Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition

Mateusz Jakub Śmietana , Marcin Koba , Predrag Mikulic , Wojtek J. Bock


In this work we report experimental results on optimizing the refractive index (RI) sensitivity of long-period gratings (LPGs) by fiber cladding etching and thin aluminum oxide (Al 2 O 3 ) overlay deposition. The presented LPG takes advantage of work in the dispersion turning point (DTP) regime as well as the mode transition (MT) effect for higher-order cladding modes (LP 09 and LP 010 ). The MT was obtained by depositing Al 2 O 3 overlays with single-nanometer precision using the Atomic Layer Deposition method (ALD). Etching of both the overlay and the fiber cladding was performed using hydrofluoric acid (HF). For shallow etching of the cladding, i.e., DTP observed at n ext = 1.429 and 1.439 RIU for an LPG with no overlay, followed by deposition of an overlay of up to 167 nm in thickness, HF etching allowed for post-deposition fine-tuning of the overlay thickness resulting in a significant increase in RI sensitivity mainly at the DTP of the LP 09 cladding mode. However, at an external RI (n ext) above 1.39 RIU, the DTP of LP 010 was noticed, and its RI sensitivity exceeded 9,000 nm/RIU. Deeper etching of the cladding, i.e., DTP observed for n ext above 1.45 RIU, followed by the deposition of thicker overlays (up to 201 nm in thickness) allowed the sensitivity to reach values of over 40,000 nm/RIU in a narrow RI range. Sensitivity exceeding 20,000 nm/RIU was obtained in an RI range suitable for label-free biosensing applications.
Author Mateusz Jakub Śmietana IMiO
Mateusz Jakub Śmietana,,
- The Institute of Microelectronics and Optoelectronics
, Marcin Koba - [Instytut Łączności PIB (IŁ PIB)]
Marcin Koba,,
- Instytut Łączności PIB
, Predrag Mikulic
Predrag Mikulic,,
, Wojtek J. Bock
Wojtek J. Bock,,
Journal seriesOptics Express, ISSN 1094-4087 []
Issue year2016
Publication size in sheets0.5
Keywords in EnglishGratings; Fiber optics sensors; Thin films; Biological sensing and sensors; Optical sensing and sensors; Materials and process characterization
projectx. Project leader: Śmietana Mateusz Jakub, , Phone: (22) 234 63 64, start date 20-05-2015, planned end date 19-05-2019, IMiO/2015/NCN/2, Implemented
WEiTI Projects financed by NSC [Projekty finansowane przez NCN]
Languageen angielski
Score (nominal)45
ScoreMinisterial score = 40.0, 27-03-2017, ArticleFromJournal
Ministerial score (2013-2016) = 45.0, 27-03-2017, ArticleFromJournal
Publication indicators WoS Impact Factor: 2016 = 3.307 (2) - 2016=3.436 (5)
Citation count*21 (2018-02-20)
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* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.