Compact Numerical Aperture 0.5 Fiber Optic Spectrometer Design Using Active Image Plane Tilt.

Area of Science:

• Optical Engineering
• Spectroscopy
• Instrument Design

Background:

• High numerical aperture (NA) is critical for sensitive detection of weak signals in spectrometers.
• Conventional transmission lens-based spectrometers face challenges in designing large aperture focusing lenses for ultra-high NA.
• Existing designs are limited by the difficulty in achieving large NA and material constraints.

Purpose of the Study:

• To propose a simplified method for designing high NA spectrometers.
• To overcome the challenges associated with large aperture focusing lens design.
• To improve the sensitivity and spectral resolution of fiber optic spectrometers.

Main Methods:

• Introducing an image plane tilt during the design of the large aperture focusing lens.
• Analyzing the specific demands on the focusing lens, including achromatism and monochromatic aberrations.
• Utilizing a fiber optic spectrometer design with NA 0.5 as a demonstration.

Main Results:

• The proposed method simplifies the high NA spectrometer design process.
• A focusing lens with image plane tilt exhibits reduced demands for achromatism and monochromatic aberrations, facilitating higher NA.
• An NA 0.5 fiber optic spectrometer was successfully designed using four lenses of two materials.
• Achieved spectral resolution of 6.5 nm with a spectral sampling ratio of 2:1.

Conclusions:

• The image plane tilt method offers a viable approach to simplify high NA spectrometer design.
• This technique is beneficial for applications with limited material choices and a need for high sensitivity.
• The developed method provides a practical reference for advancing spectrometer performance.