Ultra-black nickel-phosphorus alloy optical absorber

To develop an optical absorber for use in the measurement of optical power, the authors have investigated and evaluated ultrablack films of nickel-phosphorus alloy which were deposited on substrates using an electroless plating process and subsequently etched. Results of varying the plating and etching bath components and conditions were studied. The result was a superior optical absorber which has a spectral reflectance of about 0.1-0.2% and a low wavelength dependence in the wavelength range of 488-1550 nm. The absorber showed almost no change in two accelerated-aging environments: 2000 h in a dry-heat environment at 100 degrees C, and 2000 h in a damp-heat environment at 85 degrees C and 85% relative humidity.<
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