Real-time digital control of optical interferometers by the mechanical-modulation technique

Area of Science:

• Optics and Photonics
• Control Systems Engineering
• Digital Signal Processing

Background:

• Traditional optical interferometers often rely on analog control systems.
• Analog components can introduce noise and limitations in precision.
• Developing fully digital control methods is crucial for advancing interferometer performance.

Purpose of the Study:

• To demonstrate the application of digital systems for automatic control of dual-wave optical interferometers.
• To show that digital techniques can replace analog components in error-signal extraction and control-signal generation.
• To present the implementation of a digital lock-in amplifier for synchronous demodulation.

Main Methods:

• Utilizing the mechanical-modulation technique for error-signal extraction.
• Implementing digital signal processing for synchronous demodulation and control-signal generation.
• Designing a digital lock-in amplifier algorithm.
• Integrating analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) with minimal front-end analog amplifiers.

Main Results:

• Digital systems can effectively perform both error-signal extraction and control-signal generation in dual-wave optical interferometers.
• The proposed digital control scheme significantly reduces the need for analog devices, requiring only essential front-end amplifiers.
• A functional digital lock-in amplifier algorithm was developed and described.
• The digital control procedure was successfully applied to a Mach-Zehnder interferometer.

Conclusions:

• Fully digital control of dual-wave optical interferometers is feasible and advantageous.
• The digital lock-in amplifier approach enables precise control with minimal analog circuitry.
• This digital control strategy offers a pathway for enhanced performance and stability in optical interferometry applications.