High-power UTC-photodiodes for an optically pumped subharmonic terahertz receiver

Area of Science:

• Terahertz (THz) technology
• Optoelectronics
• Microwave engineering

Background:

• Photonic-based terahertz systems require efficient frequency conversion components.
• Existing terahertz mixers often face limitations in local oscillator (LO) power and conversion loss (CL).
• Optically subharmonic pumping offers a promising approach for terahertz signal generation and mixing.

Purpose of the Study:

• To develop and characterize an optically subharmonic pumped WR3-mixer for terahertz imaging and spectroscopy.
• To integrate a high-power uni-travelling carrier photodiode (UTC-PD) as a local oscillator (LO) source for the mixer.
• To evaluate the performance of the integrated terahertz mixer module in terms of conversion loss.

Main Methods:

• Design and fabrication of a WR3-mixer utilizing gallium arsenide (GaAs)-based low barrier Schottky diodes (LBSDs).
• Development of an indium phosphide (InP)-based UTC-PD optimized for high output power in the WR6-band (135-160 GHz).
• Integration of the UTC-PD with the WR3-mixer using an E-plane transition and a microstrip line low-pass filter (MSL-LPF).

Main Results:

• The UTC-PD achieved a record output power of +3.38 dBm at 150 GHz with 21 mA photocurrent.
• The fabricated WR3-mixer demonstrated an average minimum conversion loss (CL) of 16.8 dB at the highest LO power.
• The achieved CL is comparable to electronically pumped mixers and is expected to improve further with packaging.

Conclusions:

• The optically subharmonic pumped WR3-mixer, powered by a high-performance UTC-PD, is a viable component for future terahertz systems.
• The developed UTC-PD provides unprecedented LO power at 150 GHz, crucial for efficient terahertz mixing.
• This work paves the way for compact and high-performance photonic-based terahertz imaging and spectroscopy systems.