Reduction in Crosstalk Using Uniform Germanium Strips for Dense Integration of Photonic Waveguides

Veer Chandra,Dablu Kumar,Rakesh Ranjan

doi:10.1007/s12633-021-01500-x

Abstract

The requirement of low crosstalk between the neighboring waveguides should be considered essentially, in order to achieve the compact photonic integrated circuit (PIC), which includes photonic waveguides. Literature shows that the lower crosstalk can be realized by using the silicon-on-insulator (SOI) based waveguide, having an appropriate separation between them. The current work is focused on reducing the waveguide separation to further improve the photonic integration over the PICs. This has been achieved by inserting the germanium strips between the photonic waveguides. The investigations of the impact of variations in heights and widths of germanium strip have demonstrated that the crosstalk can be reduced by a significant amount, which provides noteworthy improvement in coupling length. The maximum coupling lengths of 81,578 μm, 67,099 μm, and 66,810 μm have been achieved at their respective end-to-end separations of 300 nm, 250 nm, and 200 nm, and their corresponding minimum crosstalk values have been noted as −29.40 dB, −27.71 dB, and − 27.70 dB. Moreover, the analysis to realize the coupling length for Ge-strip, have been compared with the Si-, and Si3N4-strips. The approach presented in the current work can be utilized for the design of many compact photonic applications, such as polarization splitter, integrated photonic switches, etc.

Highlights

Photonic waveguides and its related devices are attracting more and more attention due to its high bandwidth capabilities, very less propagation delay time, and smaller size
For g1 = 200 nm, the corresponding maximum values of coupling lengths for Si-strip are 216 μm, and 302 μm, and the same for SiN-strip are 74 μm, and 73 μm, at their respective w2 = 30 nm, and 50 nm. These analyses clearly show that the coupling lengths for Gestrip have very high values, as compared that with Si/SiN strips
The proposed approach of introducing uniform Ge-strips, can be utilized as a promising approach to suppress the crosstalk between two adjacent photonic waveguides, and to achieve the dense photonic integration over the photonic integrated circuit (PIC)

Summary

Introduction

Photonic waveguides and its related devices are attracting more and more attention due to its high bandwidth capabilities, very less propagation delay time, and smaller size. The authors in [7] have presented the approach of subwavelength silicon gratings technique for the photonic waveguide, to control the guided light in PICs, and to reduce the crosstalk. The silicon gratings show the high index, in the direction parallel to the interface This leads to the fast decay of evanescent field, which is leaked from the waveguide core. Following this principle, the investigations of the three subwavelength strips between the two adjacent waveguides have been done in [8], to improve the crosstalk performance. With lower waveguide spacing of 200 μm, the coupling length up to 66810 μm has been obtained, which demonstrates very low crosstalk, and dense photonic integration over the PICs

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Discussion

Conclusion