+

WO1998036298A1 - Films polymeres contenant de l'azobenzene - Google Patents

Films polymeres contenant de l'azobenzene Download PDF

Info

Publication number
WO1998036298A1
WO1998036298A1 PCT/US1998/001194 US9801194W WO9836298A1 WO 1998036298 A1 WO1998036298 A1 WO 1998036298A1 US 9801194 W US9801194 W US 9801194W WO 9836298 A1 WO9836298 A1 WO 9836298A1
Authority
WO
WIPO (PCT)
Prior art keywords
film
sinusoidal component
light
spatially
profile
Prior art date
Application number
PCT/US1998/001194
Other languages
English (en)
Inventor
Lian Li
Dong Yu Kim
Xinli Jiang
Aloke Jain
Sukant Tripathy
Javant Kumar
Original Assignee
University Of Massachusetts
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by University Of Massachusetts filed Critical University Of Massachusetts
Priority to BR9805897A priority Critical patent/BR9805897A/pt
Publication of WO1998036298A1 publication Critical patent/WO1998036298A1/fr

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1847—Manufacturing methods
    • G02B5/1857—Manufacturing methods using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams

Definitions

  • This invention relates to polymer films, optical recording, and diffractive optical elements.
  • DOEs Surface relief diffractive optical elements
  • Gratings and DOEs are used to manipulate the spatial properties of light.
  • a conventional and important example of this manipulation is to use a grating to separate incident light having many wavelengths into multiple beams each having a single wavelength. More generally, the surface profile of a DOE can be thought of as storing optical information which can be imparted onto an incident optical beam.
  • Polymer films are attractive materials for DOEs. They typically have several advantages such as light weight, low cost, and easy fabrication on various substrates. Substrates commonly used are hard materials such as glass slides and silicon wafers.
  • gratings have usually been made using photoresists coated onto substrates. Processes using photoresists involve exposing the photoresist to a spatially-varying light field at a wavelength absorbed by the photoresist. After exposure, the photoresist is developed (usually by a wet chemical process) and followed by a baking process. In other methods, lasers have been used to inscribe a grating on the surface of a substrate by ablating the surface. Surface relief gratings have also been recorded on thermoplastic photoconductor polymeric materials. Surface deformations of such polymeric materials are produced when charged films are exposed to a spatially varying light pattern and heated close to the glass transition temperature (Tg) of the polymer. Recently, Kim et al.
  • the invention features a method of forming complex structured surface profiles on azobenzene-containing polymer (azo-polymer) films by the controlled exposure of the film to multiple spatially-varying light fields.
  • the invention recognizes the important result that the surface profile produced when an azo-polymer film is exposed to two spatially-varying light fields is given by the superposition of a first pattern written by the first light field with a second pattern written by the second light field.
  • the second pattern (or more generally, subsequent patterns) must be written such that the second (or subsequent) pattern overlap correctly with the first pattern written on the film.
  • the relative overlap must be specified and deliberately set. Desired surface profiles having complicated features can thereby be formed on the film.
  • a blazed grating which has triangular grooves
  • individual patterns must be deliberately superposed with the correct amplitude (i.e. modulation depth) and phase (i.e. relative position or overlap) .
  • the invention also features polymer films having complex surface structure profiles fixed to flexible or curved substrates. These composite optical structures combine the diffractive properties of the structured surface profile and the focussing properties of a curved surface into a single optical element.
  • the invention features a method of forming a polymer film having a specified surface profile, by i) providing a film comprising an azobenzene- containing polymer; ii) maintaining the film at a temperature below the glass transition temperature of the polymer; iii) exposing the film to light having a first spatially-varying amplitude profile along an orientation axis lying along a surface of the film for a first length of time, to form a first pattern on the film having a first sinusoidal component; and iv) exposing the film to light having a second spatially-varying amplitude profile along the orientation axis for a second length of time, to form a second pattern on the film having a second sinusoidal component, wherein the second sinusoidal component overlaps the first sinusoidal component with a
  • Embodiments can include one or more of the following features: the azobenzene-containing polymer contains an azobenzene side group selected from PD03 , PNA, and CH-1A-CA; the light exposing steps occur concurrently; the light exposing steps occur at different times; the spatial frequency of the second sinusoidal component is a harmonic of the spatial frequency of the first sinusoidal component; the light having the first spatially-varying amplitude profile is formed by crossing a first and second beam of light so that they overlap on the film; the light originates from a laser; the light is circularly polarized; the film is supported by a substrate, which can be flexible or curved; the additional step of adhering the polymer film, which is supported on a flexible substrate, to another non- flexible substrate; the second sinusoidal component is the first harmonic of the first sinusoidal component, the predetermined phase is zero, the first length of time is approximately twice as long as the second length of time, and the specified surface profile is periodic with substantially triangular grooves.
