Room temperature laser power standard using a microfabricated, electrical substitution bolometer

Area of Science:

• Optical Metrology
• Radiometry
• Materials Science

Background:

• Accurate measurement of continuous-wave (CW) laser power is essential for numerous scientific and industrial applications.
• Existing standards may have limitations in terms of wavelength range, beam diameter accommodation, or power levels.
• Development of a versatile and accurate absolute standard is needed to meet evolving metrological demands.

Purpose of the Study:

• To design and characterize a room temperature electrical substitution radiometer (ESR) for use as an absolute standard.
• To establish a reliable instrument for measuring CW laser power with high accuracy across a broad spectral range and beam sizes.
• To validate the performance of the developed ESR against established primary and legacy standards.

Main Methods:

• The instrument utilizes a planar, silicon microfabricated bolometer as its core sensing element.
• Vertically aligned carbon nanotube absorbers are integrated for enhanced optical absorption.
• Commercial surface mount thermistors and an integrated heater, along with commercial electronics, are employed for precise control and measurement.

Main Results:

• The ESR achieves an accuracy of 0.46% (k = 2) for powers between 10 mW and 100 mW, and 0.83% (k = 2) for powers between 1 mW and 10 mW.
• The standard accommodates laser beam diameters (1/e²) up to 11 mm and operates across wavelengths from 300 nm to 2 μm.
• Performance validation confirmed agreement with a National Institute of Standards and Technology (NIST) primary standard and U.S. Air Force Metrology and Calibration Division (AFMETCAL) legacy standards.

Conclusions:

• The developed room temperature ESR serves as a highly accurate absolute standard for CW laser power measurement.
• Its wide operational range in wavelength, beam diameter, and power levels makes it a versatile tool for metrology.
• The successful validation demonstrates its reliability and suitability for replacing or augmenting existing standards in critical calibration applications.