Capability for Fine Tuning of the Refractive Index Sensing Properties of Long-Period Gratings by Atomic Layer Deposited Al2O3 Overlays

Sensors

Mateusz Śmietana¹  Marcin Myśliwiec¹  Predrag Mikulic³  Bartłomiej S. Witkowski² 

[1] Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, Warsaw 00-662, Poland; E-Mail:;Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw 02-666, Poland; E-Mail:;Centre de Recherche en Photonique, Université du Québec en Outaouais, 101 rue Saint-Jean-Bosco, Gatineau, QC J8X 3X7, Canada; E-Mails:

关键词: optical fiber sensors;    refractive index sensor;    long-period gratings (LPG);    Atomic Layer Deposition (ALD);    thin films;    optical properties;    aluminum oxide (Al₂O₃);   

DOI  :  10.3390/s131216372

来源: mdpi

【 摘 要 】

This work presents an application of thin aluminum oxide (Al₂O₃) films obtained using atomic layer deposition (ALD) for fine tuning the spectral response and refractive-index (RI) sensitivity of long-period gratings (LPGs) induced in optical fibers. The technique allows for an efficient and well controlled deposition at monolayer level (resolution ∼ 0.12 nm) of excellent quality nano-films as required for optical sensors. The effect of Al₂O₃ deposition on the spectral properties of the LPGs is demonstrated experimentally and numerically. We correlated both the increase in Al₂O₃ thickness and changes in optical properties of the film with the shift of the LPG resonance wavelength and proved that similar films are deposited on fibers and oxidized silicon reference samples in the same process run. Since the thin overlay effectively changes the distribution of the cladding modes and thus also tunes the device's RI sensitivity, the tuning can be simply realized by varying number of cycles, which is proportional to thickness of the high-refractive-index (n > 1.6 in infrared spectral range) Al₂O₃ film. The advantage of this approach is the precision in determining the film properties resulting in RI sensitivity of the LPGs. To the best of our knowledge, this is the first time that an ultra-precise method for overlay deposition has been applied on LPGs for RI tuning purposes and the results have been compared with numerical simulations based on LP mode approximation.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.