Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces

Abstract

We report on the design and characterization of focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. With implementation of waveguide dispersion engineered subwavelength structures, an ultra-wide 1-dB bandwidth of over 100 nm (largest reported to date) near 1550 nm is experimentally achieved for transverse-electric polarized light. By tapering the subwavelength structures, back reflection is effectively suppressed and grating coupling efficiency is increased to -4.7 dB. A compact device footprint of 40 µm × 20 µm is realized by curving the gratings in a focusing scheme.

Fully etched apodized grating coupler on the SOI platform with −058 dB coupling efficiency

“…In addition, the highest CE of only −0.58 dB with 3 dB bandwidth of 71 nm was obtained at a coupling angle of 13°. The back reflection of the grating coupler was extracted from the contrast of the Fabry-Perot (FP) fringes of the fiber-to-fiber transmission spectrum, and is lower than 1.4% at the peak coupling wavelength, which is comparable to previous demonstrations [12][13][14][15][16].…”

“…Moreover, the CE of such uniform shallowly etched grating couplers is limited not only by power leakage to the substrate, but also by the intrinsic mode mismatch between the gratings and SSMFs. For applications where only fully etched silicon waveguides are present on a photonic-integrated circuit, such as multimode multiplexers [9] or multicore fiber couplers [10], fully etched grating couplers are preferred [11][12][13][14][15][16] in order to simplify the fabrication process. Table 1 summarizes the performances of state-of-theart fully etched and shallowly etched grating couplers that have been demonstrated over the past few years.…”

Multilayer Silicon Nitride-on-Silicon Integrated Photonic Platforms and Devices

“…out-of-plane fiber-to-chip coupling without the need for backreflectors as in [43] or electron beam lithography of ≈50 nm features as in [48].…”

Generating UWB and Microwave Waveforms Using Silicon Photonics

“…Vertical grating couplers (VGCs) are used for input and output coupling and to ensure operation with TE-polarized light in the SNW. The total fiber-to-fiber coupling loss is ∼22 dB and each VGC introduces ∼10 dB insertion loss (recent designs can reduce this loss further to ∼4 dB per coupler [21]). …”