Researchers at NIST’s Physical Measurement Laboratory have developed two types of force-measurement devices that use laser light to create and measure minute forces. The first is a chip-sized sensor that can use micro- to milliwatt-power light, while the second is a tabletop device designed for 1-watt laser light, potentially scalable to tens of kilowatts.
The devices can measure forces as small as 15 femtonewtons (1e-15 newtons), which is the level of atomic interactions. Potential applications include sensors with built-in laser light references for accurate force measurements, compact laser power meters, and field-portable balances for measuring milligram masses.
The chip-sized sensor uses a miniature cantilever (diving board) made of fused quartz, with a highly reflective gold-coated surface. Laser light shining on the surface transfers momentum to the cantilever, causing it to vibrate. The interferometer measures the motion, allowing force calculations based on laser power.
The tabletop device uses an electrostatic force balance (EFB) with a capacitor to measure forces created by reflected laser light. Both devices can operate at room temperature and in real time, offering advantages over traditional methods like cryogenic radiometers.
The research is still in the basic phase, allowing for new methods and approaches to be developed. Future goals include single-photon detection for measuring forces as small as zeptonewtons (1e-21 newtons), requiring cryogenic cooling and vibration reduction.
Source: https://www.nist.gov/news-events/news/2016/08/measuring-tiny-forces-light
Keywords: Laser, Photon, Force, Sensitivity, Metrology
