Refractive Index Matching in Capillary Illumination

Abstract

System and method for fluorescent light excitation and detection from samples to enhance the numerical aperture and/or reduce the cross-talk of the fluorescent light.

1 . An excitation system for analyzing samples comprising:
 a light source;   a housing, wherein the housing transports samples and propagates light from the light source by total internal reflection;   a coupling optical element configured to introduce light from the light source into the housing through a wall of the housing; and   an index matching compound disposed in such a manner so as to optically couple the housing and the coupling optical element.   
   
   
       2 . The system of  claim 1 , wherein at least a portion of the index matching compound is disposed in a region between the housing and the coupling optical element. 
   
   
       3 . The system of  claim 1 , wherein the composition of the index matching compound is selected from the group consisting of: a solid material, a semisolid material, a liquid material, a viscous material, and a gel material. 
   
   
       4 . The system of  claim 1 , wherein the housing, the coupling optical element and the index matching compound have respective refractive indices and the refractive index of the index matching compound is configured to provide a selected degree of coupling efficiency between the housing and the coupling optical element. 
   
   
       5 . The system of  claim 4 , wherein the refractive index of the index matching compound is similar to the refractive index for the housing. 
   
   
       6 . The system of  claim 4 , wherein the refractive index of the index matching compound is similar to the refractive index for the coupling optical element. 
   
   
       7 . The system of  claim 4 , wherein the refractive index of the index matching compound is less than refractive index than the coupling optical element. 
   
   
       8 . The system of  claim 7 , wherein the refractive index of the index matching compound is in the range from approximately 1.4 to approximately the refractive index of the coupling optical element. 
   
   
       9 . The system of  claim 1 , wherein an index of refraction of the coupling optical element is greater than an index of refraction of the housing. 
   
   
       10 . The system of  claim 1 , wherein an index of refraction of a material comprising the housing is greater than an index of refraction of a fluid sample transported within the housing. 
   
   
       11 . The system of  claim 1 , wherein the light source is selected from the group consisting of: a coherent light source, a non-coherent light source, and a combination coherent/non-coherent light source. 
   
   
       12 . The system of  claim 1 , wherein the housing comprises a plurality of capillaries. 
   
   
       13 . The system of  claim 1 , wherein the coupling optical element has a shape selected from the group consisting of: a truncated sphere, a hemisphere, a cone, a hyperhemisphere, a spherical surface combined with a cylindrical surface, a spherical surface combined with a planar surface, and a meniscus lens. 
   
   
       14 . The system of  claim 13 , wherein the truncated sphere further comprises;
 a coupling section joined to a portion of the housing;   a lens section joined to a first portion of the coupling section; and   a second lens section joined to a second portion of the coupling section.   
   
   
       15 . The system of  claim 1 , wherein the coupling optical element is constructed to permit light to enter the housing and propagate by total internal reflection. 
   
   
       16 . A method for exciting fluorescence of samples comprising:
 transporting a plurality of samples through a detection zone with a capillary;   directing a non-coherent light into the capillary with a coupling optical element and an index matching compound that optically couples the coupling optical element and the capillary.   
   
   
       17 . The method of  claim 16 , wherein at least a portion of the index matching compound is disposed in a region between the capillary and the coupling optical element. 
   
   
       18 . The method of  claim 16 , wherein the composition of the index matching compound is selected from the group consisting of: a solid material, a semisolid material, a liquid material, a viscous material, and a gel material. 
   
   
       19 . The method of  claim 16 , wherein the capillary, the coupling optical element and the index matching compound have respective refractive indices and the refractive index of the index matching compound is configured to provide a selected degree of coupling efficiency between the capillary and the coupling optical element. 
   
   
       20 . The method of  claim 19 , wherein the refractive index of the index matching compound is similar to the refractive index for the capillary. 
   
   
       21 . The method of  claim 19 , wherein the refractive index of the index matching compound is similar to the refractive index for the coupling optical element. 
   
   
       22 . The method of  claim 16 , wherein the refractive index of the index matching compound is less than refractive index than the coupling optical element. 
   
   
       23 . The method of  claim 22 , wherein the refractive index of the index matching compound is in the range from approximately 1.4 to approximately the refractive index of the coupling optical element. 
   
   
       24 . The method of  claim 16 , wherein an index of refraction of the coupling optical element is greater than an index of refraction of the capillary. 
   
   
       25 . The method of  claim 16 , wherein an index of refraction of a material comprising the capillary is greater than an index of refraction of the sample transported within the capillary. 
   
   
       26 . The method of  claim 16 , further comprising directing the non-coherent light into the capillary with a second coupling optical element. 
   
   
       27 . The method of  claim 16 , further comprising removing the non-coherent light from the housing after the non-coherent light passes through the detection zone. 
   
   
       28 . The method of  claim 16 , wherein the samples are transported through the detection zone by a fluid having an index of refraction lower than an index of refraction of a material comprising the capillary.