-dimensional structure by holographic optical tweezers, including the quasicrystalline embodiments of fig. 1(a) - (d). Fig. 1(a), (b) and (c) show planar pentagonal, heptagonal and octagonal quasicrystalline domains, respectively, each consisting of more than 100 particles. The highlighted spheres emphasize the symmetry of each domain. These structures all appear to act as two-dimensional PBG materials in microfabricated arrays of pillars and wells. Fig. 1(d) shows an octagonal quasicrystalline domain with embedded waveguides.

While preferred embodiments have been illustrated and described, it will be clear to those skilled in the art that changes and modifications may be made in light of the foregoing without departing from the invention in its broader aspects. Various features of the invention are defined in the following claims.

Claims (20)

1. A method for assembling a quasicrystalline heterostructure having selectable properties, comprising:

providing a plurality of particles having a predetermined characteristic;

suspending the plurality of particles in a fluid medium; and

holographic optical traps are formed in a particular quasicrystalline arrangement to position the plurality of particles in that particular arrangement to achieve selectable performance.

2. The method of claim 1, wherein the specific quasicrystalline arrangement of the plurality of particles provides a preselected symmetry not attainable with crystalline materials.

3. The method of claim 1, wherein the particles are selected from objects operable by optical traps including at least one of microparticles, nanoparticles, macromolecules and biological cells.

4. The method of claim 1, wherein the predetermined characteristic comprises at least one of a desired chemical characteristic, optical characteristic, biological characteristic, magnetic characteristic, electronic characteristic, and mechanical property.

5. The method of claim 1, wherein the selectable property is selected from the group consisting of photonic band gap, chemical functionality, electrical conductivity properties, biological properties, and magnetic properties.

6. The method of claim 5, wherein the photonic band gap controls light propagation in a dielectric material composite.

7. The method of claim 5, wherein the chemical functionality comprises catalytic activity.

8. The method of claim 5, wherein the conductivity is selected from the group consisting of metallic conductivity, semiconductor conductivity, and superconducting conductivity.

9. The method of claim 5, wherein the magnetic properties include a high magnetic flux exhibited by the plurality of particles.

10. The method of claim 5, wherein the chemical functionality comprises a preselected altered chemical property.

11. The method of claim 5, wherein the chemical functionality comprises a change in property relative to a corresponding crystal structure consisting of the same chemical composition.

12. The method of claim 1, further comprising the step of dynamically changing said particular arrangement to obtain different ones of the selectable properties for a selected application.

13. The method of claim 12, wherein the selected application comprises at least one of: altering quasicrystalline properties selected from the group consisting of mechanical properties, electrical properties, chemical properties, magnetic properties, and biological functionality.

14. The method of claim 1, further comprising the step of applying at least one of an electromagnetic field, an electric field, and a magnetic field to further alter the quasicrystalline alignment properties.

15. The method of claim 1, further comprising the step of embedding the quasicrystalline arrangement in a system for industrial applications.

16. An article comprising a quasicrystalline material having a grain structure arranged using optical traps, the quasicrystalline material having properties different from its corresponding crystalline chemical counterpart.

17. The article of claim 16, wherein the property different from its corresponding crystalline chemical counterpart comprises at least one of: photonic band gap, mechanical properties, biological properties, magnetic properties, electrical properties, and chemical properties.

18. The article of claim 16, wherein the quasicrystalline material comprises at least one of: engineered defects, those of different size or shape of the particles, phase slip boundaries, and a mixture of at least one quasicrystalline domain and different ones of the crystalline domains.

19. A method of assembling a heterostructure having selectable properties, comprising:

providing a plurality of particles having a predetermined characteristic selected from the group consisting of size, shape, biological property, or chemical property;

providing a particle movement force to establish a specific quasicrystalline arrangement; and

the plurality of particles are positioned using the particle-moving force to establish a quasicrystalline arrangement of the particles.

20. The method of claim 19, further comprising at least one of the following steps: creating a defect state in the quasicrystalline arrangement, replacing at least one of the plurality of particles with a particle of a different size or shape or property, creating a different quasicrystalline domain in the quasicrystalline arrangement, mixing the quasicrystalline arrangement within the crystalline domain and positioning the plurality of particles by self-assembly.