Posted: March 20, 2009 |
Shifting sound to light may lead to better computer chips |
(Nanowerk News) By reversing a process that converts electrical signals into sounds heard out of a cell phone, researchers may have a new tool to enhance the way computer chips, LEDs and transistors are built.
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Lawrence Livermore National Laboratory scientists have for the first time converted the highest frequency sounds into light by reversing a process that converts electrical signals to sound.
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Commonly used piezo-electric speakers, such as those found in a cell phone, operate at low frequencies that human ears can hear.
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A plasma is generated by a laser pulse similar to how sound is converted to light
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But by reversing that process, lead researchers Michael Armstrong, Evan Reed and Mike Howard, LLNL colleagues, and collaborators from Los Alamos National Laboratory and Nitronex Corp., used a very high frequency sound wave - about 100 million times higher frequency than what humans can hear - to generate light.
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“This process allows us to very accurately ‘see’ the highest frequency sound waves by translating them into light,” Armstrong said.
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The research appears in the March 15 edition of the journal Nature Physics.
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During the last decade, pioneering experiments using sub-picosecond lasers have demonstrated the generation and detection of acoustic and shock waves in materials with terahertz (THz) frequencies. These very same experiments led to a new technique for probing the structure of semiconductor devices.
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However, the recent research takes those initial experiments a step further by reversing the process, converting high-frequency sound waves into electricity. The researchers predicted that high frequency acoustic waves can be detected by seeing radiation emitted when the acoustic wave passes an interface between piezoelectric materials.
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Very high-frequency sound waves have wavelengths approaching the atomic-length scale. Detection of these waves is challenging, but they are useful for probing materials on very small length scales.
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But that’s not the only application, according to Reed.
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“This technique provides a new pathway to generation of THz radiation for security, medical and other purposes,” he said. “In this application, we would utilize acoustic-based technologies to generate THz.” Security applications include explosives detection and medical use may include detection of skin cancer.
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And the Livermore method doesn’t require any external source to detect the acoustic waves.
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“Usually scientists use an external laser beam that bounces off the acoustic wave – much like radar speed detectors – to observe high frequency sound. An advantage of our technique is that it doesn’t require an external laser beam – the acoustic wave itself emits light that we detect,” Armstrong said.
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