Low-loss germanium strip waveguides on silicon for the mid-infrared (original) (raw)
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Low-loss Ge-rich Si0.2Ge0.8 waveguides for mid-infrared photonics
Optics letters, 2017
We demonstrate low-loss Ge-rich Si<sub>0.2</sub>Ge<sub>0.8</sub> waveguides on Si<sub>1-x</sub>Ge<sub>x</sub> (x from 0 to 0.79) graded substrates operating in the mid-infrared wavelength range at λ=4.6 μm. Propagation losses as low as (1.5±0.5)dB/cm and (2±0.5)dB/cm were measured for the quasi-TE and quasi-TM polarizations, respectively. A total coupling loss (input/output) of only 10 dB was found for waveguide widths larger than 7 μm due to a good fiber-waveguide mode matching. Near-field optical mode profiles measured at the output waveguide facet allowed us to inspect the optical mode and precisely measure the modal effective area of each waveguide providing a good correlation between experiments and simulations. These results put forward the potential of low-index-contrast Si<sub>1-x</sub>Ge<sub>x</sub> waveguides with high Ge concentration as fundamental blocks for mid-infrared photonic integrated circuits.
Mid-infrared all-optical modulation in low-loss germanium-on-silicon waveguides
Optics letters, 2015
All-optical modulation has been demonstrated in a germanium-on-silicon rib waveguide over the mid-infrared wavelength range of 2-3 μm using a free-carrier absorption scheme. Transmission measurements have shown the waveguides to have low propagation losses that are relatively independent of wavelength out to 3.8 μm, indicating that the modulation could be extended further into the mid-infrared region for applications in sensing and spectroscopy. By monitoring the material recovery, the free-carrier lifetime of the micron-sized waveguides has been estimated to be ∼18 ns, allowing for modulation speeds within the megahertz regime.
Low loss SiGe graded index waveguides for mid-IR applications
Optics Express, 2014
In the last few years Mid InfraRed (MIR) photonics has received renewed interest for a variety of commercial, scientific and military applications. This paper reports the design, the fabrication and the characterization of SiGe/Si based graded index waveguides and photonics integrated devices. The thickness and the Ge concentration of the core layer were optimized to cover the full [3 -8 µm] band. The developed SiGe/Si stack has been used to fabricate straight waveguides and basic optical functions such as Y-junction, crossings and couplers. Straight waveguides showed losses as low as 1 dB/cm at λ = 4.5 µm and 2 dB/cm at 7.4 µm. Likewise straight waveguides, basic functions exhibit nearly theoretical behavior with losses compatible with the implementation of more complex functions in integrated photonics circuits. To the best of our knowledge, the performances of those Mid-IR waveguides significantly exceed the state of the art, confirming the feasibility of using graded SiGe/Si devices in a wide range of wavelengths. These results represent a capital breakthrough to develop a photonic platform working in the Mid-IR range.
Low-Loss Surface-Mode Waveguides for Terahertz Si–SiGe Quantum Cascade Lasers
IEEE Journal of Quantum Electronics, 2000
A new design of low-loss terahertz waveguide for Si-SiGe quantum-cascade lasers (QCLs) is presented. Periodic surface gratings are used to define waveguides without the requirement of cleaved or etched end facets. As Si cleaves along the (111) planes and not in the vertical direction for standard Si (100) substrates, this significantly aids the fabrication of waveguides. Losses down to 2 cm 1 with modal overlap of 0.4 can be achieved for shallow gratings with etched depths of only 0.56 m for an active material layer thickness of 8 m. Such low loss and high modal overlap is key to any Si-SiGe QCL being realized.
IEEE Journal of Selected Topics in Quantum Electronics, 2019
Mid-infrared light sources are attracting attention for use in spectroscopic sensing, thermal imaging, and infrared countermeasures. Integration of these sources on Si-based waveguides allows for more functional and complex photonic circuits to be integrated on a single chip. This paper focuses on the key aspects of this integrated platform. The operation of silicon-on-insulator waveguides beyond 4.0 µm wavelength with increasing waveguide core thickness is discussed, and the effects of various cladding materials on waveguide propagation loss is demonstrated. Low loss waveguides and Mach-Zehnder interferometers in Ge-on-Si waveguide platform are discussed and beam combiners in the form of arrayed waveguide gratings are demonstrated in both the platforms. Interband cascade lasers are integrated on silicon-oninsulator waveguides with direct bonding to realize Fabry-Perot lasers. Power scaling of integrated lasers is validated by integrating quantum cascade lasers with silicon-on-insulator beam combiners. Results for the first integrated Fabry-Perot quantum cascade lasers on Ge-on-Si waveguides are discussed, together with the potential use of these waveguides to provide a better heat sink for integrated mid-infrared light sources.
High-contrast, all-silicon waveguiding platform for ultra-broadband mid-infrared photonics
Applied Physics Letters, 2013
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
Nonlinear optical response of low loss silicon germanium waveguides in the mid-infrared
Optics Express, 2015
We have investigated the nonlinear optical response of low loss Si 0.6 Ge 0.4 / Si waveguides in the mid-infrared wavelength range from 3.25-4.75μm using picosecond optical pulses. We observed and measured the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index. The dynamics of the spectral broadening suggests that, in addition to multiphoton absorption, the corresponding higher order nonlinear refractive phenomena also needs to be included when high optical pulse intensities are used at mid-infrared wavelengths in this material.
Low loss silicon waveguides for the mid-infrared
Optics Express, 2011
Silicon-on-insulator (SOI) has been used as a platform for nearinfrared photonic devices for more than twenty years. Longer wavelengths, however, may be problematic for SOI due to higher absorption loss in silicon dioxide. In this paper we report propagation loss measurements for the longest wavelength used so far on SOI platform. We show that propagation losses of 0.6-0.7 dB/cm can be achieved at a wavelength of 3.39 µm. We also report propagation loss measurements for silicon on porous silicon (SiPSi) waveguides at the same wavelength.