This work explores reactive ion etching parameters in order to identify and optimize key characteristics in gratings that govern their overall performance, including minimization of sidewall and trench structural defects and modification of fused silica via intrinsic molecular-level defects. This study is performed using grating-like samples with 5-µm-wide lines and trenches generated in fused silica by the photolithographic process and inductively coupled plasma-reactive ion etching. The analysis compiles metrology, simulation, and damage-testing results to obtain a better understanding of how to modify the fabrication process of gratings toward achieving better laser-induced–damage performance.
The long-term performance of high-power laser systems is adversely affected by particle contaminants that are introduced into the system during the manufacturing of optical components and the handling during installation and operation of the laser system. Such particles can absorb or focus laser energy, reducing the laser-induced–damage threshold (LIDT) values. We developed ultrathin coatings that can decrease the overall load of contamination and aid with the removal of the already-accumulated particles using simple gas-flow cleaning. These coatings do not alter the intrinsic LIDT values, and they remain stable over time and during the system operation.
Silica substrates coated with organic thin films were exposed to stainless steel and silica micro-particles to determine the effectiveness in preventing particle contamination and cleaning efficiency by air flows. Three specially designed monolayers coatings were developed and tested. Laser induced damage tests were conducted to confirm that the coatings do not affect the LIDT values. The results suggest that although the accumulation of particles is not significantly affected, the coated substrates exhibit significantly improved cleaning efficiency with air flow. A size distribution analysis was conducted to study the adsorption and cleaning efficiency of particles of different sizes.
KEYWORDS: Contamination, Reactive ion etching, Etching, Laser damage threshold, Chemical analysis, Systems modeling, Silica, Scanning electron microscopy, Polymers, Optical fabrication
We investigate contamination induced in grating-like structures during the etching process as a possible precursor to laser-induced damage. Our experimental model utilizes 5-mm line structures fabricated in E-beam–deposited coatings of silica using reactive ion etching (RIE) and reactive ion beam etching (RIBE). This makes it possible to compare the behavior in the pillars and trench regions. The results suggest that surface contaminants are primarily fluorinated polymers, while embedded contaminants consist primarily of carbon with very low detection of fluorine. Samples fabricated by the RIBE method exhibit significantly reduced roughness in the trenches, yet still present similar embedded contamination.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.