  • Embodiments can also include additional steps during step iv) .
  • step iv) can include the steps of exposing the film to light having the second spatially-varying amplitude profile at a first intensity insufficient to modify the surface profile of the film; observing a diffraction pattern produced by light having the second spatially-varying amplitude profile being diffracted by the first pattern; modifying the position of the light having the second spatially-varying amplitude profile relative to the first pattern such that a specific diffraction pattern is observed; and exposing the film at a second intensity sufficient to modify the surface profile of the film, wherein the specific diffraction pattern indicates that the second sinusoidal component subsequently produced will overlap with first sinusoidal component with the predetermined phase.
  • step iv) can include the steps of: forming the second spatially-varying amplitude profile by crossing a first and second beam of light so that they overlap on the film; and retarding the first beam relative to the second beam so that the second sinusoidal component overlaps with the first sinusoidal component with the predetermined phase.
  • the invention features an optical element including: i) a substrate; and ii) a film comprising an azobenzene-containing polymer formed on the substrate, wherein the film has a varying surface profile along an orientation axis lying on a surface of the substrate, the surface profile having: a first sinusoidal component having a first spatial frequency and a first amplitude; and a second sinusoidal component having a second spatial frequency and a second amplitude, wherein the second sinusoidal component overlaps with the first sinusoidal component with a predetermined phase, and wherein the spatial frequency of the second sinusoidal component is different than the spatial frequency of the first sinusoidal component.
  • Embodiments can include any of the following features: the azobenzene-containing polymer includes an azobenzene side group selected from PD03, PNA, and CH-lA- CA; the second spatial frequency is a harmonic of the first spatial frequency; the second sinusoidal component is the first harmonic of the first sinusoidal component, the predetermined phase is zero, the first amplitude is approximately twice as large as the second amplitude, and the varying surface profile is periodic with substantially triangular grooves; the substrate is curved; the substrate is flexible.
  • the invention features a method of forming a polymer film having a specified surface profile, by: i) providing a film comprising an azobenzene-containing polymer on a flexible substrate; ii) maintaining the film at a temperature below the glass transition temperature of the polymer; iii) exposing the film to light having a spatially-varying amplitude profile; iv) thereby forming the polymer film having the specified surface profile.
  • the terms “structured surface profile” or “surface structure” describe variations created in the relative height of the film along any combination of the two dimensions within the plane of the film. These variations are always greater than the dimension of random surface features, which are typically on the order of 1 nm.
  • the term “spatially-varying amplitude profile of light” describes the spatial profile of the amplitude and/or direction of the time-varying electric field vector inherent in light.
  • the invention includes a number of advantages. It allows complex surface structure (which can be used as DOEs) to be written on a polymer film in a versatile manner. Films are made without cumbersome postprocessing steps including wet chemistry and baking, thereby reducing fabrication costs. Furthermore, design to fabrication can be software driven leading to tremendous design flexibility (e.g., from current batch processes to single, made to order devices) . The versatility of the invention is even further enhanced by the ability to fabricate films on flexible substrates.
  • the invention requires much lower laser intensities and there is no residual debris (e.g., ablated fragments) that might hinder the quality of the grating. Furthermore, gratings or more complicated diffractive optics can be written over a large area since the polymer film can be formed over a large area and need only be exposed to modest laser intensities.
  • Fig. 1 is a diagram of the chemical structure of polymers studied in the invention.
  • Fig. 2 is a schematic diagram of an apparatus for writing a grating on an azo-polymer film.
  • Fig. 3 is a 3-dimensional atomic force microscopy (AFM) image of a typical surface relief grating written on an azo-polymer film.
  • AFM atomic force microscopy
  • Fig. 4 is a graph showing diffraction efficiency of an azo-polymer grating as a function of exposure time.
  • Fig. 5 is a graph showing diffraction efficiency of an azo-polymer grating as a function of total beam energy for different laser powers.
  • Fig. 6 is a graphical representation of the in- phase addition of a fundamental sinusoid with its first harmonic.
  • Fig. 7 is a schematic of an apparatus for correctly overlapping a second pair of writing beams.
  • Fig. 8 is a 3-dimensional AFM image of a surface relief structure of a blazed grating formed on an azo- polymer film.
