Locking lasers with large FM noise to high-Q cavities

Area of Science:

• Physics
• Optical Engineering
• Laser Technology

Background:

• Achieving stable laser frequency stabilization is crucial for many scientific applications.
• Traditional laser locking techniques often require the laser linewidth to be narrower than the optical cavity linewidth.

Purpose of the Study:

• To demonstrate direct laser locking to an optical cavity when the laser linewidth significantly exceeds the cavity linewidth.
• To investigate the feasibility of locking a noisy laser to a high-finesse optical cavity.

Main Methods:

• Utilizing an external-cavity diode laser with over 1 MHz of frequency noise.
• Locking the laser to a narrow (3.5 kHz) cavity resonance.
• Employing an analog servo system for feedback control.
• Developing theoretical analysis to model the locking mechanism.

Main Results:

• Successfully achieved direct laser locking to the optical cavity.
• Demonstrated stable frequency stabilization despite the laser linewidth being much greater than the cavity linewidth.
• Confirmed that the analog servo can acquire lock even when the laser frequency sweeps through resonance faster than the cavity buildup time.

Conclusions:

• Direct laser locking to an optical cavity is achievable even with a laser linewidth substantially broader than the cavity linewidth.
• The developed analog servo system and theoretical framework provide a robust method for laser frequency stabilization in challenging conditions.
• This technique offers new possibilities for laser stabilization in various scientific and technological fields.