Photonic Computing: Mimicking the Brain
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research highlights LASER SCANNERS is transformed according to this function, of the modes. These combinations support No moving parts and in turn undergoes a complex feedback subwavelength features of the electromagnetic Sci. Rep. 2, 445 (2012) mechanism involving randomly weighted field that can be accessed (that is, radiation delay lines. They evaluated the performance of coupled in and out) from the far-field. the device’s computation through a standard Calculations suggest that it should be possible spoken digit-recognition test consisting of ten to focus optical waves onto a 30-nm-wide different female speakers reading aloud digits focus at the centre of a 700 nm pulse by from 0 to 9. The computational efficiency employing a time-reversal approach while of the scheme was comparable to the best performing polychromatic interferometric results achieved so far in other systems. far-field subwavelength imaging. DP The processing time for the recognition of one spoken digit was around 20 ms, but BIOPHOTONICS the researchers say this could be reduced to Low-power nanosurgery 100 ns by modifying the system to include J. Biomed. Opt. 17, 101502 (2012) telecommunications-grade devices. SA LIGHT SOURCES 2012 NPG © Sun-powered lasers Opt. Lett. 37, 2670–2672 (2012) Laser scanners are highly useful devices for Thanh Hung Dinh and colleagues in Japan sensing and imaging a wide variety of objects, have constructed a solar-powered laser that but their mechanical and active electronic provides 120 W of continuous-wave output at components limit scanning rates to around a wavelength of 1,064 nm. In the future, lasers 100 kHz. Now, Keisuke Goda and co-workers pumped by sunlight may play a key part in at the University of California at Los Angeles the conversion of solar energy into chemical and the California NanoSystems Institute, energy for storage in magnesium by reducing USA, have developed a laser scanner that magnesium oxide to magnesium. Traditional avoids the use of mechanical parts. Instead, solar-pumped lasers employ hybrid 2012 SPIE their device performs the scanning by using concentrator schemes that comprise a conical © dispersive Fourier transformation to control cavity surrounding a rod containing the the light dispersion. The two-step process gain medium. Instead, Dinh and co-workers Laser-assisted surgery based on the of frequency-to-time conversion followed sheathed their lasing medium in a cylinder multiphoton absorption of near-infrared by time-to-space conversion allows the light of coolant, thus providing an additional laser light has significant potential for high- to spread out both in space and time, which focusing structure called a ‘liquid light-guide precision surgery at various depths within increases the amount of information that lens’. Sunlight entering the lens from the air cells and tissues. Although low-energy can be encoded onto the light. Scanning in the conical cavity is refracted towards the femtosecond pulses can be used to achieve is conducted in the industrially important gain medium. The system uses an automatic safe, highly localized and ultraprecise spectral band around 800 nm at speeds of up solar tracking system and a 2 m × 2 m Fresnel manipulation of subcellular organelles, to 90.8 MHz. The technique can discriminate lens at the large opening of the cavity. The conventional systems for laser micro- and between MCF7 breast cancer cells and gain medium is a rod of Nd:YAG measuring nanoprocessing employ micro- to millijoule white blood cells. They expect the method 6 mm in diameter and 100 mm in length. The energies, which can induce destructive effects to be useful more broadly in the biomedical researchers say that the low scattering loss of in cells. Karsten König and co-workers have industry, for example in the sensing of cells. SA Nd:YAG, compared with previous solar lasers now demonstrated an ultrashort femtosecond based on Cr:Nd:YAG, provided a 1.4-times laser scanning microscope that can perform PHOTONIC COMPUTING increase in output power. DP precise (sub‑100‑nm spatial resolution) Mimicking the brain surgery of human cells and metaphase Phys. Rev. Lett. 108, 244101 (2012) SUBWAVELENGTH IMAGING chromosomes. The researchers used a mode- Polychromatic metalens locked, 85 MHz repetition rate Ti:sapphire The idea of performing computations based Nature Commun. 3, 889 (2012) laser with an ‘M’-shaped ultrabroadband on how the brain processes information has spectrum (maxima at around 770 nm and gained increasing popularity over the past Far-field polychromatic focusing and imaging 830 nm), with pulse durations of between decade. Now, Romain Martinenghi and fellow at visible wavelengths may be possible by 12 fs and 3 ps. Such picojoule pulses were researchers in France have demonstrated a exploiting the dispersive properties of optical sufficient to induce sub‑100‑nm multiphoton brain-inspired optoelectronic neuromorphic resonator arrays. That is the prediction of ablation effects, which are nearly an order of computer. It uses the nonlinear transient Fabrice Lemoult and colleagues in France, magnitude smaller than the wavelength of response of an optical system to perform who considered a single silver rod measuring light used. The researchers say that this work processing in a higher dimensional phase 30 nm in diameter and 100 nm in length, may lead to compact, cost-effective laser space. The wavelength of a tunable laser is with a resonance at around 600 nm. A sources for use in future femtosecond laser used as the dynamic variable that determines 50-nm-period array of such resonators nanoprocessing and imaging microscopes. JB the output of an interferometer, which in turn should create a continuous band of collective controls the precise expression of a nonlinear modes thanks to the numerous possible Written by Seiji Armstrong, James Baxter, function. The information to be processed symmetric and antisymmetric combinations Noriaki Horiuchi, David Pile and Rachel Won. NATURE PHOTONICS | VOL 6 | SEPTEMBER 2012 | www.nature.com/naturephotonics 573 © 2012 Macmillan Publishers Limited. All rights reserved. .