  • Structured surface profiles can be formed on azobenzene-containing polymer films by exposing the film to laser light having a varying spatial profile.
  • large amplitude (100 n ) holographic (i.e., sinusoidal) surface relief gratings can be made by exposing an azobenzene-containing polymer film to a pair of crossed laser beams at modest intensities without any subsequent processing steps.
  • More complicated surface profiles can be formed by exposing the polymer film to more than one pair of crossed laser beams, thereby forming structured surface profiles that are superpositions of multiple gratings.
  • polymer film preparation and selection will describe: 1) polymer film preparation and selection; 2) light conditions and apparatus; 3) complex surface structures; 4) flexible and/or curved substrates, and diffractive optical elements; and 5) some examples.
  • Polymer Film Preparation and Selection The film can be made of any polymer containing azobenzene groups in the side-chain or in the main-chain.
  • azobenzene-containing polymers will be referred to as azo-polymers.
  • Fig. 1 shows chemical structures of side-chain polymers PD03, PNA, PNB, PNS, CH-1A-CA and main-chain polymer PU1.
  • PD03, PNA, PNB, PNS and PNI are condensation polymers synthesized from diglycidyl ether of bisphenol A (Epon 828"') and respective chromophore side groups, 4-(4'-nitrophenylazo) aniline (PD03) , 4- phenylazoaniline (PNA), 4-amino-4 , -nitrobiphenyl (PNB), 4-amino-4'-nitrostilbene (PNS) and 4-(4'- nitrobenzylideneamino) aniline (PNI) .
  • CH-IA-CA is a polymer from 1,4-cyclohexanedimethanol diglycidyl ether and 4-(4 , -aminophenylazo)benzoic acid which can be synthesized by post azo coupling reaction.
  • PU1 is a polyurea synthesized from 4,4'-diaminoazobenzene and isophorone diisocyanate.
  • the glass transition temperatures (Tgs) of the side-chain polymers are near 100°C and the glass transition temperature (Tg) of the main-chain polymer PU1 is 197°C. All of these polymers are amorphous.
  • Epon 828TM can be purchased from Shell Chemical Co. (Houston, TX) and all other chemicals can be purchased from Aldrich Chemical Co. (Milwaukee, I) .
  • Good optical quality polymer films are prepared by spincasting on glass slides. The films are dried at 70°C under vacuum for 12 hours. Typical thicknesses of the films range from 0.4 to 2.0 ⁇ m.
  • side-chain azo-polymers PD03, PNA, and CH-IA-CA form structured surface profiles in response to spatially-varying light.
  • a structured surface profile is barely noticeable when a non-azo-polymer, such as biphenyl side-chain polymer PNB, film is exposed to spatially-varying light at a comparable exposure level.
  • PNB has the same backbone as the other side-chain azo-polymers, but lacks an azobenzene side-group which can undergo trans-cis photoisomerization. This indicates that having an azobenzene side-group that can undergo trans-cis photoisomerization is a critical structural requirement for forming surface structure.
  • the light source for the writing beams is a linearly polarized beam at 488 nm from an Ar + laser 2. Lasers operating at other wavelengths can also be used. Preferably, writing is performed with light having wavelengths within the range of 400 to 600 nm, e.g. , 450-550 nm, since the azo-polymers absorb light best at these wavelengths.
  • the polarized laser beam passes through a halfwave plate 3, is expanded by spatial filter 4 and collimated by lens 6.
  • Half of the collimated beam (forming a first writing beam 20) optionally passes through another halfwave plate 12 and is incident directly on polymer film 10.
  • the other portion of the beam (forming a second writing beam 22) is reflected onto the sample from a mirror 8.
  • the intensity of the writing laser beam used to create a structured surface profile can range from 1 to 500 mW/cm 2 , e.g., from 50 to 100 mW/cm 2 .
  • a reading beam 14 from a Helium-Neon (HeNe) laser 16 probes the diffraction efficiency of a grating formed on polymer film 10. Diffracted light is monitored by detector 18 and data stored in computer 19. Rather than using separate halves of the same laser beam to form writing beams 20 and 22, two separate beams derived from the same laser can also be used.
  • Writing beams 20 and 22 cross at an angle "A” and overlap each other at the sample. In the region of overlap, writing beams 20 and 22 will interfere with one another producing a sinusoidal spatially-varying intensity profile at polymer film 10.
  • Fig. 3 shows an image of the surface profile of film 10 measured using atomic force microscopy (AFM) .
  • the surface grating has a regularly spaced sinusoidal surface profile with a modulation depth of over 100 nm. Prior to exposure, the film surface was approximately uniform with random fluctuations on the order of 1 nm.
  • the grating spacing can be controlled by changing the angle "A", which changes the spatial period of the light field amplitude as shown in equation (1) .
  • the spatially-varying light field modulates the surface profile of the polymer film according approximately to the equation:
  • the diffraction efficiency of a typical grating formed on a PD03 film as a function of exposure time is shown in Fig. 4.
  • the laser intensity for the writing beams was 110 mW/cm 2 .
  • the diffraction efficiency increases almost linearly until saturation. In this region, the diffraction efficiency is proportional to the modulation depth of the surface relief grating.
