WORLDS SMALLEST EAR

Have you ever wondered what a virus sounds like? Or what noise a bacterium makes when it moves between hosts? If the answer is yes, you may soon get your chance to find out, thanks to the development of the world’s tiniest ear. The “nano-ear,” a microscopic particle of gold trapped by a laser beam, can detect sound a million times fainter than the threshold for human hearing. Researchers suggest the work could open up a whole new field of “acoustic microscopy,” in which organisms are studied using the sound they emit.

U.S. Navy Laser Weapon

PHALANX WITH LASER CANNON: An artist’s rendering of a weapon featuring a laser cannon and Gatling gun side by side on a naval vessel, with the laser shooting down a UAV.Image: © RAYTHEON CO.

In a grainy, black-and-white video that looks like a home movie of a UFO attack a sleek aircraft streaks through the sky one minute, only to burst into flames the next and plummet into the sea.

The silent video, which Raytheon Co. debuts Monday at the U.K.’s Farnborough International Air Show 2010, however, is not science fiction. The defense contractor says it depicts part of a test conducted in May during which the U.S. Navy used a  solid-state laser to shoot down unmanned aerial vehicles over the Pacific Ocean.

During the test, the Navy’s Laser Weapon System (LaWS), guided by Raytheon’s Phalanx Close-In Weapon System sensors, engaged and destroyed four UAV targets flying over water near the Navy’s weapons and training facility on  San Nicolas Island in California’s Santa Barbara Channel, about 120 kilometers west of Los Angeles. The Phalanx—a rapid-fire, computer-controlled, radar-guided gun system—used electro-optical tracking and radio frequency sensors to provide range data to the LaWS, which is made up of six solid-state lasers with an output of 32 kilowatts that simultaneously focus on a target.

The maritime UAV target practice session could be a significant step in a decades-long quest undertaken by the U.S. military and several defense contractors to bring lasers to the battlefield. Raytheon’s latest test follows related experiments in 2006 and 2008. In the former, Raytheon used a solid-state laser to destroy a static mortar, whereas in the latter, the laser blew up an incoming mortar shell over land.

Knocking down drones over water is a different matter though. The effect of the moist maritime environment on a laser’s ability to propagate has been a nagging question for the technology, says Mike Booen, vice president of Raytheon’s Advanced Security and Directed Energy Systems product line. Now that the laser-enhanced Phalanx has demonstrated the ability to find and hit incoming UAVs, the weapon will be installed on an operational Navy test ship for additional testing, he adds. Still, even if the laser system continues to test successfully, such a weapon would not be fully developed for combat before 2016, according to Booen.

The U.S. military has used Phalanx for decades to shoot down mortars and rockets. The weapon combines a 20-millimeter  Gatling gun that fires at a rate of either 3,000 or 4,500 shots per minute, with radar to search for and track targets. The U.S. Navy has used a land-based version of Phalanx in Iraq since 2005. Mounting a laser cannon beside the Gatling gun should extend the range at which incoming ordinance and UAVs can be eliminated. Although Booen says that for security reasons he cannot divulge the distance at which the laser-based systems can shoot down incoming threats (or the UAVs’ altitudes during the Navy test), he notes that the military would not be interested in the new laser technology if it could not at least double the range of existing weapons.

A UAV’s altitude depends largely on its design and its mission. Hand-launched unmanned aircraft systems made by AeroVironment, Inc., for example, typically operate at altitudes below 150 meters but are able to fly much higher, according to Steve Gitlin, a spokesman for the Monrovia, Calif.–based company. “[Altitude] is largely driven by the resolution of their imaging sensors,” he adds. Larger aircraft that AeroVironment and others are developing are expected to be able to operate at upward of 16.5 kilometers.

Much of what the public knows about UAVs comes from news reports describing how the U.S. and its allies use drones to attack enemy fighters as well as incidents where civilians have been killed by unmanned aircraft. Booen points out, however, that enemies of the U.S. and its allies are also using UAVs either to attack troops or to track troop movements. Iran reportedly has been doing this for years.

In addition to Raytheon’s work, fellow defense contractor Northrop Grumman plans to test its solid-state Maritime Laser Demonstration (MLD) system with the Navy by the end of the year. For the at-sea demonstration, Northrop will power its laser up to 15 kilowatts in order to defend against simulated attacks of a Navy ship by smaller boats. A relatively low-power laser beam could set alight wood or fiberglass hulls, fuel or vulnerable weapons from stand-off distances of a kilometer or more, according to a May 14 Scientific American article.

Navy planners are interested in using lasers in to help naval vessels fend off potential attacks by squadrons of small boats, citing an incident that occurred in early 2008 in the Strait of Hormuz (a waterway connecting the Gulf of Oman and Persian Gulf). “The MLD system we are under contract to build for [the U.S. Office of Naval Research] will be scalable to a variety of power levels,” according to Northrop spokesman Bob Bishop. “That means that laser power can be added—or subtracted—to meet the level of response necessary to address the threat, all within the same modular laser weapon system.”

The military hopes that, in addition to extending the range of their weapons, lasers will also improve targeting precision. Another advantage, Booen says, is that lasers require electricity rather than ordinance. As long as there is current, the weapon will not run out of ammo.

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Hari Hara Sravan( MGIT ECE 2nd year)

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Lasers Used to Form 3-D Crystals Made of Nanoparticle

The technique could someday be used to analyze the structure of materials of biological interest, including bacteria, viruses and proteins, said U-M physicist Georg Raithel.

Raithel is co-author of a research paper on the topic published online May 31 in the journal Physical Review E. The other author is U-M research fellow Betty Slama-Eliau.

The standard method used to characterize biological molecules like proteins involves crystallizing them, then analyzing their structure by bombarding the crystals with X-rays, a technique called X-ray crystallography. But the method cannot be used on many of the proteins of highest interest — such as cell-membrane proteins — because there’s no way to crystallize those molecules.

“So we came up with this idea that one could use, instead of a conventional crystal, an optically induced crystal in order to get the crystallization of a sample that could be suitable for structural analysis,” said Raithel, professor of physics and associate chair of the department.

To move toward that goal, Raithel and his colleagues are developing the laser technique using microscopically small plastic spheres instead of the molecules. Other researchers have created 3-D optically induced crystals, but Raithel said the crystals his team created are denser than those previously achieved.

The process involves shining laser beams through two opposed microscope lenses, one directly beneath the other. Two infrared laser beams are directed through each lens, and they meet at a common focal point on a microscope slide that holds thousands of plastic nanoparticles suspended in a drop of water.

 

The intersecting laser beams create electric fields that vary in strength in a regular pattern that forms a 3-D grid called an optical lattice. The nanoparticles get sucked into regions of high electric-field strength, and thousands of them align to form optically induced crystals. The crystals are spherical in shape and about 5 microns in diameter. A micron is one millionth of a meter.

Imagine an egg crate containing hundreds of eggs. The cardboard structure of the crate is the optical lattice, and each of the eggs represents one of the nanoparticles. Stack several crates on top of each other and you get a 3-D crystal structure.

“The crate is the equivalent of the optical lattice that the laser beams make,” Raithel said. “The structure of the crystal is determined by the egg carton, not by the eggs.”

The optical crystals dissipate as soon as the laser is switched off.

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Jyothsna (MGIT ECE 4th year)

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