Abstract: A refractive index modulation element made of a refractive index modulation material. The refractive index can be thermally modulated. The refractive index modulation material can be a silicone resin represented by the following formula R.sub.n SiO.sub.(4--n)/2,where the average value of n is 0.5 to 3 and where K is an aliphatic or aromatic group with 1 to 18 carbon atoms or other functional group. The silicone resin has a spectral transmission factor that on average is higher than 80%, within the wavelength range of 350 nm to 1,600 nm, and a refractive index temperature dependence of -0.001/.degree.C. to -0.00005/.degree.C.

Abstract: An active biological material encapsulated in a glass is formed using a sol-gel process. A metal alkoxide is mixed with water and exposed to ultrasonic energy at a pH.ltoreq.2 to form a single phase solution which is then buffered to a pH between about 5 and 7. The buffered solution is then mixed with the active biological material and the resultant gel is aged and dried. The dried product is a transparent porous glass with substantially all of the added active biological material encapsulated therein, the biological material retaining a high level of activity.