Tunable filter and modulator with controlled bandwidth and wide dynamic range based on planar thin films structure.

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Tunable narrowband spectral filters are crucial for various applications.
• Existing filters often face trade-offs between dynamic range, throughput, and cost.

Purpose of the Study:

• To demonstrate a new method for creating tunable narrowband spectral filters.
• To overcome the limitations of current filter technologies.

Main Methods:

• Utilizing coupling between waveguide and lossy modes (LMs) in ultrathin films.
• Employing a thin film coupling layer and an absorptive layer (e.g., 6nm Cr) for broadband LM excitation.
• Investigating TE and TM polarization effects.

Main Results:

• Achieved reflection peaks with controllable width (sub-Angstroms to tens of nm) and wide spectral tunability (>500nm).
• Demonstrated tuning via incidence angle or waveguide layer modulation.
• Observed wider dynamic range and higher contrast with TE polarization.
• Reported Rabi-type splitting with ultrahigh tuning under specific conditions.

Conclusions:

• The proposed method offers a cost-effective approach to high-performance tunable filters.
• The thin waveguide design enables ultrahigh-speed tuning using various external stimuli.
• This technology has potential for broad applications in spectroscopy and optical communications.