  • the modulation depth and diffraction efficiency do not depend significantly on the intensity of the writing beam over the range of 3mW/cm 2 to 110mW/cm 2 . Rather, the modulation depth and diffraction efficiency depend on the total energy imparted to the surface of the polymer film, i.e., the product of exposure time and intensity.
  • the diffraction efficiency of a typical grating formed on a PD03 film is shown in Fig. 5 as a function of total energy for a number of different writing beam intensities. As shown, the diffraction efficiency increases in a mostly linear fashion, and is essentially the same for all four writing beam intensities (3, 10, 55, and 110 mW/cm 2 ) .
  • Polarization recording refers to the condition in which writing beams 20 and 22 are both linearly polarized, but second half- wave plate 8 is set so that writing beam 20 is s- polarized and writing beam 22 is p-polarized.
  • Very low diffraction efficiency and small surface modulation are obtained in this case.
  • the electric field produced by the interference of writing beams 20 and 22 produces large spatial variations in the direction of the electric field vector.
  • the light intensity on the film is uniform over the entire irradiated area.
  • Very small surface modulation and diffraction efficiency are also obtained under this recording condition.
  • exposing the polymer film to light will produce surface structure only if: 1) the light has a spatially-varying intensity profile, and 2) the light has an electric field component along the direction of the spatially-varying intensity profile. More Complex Surface Structures
  • multiple patterns can be written along a particular direction and added together to produce a desired surface profile along that direction.
  • two sinusoidal patterns having different spatial frequencies can be written on the film by exposing the film to a first pair of crossed writing beams and thereafter exposing the film to a second pair of co- planar, crossed writing beams having a different crossing angle.
  • the superposition of the patterns produced on the film by the two sets of crossed writing beams will include a "beat" structure, i.e., a low spatial frequency sinusoid modulating a high spatial frequency sinusoid.
  • an azo-polymer film can be exposed to a large number of coplanar, crossed writing beams each writing a sinusoidal pattern having a spatial period corresponding to their crossing angle.
  • the superposition of these patterns can produce varied and complicated surface structure.
  • Subsequent patterns can be written along another direction in the same way and these patterns will add to the surface structure written along the first direction, thereby producing desired two- dimensional surface structure.
  • the structure is Fourier decomposed into sinusoidal component patterns.
  • Crossed writing beams having the correct crossing angle can produce each of these sinusoids.
  • the amplitude (i.e., modulation depth) and phase (i.e., relative overlap) of each of the sinusoidal patterns must be correct.
  • the modulation depth of a particular sinusoidal patterns is controlled by the total energy of the crossed writing beams used to form that pattern. The control of the relative overlap of one sinusoidal pattern with respect to another is described herein, and in detail in Example 1.
  • the intensity of subsequent writing beams is first reduced so they do not write additional surface structure.
  • Low-intensity light from the writing beams is diffracted by existing surface structure and the resulting diffraction pattern is monitored.
  • the relative overlap of the writing beams with the existing surface structure is inferred from the diffraction pattern.
  • the position of the writing beams is then optimized to give the diffraction pattern that indicates the correct overlap.
  • the intensity of the writing beams is increased to correctly add the additional surface structure.
  • a general description of interference and diffraction properties of light is given in: Hecht and Zajac, Optics (Addison-Wesley Publishing Co. , Reading MA, 1975) .
  • mechanical mounts used to position the writing beams allow direct mechanical control over, and determination of, interferometric overlap between different pairs of crossed writing beams.
  • the precision and stability of the mounts needs to be much better than the wavelength of the writing beam.
  • Example 1 below describes forming a Fourier blazed (i.e., triangular grooves) surface relief grating on an azo-polymer film.
  • This example is illustrative of the Fourier superposition technique described above.
  • complicated surface structures can also be written on the azo-polymer films in other ways.
  • spatially-varying light fields that are different than the sinusoidal interference pattern produced by crossing two beams can also form surface structure.
  • a mask or spatially-varying filter can be used to spatially shape a light field. In this case, either the mask pattern or a diffraction pattern produced by the mask pattern can be imaged onto the polymer film to form surface structure. Spatial filtering and imaging are also described by Hecht and Zajac, supra.
  • Spatially-varying light fields can also be formed by crossing two beams in which at least one of the beams has a curved phase front.
  • overlapping a plane wave with a spherical wave i.e., a wave having spherical wavefronts
  • a light field having intensity variations that are radially symmetric (e.g., annular fringes with a decreasing period)
  • overlapping a plane wave with a cylindrical wave i.e., a wave having cylindrical wavefronts
  • will produce a light field having intensity variations i.e., fringes
