High étendue Fourier transform spectroscopy by quadratic off-axis path difference error cancellation

Area of Science:

• Spectroscopy
• Optical Instrumentation
• Physical Chemistry

Background:

• Fourier transform spectroscopy (FTS) design is traditionally limited by a tradeoff between étendue and spectral resolution.
• Existing freespace scanning Michelson interferometers face limitations, e.g., a 1° field of view for 4 cm^-1 resolution at 800 nm.
• This tradeoff is often considered a fundamental constraint in instrument design.

Purpose of the Study:

• To demonstrate a novel method for enhancing instrumentation design in Fourier transform spectroscopy.
• To overcome the established tradeoff between étendue and spectral resolution.
• To increase the potential signal-to-noise ratio for spectroscopic measurements.

Main Methods:

• Development of a new instrumentation design approach for scanning Fourier transform spectrometers.
• Theoretical analysis and demonstration of a method to increase the allowable angular field of view for a given spectral resolution.
• Comparison of the proposed method against traditional freespace Michelson interferometer limitations.

Main Results:

• The proposed method increases the allowable angular field of view by an order of magnitude for a given spectral resolution.
• This leads to a two-orders-of-magnitude increase in étendue and potential signal-to-noise ratio compared to freespace Michelson interferometers.
• The study suggests the tradeoff may not be fundamentally limited by thermodynamics.

Conclusions:

• A new design principle for Fourier transform spectroscopy instruments has been established.
• Scanning FTS instruments can theoretically achieve arbitrarily high étendue and spectral resolution simultaneously.
• This breakthrough has significant implications for enhancing spectroscopic measurement capabilities.