Art and practice to emboss gratings into sol-gel waveguides

Recent interest in optical sensors, especially optical biosensors, has led to the introduction of commercially available instrumentation and sensor schemes for label free, real time monitoring of intermolecular interactions. One of the promising optical structure is the grating coupler planar waveguide sensor, where high precision surface relief grating is used and a low cost manufacturing is needed. A practical method to mass-produce gratings with limited lateral dimension is to emboss master grating into a sol-gel waveguide film. With proper optimization of the sol-gel process, a wide time window is available to perform embossing and highly reproducible, cost effective grating structures can be replicated. In our practice SiO2, TiO2, SiO2/TiO2, Ta2O5 and a mixture of these sol-gel thin films are proved to be good candidates for low optical loss waveguide materials in which grating with 2400 line/mm periodicity could be directly embossed. The relatively wide time window for optimal embossing opens the possibility to develop grating structures with more than one grating. Producing multiple gratings separated laterally and/or vertically from each other is demonstrated.