24 Sep 2004
A look at some of the innovations in optics that have been reported in journals this month.
The use of excimer lasers in LASIK eye surgery is well known but Nd:glass lasers could also play a useful role, according to scientists in Germany. A team from Heidelberg and Mannheim has shown that a fs Nd:glass laser can cut flaps of cornea that are just 260 µm thick and very smooth. "The average roughness was below 5 µm which is comparable to the performance of a mechanical microkeratome," report the paper's authors. "However, fs laser flap cutting is more deterministic, safe, and independent of surgical skills." (Optics Express 12 4275)
Fluorescence polarization imaging (FPI) can accurately reveal the extent of skin cancer say scientists from Wellman Laboratories of Photomedicine at Massachusetts General Hospital. Their method uses a polarized monochromatic light source (a filtered xenon arc lamp) to excite fluorescence from flurophores that are retained by tumors. The fluorescence is then imaged by a CCD camera with a rotating linear polarizer. (Optics Letters 29 2010)
Scientists from the Shanghai Institute of Optics and Fine Mechanisms have fabricated germanium oxide glasses doped with bismuth and aluminium. The Chinese team says that the glasses have long fluorescence lifetimes and "super-broadband" luminescence spanning 320 nm (full-width half-max) with a peak at 1300 nm. The results suggest that the glasses could be promising for making very broadband optical fibre amplifiers for telecommunications. (Optics Letters 29 1998)
Japanese researchers have developed an optical technique for measuring friction between two parts. The technique, tested with model cars and a metal plate, involves using a He:Ne laser and an optical inteferometer to measure the Doppler frequency shift, and thus velocity, of a moving mass attached to one of the materials. Yusaku Fuji and Takao Yamaguchi from Gunma University in Japan are now planning on using the method to measure the friction between a ballpoint pen and paper as well as a car windscreen wiper and a glass plate. (Measurement Science and Technology 15 1971)
By combining a blue emitting LED chip with a new type of ceramic phosphor (CaEuSiAlON) a Japanese team has created a warm-white LED. The prototype devices developed by Fujikura and the National Institute of Materials Science have a color temperature of 2750 K and a luminous efficacy of 25.9 lm/W. In contrast conventional white LEDs emit a bluish-white light with a color temperature of more than 3000 K. (Optics Letters 29 2001)
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