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RISS 인기검색어
- 검색키워드
- 저자 : Digonnet, Michel J. F. (검색결과 2 건)
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Silicon-Nanocrystal-Coated Silica Microsphere Thermooptical Switch
Tewary, Anuranjita,Digonnet, Michel J. F.,Sung, Joo-Yeon,Shin, Jung H.,Brongersma, Mark L. IEEE 2006 IEEE journal on selected topics in quantum electro Vol.12 No.6
<P>We report on a low-switching-energy, all-optical fiber switch that consists of a silica microsphere resonator coated with a silica layer containing silicon nanocrystals. A signal at 1450 nm and a pump at 488 nm are coupled into the microsphere through a tapered fiber. When a pump pulse is launched into the sphere, it is absorbed by the nanocrystal layer, causing the sphere to heat up and change its refractive index. The index change can be exploited to switch the signal by shifting the microsphere resonance. A resonance wavelength shift of 5 pm, sufficient to fully switch the signal, was observed with a pump pulse energy of only 85 nJ. The rise time of the switch was ~25 ms (limited by the pump peak power) and its fall time was ~30 ms (limited by the sphere's thermal time constant). The product of the switching peak power (3.4 mu W) and the device's characteristic dimension (a diameter of 150 mum) is 5.1times10<SUP>-10</SUP> Wm, one of the lowest values reported for an all-optical fiber switch</P>
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Optically Managing Thermal Energy in High-power Yb-doped Fiber Lasers and Amplifiers: A Brief Review
Nanjie Yu,John Ballato,Michel J. F. Digonnet,Peter D. Dragic 한국광학회 2022 Current Optics and Photonics Vol.6 No.6
Fiber lasers have made remarkable progress over the past three decades, and they now serve farreaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.
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