Modulation-free frequency stabilization of external-cavity diode laser based on a phase-difference biased Sagnac...

Area of Science:

• Optics and Photonics
• Laser Physics
• Spectroscopy

Background:

• External-cavity diode lasers (ECDLs) require precise frequency stabilization for various applications.
• Traditional stabilization methods often involve complex modulation techniques.
• Developing modulation-free, robust, and cost-effective stabilization schemes is crucial.

Purpose of the Study:

• To introduce a novel modulation-free technique for stabilizing ECDL frequency.
• To utilize a phase-difference biased Sagnac interferometer for generating error signals.
• To demonstrate the effectiveness of this technique in locking laser frequency to atomic transitions.

Main Methods:

• Implementation of a Sagnac interferometer with a half-wave plate and total internal reflection prism.
• Introduction of a phase-difference bias between counterpropagating beams with perpendicular polarizations.
• Locking the frequency of a Littman-Metcalf ECDL to a Rubidium (Rb) atomic vapor transition.

Main Results:

• Achieved frequency stabilization of the ECDL without modulation.
• Significantly suppressed frequency fluctuations from 8 MHz to below 0.5 MHz peak-to-peak.
• Demonstrated a simple, robust, and low-cost laser stabilization system.

Conclusions:

• The proposed modulation-free Sagnac interferometer technique provides effective ECDL frequency stabilization.
• This method offers a practical and cost-efficient alternative to existing stabilization techniques.
• The technique shows potential for broad applicability in laser systems requiring high frequency stability.