Overview of OptiLayer Monitoring Options

A primary subdivision of monitoring techniques is their subdivision into non-optical techniques (quartz crystal and time monitoring) and optical monitoring techniques.

Optical monitoring techniques can be then subdivided into monochromatic monitoring (on-line measurements are performed at a single or several subsequent wavelengths) and broadband monitoring (on-line measurements are performed in a spectral range) techniques.

• Monochromatic monitoring strategies provide strong error self-compensation for quarter-wave designs. For non-quarter-wave designs, more complex monochromatic monitoring strategies are required. 
• Broadband monitoring (BBM) data is noisier but more informative.  BBM provides an error self-compensation effect.
• The production potential of BBM techniques was first demonstrated nearly three decades ago. Broadband optical monitoring is especially useful for deposition systems with on-line reoptimization of optical coatings.
• Monochromatic optical monitoring remains an important and widely used tool. OptiLayer proposes a algorithms for choosing a proper sequence of monitoring wavelengths for all coating layers (monitoring strategy).

Monitoring techniques can be divided into direct and indirect ones. In the case of direct monitoring, transmittance or reflectance measurements are performed on at least one of the coatings to be manufactured while in the case of indirect monitoring layer thicknesses are monitored on separate witness substrates.

• In the case of the direct monitoring, errors are accumulated.
• In the case of the indirect monitoring (monitoring with witness chips), the errors are not accumulated. At the same time, correlation factors between thicknesses of the sample and of the witness glass are to known with high accuracy.

Classification of optical monitoring strategies.

• Broadband monitoring simulation;
• Specification of the Monitoring Spreadsheet;
• Advanced monochromatic monitoring strategies;
• Monochromatic Monitoring simulation;
• Monochromatic monitoring with witness chips (indirect monitoring);
• Broadband monitoring with witness chips;
• Pre-production estimation of errors;
• WDM monitoring simulation.

OptiLayer Automation options and OptiReOpt library propose tools for on-line characterization and re-optimization of optical coatings.