Tunable optical filters with wide wavelength range based on porous multilayers

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Tunable optical filters (TOF) are crucial for spectroscopic applications.
• Existing TOF technologies face limitations in tuning range and speed.
• Porous silicon photonic crystals offer unique optical and mechanical properties.

Purpose of the Study:

• To present a novel micromechanical tunable optical filter (TOF) concept.
• To achieve wide wavelength tuning (±20%) at high frequencies (kilohertz).
• To demonstrate the feasibility using porous silicon-based photonic crystals.

Main Methods:

• Fabrication of porous silicon multilayer structures.
• Integration of micromechanical tilting for filter adjustment.
• Utilizing pore-filling techniques to further enhance tuning range.
• Optical simulations and experimental validation across visible and near-infrared spectra.

Main Results:

• Demonstrated wavelength tuning of approximately ±20% around the working wavelength.
• Achieved tuning frequencies up to kilohertz.
• Extended the tunable range to over 200 nm through combined mechanical tilting and pore-filling.
• Validated the approach with experimental and simulation data.

Conclusions:

• The proposed micromechanical TOF design based on porous silicon photonic crystals is effective.
• The technology enables significant wavelength tuning and high-speed operation.
• This advancement holds promise for improved spectroscopic analysis and process monitoring.