Ultra-fast Mode Switching on Ge-Sb-Te Cored Optical
Fibers
Duc Minh Nguyen 1,2 , Behrad Gholipour 1 , Long Cui 1 and Cesare Soci 1,2
csoci@ntu.edu.sg
1 Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371
2 CINTRA CNRS/NTU/THALES, UMI 3288, Singapore 637553
Abstract
: We present a new concept of an ultra-fast optical mode switch using phase change materials cored optical fibers that can be triggered thermally by optical pulses to switch between single-mode and multimode operation at telecommunication wavelength.
1. Introduction
• Limit of data-carrying capacity on single-mode-fiber-based transmission systems can be overcome by the use of space-division multiplexing (SDM) on multi-core fibers or few-modefibers.
• Phase-change materials (PCMs), which typically consist of chalcogenide elements, such as Ge-
Sb-Te (GST) have drawn large interests due to switchable optical properties [1,2].
• We report a spatial mode modulator based on GST cored step index optical fibers that can modulate actively spatial modes in a few-mode-fiber on nanosecond and sub-nanosecond time scale.
2. Principle and modelling
• GST cored fibers will become a monomode/multimode switch, if the core diameter is designed around the cut-off condition at the amorphous state due to large shift of refractive index (
n~2.5 for GST at 1.5
m) when changing between amorphous and crystalline states.
• In our work, the core diameter of 400 nm is designed at the amorphous cut-off condition, and optical pulses are illuminated from the fiber side to induce phase change within the nano-core to switch the fiber between different modal states.
• Because the refractive index n of amorphous GST is around 2 at 1.5 um, only a small shift of n
(~0.1) is required to switch the fiber to multimode operation. The reversible phase change of
GST can occur at sub-nanosecond time scale and thus allow an ultrafast modulation of the core refractive index and the excited optical modes.
GLSO cored fiber
3. Conclusions:
We present a new concept of optical mode switching realized by implementing phase change materials into the fiber core. This paves the way to different optical fiber designs using PCMs that can be extended to mode selection and sensing applications.
References:
[1] B. Gholipour et al., Adv. Mater. 25 (22), (2013)
3050 − 3054.
[2] A-K. U. Michel et al., Nano. Lett. 13 (2013)
3470-3475.
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