OPTICAL WAVEGUIDES

Our lattice characteristics will depend heavily on the characteristics of our waveguides. In Christandl et al, 2004, it is shown that the field strengths of the two interfering modes are important to the distance the trap lies above the surface of the waveguide. With these strengths, such height is tunable. If light that is coupled in is lost to surface or bulk scattering, the field at different points will be different, leading to a different trapping height at different positions. Two different trapping heights in two dimensions will possibly lead to misshapen lattice wells. So, waveguide losses are important for trap location and shape.

Optical losses are given as with .

For thinner waveguides, scattering losses are dominant.

So, it is very important for us to have the least lossy waveguides which requires us to have the smoothest waveguides possible. Currently we are working with fused silica substrates that have <1/2 angstrom rms roughness. Using ion beam sputtering techniques, we hope to get Ta₂O₅ films that are limited by this substrate roughness.