Phase locked laser diode interferometry for surface profile measurement

Area of Science:

• Optical Engineering
• Metrology
• Instrumentation

Background:

• Traditional interferometers often rely on mechanical components, limiting measurement accuracy due to mechanical properties.
• Developing non-mechanical phase-locking mechanisms is crucial for advancing precision metrology.

Purpose of the Study:

• To propose and evaluate a novel phase-locked interferometer design.
• To demonstrate phase lock control via laser diode injection current modulation.
• To assess the system's performance without mechanical elements.

Main Methods:

• A phase-locked interferometer employing a tunable laser diode was developed.
• Phase lock was achieved by modulating the laser diode's injection current.
• A CCD image sensor served as a photodetector for electrical scanning of measurement points.
• Surface profiles of diamond-turned aluminum disks were measured to characterize the system.

Main Results:

• The interferometer successfully achieved phase lock by controlling laser diode injection current.
• Electrical scanning using a CCD sensor enabled precise point-by-point surface measurement.
• The absence of mechanical components, like piezoelectric transducers or galvanomirrors, removed mechanical limitations on accuracy.
• System characteristics were evaluated through surface profile measurements.

Conclusions:

• The proposed phase-locked interferometer offers a new approach to high-accuracy surface metrology.
• Controlling laser diode injection current provides an effective method for phase lock.
• Eliminating mechanical scanning elements enhances measurement precision and reliability.