  • Beams having curved phase fronts can be produced by using focussing optics and overlapping beams outside . of the focal planes of the focussing optics.
  • the spatially-varying light field will write surface structure that is proportional to the derivative of the light field intensity, as shown in equation 2.
  • Azo-polymer films having shaped surface profiles can be formed on both flexible and curved surfaces, in addition to flat glass substrates.
  • Flexible substrates such as paper or plastics, can be dipped into a solution containing the appropriate azo-polymer.
  • a free-standing azo-polymer can be used. Spatially varying light fields expose the film producing a shaped surface profile as described previously. The flexible characteristics of both polymer film and the substrate can then be exploited for a particular application.
  • Structure also can be written on an azo-polymer film formed on a flexible substrate or on a free-standing polymer film which is then fixed to a curved non-flexible substrate, such as metal or glass.
  • polymer films can be coated directly onto a curved substrate and then exposed to a spatially-varying light field that writes a surface structure on the film as described above.
  • the polymer film could be formed on a non-flexible substrate and then removed from the substrate.
  • a polymer film having a written structure could be removed from glass or metal substrate by "floating" the film from the substrate in a solvent bath using standard techniques. Subsequently, the free-standing film could be adhered to another substrate, such as a curved substrate.
  • the resulting optical elements have diffractive properties resulting from the shaped surface profile and focusing properties resulting from the curved substrate.
  • Such composite optical devices combine into a single optical element multiple properties that would otherwise be found only in two or more separate optical elements, e.g., a grating having dispersive properties and a lens having focussing properties.
  • Any of the embodiments described above can be implemented as integrated diffractive optical elements (DOE) .
  • the shaped azo-polymer films can be used as waveguide input and output couplers, integrated optic beam splitters, semiconductor laser-feedback gratings, planar Notch filters, and integrated planar resonators.
  • the integrated DOEs can be formed with complex structures such as chirped gratings, i.e., gratings with groove spacings that vary linearly with position.
  • chirped gratings can be formed by exposing the polymer film to a pair of crossed writing beams in which the curvature of the first beam is equal and opposite to the curvature of the second beam, i.e., the first beam is diverging while the second beam is converging or vice versa.
  • gratings with varying fringe spacings can be formed by overlapping beams having different curvature.
  • the azo-polymer film can also be formed on large area substrates and then exposed to a spatially-varying optical field that extends over that large area.
  • the resulting large-area elements could be useful in fields such as astronomy.
  • Structured surface profiles produced by this invention can also be used in applications that require gratings with very large groove spacings, such as dispersing infrared (IR) light.
  • IR infrared
  • two sinusoidal gratings having different spatial frequencies kl and k2 and written along the same direction on an azo- polymer film will form a "multiple" grating, which can be used to diffract light at an angle corresponding to the difference between the two spatial frequencies.
  • second order diffraction from the structured surface profile will include the difference frequency term (kl-k2) .
  • Higher order diffraction will also include additional spatial frequencies that are sums or differences of integral numbers of kl and k2.
  • higher-order diffraction from a single grating having spatial frequency k produces diffraction at spatial frequencies that are integral numbers of k.
  • IR gratings can be made using writing beams having wavelengths in the visible.
  • Blazed gratings have triangular shaped grooves that optimize diffraction into a particular order for a selected wavelength.
  • Fig. 6 shows the Fourier synthesis of a blazed grating profile.
  • the blazed grating profile can be approximated by the sum of two sinusoids: a fundamental yl (with grating spacing ⁇ ) and its first harmonic y2 (with grating spacing ⁇ /2) .
  • the amplitude of the fundamental is twice that of the first harmonic and the two sinusoids have a phase shift of zero, i.e., a peak in the fundamental overlaps with a peak in the first harmonic.
  • Blazed gratings of this type were fabricated by the following procedure (with reference to Figs. 2 and
  • a PD03 film was spincast on a glass slide to a thickness of approximately 600 nm and dried at 70°C under vacuum for 12 hours (step 100) .
  • the temperature was kept below the glass transition temperature of PD03 , i.e., below 100°C (step 110) .
  • the film was exposed to the crossed writing beams for 20 minutes (step 120) . This produced the fundamental sinusoid pattern on the film.
  • the intensity of laser 2 was then reduced to 3 mW/cm 2 (step 130) .
  • the surface of film 10 is modified by beams 20 and 22 only if it is exposed for a long time (e.g., five hours).
  • Mirror 8 and film 10, which are integrally connected at a right angle, were then rotated so that writing beams 20 and 22 cross at approximately 28° (step 140) .
  • the sinusoidal grating produced in step 120 partially diffracted writing beams 20 and 22 back away from the film as shown in Fig. 7, producing diffracted beams 40, and 42.
