1 March 2006 Silicon-nanocrystal-coated silica microsphere thermo-optical switch
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We report the development of a novel low energy optical switch that consists of a silica microsphere optical resonator coated with a layer of silicon nanocrystals. A 150 μm-diameter silica microsphere was coated with a 140 nm thick layer of silicon rich silicon oxide (SRSO) by PECVD. The microsphere/SRSO was annealed in argon at 1100C to facilitate nanocrystal growth. The optical properties of the microsphere were characterized by evanescently coupling 1450 μm tunable laser light through a tapered optical fiber into the whispering gallery mode resonances of the microsphere. A quality factor of 3×105 was measured at this wavelength. Light from an Ar+ laser at 488 nm was introduced into the tapered fiber and was used to excite the nanocrystals near the whispering gallery modes (WGM) of the sphere. WGM resonance wavelengths shifts of 5 pm at an operating wavelength of 1450 nm were observed when the Ar+ light was coupled into the tapered fiber. Powers as low as 3 μW were sufficient to shift the resonance by a half a linewidth and cause full switching of the 1450 nm signal with a fast rise time (which was limited by the time width of the laser pulse). The speed of the switch is limited by the fall time, which has a time constant of 30 ms.
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Anuranjita Tewary, Michel J. F. Digonnet, Mark L. Brongersma, Joo-Yeon Sung, Jung H. Shin, "Silicon-nanocrystal-coated silica microsphere thermo-optical switch", Proc. SPIE 6125, Silicon Photonics, 61250U (1 March 2006); doi: 10.1117/12.669392; https://doi.org/10.1117/12.669392

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