High-contrast, all-silicon waveguiding platform for ultra-broadband mid-infrared photonics

Abstract

Suspended silicon-membrane ridge waveguides are fabricated and characterized on a single-material photonic device platform. By using direct bonding, a thin layer of silicon is fused to a bulk silicon substrate, which is patterned with narrow trenches. Waveguides are etched on the resulting suspended membranes and are characterized at mid-and near-infrared wavelengths. Transverse magnetic-mode propagation losses of 2.8 6 0.5 and 5.6 6 0.3 dB/cm at 3.39 and 1.53 lm wavelengths are measured, respectively. This all-silicon optical platform is capable of continuous low-loss waveguiding from wavelengths of 1.2-8.5 lm, enabling numerous applications in frequency conversion and spectral analysis. V

Mid-infrared integrated photonics on silicon: a perspective

“…One strategy involves replacing the lossy silicon oxide cladding with other materials exemplified by silicon-on-nitride ( Figure 3A-B) [10] and germanium-on-nitride [17] or with air cladding in pedestal [11,18,19] or suspended silicon structures [12][13][14][20][21][22][23] (Figure 3C-H). Another option is Ge-on-Si (or SiGeon-Si), which claims the advantage of compatibility with Si CMOS processing, as high-quality Ge can be epitaxially grown on Si ( Figure 3I-J) [15,17,[24][25][26][27][28].…”

Emerging heterogeneous integrated photonic platforms on silicon

“…Similar to the discussed SON processing steps, the SOI substrate and BOX are subsequently removed and a thin Si film on the buried trench is exposed. The air-filled trench acts as the bottom 16-μm-wide trenches and the membranes are mechanically very stable [200]. In an unpublished second generation of the devices, the width has been reduced to 12 μm.…”

“…The author's group has demonstrated SON and allsilicon waveguides for the first time [199,200]. We have also proposed and demonstrated the silicon on lithium niobate (SiLN) waveguide and modulator platform (see Figure 10D) [201,202].…”

“…The next Si-based platform discussed in this review paper is perhaps not heterogeneous per se but indeed an all-silicon optical platform (ASOP) [200], i.e., air-clad suspended membrane waveguides. Nonetheless, since the processing steps for this truly homogeneous platform are based on bonding techniques discussed throughout this paper and it can be applied to enjoy the largest transparency range of ∼2.5 octaves offered by silicon (1.2-6.9 μm), it is discussed here for completeness.…”

“…Suspended membrane waveguides for mid-IR were first demonstrated by local removal of BOX in SOI waveguides via forming an array of periodical holes in the [199]; (C) all-silicon optical platform (ASOP) [200]; (D) silicon-onlithium-niobate (SiLN) [201,202]. Figure 11 Fabrication steps of SON dies [199].…”