Exploratory Development of Ultra-narrow, High Throughput, Infrared Thin Film Interference Bandpass Filters

Thin film interference filters are available for isolating a narrow range of wavelengths from a broader wavelength spectrum with high signal to noise ratios. Ion assisted deposition (IAD) of refractory oxides produces filters that have high throughput, withstand harsh environments, are thermally stable, and have a simple compact construction, all of which make them superior to competing technologies. These filters are useful in any optical system that requires that a given wavelength band of light be separated from a broad wavelength source. Filters with bandwidths as small as one nanometer are commercially available from Barr Associates and other companies. Barr Associates proposes to build on its extensive experience in the IAD of thermally stable oxide filters for the near infrared by producing and characterizing a three cavity bandpass filter with a five angstrom bandwidth that has existing potential in the fiberoptic telecommunications industry. The investigation of the Phase I project will provide direction for further development of thin film narrow bandpass filters for the infrared. Process improvement resulting from these investigations will aid in producing a narrow bandpass infrared filter to the specifications of the user.