BUFFALO, N.Y. A team from the University of Buffalo has developed an organic material which is capable of absorbing three photons at infrared (IR) wavelengths and re-emitting the light in the visible spectrum.
The group, led by Professor Paras Prasad of the university's Institute for Lasers, Photonics and Biophotonics, designed the material specifically with the aim of developing three-photon absorption at 1.3 micrometers, a frequency used for fibre optic communications.
Materials that absorb two photons have been around for more than decade, but they tend to absorb around 800 nanometers, a wavelength not as useful for communications applications.
"The conversion process is very efficient," said Prasad. "It could form the basis for upcon-version lasing. The strong non-linear absorption properties should help with power stabilization and limitation, which would mean a power surge could not do any damage."
Converting light from IR to visible has potential memory applications as shorter wavelength light allows for denser information storage.
Currently, the technique converts light from the IR to the yellow-green area of the visible. Prasad is confident that materials can be developed to convert IR to a range of visible frequencies and even UV, which would offer the possibility of lithographic applications.
"We developed the material based on our theoretical understanding and on intuition," he said. "We haven't got to the stage yet where we can predict a material's optical qualities using computer simulation, but we have now developed guiding principles."
As well as producing a material for 1.3-micrometer wavelength light, the team is working on a material that converts IR light at 1.55 micrometers into visible red light. 1.3 and 1.55 micrometers are two key wavelengths at which light is transmitted along fibre optic cables.
The technique has applications in medical imaging as well as communications. At visible wavelengths, biological tissue material rapidly absorbs and scatters light. It is not very effective at building up three dimensional images of living material.
At around 1.3 micrometers, it is possible to penetrate much more deeply into organic tissue, offering the potential to build up better 3D images of internal organs.
Prasad and his team published their work in Nature.