Surface-Grating-Coupled Low-Loss Ge-on-Si Rib Waveguides and Multimode Interferometers

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]. Furthermore, the high index of Ge means that the Si substrate can function as the bottom cladding.…”

“…For photonic devices operating at even longer wavelengths, alternative materials other than Reprinted with permission from [11], (D, E) schematic view and top-view SEM image of suspended Si mid-IR micro-ring resonators [12] (© 2013 Optical Society of America), the waveguides assume a ridge geometry and an undercut etch removes the silicon dioxide cladding through access holes on the slab layer, (F, G) SEM micrographs of a suspended mid-IR Si photonic crystal cavity [13] (© 2011 Optical Society of America), (H) suspended mid-IR Si waveguides with sub-wavelength grating (SWG) claddings [14] (© 2016 Optical Society of America); here the SWG provides both lateral optical confinement as well as access to the oxide under cladding during wet etch structure release; the arrows indicate light propagation direction in the suspended core. (I, J) Ge-on-Si [15] (© 2015 IEEE): (I) a mid-IR Ge-on-Si ridge waveguide; (J) TEM cross-sectional image of the Ge-on-Si film showing that the dislocations are confined at the Si/Ge interface. (K, L) Chalcogenide glass-on-silicon [16] (© 2013 Optical Society of America): (K) top-view optical micrograph of a ChG micro-disk resonator, (L) cross-sectional structure and simulated whispering gallery mode profile in the micro-disk at 5.2-μm wavelength; the high-index As 2 Se 3 glass forms the core layer surrounded by low-index Ge 23 Sb 7 S 70 glass cladding.…”

Heterogeneously Integrated Distributed Feedback Quantum Cascade Lasers on Silicon

“…Scientific, medical, industrial, and military technologies using MIR wavelengths can potentially be addressed with applications in spectroscopic analysis [1], biological sensing [2], environmental monitoring [3], and astronomy [4]. While a number of passive MIR photonic waveguides and devices have been constructed on a variety of silicon waveguide platforms [5][6][7][8], the development of integrated active components on silicon for longer wavelengths has been more limited. Thermo-optic phase shifters for the 5 µm range [9], heterogeneously integrated InP-based type-II photodiodes for wavelengths up to 2.4 µm [10], demultiplexers for the 2 µm range utilizing an array of similar photodiodes [11], a fully integrated spectrometer utilizing an array of InAs 0.91 Sb 0.09 -based photodiodes for 3-4 µm [12], and multiple-quantum-well InGaAs lasers which emit 2.01 µm light in continuous wave (CW) mode at room temperature [13] have been reported.…”

Silicon and silicon nitride photonic circuits for spectroscopic sensing on-a-chip [Invited]

“…Germanium-on-silicon offers a waveguide platform that 1) is widely transparent from 2 to 14 μm (appropriate waveguide design can ensure high mode confinement and large bend radius that allows us to overcome higher loss due to silicon underneath at wavelengths >10 μm), 2) has a straightforward fabrication scheme, and 3) can be mass manufactured in CMOS or MEMS foundries. Several passive and active functionalities [19][20][21] have been demonstrated on this waveguide platform.…”