Offset phase locking of noisy diode lasers aided by frequency division.

Area of Science:

• Optical physics and laser systems engineering.
• Advanced signal processing and control theory.

Background:

• Heterodyne phase locking is crucial for synchronizing oscillators, but its reliability can be challenged by large frequency offsets.
• Current methods may require bulky and expensive microwave synthesizers in the control loop, increasing system size, weight, and power consumption.

Purpose of the Study:

• To investigate the efficacy of incorporating a frequency divider into an optical phase-lock loop (OPLL).
• To compare phase stability and synchronization quality with and without a frequency divider for diode lasers.
• To analyze the impact of frequency division on noise properties and loop dynamics.

Main Methods:

• Experimental implementation of a frequency divider within an optical phase-lock loop.
• Comparative analysis of residual phase fluctuations between two diode lasers using two configurations: with and without frequency division.
• Numerical modeling to assess noise characteristics and internal dynamics of phase-locked loops.

Main Results:

• Comparable phase stability achieved with and without frequency division, provided adequate loop gain is maintained post-division.
• Frequency division enables the exclusion of microwave synthesizers for large heterodyne offset frequencies (5-10 GHz).
• Numerical analysis confirms the benefits of an in-loop frequency divider for noise reduction and improved loop dynamics.

Conclusions:

• Frequency division is a viable technique to improve heterodyne phase locking reliability and synchronization.
• This method offers significant advantages in reducing instrument size, weight, power, and cost.
• The study validates the theoretical benefits of frequency division in OPLLs through experimental and numerical evidence.