Sub-terahertz feedback interferometry and imaging with emitters in 130 nm BiCMOS technology.

Area of Science:

• Terahertz (THz) technology
• Semiconductor device physics
• Integrated photonics

Background:

• Compact terahertz (THz) sources are essential for various applications.
• Self-mixing effects in oscillators can be exploited for sensing and measurement.
• SiGe BiCMOS technology offers a platform for integrated THz devices.

Purpose of the Study:

• To investigate the self-mixing phenomenon in compact THz emitters.
• To demonstrate the feasibility of feedback interferometry for THz imaging.
• To characterize the performance of SiGe BiCMOS-based THz sources.

Main Methods:

• Implementation of differential Colpitts oscillators in 130 nm SiGe BiCMOS.
• Optimization of emission frequency at the fundamental harmonic.
• Substrate-side radiation out-coupling via a hyper-hemispheric silicon lens.
• Analysis of bias current changes due to feedback radiation.

Main Results:

• Two THz sources developed, optimized for 200 GHz (0.525 mW) and 260 GHz (0.325 mW).
• Self-mixing induced bias current changes up to several percent.
• Demonstrated coherent reflection-type raster-scan imaging using feedback interferometry.

Conclusions:

• Self-mixing in SiGe BiCMOS THz emitters enables sensitive interferometric measurements.
• Feedback interferometry is a viable technique for THz imaging with these compact sources.
• The developed THz emitters show promise for integrated sensing and imaging systems.