Abstract

We have designed and fabricated birefringent rugate filters (birugates) by modulating the columnar nanostructure of titanium oxide and zirconium oxide during vacuum deposition. To produce the modulation the angular position of the substrate, and hence the deposition angle, is changed in a systematic way by a computer-controlled stepper drive. The deposition parameters (deposition rate ≈ 0.1nm/s, oxygen back-fill pressure ≈ 2×10^–4mbar and substrate temperature ≪ 300°C) are within a regime where columnar growth tracks the applied deposition angle, according to a modified version of the tangent rule.¹

© 1998 Optical Society of America