High-Q diamond microresonators in the long-wave infrared

Area of Science:

• Optics and Photonics
• Materials Science
• Infrared Technology

Background:

• High quality factor (Q) photonic devices are crucial for sensitive optical measurements.
• Previous research has not achieved high-Q devices in the deep long-wave infrared (LWIR) spectrum (>9 µm) at room temperature.

Purpose of the Study:

• To demonstrate the first high-Q photonic devices operating in the room temperature thermal infrared region (>9 µm).
• To explore the fabrication and characterization of whispering gallery mode diamond microresonators for LWIR applications.

Main Methods:

• Fabrication of whispering gallery mode diamond microresonators using single crystal diamond substrates and high-angle oxygen-based inductively coupled plasma (ICP) reactive ion etching (RIE).
• Characterization of spectral properties at room temperature using a tunable quantum cascade laser and free-space coupling.
• Light extraction using an arsenic selenide (As2Se3) chalcogenide infrared fiber coupled to a cryogenically cooled mercury cadmium telluride (HgCdTe) detector.

Main Results:

• Demonstrated high quality factor (Q) photonic devices in the room temperature thermal infrared region (9-9.7 µm).
• Achieved a Q factor of 3648 at 9.601 µm for one microresonator.
• Observed free spectral ranges slightly greater than 40 GHz, consistent with theoretical predictions for the microresonator dimensions.

Conclusions:

• Successful fabrication of high-Q whispering gallery mode diamond microresonators for the deep long-wave infrared spectrum at room temperature.
• These devices represent a significant advancement for infrared sensing and photonic applications.
• The results validate the fabrication technique and the potential of diamond microresonators for LWIR applications.