  • Diffracted beam 40 is the +1 order of diffraction from writing beam
  • diffracted beam 42 is the -1 order of diffraction from writing beam 22.
  • the overlapping beams interfered with one another producing interference fringes that were observed in viewing plane 44.
  • These interference patterns are known as Moire fringes.
  • the correct crossing angle is reached when diffracted beams 40 and 42 exactly overlap with one another.
  • the fringe spacing disappears, or more exactly, the fringe spacing becomes larger than the spot size of diffracted overlapping beams 40 and 42, so that only a single fringe having a smooth intensity distribution remains visible in viewing plane 44.
  • the light field intensity pattern produced by writing beams 20 and 22 at film 10 has a spatial frequency that is exactly twice the spatial frequency of the fundamental sinusoid pattern written on the film in step 120.
  • Mirror 8 and film 10 were further rotated until the fringe spacing became larger than the spot size of overlapping diffracted beams 40 and 42 in viewing plane 44 (step 150) .
  • the light field intensity pattern produced by writing beams 20 and 22 in step 150 needs to overlap correctly with the fundamental sinusoid pattern written in step 120.
  • the correct overlap occurs when the peak of the light field intensity pattern produced by writing beams 20 and 22 in step 150 coincides with a midpoint of the fundamental sinusoid pattern written on film 10 in step 120.
  • Film 10 was positioned along the axis parallel to the surface and coplanar to writing beams 20 and 22 so that writing beams 20 and 22 overlapped correctly (step 160) . Correctly positioning film 10 in step 160 also can be accomplished by observing the Moire fringes in viewing plane 44.
  • the crossing angle is correct when overlapping diffracted beams 40 and 42 yield only a single smoothly-varying fringe in viewing plane 44.
  • the intensity of that single fringe indicates the relative position of film 10 with respect to the pattern produced by crossed writing beams 20 and 22 in step 160.
  • the intensity of the single fringe varies from a zero or near zero minimum value when diffracted beams 40 and 42 destructively interfere completely with one another, to a maximum value when diffracted beams 40 and 42 constructively interfere completely with one another.
  • positions on the fundamental grating written in step 120 having maximum positive slope coincide with positions of the light field intensity pattern produced in step 150 having maximum positive slope.
  • positions on the fundamental grating written in step 120 having maximum negative slope coincide with positions of the light field intensity pattern produced in step 150 having maximum negative slope.
  • the position of film 10 in step 160 is correct when the intensity of the single fringe is halfway between the minimum and maximum values.
  • step 170 Polymer film 10 was then exposed to the light beam and the first harmonic sinusoid pattern was written on the film (step 170) .
  • the exposure time in step 170 was 10 minutes so that the modulation depth of the first harmonic sinusoid pattern was half that of the fundamental sinusoid pattern.
  • Fig. 8 The resulting surface profile of the film is shown in Fig. 8 as measured by AFM.
  • the triangular shaped grooves of blazed grating are clearly seen and is evidence that the fundamental sinusoid pattern was correctly superposed with the first harmonic sinusoid pattern.
  • one of writing beams 20 or 22 can be retarded with respect to the other before they interfere at film 10. This will shift the position of the light field intensity pattern. For example, if writing beam 20 is retarded by half a wavelength with respect to writing beam 22, what was a peak in the light field intensity pattern will become a null and vice versa.
  • the relative position of one sinusoidal pattern written on film 10 with another sinusoidal pattern written on film 10 can be set to any value.
  • methods employing Moire fringes can be used to determine and correct the position of light field interference patterns used to write a subsequent grating with an existing grating previously written on film 10.
  • Moire fringes M. Breidne et al. (Optica Acta , 26: 1427-1441,. 1979) and John Guild, The interference systems of crossed diffraction gratings: Theory of moire fringes (Clarendon Press, 1956) .
  • Example 2 In another example, PD03 was dissolved in a propylene glycol methyl ether acetate (PGMEA) /dimethyl formamide (DMF) solvent mixture (3:1 ratio, v/v) .
  • Waxed paper was used as substrates which were dipped into the polymer solution.
  • the polymer coating was solidified by drying the film at room temperature for several days. Sinusoidal gratings were written on the film using the methods described above for glass substrates. Strong diffraction of ambient light from the recorded film showed that large surface modulation occurred on the film.
  • Diffraction efficiency in the reflection mode was measured at 633 nm. Due to the relatively nonuniform coating which is attributed to the surface morphology of paper, the diffracted beam was diverged and blurred. Nonetheless, a first order diffraction efficiency of 1-3 percent could be easily measured.
  • the back face of the wax paper substrate containing (on the front face) the polymer film having the surface relief grating can also be glued to a non- flexible curved substrate (e.g., aluminum), producing an optic having both dispersive and focussing properties.
  • a non- flexible curved substrate e.g., aluminum

