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Light engine
drives nanocar

In follow-on work to last year’s invention of a single-molecule car (see www.laserfocusworld. com/articles/252650), chemists at Rice University (Houston, TX) have produced the first motorized nanocar. The car’s light-powered motor rotates in one direction, pushing the car along like a paddlewheel. “Everything that’s produced through biology— from the tallest redwood to largest whale—is built one molecule at a time,” said lead researcher James Tour. “Nanocars and other synthetic transporters may prove to be a suitable alternative for bottom-up systems where biological methods aren’t practical.”

The nanocar consists of a rigid chassis and four alkyne axles that spin freely and swivel independently of one another. Four buckyball wheels were used in the original version of the nanocar drained energy from the motor and were replaced with spherical molecules of carbon, hydrogen, and boron called p-carborane. Initial tests in a bath of toluene solvent found that the motor rotates as designed when struck by light. Follow-up tests are under way to determine whether the motorized car can be driven across a flat surface. The nanocars, which measure just 3 by 4 nm, are about the same width as a strand of DNA but much shorter. About 20,000 of these nanocars could be parked side-by-side across the diameter of a human hair. Contact James Tour at tour@rice.edu.

Single fluoride-fiber laser produces
white laser light

Sumita Optical Glass claims to have achieved the first continuous-wave white-laser oscillation with a new single fluoride glass fiber by combining three primary colors (red, green, and blue).

The white-light laser resulted from the combination of 522 and 635 nm laser energy, si- ¹⁰ multaneously excited by guid- ⁰ ing 440 nm blue diode-laser ^{- 10} light into a fluoride-glass fiber, ^{- 20} plus residual light from the blue ^{- 30} diode laser. The fiber consists - 40 of aluminum fluoride glass - 50 doped with praseodymium, - 60

Intensity/dBm

400 500 600 700 800

which emits green and red fluo- _{Wavelength/nm} rescence upon absorbing light from the blue diode laser. Some commercial fluoride-glass fibers are available, but most are made of a combination of zircon-fluoride glasses, which is less practical.

To date, white laser light has typically been created by combining three primary colors generated separately in some way, for example, in a gas laser or by guiding IR laser energy into a nonlinear crystal. However, those methods suffer from issues such as conversion inefficiency, which increases energy consumption, requires a larger laser oscillator, and high cost. Because Sumita’s white-light laser is configured with a single fluoride-glass fiber and 440 nm diode laser it results in better conversion efficiency, energy consumption, size, cost, and performance. Contact Masatoshi Sumita at w-info@sumita-opt.co.jp.

3-D particle imaging uses wavefront sensing

To eliminate the optical inefficiency and sensitivity to wavefront-slope error and vibration of 3-D particle-imaging techniques such as stereoscopic methods, defocusing digital particle-image velocimetry (PIV), and holographic techniques, researchers from Leeds University (Leeds, England) and Heriot-Watt University (Edinburgh, Scotland) have developed a new particle-imaging method that eliminates many of these problems and provides 3-D resolution from a single viewpoint with simple, inexpensive optics.

In the phase-diversity (PD) wavefront-sensing technique, the raw data is the image-intensity distribution measured in two planes within the imaging system. Particle depths are determined from the wavefront curvatures (or PD data) and lateral positions from the particle-image centroids. Two imaging systems were used to simultaneously capture the multiplane image data: one used quadratically distorted gratings to record images from three planes in the measurement volume on a CCD (yielding an 8 μm out-of-plane resolution over a 28 mm field of view), the other used anamorphic imaging to encode the intensity from two discrete planes of the image volume along orthogonal axes in a single volume (achieving a depth resolution of 30 μm over a range of 10 mm). Contact Catherine Towers at c. e.towers@leeds.ac.uk.