Abstract
A polarization-insensitive phase modulator concept is presented, based on an embedded silicon-graphene-silicon waveguide. Simulation results show that the effective mode index of both transverse electric (TE) and transverse magnetic (TM) modes in the silicon-graphene-silicon waveguide undergoes almost the same variations under different biases across a broad wavelength range, in which the real-part difference is less than 1.2 × 10−3. Based on that, a polarization-insensitive phase modulator is demonstrated, with a 3-dB modulation bandwidth of 135.6 GHz and a wavelength range of over 500 nm. Moreover, it has a compact size of 60 μm, and a low insertion loss of 2.12 dB. The proposed polarization-insensitive waveguide structure could be also applied to Mach-Zehnder modulators and electro-absorption modulators.
Highlights
Electro-optic phase modulators (PMs) have been widely and intensively investigated for their applications in advanced optical communication systems, thanks to their intrinsically bias-free and linear modulation properties [1,2,3]
Several methods have been proposed for realizing polarization-insensitive modulators by using, for example, electrode sets [4,5,6], bidirectional modulation [7,8,9,10], or tensile strained quantum wells [11,12,13]
The bidirectional modulation method is based on bidirectional phase modulation for the transverse electric (TE) and transverse magnetic (TM) modes through a Sagnac loop, which overcomes the intrinsic polarization dependence of silicon photonic modulators [8]
Summary
Electro-optic phase modulators (PMs) have been widely and intensively investigated for their applications in advanced optical communication systems, thanks to their intrinsically bias-free and linear modulation properties [1,2,3]. Several methods have been proposed for realizing polarization-insensitive modulators by using, for example, electrode sets [4,5,6], bidirectional modulation [7,8,9,10], or tensile strained quantum wells [11,12,13]. The most effective method is to introduce two independent electrode sets for the desired transverse electric (TE) and transverse magnetic (TM) polarizations This method leads to have long waveguides and large operating voltages, limited by the small change in the refractive index change of common electrooptic crystals [5], which is not efficient for high-speed modulation [7]. Polarization-insensitive PMs with large bandwidth, low insertion loss, and compact size, are of great interest. The proposed PM has a compact size and low insertion loss
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