Quantitative theory of integrating sphere throughput: comparison with experiments.

Area of Science:

• Optical Metrology
• Radiometry
• Photonics

Background:

• Integrating spheres are crucial for optical measurements, but their throughput determination is complex.
• Existing methods often neglect non-ideal port effects and fiber optic collection characteristics.
• Accurate sphere multiplier (M) derivation is essential for reliable absolute throughput measurements.

Purpose of the Study:

• To present a rigorous approach for measuring integrating sphere throughput and deriving the sphere multiplier (M).
• To experimentally validate the impact of non-ideal port effects and optical fiber collection on throughput measurements.
• To provide experimental evidence supporting recent theoretical predictions on realistic port behavior.

Main Methods:

• Measuring transmitted power at the base of the integrating port to mitigate port wall reflections.
• Utilizing optical fibers for light collection, defining collection area and numerical aperture.
• Experimentally determining and correcting for angular-dependent fiber throughput and detector sensitivity, including skew ray propagation.

Main Results:

• Failure to implement the described methods can lead to measurement errors up to 50%.
• Accurate sphere multiplier derivation, considering realistic ports with non-zero reflectivity, achieves agreement with theory.
• Experimental confirmation of theoretical predictions regarding altered angular distribution and reduced transmittivity for high aspect ratio ports.

Conclusions:

• The presented rigorous approach significantly enhances the accuracy of integrating sphere throughput measurements.
• Realistic port modeling and precise optical fiber characterization are critical for quantitative measurements.
• This work establishes a foundation for advanced integrating sphere metrology and theoretical development.