Three-stage Fabry-Perot liquid crystal tunable filter with extended spectral range

Area of Science:

• Optics and Photonics
• Optical Engineering
• Filter Technology

Background:

• Tunable optical filters are crucial components in various spectroscopic and photonic applications.
• Extending the spectral range of tunable filters while maintaining performance is a significant challenge.
• Fabry-Perot etalons offer tunable filtering capabilities but often have limited free spectral ranges.

Purpose of the Study:

• To propose and demonstrate a novel method for extending the spectral range of tunable optical filters.
• To reduce sidelobes in the filter's spectral response.
• To achieve a compact and easily attainable extended tunable spectral range.

Main Methods:

• Cascading two identical tunable Fabry-Perot filters with an additional tunable filter possessing a different free spectral range.
• Detailed design procedures and simulations were performed.
• Experimental validation using a 3-stage tunable Fabry-Perot filter covering visible and infrared spectra.

Main Results:

• Achieved an extended free spectral range exceeding 400 nm.
• Obtained a narrow full width at half maximum of 4 nm.
• Experimental results validated the theoretical analysis and demonstrated the method's effectiveness.

Conclusions:

• The proposed method effectively extends the tunable spectral range of Fabry-Perot filters.
• The technique allows for the reduction of sidelobes, improving filter performance.
• This approach offers a compact and straightforward way to achieve extended tunable spectral range filters.