Experimental study of perfectly patterned silica-titania optical waveguide

Rimlee Deb Roy,Devika Sil,Sunirmal Jana,Shyamal Kumar Bhadra,Prasanta Kumar Biswas

doi:10.1007/s13320-011-0035-2

Rimlee Deb Roy, Devika Sil + Show 3 more

Open Access

https://doi.org/10.1007/s13320-011-0035-2

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Abstract

Inorganic silica-titania thin films with thicknesses 150 nm–200 nm are deposited on high purity and polished silicon wafer and silica glass substrates by sol-gel dipping process and are patterned by capillary force lithography technique. Subsequently grating structure is embossed in green stage. The patterned gel films are subjected to stepwise heat treatment to 500 °C and above in pure oxygen atmosphere in order to achieve major conversion of mixed-gel to oxide optical films which are characterized by Ellipsometry, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) to optimize the fabrication parameters and to get perfectly matched film. Removal of organics and formation of perfectly inorganic silica-titania network at optimized heat treatment in controlled environment are ensured by FTIR spectral study. The difference in refractive indices between the substrate and coated film as calculated theoretically matches exactly with the developed waveguides for operating wavelength (632.8 nm) and the measured optical properties show the planar waveguide behavior of the films.

Highlights

Increasing interest in photonics integrated circuits has stimulated studies on newer optical materials
Inorganic silica-titania thin films with thicknesses 150 nm–200 nm are deposited on high purity and polished silicon wafer and silica glass substrates by sol-gel dipping process and are patterned by capillary force lithography technique
The patterned gel films are subjected to stepwise heat treatment to 500 °C and above in pure oxygen atmosphere in order to achieve major conversion of mixed-gel to oxide optical films which are characterized by Ellipsometry, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) to optimize the fabrication parameters and to get perfectly matched film

Summary

Introduction

Increasing interest in photonics integrated circuits has stimulated studies on newer optical materials. The synthesis of transparent SiO2 based sol-gel coatings has been of great interest in recent years since this process of using metal alkoxide solutions can be applied to various substrates by spin or dip coating and enables good control of composition and optical properties [6, 7] It is capable of coating large surfaces and does not require high processing temperatures. It is a simple and effective tool for patterning, and it employs the concept of capillarity [17], where a polymer melt is molded by the use of an elastomeric stamp i.e. the PDMS stamp We have used this soft lithographic technique to emboss grating structures on as-deposited silica-titania gel films of desired configurations for targeted operating wavelength of waveguide. Rimlee DEB ROY et al.: Experimental Study of Perfectly Patterned Silica-Titania Optical Waveguide

Theory

Fabrication and experimental details

TM c tan 1

Results and discussion

Conclusions