A photolithographic process has been used to form cross-shaped patterns in 3-μm-thick nickel foils. Patterns with cross arm dimensions in the 10–20-μm range, and with periodicities in the 16–26-μm range, yield self-resonant bandpass filters for wavelengths in the 20–25-μm region. Transmittances as high as 80% were achieved with center wavelength-to-bandwidth ratios (λ R /Δλ) of ∼5. We present a simple empirical formula that relates the wavelength of peak transmittance, or resonant frequency, with cross dimensions and periodicity.
© 1996 Optical Society of America
K. D. Möller, J. B. Warren, J. B. Heaney, and C. Kotecki, "Cross-shaped bandpass filters for the near- and mid-infrared wavelength regions," Appl. Opt. 35, 6210-6215 (1996)