FPGA-based phase control of acousto-optic modulator Fourier synthesis system through gradient descent phase-locking...

Area of Science:

• Optics and Photonics
• Laser Physics
• Control Systems Engineering

Background:

• Fourier synthesis systems require precise phase control for stable operation.
• Existing active phase control methods may lack the speed and efficiency needed for high-repetition-rate systems.
• Semiconductor laser arrays present challenges in synchronized phase management.

Purpose of the Study:

• To introduce a novel application of the stochastic parallel gradient descent (SPGD) algorithm for rapid active phase control.
• To demonstrate the effectiveness of SPGD in stabilizing laser pulse generation within a Fourier synthesis system.
• To explore the scalability of this technique for multi-emitter diode laser arrays.

Main Methods:

• Implementation of the SPGD algorithm on a field-programmable gate array (FPGA) for real-time processing.
• Utilizing fast current modulation of a tapered amplifier for phase adjustment.
• Employing a single phase-sensitive metric for feedback control of laser pulses (4.9 ns duration, 80 MHz repetition rate).

Main Results:

• Successfully achieved fast active phase control in a Fourier synthesis system.
• Maintained stable generation of laser pulses through constant active feedback from the FPGA.
• Demonstrated the feasibility of the SPGD approach for precise waveform control.

Conclusions:

• The SPGD algorithm offers an effective solution for fast active phase control in Fourier synthesis systems.
• The FPGA-based implementation provides robust and real-time waveform stabilization.
• The presented technique shows significant potential for application in complex diode laser arrays.