Method for altering light interactions with complex structured light

Abstract

Structured beams, Bessel beams Laguerre beams, and focused Gaussian are used as a natural waveguide and its group velocity can be subluminal (slower than the speed of light) as compared to a Gaussian beam in free space. A free space dispersion relation for a Bessel beam, i.e., the dependence of its wavenumber on its angular frequency, is outlined from which the Bessel beam's subliminal group velocity is derived. For reasonable conditions a Bessel light beam has associated parameters that allow slowing near a critical frequency. The application of Bessel beams for a natural optical buffer in free space is presented. Optical transitions and selection rules in materials are altered by structured light carrying orbital angular momentum (OAM). Nano antennas are used to enhance the interactions of structured light.

What is claimed is: 
     
         1 . An optical buffer comprising
 an optical beam generator configured to generating a nonplanar optical beam having an angular frequency (ω) and a constant beam diameter (a) between 0.1 μm and 10 μm;   a medium through which the nonplanar optical beam is propagated, the medium having an index of refraction (n), wherein the angular frequency (ω) of the nonplanar optical beam is within 25% of a critical angular frequency (ω c ) given by   
       
         
           
             
               ω 
               ≡ 
               
                 
                   ck 
                   ⊥ 
                 
                 n 
               
             
           
         
         
           wherein k ⊥  is a transverse wavenumber given by 
         
       
       
         
           
             
               
                 
                   k 
                   ⊥ 
                 
                 = 
                 
                   
                     2 
                      
                     π 
                   
                   a 
                 
               
               , 
             
           
         
         
           wherein the nonplanar optical beam is closed to a subluminal speed by propagating through the medium, thereby providing an optical buffer. 
         
       
     
     
         2 . The optical buffer as recited in  claim 1 , wherein the medium is a fiber optic cable. 
     
     
         3 . The optical buffer as recited in  claim 1 , wherein the medium is air. 
     
     
         4 . A method for producing subluminal light, the method comprising steps of:
 generating a nonplanar optical beam having an angular frequency (ω) and a constant beam diameter (a) between 0.1 μm and 10 μm;   propagating the nonplanar optical beam through a medium, the medium having an index of refraction (n), wherein the angular frequency (ω) of the nonplanar optical beam is within 25% of a critical angular frequency (ω c ) given by   
       
         
           
             
               
                 ω 
                 c 
               
               ≡ 
               
                 
                   ck 
                   ⊥ 
                 
                 n 
               
             
           
         
         
           wherein k ⊥  is a transverse wavenumber given by 
         
       
       
         
           
             
               
                 k 
                 ⊥ 
               
               = 
               
                 
                   
                     2 
                      
                     π 
                   
                   a 
                 
                 . 
               
             
           
         
       
     
     
         5 . The method as recited in  claim 4 , wherein the nonplanar optical beam is a Bessel beam. 
     
     
         6 . The method as recited in  claim 4 , wherein the nonplanar optical beam is an Laguerre Gaussian beam. 
     
     
         7 . The method as recited in  claim 4 , wherein the medium is air for free space. 
     
     
         8 . The method as recited in  claim 7 , wherein the index of refraction (n) is 1. 
     
     
         9 . The method as recited in  claim 4 , wherein the medium is a fiber optic cable. 
     
     
         10 . The method as recited in  claim 4 , wherein the step of propagating confines the nonplanar optical beam in X and Y directions but permits propagation in a Z direction, thereby providing a waveguide. 
     
     
         11 . The method as recited in  claim 4 , wherein the waveguide is a rectangular waveguide. 
     
     
         12 . The method as recited in  claim 11 , wherein the nonplanar optical beam is slowed in the Z direction. 
     
     
         13 . The method as recited in  claim 11 , wherein the nonplanar optical beam is an Laguerre Gaussian with a Rayleigh zone 2z 0 . 
     
     
         14 . The method as recited in  claim 4 , further comprising exposing an antenna to the nonplanar optical beam after the step of propagating. 
     
     
         15 . The method as recited in  claim 14 , wherein the antenna comprises a plurality of cavities, each cavity having a volume of less than 5 μm 3 . 
     
     
         16 . The method as recited in  claim 14 , wherein the antenna provides a plurality of cavities, each cavity having a volume between 0.5 and 3 μm 3 . 
     
     
         17 . The method as recited in  claim 14 , wherein the antenna is selected from the group consisting of an elongated box antenna, an antenna with a plurality of grating cones disposed on a planar surface; a nanoantenna, a fly eye antenna and a black silicon antenna. 
     
     
         18 . A method of enhancing an optical beam, the method comprising steps of:
 exposing an antenna to an optical beam with a wavelength (λ), the optical beam being selected from the group consisting of a Bessel beam, a Laguerre Gaussian beam, and a Gaussian beam, the optical beam having a constant beam diameter (a) between 0.1 μm and 10 μm, wherein the antenna comprises a plurality of cavities, each cavity having a volume (V) of less than 5 μm 3 ;   permitting the optical beam to interact with the cavity to produce an optical enhancement given by a Purcell Factor (F p ) where:   
       
         
           
             
               
                 F 
                 p 
               
               = 
               
                 
                   3 
                    
                   Q 
                    
                   
                       
                   
                    
                   
                     λ 
                     3 
                   
                 
                 
                   4 
                    
                   
                     π 
                     2 
                   
                    
                   V 
                 
               
             
           
         
         
           where Q is between 1 and 100 and V is a non-zero number that is less than 5 μm 3 . 
         
       
     
     
         19 . The method as recited in  claim 18 , wherein the optical enhancement is an enhanced emission. 
     
     
         20 . The method as recited in  claim 18 , wherein the optical enhancement is an enhanced absorption. 
     
     
         21 . The method as recited in  claim 18 , wherein the optical enhancement is an alteration in selection rules, for dipole and quadruple transitions between states in materials, wherein the materials are bulk materials and nanoparticle materials or quantum dot materials. 
     
     
         22 . The method as recited in  claim 18 , wherein the antenna is selected from the group consisting of an elongated box antenna, an antenna with a plurality of grating cones disposed on a planar surface; a nanoantenna, a fly eye antenna, a black silicon antenna and a cavity to trap radiation of nonplanar light.