In This Issue...
NIST Tests Underscore Potential Hazards of Green Laser Pointers
Using a low-cost apparatus designed to quickly and accurately measure the properties of handheld laser devices, National Institute of Standards and Technology (NIST) researchers tested 122 laser pointers and found that nearly 90 percent of green pointers and about 44 percent of red pointers tested were out of compliance with federal safety regulations. The NIST test apparatus was designed so that it can be replicated easily by other institutions.
As NIST researchers reported at a conference on March 20, 2013,* both red and green laser pointers often emitted more visible power than allowed under the Code of Federal Regulations (CFR), and green pointers often emitted unacceptable levels of infrared light as well.
Anecdotal reports of green laser hazards have previously appeared in scientific journals and the media, but the new NIST tests are the first reported precision measurements of a large number of handheld laser devices. The NIST tests point out that many red laser pointers are also—unexpectedly—out of compliance with federal regulations. "Our results raise numerous safety questions regarding laser pointers and their use," the new paper states.
The NIST tests were conducted on randomly selected commercial laser devices labeled as Class IIIa or 3R and sold as suitable for demonstration use in classrooms and other public spaces. Such lasers are limited under the CFR to 5 milliwatts maximum emission in the visible portion of the spectrum and less than 2 milliwatts in the infrared portion of the spectrum. About half the devices tested emitted power levels at least twice the CFR limit at one or more wavelengths. The highest measured power output was 66.5 milliwatts, more than 10 times the legal limit. The power measurements were accurate to within 5 percent.
According to the American National Standards Institute (ANSI), laser devices that exceed 3R limits may be hazardous and should be subject to more rigorous controls such as training, to prevent injury.**
NIST is a non-regulatory agency with decades of experience providing industry, research and military agencies with laser power measurements traceable to international standards. NIST also has a history of innovation in devices for making such measurements. Technical staff from NIST's Laser Radiometry Project built the laser pointer test bed and collaborated with the NIST Office of Safety, Health and Environment on the tests. NIST has provided its data on laser pointer power measurements to the Food and Drug Administration, which regulates laser product safety.
Green lasers generate green light from infrared light. Ideally, the device should be designed and manufactured to confine the infrared light within the laser housing. However, according to the new NIST results, more than 75 percent of the devices tested emitted infrared light in excess of the CFR limit.
NIST Laser Safety Officer Joshua Hadler designed the measurement test bed.*** The system consists of a laser power meter and two optical filters to quantify the emissions of different wavelengths of visible and infrared light. The power meter and filters were calibrated at NIST. Lens holders ensure repeatable laser alignment, and an adjustable aperture contains the laser light around the output end of the laser.
"The measurement system is designed so that anyone can build it using off-the-shelf parts for about $2,000," Hadler says. "By relying on manufacturers' traceability to a national measurement institute such as NIST, someone could use this design to accurately measure power from a laser pointer."
* J. Hadler. Random testing reveals excessive power in commercial laser pointers. Presentation at the International Laser Safety Conference, Orlando, Fla., March 20, 2013; J. Hadler, E.L. Tobares and M. Dowell. Random testing reveals excessive power in commercial laser pointers. Journal of Laser Applications. (Forthcoming.)
** American National Standard for the Safe Use of Lasers (ANSI Z136-2007) Section 1.2 and Table 1. Lasers that exceed 3R emissions limits are classified as 3B or 4.
*** J. Hadler and M. Dowell. Accurate, inexpensive testing of laser pointer power for safe operation. Measurement Science and Technology. Published online March 7, 2013.
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NIST Mechanical Micro-Drum Used as Quantum Memory
One of the oldest forms of computer memory is back again—but in a 21st century microscopic device designed by physicists at the National Institute of Standards and Technology (NIST) for possible use in a quantum computer.
The NIST team has demonstrated that information encoded as a specific point in a traveling microwave signal—the vertical and horizontal positions of a wave pattern at a certain time—can be transferred to the mechanical beat of a micro-drum and later retrieved with 65 percent efficiency, a good figure for experimental systems like this. The research is described in the March 14 issue of Nature.* "We believe the mechanical drum motion could be used as a kind of local memory for quantum information systems," NIST physicist Konrad Lehnert says. "These experiments live at the boundary between classical and quantum systems."
The technique harks back to "delay line memory" that was used in some of the earliest electronic computers, including NIST's own 1950s computer, SEAC.** Those devices were fairly simple. They temporarily stored values during computation in the form of acoustic waves traveling down a column of mercury or other fluid. By contrast, the NIST micro-drum memory would exploit a mechanical form of quantum physics.
NIST scientists introduced the micro-drum in 2011.*** The micro-drum is embedded in a resonant circuit and can beat at different frequencies. By applying microwaves at specific frequencies, researchers can achieve rapid, reliable exchanges between the circuit's electrical energy, in the form of microwave photons (light particles), and the drum's mechanical energy in the form of phonons (units of vibration).
