Abstract
Transmission of the fundamental mode in multi-mode waveguides is an effective scheme for a silicon-based platform to reduce scattering loss. However, the application of the scheme is usually limited to straight waveguides and restricted in multi-mode bending waveguides. This is because the fundamental mode of a straight waveguide is seriously disordered after passing the bend. In this work, we have presented a “matched bending radius” approach, by which an ultra-low loss and negligible modal disorder have been demonstrated in the Si and Si3N4 multi-mode waveguides. The estimated TE0 mode transmission factor is almost 0 dB at the matched bending radius, indicating that the fundamental mode can be re-generated after passing the multi-mode bending waveguide. The proposed approach will contribute to applying the low loss scheme in large-scale photonic integrated circuits.
Highlights
Photonic integrated circuits (PICs) have been remarkably successful in supporting the explosive growth of information technology over the past decades(Luo et al 2014)
In order to minimize the modal interaction with the sidewalls, it has been shown that low propagation loss can be achieved by propagating the fundamental mode in a large size multi-mode waveguide(Frigg et al 2019)
To overcome the model distortion, some methods have been suggested, mainly including using a deliberately designed Euler bending(Vogelbacher et al 2019), curving a straight multi-mode waveguide 90° bend based on transformation optics and etching a subwavelength grating in the bent section [15-17](Gabrielli et al 2012; Xu,Shi 2018; Wu et al 2019)
Summary
Photonic integrated circuits (PICs) have been remarkably successful in supporting the explosive growth of information technology over the past decades(Luo et al 2014). Serious model distortion may restrict the applications of the above low loss scheme in PICs. To overcome the model distortion, some methods have been suggested, mainly including using a deliberately designed Euler bending(Vogelbacher et al 2019), curving a straight multi-mode waveguide 90° bend based on transformation optics and etching a subwavelength grating in the bent section [15-17](Gabrielli et al 2012; Xu,Shi 2018; Wu et al 2019). To overcome the model distortion, some methods have been suggested, mainly including using a deliberately designed Euler bending(Vogelbacher et al 2019), curving a straight multi-mode waveguide 90° bend based on transformation optics and etching a subwavelength grating in the bent section [15-17](Gabrielli et al 2012; Xu,Shi 2018; Wu et al 2019) It is still an issue, to propagate the fundamental mode in a normally bending multi-mode waveguide without any specially design. The obtained results should be attractive to the flexible application of the above low loss scheme
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