Optical monitoring strategies for optical coating manufacturing

In-situ interferometric monitoring of optical coatings

“…The realization of complex optical filtering functions requires perfect control of the deposition process as well as accurately monitoring the optical thicknesses of the deposited layers in real time. This is today achieved through the simultaneous use of energetic deposition techniques, that provide dense layers with stable refractive index properties, and in situ optical monitoring systems [1,2].…”

Online Characterization Algorithms for Optical Coating Production with Broadband Monitoring

“…Almost four decades ago, Angus Macleod indicated that in the case of optical monitoring "one monitors layer optical thicknesses and this has always been a strong argument in support of optical monitoring techniques" [1]. Nowadays, various optical monitoring techniques are widely used for the production of the most challenging optical coatings [2][3][4]. Among them, direct broadband monitoring [2][3][4] is attracting more and more attention from optical coating engineers.…”

“…Nowadays, various optical monitoring techniques are widely used for the production of the most challenging optical coatings [2][3][4]. Among them, direct broadband monitoring [2][3][4] is attracting more and more attention from optical coating engineers. This type of monitoring is successfully used for the control of stable low-rate deposition processes, like ion beam sputtering [5,6], and also for the control of such widely-used coating processes as ion-assisted deposition [7][8][9].…”

“…One of the advantages of this technique as compared to monochromatic monitoring techniques is its much lower sensitivity to random errors in measurement data [4]. Another advantage is the presence of the error self-compensation effect associated with direct broadband monitoring [1,10].…”

“…Along with the positive error self-compensation effect there is also a negative effect associated with all direct monitoring techniques. This is the effect of accumulation of thickness errors that manifests itself as a rapid growth of these errors with the growing number of deposited layers [2,4,10,12]. The necessity of preventing the development of the cumulative effect of thickness errors is often the main argument for choosing indirect broadband monitoring techniques instead of direct ones [2,4].…”