Analysis of silicon nitride partial Euler waveguide bends

Abstract

In this work we present a detailed analysis of individual loss mechanisms in silicon nitride partial Euler bends at a wavelength of 850 nm. This structure optimizes the transmission through small radii optical waveguide bends. The partial Euler bend geometry balances losses arising from the transition from the straight to the bend waveguide mode, and radiative losses of the bend waveguide mode. Numerical analyses are presented for 45-degree bends commonly employed in S-bend configurations to create lateral offsets, as well as 90-and 180-degree bends. Additionally, 90-degree partial Euler bends were fabricated on a silicon nitride photonic platform to experimentally complement the theoretical findings. The optimized waveguide bends allow for a reduced effective radius without increasing the total bend loss and, thus, enable a higher component density in photonic integrated circuits.

Slot-Waveguide Silicon Nitride Organic Hybrid Distributed Feedback Laser

“…The laser light emission confined in the single-mode silicon nitride strip-waveguide was routed to the edge of the chip employing low-loss waveguide bends 53 and coupled to a fiber via end-face coupling. For spectral measurements and determination of the threshold a multi-mode fiber (NA 0.20, 50 µm) was employed, whereas an polarization maintaining fiber (NA 0.12, 3.3 µm) was used to measure the polarization state of the integrated laser light source.…”

Ultra-Broadband Polarization Beam Splitter Based on Cascaded Mach-Zehnder Interferometers Assisted by Effectively Anisotropic Structures

“…5(a). Bends based on Euler curves have varying radium of curvature, which can reduce the generation of highorder modes compared to traditional bends [26], [27]. Here, we set Rmin=0.72 μm to make sure that the loss of these bends is large for the TM polarization but small for the TE polarization.…”

Propagation of fundamental mode in regularly bending multi-mode waveguides

“…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][16][17] (Gabrielli et al 2012;Xu,Shi 2018;Wu et al 2019). It is still an issue, however, to propagate the fundamental mode in a normally bending multi-mode waveguide without any specially design.…”