Low loss (~6.45dB/cm) sub-micron polycrystalline silicon waveguide integrated with efficient SiON waveguide coupler

Abstract

In this communication, the sub-micron size polycrystalline silicon (poly- Si) single mode waveguides are fabricated and integrated with SiON waveguide coupler by deep UV lithography. The propagation loss of poly-Si waveguide and coupling loss with optical flat polarization-maintaining fiber (PMF) are measured. For whole C-band (i.e., lambda approximately 1520-1565nm), the propagation loss of TE mode is measured to approximately 6.45+/-0.3dB/cm. The coupling loss with optical flat PMF is approximately 3.4dB/facet for TE mode. To the best of our knowledge, the propagation loss is among the best reported results. This communication discusses the factors reducing the propagation loss, especially the effect of the refractive index contrast. Compared to the SiO(2) cladding, poly-Si waveguide with SiON cladding exhibits lower propagation loss.

Nanophotonic integration in state-of-the-art CMOS foundries

“…There is a path to reducing this loss further -enabling higher Q resonators and longer distance waveguide routing -through optimizing the in-foundry polysilicon deposition conditions. Similar work performed for micrometer-sized waveguides [44] and then for single-mode nanowire waveguides [45], successfully demonstrated polysilicon waveguide losses below 10 dB/cm. Such an approach, however, would limit the ability of photonic devices to leverage existing infrastructure.…”

Hot-wire polysilicon waveguides with low deposition temperature

“…A. Woollam spectroscopic ellipsometry system (192-1700 nm) and a multilayer model to calculate the extinction coefficient from which the material-induced loss was found to be approximately 5.1 dB∕cm. Provided the scattering loss is completely eliminated, the material-induced loss is similar to those of previously reported polysilicon waveguides [7,10]. The loss can be further reduced by surface planarization by means of chemical mechanical polishing or similar methods.…”

“…Multilayered integration is desirable due to several advantages such as reduced chip size and improved thermal isolation. Recently, there has been an increased interest in polysilicon waveguides due to their low cost and added design flexibility [3][4][5][6][7][8][9][10]. However, most of the reported polysilicon films were deposited or posttreated at high temperatures (≥900°C), e.g., [3,[6][7][8][9][10].…”

Demonstration of Silicon-on-insulator mid-infrared spectrometers operating at 38μm

“…While less performant in terms of waveguide losses, the imecAP process has the advantage that near-infrared and mid-infrared circuits can be implemented side by side on the same multi-project wafer, thereby leveraging cost-sharing. Methods to further reduce the scattering losses have been presented in literature [13,14], which can in principle also be applied to this imecAP process. The lower substrate leakage contribution for WG1 is related to the rib type geometry used, compared to the strip waveguide configurations for WG2 and WG3.…”