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Free-carrier detection in a silicon slab via absorption measurement in 2D integrating cells
Publikationstyp
Journal Article
Date Issued
2019-01-01
Sprache
English
TORE-URI
Journal
Volume
44
Issue
1
Start Page
175
End Page
178
Citation
Optics Letters 1 (44): 175-178 (2019-01-01)
Publisher DOI
Scopus ID
© 2018 Optical Society of America. 2D integrating cells provide long optical path lengths on a chip by multiple reflections at highly reflective mirrors similar to integrating spheres in free space. Therefore, they build a promising platform for integrated optical absorption sensing. Here, we present first absorption measurements of free carriers generated by a modulated pump laser inside a 2D integrating cell in a silicon slab. The results can be used to evaluate the lifetimes of free carriers in silicon slabs for integrated optics. Employing a silicon-on-insulator platform with a silicon thickness of 220 nm, we demonstrate measurements of the access free-carrier concentration on the order of 1 − 8 · 10 15 cm −3 with lifetimes on the order of 0.1–1 μs governed by surface recombination at the silicon interfaces. The measured lifetimes are dependent on free-carrier concentration, which confirms previous observations. The presented free-carrier absorption experiment verifies the sensitivity of 2D integrating cells to changes in the absorption coefficient and thus demonstrates the potential of 2D integrating cells for absorption sensing.