III-V-on-silicon integrated micro - spectrometer for the 3 μm wavelength range.

Area of Science:

• Photonics and Spectroscopic Instrumentation
• Mid-Infrared (Mid-IR) Spectroscopy
• Integrated Photonics

Background:

• The mid-IR wavelength range (approx. 3-25 μm) is crucial for identifying organic compounds due to their unique molecular vibrations.
• Existing integrated spectrometers often lack optimal performance in this vital spectral region.
• Developing compact, fully integrated spectrometers for mid-IR analysis is essential for portable and advanced sensing applications.

Purpose of the Study:

• To present a novel, compact, and fully integrated mid-infrared spectrometer.
• To achieve operation at a 3 μm wavelength, a key window for organic compound spectroscopy.
• To demonstrate heterogeneous integration of photodetectors for enhanced functionality.

Main Methods:

• Utilized a silicon-on-insulator (SOI) platform for the arrayed waveguide grating (AWG) filter.
• Employed heterogeneous integration of InAs_0.91Sb_0.09 p-i-n photodiodes.
• Used adhesive bonding for integrating photodiodes onto the spectrometer's output grating couplers.

Main Results:

• Achieved a compact spectrometer size of 1.2 mm².
• Demonstrated operation in the 3 μm wavelength range, the longest reported for an integrated spectrometer in this window.
• Reported a spectrometer insertion loss of less than 3 dB.
• Achieved a waveguide-referred responsivity of 0.3 A/W for the integrated photodiodes at room temperature.

Conclusions:

• Successfully developed the longest wavelength integrated spectrometer to date operating at 3 μm.
• The device is suitable for spectroscopy of organic compounds, enabling new sensing possibilities.
• Heterogeneous integration of photodetectors offers a viable path for compact and efficient mid-IR spectroscopic systems.