Iodine-stabilized VECSEL at 689 nm with 3 × 10^-13 stability

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Technologies
• Laser Spectroscopy

Background:

• Precise laser frequency stabilization is crucial for high-resolution spectroscopy and quantum technologies.
• Neutral strontium (Sr) atoms have narrow transitions suitable for atomic clocks and quantum information processing.
• Conventional laser locking methods often rely on complex reference cavities, limiting portability and stability.

Purpose of the Study:

• To demonstrate frequency stabilization of a 689 nm AlGaInP-based vertical-external-cavity surface-emitting laser (VECSEL) directly to molecular iodine.
• To evaluate the performance of an iodine-locked VECSEL for applications requiring narrow linewidth lasers, particularly for neutral Sr atom transitions.
• To explore a simplified and potentially more compact laser stabilization technique compared to traditional cavity-locking methods.

Main Methods:

• Performed sub-Doppler saturation spectroscopy of molecular iodine around 689 nm to identify suitable absorption features.
• Locked a 689 nm AlGaInP VECSEL to a specific iodine transition located 1.77 GHz above the neutral strontium-88 (Sr-88) 1S0 → 3P1 transition frequency.
• Measured laser linewidth and frequency instability using beat note measurements against a reference VECSEL and Allan deviation analysis.

Main Results:

• Identified four spectral features in molecular iodine within ±2 GHz of the Sr-88 transition.
• Achieved a locked VECSEL linewidth of 6.2(1) kHz (4 s averaging) with an integrated linewidth of approximately 400 Hz.
• Demonstrated a minimum frequency instability of 2.7×10⁻¹³ at 4 s averaging time.
• Observed a frequency drift of only 18 kHz over 20 minutes, significantly less than the 88 kHz drift of a cavity-locked system.

Conclusions:

• Directly locking a VECSEL to molecular iodine provides a robust and simplified frequency stabilization method.
• The iodine-locked VECSEL exhibits excellent stability and narrow linewidth, suitable for addressing narrow transitions in neutral Sr atoms.
• This approach offers a pathway towards more compact and less complex laser systems for quantum technology applications.