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Industrial Applications of Micro Lasers

Le 5 décembre 2016, 10:33 dans Technologie 0

The combination of silicon materials and light emitting semiconductor materials is expected to help develop a new micro scale laser pointer, which is studied by Keh-Ting Ng Doris and colleagues at the Data Storage A*STAR Institute.

Silicon material completely changed the form of electrical equipment manufacturing. This semiconductor rich is easy to be processed into small components, such as transistors, and method which is used can be extended to the level of manufacturing industry, which makes the production of tens of thousands of components can be integrated on a single chip. Electronic engineers want to further expand the capabilities of these integrated circuits, so that they can create, process and detect light.

These optoelectronic devices can speed up the processing speed of digital information, and can realize the micro scale laser, for example, can be used in bar code scanner. The problem, however, is that the silicon material is not an effective light generator. Ng's team has designed and produced a combination of silicon and light emitting semiconductor green laser pointer, which are indium gallium arsenic compounds (InGaAsP). "Our results show that this method can achieve a high efficiency and compact active optoelectronic device for silicon substrate, that is, using a very thin III-V family of semiconductor silicon layers," Ng said.

One of the important considerations in any laser structure is the ability to capture light within the structure, namely, the ability to capture light in order to further drive the generation of light. In conventional lasers, this is achieved by placing a mirror on any side of the light producing area. Instead, Ng and the team used a cylindrical geometry device. This will capture some of the light that is generated on the wall of the device and force it to spread within the cylinder. This is called whispering gallery mode, because the same effect will occur in a circular room, such as the dome of the cathedral in the sound wave.

The team started using a silicon substrate, they deposited a thin layer of silicon oxide. Thin film with optically active InGaAsP, only 210 nm thick, is individually made, and then bonded to silicon oxide. Then, the team through a number of materials to create the cylinder, with two or three microns in diameter. Three micron devices emit a 30mw laser pointer light at a wavelength of 1519 nm, which is very close to the wavelength used in commercial optical communication systems.

This device has a unique feature that extends the whispering gallery mode to the silicon and InGaAsP regions. InGaAsP can provide light amplification, and silicon can be passive guide light. "The next step, we want to apply these ideas to the devices at room temperature," Ng said. "Operation at higher temperatures will require adjustments to the design and fabrication of the laser."

Wind - measuring Lidar

Le 16 novembre 2016, 12:24 dans Humeurs 0

University of Science & Technology China professor Dou Xiankang research group Xia Haiyun and academician China Academy of Sciences Research Group Pan Jianwei Zhang Qiang, after three years of cooperation, for the first time in the world developed single photon frequency upconversion quantum high power laser pointer radar, the aerosol and atmospheric boundary layer wind field day and night continuous observation, made a series of achievements in the International Journal of optical Optics Letters Optics and Express.

Accurate atmospheric wind field detection is of great significance for numerical weather prediction, climate model improvement, military environment prediction, biochemical gas monitoring, airport wind shear warning and so on. Doppler laser radar is recognized as the best method for remote sensing of atmospheric wind field is global, the World Meteorological Organization listed as one of the most challenging of burning laser pen radar. Researchers can monitor the atmospheric aerosol and wind field, not only to monitor the state of atmospheric pollution, real-time atmospheric pollution sources, but also to predict the formation and evolution of haze.

The primary prerequisite for the application of laser radar is the safety of the human eye. In 2007, the National Center for atmospheric research has reported the work of the human eye safe laser radar with a wavelength of 1.55 microns. The near infrared wavelength single photon energy is only 1.28 * 10-19 Joule, Doppler frequency and relative quantum lidar to detect single photons of 6.67 x 10-10 shift, can achieve 0.1 meters / second precision radial velocity measurement. The traditional view is that only to improve the output power of the 2000mw laser pointer radar and increase the area of the telescope, to improve the laser radar detection signal to noise ratio. Due to the low efficiency and high noise of the laser radar, the laser pulse energy is 0.125 J, and the telescope is 0.4 meters in diameter, which leads to complex structure, several tons of weight and large power consumption. Due to the limitation of the optical damage threshold and the processing technology of the large aperture telescope, the performance of the traditional laser radar has reached its peak.

