The National Institute of Standards and Technology (NIST) has been involved in developing a new laser power sensor that can be built by assembling of gadgets facilitating real-time estimations. This new device or smart mirrors makes use of radiation pressure or a force equivalent to the pressure that light has on an object.
Preeminence of lasers in manufacturing applications including welding of car parts to creating engine components using 3D printers, has made it imperative for manufacturers to develop lasers that fire with appropriate power. Until recently, this was just a next-to-impossible task, as it was difficult to precisely measure power of lasers during manufacturing processes from a real-time perspective. Deprived of this information, manufacturers either needed to spend money or time in a bid to assess if their parts were meeting manufacturing specifications post production.
Addressing this need researchers from NIST have introduced smart mirrors – a chip sized pressure power meter designed for lasers of the order of more than 100 watts. Unlike old fashioned shoe sized RPPM (Radiation Pressure Power Meter), smart mirror is comparatively smaller yet relatively much faster. With around 250 times the speed of measurement of larger pressure power meter, the sensitivity of smart mirror is 40 times more than that of radiation pressure power meter.
This new technology can find its way into various manufacturing applications, ranging from automobiles and airplanes to medical devices and cellphones. Versatility and credibility of smart mirror further expands as it can be integrated in machines that are used in additive manufacturing – a 3D printing technology that carries out a layer-by-layer formation of an object using laser to melt material used in its development.
This new device uses radiation pressure to measure the beam when it is being used in manufacturing process. Although light has zero mass, it has tremendous momentum that permits it to develop a significant force after it strikes an object. A laser beam of 1 KW power, although small, has a noticeable force – near to weight of one grain of sand.
Smart mirror works like a capacitor and measures the change in capacitance occurring between two charged plates. One of the plates is coated with Bragg reflector. The laser impacting the top plate (the reflector) imparts a force that moves the plate closer to the other plate. This results in capacitance change and its capacity to store charge. More the power of the laser more would be the force on top plate. In addition, NIST researchers developed the smart sensor that is not sensitive to vibrations. This prevents impact and effect of other forces acting on plates ensuring accurate measurement.
Smart mirrors can enable an accurate real-time measurement with a background noise of 2.5 watts. This prototype is being tested for a 250 watts laser power. NIST researchers are focusing on further improving stability and sensitivity of smart mirrors in a bid to extend the capacity to reach around 1 KW making it a suitable device for most manufacturing procedures.