Ink shield against laser
doi:10.1038/nindia.2011.41 Published online 24 March 2011
Researchers have designed a new kind of optical limiter by smearing fluorescent ink on carbon nanotubes (CNTs). The ink-CNT nanocomposite optical limiter will be very handy to protect sensitive detectors and human eyes from high intensity laser radiation.
Many of the lasers used today damage the crystals used to control, guide or manipulate it inside photonic devices. To counter this damage, optical limiters, devices used as protective shield against laser-induced damage, are built. Materials such as carbon black suspension, CNTs and CNTs modified with light emitting molecules have been explored for their light absorbing properties. Among the materials, CNTs have shown response from visible to infrared optical region.
Taking cues from these studies, the researchers chose single walled CNTs and coated them with fluorescent ink. The ink-coated CNTs gave rise to nanocomposite. Molecular clusters of ink were attached to the surface of the CNTs in the form of tiny spheres of diameter from 50 to 185 nm.
To find out ink-CNTs' role as optical limiter, the nanocomposite was exposed to 100 femtosecond laser pulses. The composite material was found to exhibit two-photon absorption in which an electron absorbs two photons at approximately the same time (or within less than a nanosecond).
The results highlight the feasibility of designing efficient nanocomposite materials by attaching well known optical materials with CNTs. The researchers say that such materials with interesting optical properties and ultrafast response hold immense potential for possible applications in optoelectronics and photonics.
The authors of this work are from: Department of Physics, Indian Institute of Technology, Madras, and Department of Chemistry, Indian Institute of Technology, Kanpur, India.