Reflectivity Measurements Of Electron Beam Written First Order Bragg Gratings On AlGaAs Rib Waveguides

Abstract

The fine tuning of a microfabrication process is a quite laborious procedure. It often resorts to destructive evaluation techniques such as observation of a cleaved structure, and can rarely be performed on the same sample that will be used for the final device. This point is of particular importance for wavelength selective devices such as Bragg gratings, as their characteristics are closely tied to the refractive index of the medium they are integrated into, and may vary from sample to sample. We demonstrate an original device structure that permits to nondestructively characterize a first order Bragg reflector, and to iteratively or continously adapt the microfabrication parameters to its design specifications. In particular, we investigate the sensitivity of the mirror characteristics to the exposure dose used during direct writing.