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Intensity influence on Gaussian beam laser based measurements using quadrant photodiodes
Yohannes Panduputra1, Tuck Wah Ng, Adrian Neild
1Laboratory for Optics, Acoustics, & Mechanics, Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Victoria 3800, Australia.
Applied Optics
|July 22, 2010
Summary
Photodiode saturation and amplifier clipping distort laser beam size measurements. A best-fit analysis helps estimate beam size and optimal laser power, but deflection measurements require recalibration with changing light intensity.
Area of Science:
- Optical Metrology
- Instrumentation and Measurement
Background:
- Quadrant photodiodes are commonly used in laser beam size and deflection measurements.
- Integrated systems typically use current-to-voltage amplifiers for signal processing.
Purpose of the Study:
- To investigate the impact of photodiode saturation and amplifier nonlinearities on measurement accuracy.
- To identify factors affecting laser beam size and deflection determination.
- To propose methods for improving measurement accuracy under varying light intensities.
Main Methods:
- Analysis of photodiode saturation effects at low light intensities.
- Evaluation of amplifier nonlinearities and voltage clipping at high light intensities.
- Development of a best-fit computation for size versus power trends.
- Assessment of light intensity's effect on beam deflection sensitivity.
Main Results:
- Photodiode saturation and amplifier clipping lead to underestimation of laser beam size.
- A best-fit computation accurately estimates beam size and optimal laser power.
- Light intensity significantly impacts beam deflection measurement sensitivity, requiring calibration.
Conclusions:
- Nonlinearities in photodiodes and amplifiers are critical error sources in laser beam measurements.
- Best-fit analysis offers a solution for beam size estimation but not for deflection under varying conditions.
- Calibration is essential for accurate beam deflection measurements when light intensity changes.
