Microstructured large-area photoconductive terahertz emitters driven at high average power.

Area of Science:

• Optoelectronics and Photonics
• Terahertz (THz) Science and Technology
• Ultrafast Laser Applications

Background:

• Photoconductive emitters driven by ultrafast lasers are established THz sources.
• Previous research primarily used moderate-power lasers (mW to few W).
• High-power, high-repetition-rate laser systems for THz generation remain underexplored.

Purpose of the Study:

• To investigate THz emission using a high-power, MHz repetition rate Ytterbium (Yb)-based oscillator.
• To explore the performance of a microstructured, large-area photoconductive emitter with a high-power laser source.
• To analyze the impact of excitation power, bias voltage, and optical fluence on THz emitter performance.

Main Methods:

• Utilized a frequency-doubled, home-built Yb-oscillator delivering 22 W average power, 115 fs pulses, and 91 MHz repetition rate at 516 nm.
• Employed a 10x10 mm² microstructured, large-area photoconductive emitter made of semi-insulating GaAs.
• Investigated emitter performance under varying optical power (up to 18 W), bias voltage, and optical fluence.

Main Results:

• Achieved 65 µW THz average power with 4 THz bandwidth using 9 W of optical power on the emitter.
• The emitter withstood up to 18 W of optical power without damage, indicating robustness.
• Optical power demonstrated a more significant impact on emitter saturation compared to electrical power.

Conclusions:

• High-power THz generation is feasible using Yb-based oscillators and large-area photoconductive emitters.
• The study highlights the critical role of optical power and suggests optimized heatsinking for improved efficiency.
• This research enables the development of high-repetition-rate, high-power THz sources for applications like THz imaging.