The "blackest" material makes a high-precision laser power detector

According to the report of the American Association for the Advancement of Science website on August 18, the National Institute of Standards and Technology of America used the world’s blackest material, forest-like multi-walled carbon nanotubes, as a coating to develop a laser power detector for optical communication. High-precision laser power measurement in advanced technologies such as laser manufacturing, solar energy conversion, and industrial and satellite-borne sensors. Research papers are published in the latest Nano Express.

This new detector barely reflects visible light. In deep purple wavelengths from 400 nm to near-infrared wavelengths of 4 μm, the reflection is less than 0.1%, and in the infrared spectrum of 4 μm to 14 μm, the reflection is less than 1%. This is similar to the super black material reported by Rensselaer Polytechnic Institute in 2008. In 2009, a Japanese team also had a similar study.

Inspired by Rensselaer Polytechnic Institute's research paper "World's Darkest Manmade Material," researchers from the National Institute of Standards and Technology conducted a sparse arrangement of fine carbon nanotubes as a thermal detector. The coating makes a device for measuring laser power. Carbon nanotubes are good conductors of heat and provide an ideal thermal detector coating. Although nickel-phosphorus alloys reflect less light at certain wavelengths, they do not conduct heat.

Cooperative researchers at Stony Brook University in New York have grown carbon nanotube coatings on a thermoelectric material, lithium niobate. The coating absorbs laser light and converts heat into heat. The temperature rises to produce current. The power of the laser can be determined by measuring the size of the current. . The darker the coating, the better the effect of light absorption and the more accurate the measurement result. What is unique is that nanotubes are grown on thermoelectric materials, while other studies have grown on silicon materials.

National Institute of Standards and Technology has used a variety of materials to make detector coatings, including flat single-wall nanotubes. The latest coating is a vertical forest-like multi-walled nanotube, each with a diameter of less than 10 nm and a length of about 160 μm. The deep tube helps absorb random scattered light and reflected light in any direction.

Due to the technical requirement that the detector be able to measure the reflection spectrum more widely, the National Institute of Standards and Technology uses five different methods to spend hundreds of hours to measure the increasingly weaker reflected light, and the accuracy can meet the requirements. The researchers plan to extend the scale operation of the device to 50 micron or even 100 micron wavelengths, which may provide a standard for terahertz ray power measurements.