On-chip Fourier-transform spectrometer based on spatial heterodyning tuned by thermo-optic effect

Area of Science:

• Photonics and Spectroscopic Technologies
• Mid-Infrared Optics
• Integrated Photonics

Background:

• Miniaturized optical spectrometers are crucial for remote sensing, medical diagnostics, and astronomy.
• Mid-infrared (MIR) spectroscopy excels at identifying chemical and biological substances via absorption fingerprints.
• Current on-chip Fourier-transform spectrometers (FTS) face limitations in balancing spectral bandwidth and resolution.

Purpose of the Study:

• To overcome the bandwidth-resolution tradeoff in on-chip Fourier-transform spectrometers (FTS).
• To introduce a novel FTS approach combining spatial heterodyning and thermo-optic path tuning.
• To demonstrate an enhanced performance miniaturized spectrometer for MIR applications.

Main Methods:

• Implemented a novel FTS architecture integrating spatial heterodyning with thermo-optic path delay tuning.
• Utilized spatial multiplexing of multiple interferometers with varying optical path imbalances for high resolution.
• Employed the thermo-optic effect for precise optical path delay tuning to achieve broadband operation.

Main Results:

• Experimentally demonstrated a mid-infrared Silicon-Germanium (SiGe) FTS.
• Achieved a spectral resolution better than 15 cm^-1.
• Obtained a bandwidth of 603 cm^-1 near 7.7 μm using a 10 Mach-Zehnder interferometer (MZI) array.
• Demonstrated a resolution comparable to state-of-the-art devices with a 4x bandwidth increase and halved footprint.

Conclusions:

• The proposed FTS design successfully overcomes the traditional bandwidth-resolution tradeoff in miniaturized spectrometers.
• This integrated photonic approach offers significant advantages in performance and size for MIR spectroscopy.
• The demonstrated SiGe FTS shows great promise for advanced applications in chemical sensing, medical diagnostics, and beyond.