Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering in optical coatings

The control and the characterization of optical losses are crucial elements in the design of high-quality thin films. Nonuniformity of losses and the existence of local defects have led us to perform simultaneous absorption and scattering mapping in exactly the same experimental conditions. An improved setup and new procedures are capable of providing such paired mappings of absorption and partial scattering at various spatial scales. The diameter of the pump beam, which governs lateral spatial resolution, can be chosen to be 3-100 microm. The detectivity threshold can be as low as 0.1 part in 10(6) for absorption and 0.01 part in 10(6) for mapping partial scattering. Spatial windows can range from micrometer-sized areas for the study of micro defects to centimeter-sized areas on which the uniformity of losses can be checked. We study the spatial distribution of absorption and scattering losses under scale transformation by changing the spatial window while keeping the spatial resolution constant. We present one-dimensional and bidimensional multiscale studies. For example, we show that one can use multiscale mapping of defects to evaluate the qualities of substrate cleaning, which are not identical on micrometric and centimetric scales.