Modulation-free laser stabilization technique using integrated cavity-coupled Mach-Zehnder interferometer

Area of Science:

• Photonics
• Optical Engineering
• Laser Physics

Background:

• Precision optical systems rely on stable lasers, often stabilized using techniques like Pound-Drever-Hall (PDH).
• Existing PDH systems face trade-offs between complexity, scalability, and noise sensitivity.
• There is a need for simpler, more scalable, and highly sensitive laser stabilization methods.

Purpose of the Study:

• To propose and demonstrate a novel modulation-free laser stabilization method.
• To simplify laser frequency stabilization architectures and enable miniaturization.
• To achieve high sensitivity comparable to PDH systems without modulation.

Main Methods:

• Utilized an integrated cavity-coupled Mach-Zehnder interferometer as a frequency noise discriminator.
• Implemented a passive photonic chip on a silicon-on-insulator platform.
• Employed an on-chip silicon microresonator with a quality factor of 2.5 × 10^6 for noise suppression.

Main Results:

• Demonstrated a modulation-free laser stabilization technique.
• Achieved a 4 orders-of-magnitude suppression of semiconductor laser frequency noise.
• The implemented photonic chip has a small footprint (0.456 mm^2).

Conclusions:

• The proposed modulation-free method simplifies laser stabilization and facilitates integration onto photonic platforms.
• This approach maintains high sensitivity without the complexity of modulation.
• The demonstrated technology offers a pathway to compact and robust laser frequency stabilization for precision systems.