Hertz-level frequency comparisons between diverse color lasers without a frequency comb.

Area of Science:

• Optics and Photonics
• Laser Physics
• Quantum Metrology

Background:

• Precise frequency control of lasers is crucial for many scientific applications.
• Measuring relative frequency noise between lasers at disparate wavelengths is challenging.
• Existing methods like frequency combs can be expensive and complex.

Purpose of the Study:

• To present a simple, cost-effective technique for measuring and stabilizing relative laser frequency noise.
• To demonstrate the cancellation of interferometer instability in the measurement protocol.
• To offer an alternative to frequency combs for cross-wavelength laser characterization.

Main Methods:

• Utilized a frequency discriminator based on an unstabilized Mach-Zehnder fiber interferometer.
• Simultaneously extracted noise from two lasers at vastly different wavelengths (895 nm and 1561 nm).
• Employed a Red Pitaya for laser stabilization with a 100 kHz control bandwidth.

Main Results:

• Achieved a direct measure of relative laser frequency noise, canceling interferometer instability.
• Demonstrated laser stabilization with high sensitivity (1 Hz²/Hz), limited by detector noise.
• Independently verified the technique's performance using a commercial frequency comb.

Conclusions:

• The presented technique provides a simple and affordable method for measuring and stabilizing relative laser frequency noise.
• This approach facilitates the transfer of frequency stability across large spectral intervals.
• It serves as a viable alternative to frequency combs for characterizing noise in diverse laser sources.