Optical coatings

With the development of next generation high-energy solid-state lasers, comes the need for laser crystals and optics to meet new demanding requirements. As pulse energy continues to increase, optic component manufacturers are challenged to meet these new needs. The laser damage threshold of the optical thin film coatings used for these critical system components has historically been one of the limiting factors. For medical, industrial, scientific, and defense applications it is becoming increasingly important to not only meet the spectral performance, but also to protect the optical surfaces with coatings that show high laser induced damage threshold (LIDT). This white paper highlights how Northrop Grumman SYNOPTICS optical coating solutions are ideally placed to meet these high LIDT needs in the UV, Visible and NIR spectrums

Laser Induced Damage Threshold (LIDT) of an optical component de nes the maximum intensity the component can resist before the onset of laser damage and as a result is a critical parameter for any modern laser system, with the LIDT de ning the maximum possible intensity. However laser damage is a multi-faceted and complex problem with multiple theoretical mechanisms depending on pulse duration, optical coating quality and the manufacturing process of the component.

In this white paper, Pro-Lite’s Robert Yeo explains the science of diffuse reflectance, presents Lambert’s cosine law and explains how a diffuse reflectance material appears equally bright from all angles of view. Commercially available diffuse reflectance materials and coatings are described from Labsphere and SphereOptics, while common applications for Lambertian materials are presented, in particular in the development of LIDAR and ADAS proximity sensors.

Advances in optical polymers coupled with developments in fabrication methods have led to more optics designers choosing polymer components over glass and metal optical parts – and its no surprise why. Lower cost, faster production, and less weight are just a few of the myriad advantages that polymer-coated optics lend manufacturers. 

Chalcogenides offer many advantages that legacy IR materials simply cannot match, but they do require a diamond-like carbon (DLC) coating so the optic can withstand the harshest environmental conditions. However, coating chalcogenides with DLC has been notoriously challenging and plagued by adhesion problems and coating defects.  Until now.   

Values for Laser Induced Damage Thresholds (LIDTs) can vary.They vary batch to batch and coating house to coating house. But more worryingly, damage thresholds can vary from test house to test house.  Inflated values present real expense issues to the end user when their optics damage under seemingly safe conditions.