1,721,123 research outputs found
Silicon photonic modulators for the mid-infrared
No full textMid-infrared group-IV material photonics is an emerging field, which aims to migrate techniques used for near-infrared silicon photonics to longer wavelengths, and to address applications in areas such as environmental and bio-chemical sensing, homeland security, telecommunications, medicine or astronomy.In order to create mid-infrared photonic systems, components such as waveguides, splitters/couplers, filters, interferometers and modulators are required. Silicon-on-insulator (SOI) waveguides, which are used in the near-infrared, have high absorption at wavelengths greater than 4µm, and therefore new material platforms will be required for some parts of the mid-infrared.In this project silicon-on-insulator waveguides operating at 3.8µm have been demonstrated with losses as low as 2.0dB/cm. Poly-Si on SOI waveguides, which can be fabricated in a commercial foundry, and germanium on silicon waveguides, which could be used throughout most of the mid-infrared, were also demonstrated at 3.8µm.The passive components required to make a modulator in the SOI material platform were designed, fabricated and characterised. SOI MMIs were demonstrated at 3.8µm with insertion losses as low as 0.10±0.01dB, which is comparable to the best achieved near-IR silicon photonic MMI performance, and Mach-Zehnder interferometers were measured to have insertion losses of 1.3-2.2dB, and extinction ratios of up to 28dB.These components were used to create thermo-optic modulators in SOI, which are the first group-IV waveguide integrated modulators at wavelengths above 3µm. Switching powers as low as 47mW, and a -3dB bandwidth of 23.8kHz, were achieved.In order to build faster modulators, the free-carrier plasma dispersion effect could be employed. However, accurate equations for prediction of this effect in the mid-infrared have not been available until now. A semi-empirical approach has been used to calculate design equations relating the change in absorption coefficient and change in refractive index to change in charge carrier concentration in silicon for wavelengths in the 1.3-14µm wavelength range
Predictions of free-carrier electroabsorption and electrorefraction in germanium
No full textGermanium is becoming an important material for mid-infrared photonics, but the modulation mechanisms in Ge are not yet well understood. In this paper, we estimate the size of free-carrier electroabsorption and electrorefraction effects in germanium across the 2 to 16 µm wavelength range at 300 K. The predictions are based as much as possible upon experimental absorption data from the literature and are supported by extrapolations from experimental data using first-principle quantum theoretical modeling. We find that free-carrier absorption is substantially stronger in Ge than in Si
Low-loss mid-infrared SOI slot waveguides
No full textMid-infrared sensing is a field that has recently attracted attention due to the potential to reach the fingerprint region for several chemical compounds, allowing enhanced sensitivity. To further enhance the sensitivity of photonic sensors slot waveguides can be used as waveguides as the electric field amplitude can be greatly increased in the gap region. In this letter, we present silicon on insulator slot waveguides with a 1.4 ± 0.2 dB/cm propagation loss at 3.8 µm wavelength, as well as strip to slot transitions with a loss of 0.09 ± 0.01 dB/transition and slot bends with a loss of 0.18 dB/bend
Towards Mid-IR Germanium Defect Detector
No full textThe feasibility of room temperature defect mediated Mid-IR Germanium detectors will be investigated. We will implant Germanium detectors with various ion species, doses and post annealing temperatures to optimize the detector response in the Mid-IR. Here, we report on the detectors design and fabrication process.</p
Free-carrier electro-refraction and electro-absorption modulation predictions for silicon over the 1-14µm infrared wavelength range
No full textWe present relationships for the free-carrier-induced electrorefraction and electroabsorption in crystalline silicon over the 1-14 µm wavelength range. Electroabsorption modulation is calculated from impurity-doping spectra taken from the literature, and a Kramers-Kronig analysis of these spectra is used to predict electrorefraction modulation. More recent experimental results for terahertz absorption of silicon are also used to improve the commonly used 1.3 and 1.55 µm equations. We examine the wavelength dependence of electrorefraction and electroabsorption, finding that the predictions suggest longer wave modulator designs will, in many cases, be different from those used in the telecom range
Experimental quantification of the free-carrier effect in silicon waveguides at extended wavelengths
No full textWe examine the electro-optic effect at wavelengths ranging from 1.31 to 2.02 µm for: (1) an Electronic Variable Optical Attenuator (EVOA); and (2) a Micro-Ring Resonator (MRR). For the EVOA, simulations were performed to ascertain the relationship between free-carrier concentration and optical attenuation, and are in agreement with our observation of an increase in attenuation with increasing wavelength. MRRs were fabricated for use around wavelengths of 2 µm to explore the sensitivity of operation to bus-to-ring coupling gap and p-n junction offset. Trends observed in the experiment are replicated by simulation, calibrated using the observations of the EVOA operation. The previously proposed efficiency increase of operation around 2 µm compared to more traditional wavelengths is demonstrated. Future development of devices for these wavelengths, supported by amplification using Thulium Doped Fiber Amplifier (TDFA) technology, is a promising route to aid in the alleviation of increasing demands on communication networks.</p
Silicon diffusion engineering in rapid melt growth of silicon-germanium on insulator
Full text linkIn this paper we focus on developing an efficient method to obtain a crystalline SiGe layer on top of an insulator. The method is aimed at enabling the fabrication of different concentration of crystalline SiGe alloy through structure engineering. This technique could enable the alloy composition to be different by design across a single wafer by using a single Germanium deposition step
Nonlinear applications in the mid-infrared regime based on germanium on silicon platform
No full textThis abstract reviews our progress in characterizing nonlinear properties of low loss germanium-on-silicon waveguides in the mid-infrared wavelength. All-optical modulation is demonstrated in these waveguides and indicates the suitability of this platform for nonlinear applications in this long wavelength regime
Mid-infrared nanometallic antenna assisted silicon waveguide based bolometers
No full textThe mid-infrared (MIR) wavelength region is attracting more and more research for applications such as medical diagnostics, environmental monitoring, and free space communications. In the MIR, thermal detectors play an important role because they can operate over a large wavelength range, can be fabricated using CMOS compatible processes, and do not require cooling. Today no other MIR detector technology is able to fill this gap. We demonstrate the first uncooled silicon waveguide-based bolometers, in the Silicon-on-Insulator (SOI) and suspended silicon waveguide platforms. The bolometers comprise gold plasmonic antennas on the waveguide surface that heat up when they absorb light, and amorphous silicon thermometers (formed by ion implantation), whose electrical resistance changes by 0.90 ± 0.26 % K-1 when they are heated. We show that suspending the bolometers improves their performance, and achieve sensitivities of up to 1.13 ± 0.04 % change in resistance per milliwatt of input power, with a noise equivalent power of 66 μW/√Hz. Calculations suggest the NEP could in future, be further reduced by 4 orders of magnitude
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