Scientists Propose Prototype of New Infrared Visualizer
Scientists from ITMO University, Saint Petersburg Academic University, and Swiss Federal Institute of Technology Zurich (ETH Zurich) have created a flexible and transparent membrane which makes infrared beams visible to the human eye. It can be used to make visualizers needed at optical laboratories and production facilities. The invention is described in a paper published in ACS Nano.
It's well known that infrared (IR) radiation is invisible to the human eye. But it often happens that people still need to see the beam of a laser working in the infrared range. It's necessary, for example, when checking a laser installation, as well as its adjustment.
"As of now, in the field of infrared optics there is the task of visualizing infrared radiation used for various purposes," says Sergey Makarov, chief research associate at ITMO University's Laboratory of Hybrid Nanophotonics and Optoelectronics. "This type of radiation is widely used in medicine, at production sites, in lidars, as well as in fundamental research. Practically every second optical laboratory has infrared laser installations, for example, we at ITMO alone have over a hundred of them."
To see whether an installation emits radiation in the infrared range, you don't necessarily have to put on a night vision device or use a special camera. Cards made of special material are used for this purpose.
"If you're using a laser that operates in the visible range, you can just take a regular sheet of paper and place it transversely to the beam, and you'll see a dot," explains Sergey Makarov. "But this isn't going to work with an IR laser – you'll notice the beam only when it starts burning the paper. However, in this case there are special cards that work in a similar way – if you place one in the beam's way, you'll see a dot on its surface. They're made with the addition of rare earth metal ions that absorb IR radiation, emit it and convert it to the visible spectrum."
Such cards are an important component for any optical laboratory or production facility using infrared lasers. But, according to the scientists, these have a number of disadvantages, ranging from their high price to their relatively short service life. What's more, they're not universal and won't be a good fit for every system out there.
Constantly experiencing difficulties related to the high cost and short service life of the infrared visualizers used, scientists from ITMO University, Saint Petersburg Academic University, and Swiss Federal Institute of Technology Zurich (ETH Zurich) decided to apply their fundamental research to the creation of a material for new-generation IR visualizers free from many disadvantages of the existing technology. Gallium phosphide (GaP) nanowires were chosen to create a prototype. Saint Petersburg Academic University scientists have been working for a long time on growing nanostructures from this material, which has some very interesting optical properties.
"Due to the fact that this material has a noncentrosymmetric crystal lattice, it can halve the wavelength of the incident radiation. Thus, infrared light with a wavelength of 1,000 nanometers is converted into visible radiation of 500 nanometers in length, the one that is greenish-blue in color. This principle works for radiation in a wide range of wavelengths, which solves the key problem of many existing IR visualizing cards – their non-versatility and spectral limitations," notes Vladimir Fedorov, a senior research associate at Saint Petersburg Academic University's Laboratory of Renewable Energy Sources.
"Our colleagues grew gallium phosphide nanowires vertically on a substrate," shares Ivan Mukhin, head of Saint Petersburg Academic University's Laboratory of Renewable Energy Sources. "Then, they covered the nanowires with a thin polymer layer, tore it off the substrate, and obtained a membrane filled with these nanostructures. This is how we got a flexible, thin, and translucent film, which transmits an infrared beam without any significant distortions, reducing its wavelength and making it visible to the human eye."
The film's transparency plays a very important role. Existing samples fail to transmit the radiation; much as a sheet of paper, they fully block the beam out. The sample obtained by the St. Petersburg scientists, however, does let the light pass through, which makes it much easier to use.
More information:
pubs.acs.org/doi/10.1021/acsnano.0c04872
Provided by ITMO University
