Nanosized Light Source Has a Bright Future

A bio-friendly nanowire based light source that is capable of emitting coherent light across the visible spectrum holds promise for photo imaging and photo-detection in subwavelength optics.

Developed by a team of researchers at the Lawrence Berkeley National Laboratory (CA, USA) and the University of California Berkeley (USA), the nanowires are composed of potassium niobate that were synthesized in a special hot water solution and separated using ultrasound. The wires were highly uniform in size, several microns long, but only about 50 nanometers in diameter. A beam from an infrared laser was used to create an optical trap that allowed individual nanowires to be grabbed and manipulated. Central to the success of the nanowire light source are the exceptional nonlinear optical properties of potassium niobate. These nonlinear properties enable the frequencies of the incoming infrared light to be mixed or doubled, through techniques known respectively as second harmonic generation (SHG) or sum frequency generation (SFG), before being emitted as visible light.

In a demonstration of the technique's potential, the nanowire light sources were used to generate fluorescence from specially treated beads. Among the many potential applications of the nano-sized light source are single cell endoscopy and other forms of subwavelength bio-imaging, and integrated circuitry for nanophotonic technology. Working with individual nanowires, the researchers developed the electrode-free, continuously tunable coherent visible light source. The nanosized light source was described in the June 28, 2007, edition of the journal Nature.

This nanowire light source is like having a tiny flashlight that we can potentially scan across a living cell, visualizing the cell while mechanically interacting with it, said co-author Jan Liphardt, a biophysicist UC Berkeley's physics department. This nanowire light source technology, if developed to its full potential, could yield an embarrassment of riches in new knowledge.


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Lawrence Berkeley National Laboratory
University of California Berkeley