https://doi.org/10.1140/epjst/e2014-02242-7
Regular Article
Elastic scattering from a sapphire microsphere placed on a silica optical fiber coupler: Possible applications to biosensing
1 Institute for Materials Research, Hasselt University, IMO, Wetenschapspark 1, Diepenbeek 3590, Belgium
2 KoçUniversity, Microphotonics Research Laboratory, Department of Physics, Rumelifeneri Yolu, Sarıyer, Istanbul 34450, Turkey
3 Currently at Intel Corporation, Silicon Photonics Systems Group, Santa Clara, CA 95054, USA
4 Currently at JDSU Corporation, 80 Rose Orchard Way, San Jose, CA 95134, USA
5 Currently at Tübitak Bilgem, Informatics and Information Security Research Center, Gebze, Kocaeli 41470, Turkey
6 Currently at Omnibil Teknoloji, Tercüman Yunus Sokak 31/6, Fatih, Istanbul 34087, Turkey
7 Currently at Teknofil Limited, Vişne 2 Mahallesi, 3. Cadde, Market Blok No. 8, Zekeriyaköy, Sarıyer, Istanbul 34450, Turkey
a e-mail: aserpenguzel@ku.edu.tr
Received: 9 June 2014
Revised: 4 August 2014
Published online: 6 October 2014
Elastic light scattering is performed in the original band of optical fiber communication at 1300 nm for a 500 μm sapphire microsphere placed on a silica optical fiber half coupler. The morphology dependent resonances (MDRs) are observed in the transverse magnetically (TM) polarized and transverse electrically (TE) polarized 0∘ transmission and 90∘ elastic scattering obtained from the sapphire microsphere. The TE and TM MDRs can be detected selectively with the use of a Glan polarizer. The TE and TM polarization selectivity provides the ability to select relative MDR to BG levels. The TM polarization provides higher MDR signal to background ratio (SBR) and is suitable for optical monitoring, biological sensing or any other optoelectronic application that requires a high resolution optical filter. The polar angular mode spacing of 0.36 nm of the resonances correlates well with the optical size of the sapphire microsphere. The autocorrelation of the 90∘ elastic scattering spectra also shows peaks at 0.36 nm. The spectral linewidths of the resonances are on the order of 0.1 nm, which corresponds to quality factors on the order of 104. A sapphire sphere with a radius of 500 μm and relative refractive index of 1.31, resonances will red-shift by 1.01 nm (0.077%). This shift is on the order of 10 linewidths, making sapphire biophotonic sensors an interesting alternative to silica biophotonic sensors.
© EDP Sciences, Springer-Verlag, 2014