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)

Abstract

L'invention concerne des procédés d'écriture de profils de surfaces structurés sur des films polymères contenant de l'azobenzène. Les procédés consistent: i) à produire un film (10) comprenant un polymère contenant de l'azobenzène; ii) à maintenir le film à une température inférieure à la température de transition vitreuse du polymère; iii) à exposer le film à de la lumière (20, 22) présentant un premier profil d'amplitude à variation spatiale le long d'un axe d'orientation situé le long d'une surface du film pendant une première durée, de manière à former un premier motif sur le film présentant une première composante sinusoïdale; et iv) à exposer le film à de la lumière présentant un second profil d'amplitude à variation spatiale le long de l'axe de l'orientation et pendant une seconde durée, de manière à former un second motif sur le film ayant une seconde composante sinusoïdale, la seconde composante sinusoïdale chevauchant la première composante sinusoïdale avec une phase prédéterminée, la fréquence spatiale de la seconde composante sinusoïdale étant différente de la fréquence spatiale de la première composante sinusoïdale, de manière que la superposition des premier et second motifs forme le profil de surface spécifiée. L'invention concerne également des films polymères contenant de l'azobenzène présentant des profils de surfaces structurés.
PCT/US1998/001194 1997-01-21 1998-01-21 Films polymeres contenant de l'azobenzene WO1998036298A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
BR9805897A BR9805897A (pt) 1997-01-21 1998-01-21 M-todos de isolamento de materiais alvo biolÄgicos que utilizam part¡culas magne-ticas de s¡lica

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US79870897A 1997-02-12 1997-02-12
US08/798,708 1997-02-12

Publications (1)

Publication Number Publication Date
WO1998036298A1 true WO1998036298A1 (fr) 1998-08-20

Family

ID=25174079

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1998/001194 WO1998036298A1 (fr) 1997-01-21 1998-01-21 Films polymeres contenant de l'azobenzene

Country Status (1)

Country Link
WO (1) WO1998036298A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006061419A2 (fr) * 2004-12-09 2006-06-15 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Film photoactif, sa preparation et son utilisation, et preparation de structures anisotropes au plan optique et a relief de surface par irradiation dudit film
US7897296B2 (en) * 2004-09-30 2011-03-01 General Electric Company Method for holographic storage
CN103204460A (zh) * 2013-03-21 2013-07-17 北京工业大学 基于激光干涉诱导交联反应的金属微纳结构的制备方法
WO2018127684A1 (fr) * 2017-01-05 2018-07-12 University Of Strathclyde Réseau de diffraction à haut rendement

