Abstract
A new instrument is required to accommodate the need for increased portability and accuracy in laser power measurement above 100 W. Reflection and absorption of laser light provide a measurable force from photon momentum exchange that is directly proportional to laser power, which can be measured with an electrostatic balance traceable to the SI. We aim for a relative uncertainty of 10-3 with coverage factor k = 2. For this purpose, we have designed a monolithic parallelogram 4-bar linkage incorporating elastic circular notch flexure hinges. The design is optimized to address the main factors driving force measurement uncertainty from the balance mechanism: corner loading errors, balance stiffness, stress in the flexure hinges, sensitivity to vibration, and sensitivity to thermal gradients. Parasitic rotations in the free end of the 4-bar linkage during arcuate motion are constrained by machining tolerances. An analytical model shows this affects the force measurement less than 0.01 percent. Incorporating an inverted pendulum reduces the stiffness of the system without unduly increasing tilt sensitivity. Finite element modeling of the flexures is used to determine the hinge orientation that minimizes stress which is therefore expected to minimize hysteresis. Thermal effects are mitigated using an external enclosure to minimize temperature gradients, although a quantitative analysis of this effect is not carried out. These analyses show the optimized mechanism is expected to contribute less than 1 × 10-3 relative uncertainty in the final laser power measurement.
Highlights
P RIMARY measurements of laser power rely on either the effect of absorbed laser power or the force transmitted in reflection
We describe the design of the mechanical components of an electrostatic balance for measuring laser power of up to 100 kW
Electrostatic force balances have been used successfully in mass metrology [10], [12] and, more recently, to measure the force exerted by light for power levels up to 3 W [11]
Summary
P RIMARY measurements of laser power rely on either the effect of absorbed laser power or the force transmitted in reflection (see [17] for a recent review). This is expected to be especially critical for laser powers above 1 kW. Custom dielectric coating stacks that have total optical loss lower than 1 × 10−4 are commercially available It is, in principle, possible to build a system that can measure the power of a multikilowatt laser at relative uncertainty of 1 × 10−3 or better with k = 2, using the photon pressure force from the reflection of laser light. We designed the electrostatic balance to be compatible with the HALO, but it can be used to measure a single laser beam application This manuscript reuses some content from thesis [6] with permission
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Instrumentation and Measurement
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