An applied microwave tone can cool the drum down to its lowest-energy ground state, with less than one quantum of energy—the quantum regime, where the drum can store and convert quantum information. The same interaction transfers information from microwaves in the circuit to the drum, while converting the drum to a temporary state beating at the received frequencies. A key innovation in the latest experiments is the ability to rapidly switch the circuit-drum interactions on and off based on the intensity of the applied microwave tone.
The drum has certain practical advantages as a quantum storage device. Its size and fabrication method are compatible with the devices used for chip-based superconducting quantum bits (qubits), which might be used to represent information in quantum computers. The drum also can retain quantum information for about the same length of time as superconducting circuits can. Quantum computers would rely on the rules of quantum mechanics, nature's rules for the submicroscopic world, to potentially solve important problems that are intractable using today's technology.
In the latest experiments, the quantum information is stored in the amplitude (vertical position) and phase (horizontal position) of the microwave pulse, or waveform, similar to the way some cellular telephones work, Lehnert says. Although this is a classical approach, the experiments are quasi-quantum because the fluctuations, or "noise," in the measurements are quantum mechanical, Lehnert says.
In 8,000 tries, the research team was able to prepare, transfer, store and recapture information 65 percent of the time. This is a good level of efficiency given the early stage of global research on quantum memories; competing quantum memory devices include special crystals and, in nonsolid systems, atomic gases. In the future, researchers plan to combine qubits with the micro-drum, which could serve as either a quantum memory or as an interface between otherwise incompatible systems such as those operating at microwave and optical frequencies. The advance may benefit fundamental physics experiments, quantum information systems and precise force sensing.
The experiments were performed at JILA, a joint institute of NIST and the University of Colorado Boulder, and co-authors include physicists from NIST's Boulder campus. The research was supported by the Defense Advanced Research Projects Agency, the National Science Foundation and NIST.
* T.A. Palomaki, J.W. Harlow, J.D. Teufel, R.W. Simmonds and K.W. Lehnert. Coherent state transfer between itinerant microwave fields and a mechanical oscillator. Nature. Vol. 495 p. 210. March 14, 2013. doi:10.1038/nature11915.
** Read about SEAC at http://museum.nist.gov/panels/seac/seacover.htm.
*** See July 6, 2011, NIST news announcement, "Cooler Than Ever: NIST Mechanical Micro-Drum Chilled to Quantum Ground State," at www.nist.gov/pml/div686/drum-070611.cfm.
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New NIST Microscope Measures Nanomagnet Property Vital to ‘Spintronics’
Researchers at the National Institute of Standards and Technology (NIST) have developed a new microscope able to view and measure an important but elusive property of the nanoscale magnets used in an advanced, experimental form of digital memory. The new instrument already has demonstrated its utility with initial results that suggest how to limit power consumption in future computer memories.
NIST’s heterodyne magneto-optic microwave microscope, or H-MOMM, can measure collective dynamics of the electrons’ spins—the basic phenomenon behind magnetism—in individual magnets as small as 100 nanometers in diameter. Nanomagnets are central components of low-power, high-speed “spintronic” computer memory, which might soon replace conventional random-access memory. Spintronics relies on electrons behaving like bar magnets, pointing in different directions to manipulate and store data, whereas conventional electronics rely on charge.
“The measurement technique is entirely novel, the capability that it has enabled is unprecedented, and the scientific results are groundbreaking,” project leader Tom Silva says.
As described in a new paper,* NIST researchers used the H-MOMM to quantify, for the first time, the spin relaxation process—or damping—in individual nanomagnets. Spin relaxation is related to how much energy is required to switch a unit of spintronic memory between a 0 and a 1 (the bits used to represent data).
The nanomagnets used in experimental spintronic systems are too big to yield their secrets to conventional atomic physics tools yet too small for techniques used with bulk materials. Until now, researchers have been forced to measure the average damping from groups of nanomagnets. The new microscope enabled NIST researchers to study, in detail, the ups and downs of spin excitation in individual magnets made of a layer of a nickel-iron alloy on a sapphire base.
The H-MOMM combines optical and microwave techniques. Two green laser beams are merged to generate microwaves, which excite “spin waves”—magnetic oscillations that vary with position across an individual nanomagnet, like waves in a bathtub. Polarized light from one laser is used to analyze the excitation pattern. By measuring excitation as a function of magnetic field and microwave frequency, researchers can deduce the damping of various spin waves in each nanomagnet.
Measurement and control of magnetic damping is crucial for spintronics, because the smaller the damping, the less energy is required to store a bit of data, and the less power a device requires to operate. The NIST study suggests that designing spintronic devices to have uniform spin waves could dramatically reduce the energy required to write a bit.
The new microscope is one outcome of an ongoing NIST effort to develop methods for measuring defects in magnetic nanostructures. At extremely small scales, defects dominate and can disrupt magnetic device behavior, resulting in errors in reading and writing information.
