Curing optical material in a plane optical resonant cavity

Abstract

A method for curing an optically sensitive material or for fabricating an optical filter is described which comprises the steps of disposing a thin film of optically sensitive material within a plane optical cavity capable of resonating at selected optical frequencies having boundary reflectivities greater than 50 percent at some wavelength, polarization and angle of incidence and being capable of resonating at selected optical frequencies and exposing cavity and material to sensitizing light, such as a laser, of preselected wavelength or wavelengths suitable for initiating cure within the material and optionally for establishing one or more specified sets of resonant standing wave patterns within the material when the cavity is oriented at a suitable angle to the incident light.

I claim: 
     
       1. A method for curing an optically sensitive material, comprising the steps of: (a) forming a plane optical resonant cavity defined by partially reflecting plane parallel boundaries which reflect greater than 50 percent within a selected optical spectral wavelength range a light beam having a selected state of polarization and incident at a selected angle relative to a normal direction to said optical cavity;   (b) disposing at least one optically sensitive or optically curable material within said optical cavity; and   (c) exposing said cavity and material therewithin to light of preselected wavelength in order to cure said material.   
     
     
       2. The method of claim 1 further comprising the step of orienting said cavity and said material disposed therein with respect to the direction of incidence of said light whereby one or more preselected optical standing wave patterns are generated within said cavity and said material in order to develop one or more distinct patterns of index modulation within said material upon cure thereof. 
     
     
       3. The method of claim 1 wherein the step of exposing said cavity and material therewithin is performed using a laser source. 
     
     
       4. The method of claim 3 wherein said laser source is selected from the group consisting of gas lasers, including argon, krypton, nitrogen, xenon, argon-krypton, xenon-chloride and xenon-fluoride lasers, dye, solid state, and semiconductor lasers, operated in a pulsed or continuous manner. 
     
     
       5. The method of claim 1 further comprising the step of using adjustable reflectors disposed adjacent said cavity for reflecting light into said cavity and for optionally establishing therewithin selective standing optical wave patterns capable of inducing a selected refractive index modulation pattern within said material. 
     
     
       6. The method of claim 5 wherein said positionable reflectors are disposed and oriented to establish within said cavity at least one selective standing wave pattern capable of inducing a selected refractive index modulation pattern within said material. 
     
     
       7. The method of claim 1 wherein said cavity is a Fabry-Perot cavity defined between a pair of partially transmissive boundaries selected from the group consisting of a pair of metallic films supported by a pair of transparent substrates, a pair of dielectric films supported by a pair of transparent substrates, means defining a pair of refractive index discontinuities, and a solid layer of electrooptic material having said metallic films or said dielectric films deposited thereon. 
     
     
       8. The method of claim 7 wherein said metallic films comprise a material selected from the group consisting of aluminum, silver, gold and copper of thickness less than about 200 A, and wherein said dielectric films comprise a material selected from the group consisting of the oxides, fluorides and nitrides of magnesium, silicon, aluminum, cerium, thorium, yttrium, lanthanum, zirconium, lead, zinc, indium, tin and titanium. 
     
     
       9. The method of claim 1 further comprising the step of enclosing said cavity, material and selected associated optical components within a temperature controlled and hermetically sealed chamber for environmental control of said cavity, material and associated optical components during cure. 
     
     
       10. The method of claim 1 wherein said optically sensitive material is one of a holographic material and an electrooptic material. 
     
     
       11. The method of claim 1 wherein said optically sensitive material is a polymer dispersed liquid crystal material. 
     
     
       12. The method of claim 3 further comprising adjustable reflectors disposed adjacent said cavity for reflecting light into said cavity and for optionally establishing therewithin selective standing optical wave patterns capable of inducing a selected refractive index modulation pattern within said material. 
     
     
       13. A method for fabricating an optical filter, comprising the steps of: (a) forming a plane optical resonant cavity defined by partially reflecting plane parallel boundaries which reflect greater than 50 per cent within a selected optical spectral wavelength range for a light beam having a selected state of polarization and incident at a selected angle relative to a normal direction to said optical cavity;   (b) disposing within said cavity a film of at least one optically sensitive or optically curable material selected from the group consisting of holographic materials and electrooptic materials; and   (c) exposing said cavity and film therewithin to light of preselected wavelength in order to cure said material and to produce a modulated refractive index pattern or a uniform refractive index through said material along said normal direction.   
     
     
       14. The method of claim 13 further comprising the step of orienting said cavity and film with respect to the direction of incidence of said light whereby one or more preselected optical standing wave patterns are generated within said cavity and film in order to develop one or more distinct patterns of index modulation within said material upon cure thereof. 
     
     
       15. The method of claim 13 further comprising the step of using adjustable reflectors disposed adjacent said cavity for reflecting light into said cavity and for optionally establishing therewithin selective standing optical wave patterns capable of inducing a selected refractive index modulation pattern within said material. 
     
     
       16. The method of claim 13 wherein the step of exposing said cavity and film therewithin is performed using a laser source selected from the group consisting of gas lasers, including argon, krypton, nitrogen, xenon, argon-krypton, xenon-chloride and xenon-fluoride lasers, dye solid state, and semiconductor lasers, operated in a pulsed or continuous manner. 
     
     
       17. The method of claim 13 wherein said cavity is a Fabry-Perot cavity defined between a pair of partially transmissive boundaries selected from the group consisting of a pair of metallic films supported by a pair of transparent substrates, a pair of dielectric films supported by a pair of transparent substrates, means defining a pair of refractive index discontinuities, and a solid layer of electrooptic or holographic material having said metallic films or said dielectric films deposited thereon. 
     
     
       18. The method of claim 17 wherein said metallic films comprise a material selected from the group consisting of aluminum, silver, gold and copper of thickness less than about 200 A, and wherein said dielectric films comprise a material selected from the group consisting the oxides, fluorides and nitrides of magnesium, silicon, aluminum, cerium, thorium, yttrium, lanthanum, zirconium, lead, zinc, indium, tin and titanium. 
     
     
       19. The method of claim 13 further comprising the step of enclosing said cavity and material within a temperature controlled hermetically sealed chamber for environmental control of said cavity and material during cure. 
     
     
       20. The method of claim 5 further comprising electrooptic or mechanical means for selectively changing the optical path length between said reflectors. 
     
     
       21. The method of claim 15 further comprising electrooptic or mechanical means for selectively changing the optical path length between said reflectors. 
     
     
       22. The method of claim 1 wherein said material is selected from the group consisting of LiNbO 3 , LiTaO 3 , BaTiO 3 , SrTiO 3 , Ba x  Sr.sub.(1-x) Nb 2  O 6 , and Pb 0 .88 La 0 .08 Ti x  Zr.sub.(1-x) O 3 . 
     
     
       23. The method of claim 13 wherein said material is selected from the group consisting of LiNbO 3 , LiTaO 3 , BaTiO 3 , SrTiO 3 , Ba x  Sr.sub.(1-x) Nb 2  O 6 , and Pb 0 .88 La 0 .08 Ti x  Zr.sub.(1-x) O 3 . 
     
     
       24. The method of claim 1 further comprising a plain optical mask disposed between the source of said light and said cavity. 
     
     
       25. The method of claim 13 further comprising a plain optical mask disposed between the source of said light and said cavity.