You told us you want to read more about research and technology developments in optics and photonics, so SPIE Professional is expanding its reports on R&D with brief summaries about your colleagues’ recent work with lasers, solar panels, displays, remote sensing, nanoparticles, and other technologies.
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NIST develops efficient photon detector
Scientists at the National Institute of Standards and Technology (NIST) have developed the world’s most efficient single-photon detector. Using essentially the same technology that permitted them to achieve 88% detection efficiency five years ago, the NIST team has enhanced its ability to detect photons in fiber optic cables to roughly 99%, largely by improving the alignment of the detector and the optical fibers that guide photons into it.
NIST team member Sae Woo Nam works with refrigeration equipment used to cool photon detectors to nearly absolute zero. Photo courtesy of NIST
The detector uses a superconductor as an ultra-sensitive thermometer. Each individual photon hitting the detector raises the temperature—and increases electrical resistance—by a minute amount, which the instrument registers as the presence of a photon.
The U.S. team’s efforts could bring improvements to secure electronic communication, advanced quantum computation, and the measurement of optical power. One of the most promising potential applications is in securing long-distance data transmission against unwanted interception. A detector that could recognize that a photon forming part of a transmission was missing would be a substantial defense against information theft.
Source: A.E. Lita, et al., Proceedings of SPIE 7681, 76810D (2010); doi:10.1117/12.852221.
Gold nanorods for imaging in UK
Researchers at the University of Strathclyde (UK) report in the March/April 2010 issue of the Journal of Biomedical Optics that two-photon luminescence from gold nanorods shows considerable potential in biological imaging.
In Gold nanorods for fluorescence lifetime imaging in biology, Yinan Zhang, Jun Yu, David J.S. Birch, and Yu Chen study the imaging of gold nanorods in Madin-Darby canine kidney (MDCK) cells using fluorescence lifetime imaging microscopy (FLIM). They report that FLIM provides images with better contrast and sensitivity than intensity imaging. The characteristic fluorescence lifetime of gold nanorods is found to be less than 100 ps, which can be used to distinguish gold nanorods from other fluorescent labels and endogenous fluorophores in lifetime imaging.
Source: Journal of Biomedical Optics 15, 020504 (2010); doi:10.1117/1.3366646.
THz-emitter arrays for spectroscopy and imaging
Sebastian Bauerschmidt of Max-Planck-Institut für die Physik des Lichts reported on continuous-wave terahertz-emitter arrays for spectroscopy and imaging applications at SPIE Defense, Security, and Sensing in April. A paper he coauthored with H. Lu, A. C. Gossard, S. Preu, S. Malzer, G. H. Döhler, and L. J. Wang, describes the arrays of THz emitters based on n-i-pn-i-p-superlattice photomixers.
In his presentation, Bauerschmidt described the outputs of two fiber lasers mixed in fiber couplers and divided to produce multiple THz interference beats that are collected by a group of detectors whose output goes to THz antennas. The detector-antenna combinations convert the optical THz beat signal into a multiple (four in this case) free-space-propagating THz wave.
These beams are coherent in phase, and simple optics are used to recombine the beams in the far field (focal distance of 4 meters). The combined beams add coherently to produce an N (4) squared peak power and reduced spot size. This greatly improves the capability of the system to achieve both THz spectroscopy and imaging experiments.
Source: Proceedings of SPIE 7671, 76710D (2010); doi:10.1117/12.850090; and SPIE staff reports.
Two multichannel biosensor for the field
An international team of researchers reported at SPIE Photonics Europe in April on two promising designs for a multichannel biological and chemical sensor system. The optical systems, for performing point-of-care diagnostics at schools or in the field and for confronting security-related problems, were developed in EU-sponsored projects SABIO and P3SENS.
The biosensors are based on the idea of a disposable biochip, integrating photonics and microfluidics, optically interrogated by a multichannel platform.
In, High performance multichannel photonic biochip sensors for future point of care diagnostics: an overview on two EU-sponsored projects, the team compared the designs, materials, performance, and cost of the two systems to show how they enable high sensitivity and multiple channel detection.
Artists view of polymer-made P3SENS photonic crystal chip.
Most biological sensing devices on the market today are limited in that they lack multichannel operation capability (either the detection of multiple analytes indicating a given pathology or the simultaneous detection of multiple pathologies), the authors report.
However, when a sensor structure is integrated into multichannel photonics, a multichannel biosensor can be established to allow simultaneous detection of numerous different analytes.
The authors, Domenico Giannone, Andrzej Kazmierczak, Fabian Dortu, Laurent Vivien, and Hans Sohlström, conclude that the SABIO system could be improved in terms of the number of sensing channels and fabrication technology cost. While SABIO used Si3N4/SiO2 ring resonators structures, P3SENS has photonic crystal devices based on polymers, potentially a much more economical option.
In addition to presenting a paper, the group won a first prize at the Photonics Innovation Village for exhibiting an optical instrument for interrogating high-sensitivity and multiparametric photonic biochips for future point-of-care diagnostic.
Source: Proceedings of SPIE 7715, 77150U (2010); doi:10.1117/12.854197.
Optical circuit board
A new optical circuit board technology funded by the Centre for Earth Observation Instrumentation (CEOI) in the UK has the potential to significantly improve performance of optical circuits. It can also make them more rugged, more compact, and much cheaper to manufacture.
The hollow-waveguide-based optical circuit board technology, originally invented by QinetiQ and developed further by University of Leicester, University College London, and the Centre for Terrestrial Carbon Dynamics, represents the optical equivalent of the electronic printed circuit board (PCB) and is designed as a miniature laser spectrometer system to measure atmospheric CO2.
Hollow waveguides (HWGs) formed in the surface of a dielectric substrate are used to guide light through a circuit of optical components, each of which is mounted in a precision alignment slot. Computer controlled milling techniques are used to create square-section channels which are the basis of the HWG circuits and the component alignment slots. A lid which caps the substrate forms the upper wall of all the waveguides.
The use of deep reactive ion etching in conjunction with silicon substrates also facilitates the formation of much smaller cross-section waveguide circuits and alignment slots compatible with micro-optical components.
In conjunction with automatic pick-and-place equipment, this approach to making an optical PCB the size of a SIM card could lead to high-volume, low-cost mass production of a range of integrated optic sensors.
Most read news articles from SPIE
Each month the SPIE Newsroom compiles a list of the top downloaded articles and videos from the previous month.
In May, David G. Stork’s Learning-based authentication of Jackson Pollock’s paintings was in the top spot. In April, Behavior subtraction, a new tool for video analytics, by Pierre-Marc Jodoin, Janusz Konrad, and Venkatesh Saligrama was the most popular.
The SPIE Digital Library also tracks the most frequently downloaded papers from SPIE journals and SPIE Conference Proceedings at spie.org/top10.