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4062628A (en) * 1976-01-19 1977-12-13 Rca Corporation Black-and-white diffractive subtractive light filter
US4247622A (en) * 1979-06-21 1981-01-27 International Business Machines Corporation Photodeformable polymeric compositions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4062628A (en) * 1976-01-19 1977-12-13 Rca Corporation Black-and-white diffractive subtractive light filter
US4247622A (en) * 1979-06-21 1981-01-27 International Business Machines Corporation Photodeformable polymeric compositions

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BREIDNE M., ET AL.: "BLAZED HOLOGRAPHIC GRATINGS.", OPTICA ACTA., vol. 26., no. 11., 1 January 1979 (1979-01-01), pages 1427 - 1441., XP002912235, ISSN: 0030-3909 *
ROCHON P., ET AL.: "OPTICALLY INDUCED SURFACE GRATINGS ON AZOAROMATIC POLYMER FILMS.", APPLIED PHYSICS LETTERS, A I P PUBLISHING LLC, US, vol. 66., no. 02., 9 January 1995 (1995-01-09), US, pages 136 - 138., XP002912234, ISSN: 0003-6951, DOI: 10.1063/1.113541 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7897296B2 (en) * 2004-09-30 2011-03-01 General Electric Company Method for holographic storage
WO2006061419A2 (fr) * 2004-12-09 2006-06-15 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Film photoactif, sa preparation et son utilisation, et preparation de structures anisotropes au plan optique et a relief de surface par irradiation dudit film
WO2006061419A3 (fr) * 2004-12-09 2007-01-04 Fraunhofer Ges Forschung Film photoactif, sa preparation et son utilisation, et preparation de structures anisotropes au plan optique et a relief de surface par irradiation dudit film
CN103204460A (zh) * 2013-03-21 2013-07-17 北京工业大学 基于激光干涉诱导交联反应的金属微纳结构的制备方法
WO2018127684A1 (fr) * 2017-01-05 2018-07-12 University Of Strathclyde Réseau de diffraction à haut rendement

Similar Documents

Publication Publication Date Title
US9983479B2 (en) Fabrication of high efficiency, high quality, large area diffractive waveplates and arrays
Lalanne et al. A transmission polarizing beam splitter grating
CN110389401B (zh) 各向异性分子3d排列方法、图案化各向异性膜及光学元件
US10031424B2 (en) Fabrication of high efficiency, high quality, large area diffractive waveplates and arrays
US4402571A (en) Method for producing a surface relief pattern
Viswanathan et al. Surface relief structures on azo polymer films
JP7452811B2 (ja) 偏光回折素子と、これを用いたベクトルビームのモード検出システム
US6322932B1 (en) Holographic process and media therefor
US8264623B2 (en) Liquid crystal geometrical phase optical elements and a system for generating and rapidly switching helical modes of an electromagnetic wave, based on these optical elements
US12092850B2 (en) Patterned anisotropic films and optical elements therewith
JP2015532468A (ja) 幾何学的位相ホログラムの製造のための直接書き込みリソグラフィ
KR20090004696A (ko) 비식각 평판형 편광­선택성 회절 광학 소자
US5812233A (en) Polarization sensitive devices and methods of manufacture thereof
Oemrawsingh et al. High-dimensional mode analyzers for spatial quantum entanglement
US6069859A (en) Polarization separating element having partially polarizing properties for diffracting an ordinary light beam and a process for producing the same
WO1998036298A1 (fr) Films polymeres contenant de l'azobenzene
Kabanova et al. Patterned Photoalignment-Based One-and Two-Dimensional Liquid Crystal Forked Gratings
JP5046154B2 (ja) 偏光回折格子の形成方法
Yan-Lan et al. Two-dimensional non-spatial filtering based on holographic Bragg gratings
Bogdanov et al. Correction of segmented mirror aberrations by phase conjugation and dynamic holography
Emoto et al. Two-dimensional anisotropic gratings formed in photocrosslinkable polymer liquid crystals by multiple interference
Cescato Diffractive optics produced by holography and RIE
Kim et al. Volume holographic quarter-wave plate
Emoto et al. Polarization gratings in photocrosslinkable polymer liquid crystals prepared using two-step ultraviolet exposure
Ozols et al. Focused Polarization Gratings in an Azobenzene-Based Molecular Glassy Film

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
点击 这是indexloc提供的php浏览器服务，不要输入任何密码和下载