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Proceedings Paper

Comparison of different types of MMI-resonators fabricated on a micron-scale SOI platform
Author(s): Matteo Cherchi; Mikko Harjanne; Sami Ylinen; Markku Kapulainen; Tapani Vehmas; Timo Aalto
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Paper Abstract

1x1 optical resonators have been designed based on multi-mode interference (MMI) splitters of different splitting ratios (85:25 and 73:27) and different types of back-reflectors as feedback mechanism. They are basically 2x2 MMIs of uneven splitting ratios with one of the ports from both sides ending in a reflector. The chosen reflectors include metal-dielectric mirrors, waveguide loops and MMI reflectors. The remaining two ports play the role of input and thru port respectively. The resonant wavelengths are reflected back in the input port, hence acting also as output port in reflection. The devices have been fabricated on SOI wafers with a 3 μm-thick silicon layer. In all cases, the quality factors of the resonances of a given resonator have been found to significantly change form peak to peak. This can be attributed to wavelength dependent losses in the feedback mechanisms, that is wavelength dependent reflectivity of the back-reflectors. Through a suitable transfer matrix model, we have found that best performing devices correspond to reflectivity as high as 92% for the metal/dielectric mirrors and 88% for the MMI reflectors, corresponding to a resonator finesse of 13.1 and 9.9 respectively. The free spectral ranges of the resonators vary from about 3 nm to about 1 nm, depending on the cavity length, which is constrained by the lengths of both the MMIs and the reflectors. When suitably combined with gain elements, the proposed resonators are promising candidates as fabrication tolerant wavelength selective reflectors for external cavity lasers.

Paper Details

Date Published: 27 February 2015
PDF: 9 pages
Proc. SPIE 9367, Silicon Photonics X, 936713 (27 February 2015); doi: 10.1117/12.2079606
Show Author Affiliations
Matteo Cherchi, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Mikko Harjanne, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Sami Ylinen, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Markku Kapulainen, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Tapani Vehmas, VTT Technical Research Ctr. of Finland Ltd. (Finland)
Timo Aalto, VTT Technical Research Ctr. of Finland Ltd. (Finland)

Published in SPIE Proceedings Vol. 9367:
Silicon Photonics X
Graham T. Reed; Michael R. Watts, Editor(s)

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