Optical coatings deposited by reactive ion plating

Area of Science:

• Materials Science
• Optical Engineering
• Thin Film Technology

Background:

• Reactive ion-plating is a key technique for depositing optical thin films.
• Hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), and silicon dioxide (SiO2) are crucial materials for optical coatings.
• Understanding the impact of process parameters on optical properties is essential for device performance.

Purpose of the Study:

• To investigate the effect of reactive ion-plating parameters on the optical properties of HfO2, Ta2O5, and SiO2 single layers.
• To characterize the optical constants of these as-deposited materials.
• To evaluate laser-damage thresholds and construct optical filters for UV and near-infrared applications.

Main Methods:

• Deposition of single layers of HfO2, Ta2O5, and SiO2 using reactive ion-plating.
• Measurement of transmittance and reflectance to determine optical constants.
• Laser-damage threshold testing at 1064 nm and 248 nm.
• Construction and characterization of single- and double-cavity filters.
• Post-annealing of filters in air and assessment of environmental effects (humidity).

Main Results:

• Optical constants for as-deposited HfO2, Ta2O5, and SiO2 were determined.
• Laser-damage threshold trends were analyzed for single- and double-layer coatings.
• Single- and double-cavity filters were successfully fabricated for UV and near-infrared regions.
• Post-annealing at 375 °C resulted in a notable increase in peak transmittance and a shift in peak wavelengths.
• Filter performance showed no significant wavelength shifts due to humidity variations.

Conclusions:

• Reactive ion-plating parameters critically influence the optical properties of HfO2, Ta2O5, and SiO2 thin films.
• Post-annealing is an effective method to enhance the performance of optical filters made from these materials.
• The fabricated filters demonstrate stability against humidity changes, indicating suitability for various applications.