Ultrabroadband integrated electro-optic frequency comb in lithium tantalate

Area of Science:

• Photonics and Integrated Optics
• Materials Science
• Microwave Engineering

Background:

• Chip-scale frequency combs are crucial for telecommunications, microwave synthesis, and sensing.
• Existing lithium niobate electro-optic combs have limited spectral range and high power requirements.
• Dissipative Kerr solitons are not required for electro-optic combs, simplifying operation.

Purpose of the Study:

• To overcome spectral limitations and high power demands of current integrated electro-optic frequency combs.
• To develop a compact, ultra-broadband chip-scale frequency comb generator.
• To demonstrate a new architecture combining microwave and photonic integrated circuits.

Main Methods:

• Utilized a triply resonant architecture integrating monolithic microwave circuits with thin-film lithium tantalate photonic integrated circuits.
• Leveraged resonantly enhanced electro-optic interaction and reduced birefringence in lithium tantalate.
• Employed a hybrid-integrated laser diode to drive the comb generator.

Main Results:

• Achieved a fourfold extension in comb span and a 16-fold reduction in microwave power compared to conventional designs.
• Generated an ultra-broadband frequency comb spanning over 450 nm (60 THz) with more than 2,000 lines.
• Demonstrated a compact 1 cm² footprint and an increased comb existence range.

Conclusions:

• The new design overcomes key limitations of previous integrated electro-optic combs, enabling wider applications.
• The technology advances chip-scale spectrometry and ultra-low-noise millimeter-wave synthesis.
• The co-design methodology for microwave and photonics is applicable to various integrated electro-optic devices.