Mid-infrared Fourier-transform spectrometer based on metamaterial lateral cladding suspended silicon waveguides

Area of Science:

• Photonics
• Spectroscopy
• Materials Science

Background:

• Integrated micro-spectrometers are crucial for environmental monitoring and space exploration.
• Silicon-on-insulator (SOI) offers cost-effective, compact photonic circuit production.
• SOI's buried oxide layer limits mid-infrared applications (>4 µm) due to absorption.

Purpose of the Study:

• To overcome the limitations of SOI in mid-infrared spectroscopy.
• To develop a compact spatial heterodyne Fourier-transform (SHFT) spectrometer operating near 5.5 µm.
• To demonstrate a metamaterial-cladded suspended silicon waveguide approach.

Main Methods:

• Utilized metamaterial-cladded suspended silicon waveguides to remove the buried oxide layer.
• Implemented a spatial heterodyne Fourier-transform (SHFT) spectrometer.
• Designed the spectrometer with 19 Mach-Zehnder interferometers (max arm length imbalance 200 µm).

Main Results:

• Achieved low propagation loss (<2 dB/cm) between 5.3-5.7 µm.
• Demonstrated a spectral resolution of 13 cm⁻¹.
• Obtained a free spectral range of 100 cm⁻¹ near 5.5 µm.

Conclusions:

• Metamaterial-cladding effectively removes SOI's mid-infrared absorption limitations.
• The developed SHFT spectrometer is suitable for mid-infrared applications.
• This technology enables compact, high-performance spectrometers for environmental and space applications.