[OPTICAL REVIEW Vol. 20, No. 4 (2013) 327-331]
© 2013 The Japan Society of Applied Physics

Dynamic Control of Mode Field Diameter and Effective Area by Germanium Doping of Hexagonal Photonic Crystal Fibers

Kazuya MIYAGI1*, Yoshinori NAMIHIRA1, Yuho KASAMATSU2, and Md. Anwar HOSSAIN2

1Electrical and Electronics Engineering, Faculty of Engineering, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
2Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan

(Received March 1, 2013; Accepted April 12, 2013)

We demonstrate dynamic control of the effective area (Aeff) of photonic crystal fibers (PCFs) in the range of 18.1–8.22 μm2 and the mode field diameter in the range of 4.78–3.42 μm. This control was realized by altering their structural properties and varying the germanium (Ge) doping rate, which changed the refractive index difference (Δ nGe) between 1.0 and 3.0% relative to the refractive index of the silica cladding. This was achieved by adjusting the Ge doping rate in the core and changing the radius (dcore) of the doped region, i.e., by changing the equivalent refractive index, using numerical calculations. Numerical results were verified by comparison with experimental results for a fabricated Ge-doped PCF obtained by far-field scanning based on the ITU-T Petermann II definition. The proposed approach will simultaneously decrease Aeff and achieves high light confinement and high nonlinearity in PCFs. It enables architectonics/controllability of highly nonlinear PCFs with passive optical devices in photonic networks and life science applications.

Key words: photonic crystal fiber (PCF), mode field diameter (MFD), effective area (Aeff), confinement loss (Lc), nonlinear constant (n2/Aeff)

*E-mail address: miyagi@eee.u-ryukyu.ac.jp