Performance of a low-pass filter for far-infrared wavelengths

Area of Science:

• Physics
• Optical Engineering
• Astrophysics

Background:

• Far-infrared spectroscopy requires highly efficient optical filters.
• Existing filters often lack sufficient performance at cryogenic temperatures.
• Rocketborne instruments demand robust and precise components.

Purpose of the Study:

• To design and characterize a novel low-pass filter for far-infrared applications.
• To achieve high transmittance in the passband (<50 cm(-1)) and excellent rejection in the stopband (>300 cm(-1)).
• To evaluate filter performance at liquid-helium temperatures.

Main Methods:

• Fabrication of a specialized low-pass filter.
• Measurement of filter component transmittance from 10 to 10,000 cm(-1) at liquid-helium temperatures.
• Integration and testing of the filter in a rocketborne far-infrared absolute photometer.

Main Results:

• The filter exhibits high in-band transmittance (>50% for ν < 50 cm(-1)).
• Exceptional out-of-band rejection (<10(-9) for ν > 300 cm(-1)) was achieved.
• Successful deployment and operation in a liquid-helium-cooled, rocketborne instrument.

Conclusions:

• The developed low-pass filter meets stringent performance requirements for far-infrared spectroscopy.
• This filter technology enables improved sensitivity and accuracy in space-based astrophysical measurements.
• The filter's performance at cryogenic temperatures is validated for demanding applications.