April 2015, China, the first time to achieve a single photon frequency conversion of aerosol laser radar. The use of periodically poled lithium niobate waveguide developed, the radar receiving 1.55 micron and 2 micron continuous single photon pumping and frequency, to produce 0.863 micron photon detection using silicon detector. At this point, the quantum efficiency of up to 55%, dark noise only 16 / sec. Compared with the current indium gallium arsenic detector which is used in the direct detection of 1.55 micron photon (quantum efficiency 10%, dark noise 5000 / sec), the detection efficiency is improved, and the system noise is reduced. This method immediately aroused the attention of the German Aerospace Bureau, Technical University of Denmark, Belarus National University and other peer, in March 2016 using the same technology to achieve atmospheric carbon dioxide detection.

In August 2016, China, using all fiber polarization discriminator of single photon frequency shift was measured by weak light source (laser pulse energy of 5 x 10-5 joule), small caliber telescope (0.08 m diameter) for the first time in the world to achieve the detection of the atmospheric boundary layer wind field. In November 2016, using time division multiplexing, China, reports the current highest integrated quantum 500mw laser pointer radar, not only simplifies the system structure, but also improves the stability and reliability of the system, and from periodic calibration.

By improving the quantum efficiency (photoelectric conversion efficiency) and optical integration (optical system efficiency), suppression detection noise, realize all fiber laser radar system and partial structure of continuous observation, day and night light and small vibration, low power consumption, room temperature operation, suitable for operation in airborne, Shipborne Satellite, etc. the platform under harsh environment. This technique provides a new idea for the small satellite borne 50mw laser pointer radar, which lays the foundation for the popularization of high performance price ratio, high stability and miniaturization.

Fiber Laser Sensor

Le 15 novembre 2016, 08:03 dans Humeurs 0

Dr Geoffrey Cranch, a research physicist at the Department of Optics at the US Naval Research Laboratory (NRL), says there is currently no US military service that uses in situ technology to manage the structural health of its equipment. "An automated, in-situ structural health monitoring (SHM) system can monitor critical structural parameters such as temperature, strain, shock and crack, and can reliably detect damage before the damage reaches a critical level," he said. A sensor for detecting the acoustic emission signal associated with the occurrence and growth of the crack in near real time. Such sensors must be smaller than existing electronic products lighter, the sensitivity of a considerable or improved, smaller.

By the US Department of Naval Research Materials Science to provide part of the investment, NRL is developing a 100mw laser pointer sensor, width is about hair width. During the test, the researchers installed a distributed feedback fiber laser acousto-optic sensor in a set of aluminum rivets and measured a 0.5-MHz bandwidth acoustic emission signal generated in a two-hour accelerated fatigue test, using an equivalent Of the electrical sensors.

Embedded sensors are used to solve the acoustic event of periodic "surface abrasion" of the rivet and acoustic emission from the crack information. The time-lapse imaging of the lap will allow the observed fracture to be correlated with the measured signal. In addition to crack detection, the fiber laser sensor also demonstrates the ability to measure the impact of damage and has the potential to integrate with existing fiber strain and temperature sensing systems. This provides a multi-parameter sensing capability to meet the security requirements of the SHM system and significantly reduces total cost of ownership.

"Our research team has demonstrated that the fiber 50mw laser pointer technology is capable of detecting ultrasonic AE emissions from cracks in a simulated fatigue environment. A new part of this work is fiber laser technology and how it can be applied." Sound signals from the crack can also be used Piezoelectric sensors, which have driven the existing failure prediction work. However, Cranch said piezoelectric technology because of its large geometric size and multi-channel capacity of cable, in many applications is not practical.

Cranch believes the technology has great potential in areas beyond the military, where he focuses on naval platforms such as airplanes, ships and submarines, but the technology can also be used in civil aircraft as well as in bridges and buildings. At present, no other fiber-optic sensor can match the fiber laser acoustical emission sensor in the laboratory to achieve performance. Fiber laser sensors have demonstrated comparable acoustic sensitivity to existing electrical sensors, or even higher. The system has been able to integrate multiple fiber blue laser pointer sensors into a bundle of fibers. The present work is explaining useful data for acoustic emission data to calculate failure probabilities.

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