Detecting Malaria With Light

The malaria parasite changes the polarization of light and this has been exploited to measure population density in blood samples using polarimetry. Melanie Campbell, a researcher at the University of Waterloo and immediate past president of the Canadian Association of Physicists, and her colleagues have extended this approach to analyzing tissue samples.

They looked at both infected and normal tissue in their experiments, and used a confocal laser scanning Macroscope to measure changes in polarization and highlight the levels of malaria parasites in the tissue samples. By using the Macroscope to image larger tissue samples at higher resolutions, the severity of infection by the malaria parasite may be accurately quantified.

The technique allows large areas to be imaged in a single scan as opposed to the smaller field available with a traditional microscope. This avoids time-consuming "stitching" of a large number of smaller images and increases data accuracy. Not only could this new approach improve the assessment of the severity of cases of malaria, but it could be extended to assessing different tissues infected with other kinds of biological abnormalities -- possibly including proteins associated with Alzheimer's disease -- that also interact with polarized light.₁

Gigantic Photoresponse Can Speed Up Optical Switches for Faster Internet Speeds New research shows that an ultrafast, ultralarge change in reflectivity can be brought about with femtolasers, those that deliver pulses just quadrillionths of a second in length. Dramatic reflectivity changes will be useful in bringing about direct ultrafast optical-to-optical switches for quicker Internet data transfer, faster computers and other applications.

In a recent experiment, femtosecond laser pulses falling on an organic salt target momentarily changed the material from an insulator (a bad reflector of light) to a semi-metal (a good reflector of light). The change in reflectivity this large -- more than 100% -- has never been achieved before in a photonic material; photo-induced changes are usually more like a few percent. Researchers found that the laser pulse required doesn't even have to be particularly intense to cause the change.

This "gigantic photoresponse" work began as a Tokyo Institute of Technology - Kyoto University collaboration but now also includes the U.S.' Lawrence Berkeley Laboratory and the U.K.'s Oxford University. The new advance is that the change in reflectivity can be brought about in tens of femtoseconds rather than 150 femtoseconds. The new results will be reported at the meeting by Jiro Itatani, who has a joint appointment at Lawrence Berkeley Laboratory and the Japan Science and Technology Agency.₂

1. Paper FThK1, "Confocal Polarimetry Measurements of Tissue Infected with Malaria"

2. Paper FWA2, "Ultrafast Gigantic Photo-Response in Organic Salt (EDO-TTF)2PF6 Initiated by 20-fs Laser Pulses"