Robust soliton crystals in a thermally controlled microresonator

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Solid-State Physics

Background:

• Microresonator-based optical frequency combs (OFCs) are crucial for precise measurements and communications.
• Generating stable soliton states in microresonators often requires complex and sensitive frequency-sweeping pump lasers.
• Developing simpler, more robust methods for soliton generation is essential for practical applications.

Purpose of the Study:

• To demonstrate a novel, simplified method for generating robust soliton crystals in a complementary-metal-oxide-semiconductor (CMOS)-compatible microresonator.
• To investigate the unique spectral properties and stability of these soliton crystals.
• To enable portable, adjustable, and low-cost optical frequency comb systems.

Main Methods:

• Utilized a thermoelectric-cooler (TEC)-based thermal-tuning approach with a fixed frequency pump laser.
• Employed a butterfly-packaged CMOS-compatible microresonator.
• Experimentally swept a cavity resonance across the pump frequency by adjusting the resonator's operating temperature.
• Observed soliton crystal states by analyzing "palm-like" optical spectra.

Main Results:

• Successfully generated robust soliton crystals with distinct "palm-like" optical spectra.
• Observed a variety of soliton crystal states resulting from strong soliton interactions.
• Achieved repeatable interconversion between chaotic modulation instability and stable soliton crystals via simple temperature or pump power tuning.
• Demonstrated the easy accessibility and excellent stability of the generated soliton crystals.

Conclusions:

• The TEC-based thermal-tuning method provides a robust and simple approach for soliton crystal generation.
• This technique avoids the need for delicate frequency-sweeping pump lasers, paving the way for practical OFC systems.
• The findings facilitate the development of portable, adjustable, and low-cost microresonator-based optical frequency combs.