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Diffraction-limited gradient-index (GRIN) microlenses with high numerical apertures produced by silver ion exchange in glass

Diffusion modeling and process optimization


Marker, A.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Inorganic optical materials : 19-20 July 1998, San Diego, California
Bellingham, Wash.: SPIE, 1998 (SPIE Proceedings Series 3424)
ISBN: 0-8194-2879-5
Conference "Inorganic Optical Materials" <1998, San Diego/Calif.>
Conference Paper
Fraunhofer IOF ()
cylindrical lens; diffraction limit; diffusion modeling; Endoskop; high-power laser diode; micro-optic lens; rod lens; silver ion exchange

Cylindrical and rod gradient-index lenses with numerical apertures of 0.5 are produced by silver ion exchange in a sodium-aluminosilicate glass. Choosing the appropriate glass composition enables the generation of refractive index changes of 0.145 in the glass without coloration in the visible range. Diffraction-limited optical performance of lenses of up to 1.3 mm in thickness or diameter is achieved by ion exchange modeling which comprises the following steps: (1) The concentration-dependent diffusion coefficient of the glass is experimentally determined by the Boltzmann-Matano method, (2) Process control is provided by the measured dopant concentration/refractive index relation and the glass/salt equilibrium dependence, (3) The ion exchange process is optimized by solving the non-linear diffusion equation for two steps under different boundary conditions, (4) Diffraction-limited lenses up to numerical apertures of 0.5 are generated by applying the optimized process parameters to the ion exchange.