* H.T. Nembach, J.M. Shaw, C.T. Boone and T.J. Silva. Mode- and size-dependent Landau-Lifshitz damping in magnetic nanostructures: Evidence for non-local damping. Physical Review Letters. 110, 117201. Published March 12, 2013.
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NIST Guides Seek Interoperability for Automated Fingerprint ID Systems
A new set of publications from the National Institute of Standards and Technology (NIST) could make it easier, faster, and most importantly, more reliable, for forensic examiners to match a set of fingerprints with those on file in any database, whether local, state or national.
Automated fingerprint identification systems (AFIS) allow forensic examiners to match latent prints—those left at a crime scene—against known (or exemplar) prints on file. Currently, forensic examiners must encode the distinctive features of a latent print into an AFIS to make this happen. If there are different identification systems involved—such as searches against prints stored at the local, state or national levels—the notation methods and data definitions may differ from one AFIS to the next. Examiners must re-encode each print for each new search on a different AFIS. This lack of latent print search interoperability impacts the ability to rapidly and accurately make positive identifications.
To address the problem, in 2008 NIST and the Department of Justice's National Institute of Justice (NIJ) convened the Latent Print AFIS Interoperability Working Group, a body made up of experts from state, local and federal law enforcement and forensic and information technology organizations. Based on one of the Working Group's recommendations, NIST's Law Enforcement Standards Office (OLES) partnered with NOBLIS, a nonprofit research corporation headquartered in Falls Church, Va., to facilitate implementation of the Extended Feature Set (EFS), a standard method for encoding fingerprint, palmprint or footprint features known as friction ridges regardless of what AFIS is used. The latest result of this partnership is the issuance of three NIST Special Publications (SP) to help forensic examiners better understand and more effectively use the EFS, and provide organizations with guidance on procuring an interoperable AFIS. These are:
NIST SP-1134—Extended Feature Set Profile Specification: This guide defines EFS Profiles, sets of reference friction ridge characteristics that let examiners "triage" their search strategies so that they are appropriate to the image quality and information content of the latent print being studied. The availability of different profiles gives examiners the flexibility to provide the AFIS with no detail (an "image only" search) all the way up to a complete input of every feature present. As a result, examiners can make effective trade-offs between encoding effort and resulting search accuracy.
NIST SP-1151—Markup Instructions for Extended Friction Ridge Features: This guide provides instructions for latent print examiners to encode a very rich set of latent ridge print information using the EFS. These instructions ensure that examiners use the same terminology, references and procedures to describe friction ridge characteristics. The common definitions are necessary for AFIS interoperability and facilitate the exchange of data between examiners.
NIST SP-1152—Latent Interoperability Transmission Specification: This guide describes the application profile language by which different AFIS can communicate with each other, define what transactions are permitted between systems, and what responses can be expected.
The EFS conforms to the ANSI/NIST-ITL 1-2011 standard* and the FBI's Electronic Biometric Transmission Specification (EBITS) .**
All three publications can be downloaded via links on the Latent Print AFIS Interoperability Working Group Web page, www.nist.gov/oles/afis_interoperability.cfm.
*Data Format for the Interchange of Fingerprint, Facial & Other Biometric Information (ANSI/NIST-ITL 1-2011) is published in NIST SP 500-290, available at www.nist.gov/customcf/get_pdf.cfm?pub_id=910136.
** Federal Bureau of Investigation Criminal Justice Information Services Electronic Biometric Transmission Specification (FBICJIS EBTS), is available at www.fbibiospecs.org/ebts.html.
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NIST Advisory Committee Issues 2012 Annual Report
The Visiting Committee on Advanced Technology (VCAT) of the National Institute of Standards and Technology (NIST) has sent its 2012 annual report to Congress.
The committee report supports NIST’s ongoing and planned work in advanced manufacturing and recognizes that NIST’s measurement science mission, its unique and longstanding relationship with industry, and its broad portfolio of programs make it a critical element of the Administration’s efforts to strengthen manufacturing in America.
The report addresses NIST’s role in support of the Public Safety Broadband Network and recognizes the need for interoperability at all levels of public safety operation. It also provides recommendations related to the proposed NIST Centers of Excellence, as well as the newly established National Cybersecurity Center of Excellence. The report endorses NIST’s new strategic planning process and emphasizes the organization’s progress in developing a positive safety culture.
The VCAT was established by Congress in 1988 to review and make recommendations on NIST's policies, organization, budget and programs to support the agency in its mission to promote and support U.S. technological innovation and industrial competitiveness. For the full text of the VCAT 2012 annual report, see www.nist.gov/director/vcat/upload/2012-VCAT-Annual-Report.pdf.
The next NIST VCAT meeting will be held June 11-12, 2013, in Gaithersburg, Md. VCAT meetings are open to the public. For more information, see www.nist.gov/director/vcat/.
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