1,721,161 research outputs found
Fabrication of arbitrarily narrow vertical dielectric slots in silicon waveguides
No full textSlot waveguides are used for many photonic applications. However, existing fabrication techniques impose restrictions on the width of the slot region. Here we propose and experimentally demonstrate a fabrication process to realize an arbitrarily narrow vertical dielectric slot in a silicon waveguide. Using this fabrication method we have realized silicon slot waveguides with a 10 nm oxide slot region. The propagation loss of the fabricated slot waveguide was 1.36±0.3 dB/mm
Crossing-free on-chip 2×2 polarization-diverse switch
No full textWe propose and demonstrate an on-chip 2× 2 polarization-diverse switch for simultaneously handling two-group polarization multiplexed signals with waveguide crossing-free design. Each input polarization tributary can be independently switched and less than 1 dB power penalties are experimentally observed.</p
Third order Bragg grating filters in small SOI waveguides
No full textThird order grating filters fabricated in small Silicon-on-Insulator rib waveguides are demonstrated. Variations in grating etch depth and duty cycle are considered, and a maximum experimental reflection of 42% is demonstrated for gratings of 1500 µm in length, with a grating period of approximately 689nm and an etch depth of 200nm. Agreement with modeling is shown to be good
Low temperature hot-wire polysilicon waveguides
No full textWe fabricated and measured low loss polysilicon waveguides deposited using Hot-Wire Chemical Vapor Deposition (HWCVD) at 240 °C. The optical propagation loss was measured to be 11.9 dB/cm at lambda = 1550 nm
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
Polarization-insensitive directional couplers based on SOI wire waveguides
No full textOptical directional couplers based on SOI-wire waveguides have been modelled by a semi-analytical approach based on the Coupled Mode Theory and Finite Element Method. The modelling is used to obtain analytically optical power at the parallel and cross ports by utilizing numerically calculated coupling coefficients. Geometrical dimensions of the couplers have been optimized to obtain a polarization-independent behaviour. The influence of non-vertical sidewalls on the coupler performance has also been addressed
Development of high-performance short-wave infrared Ge-on-Si linear mode avalanche photodiodes
Full text linkShort-wave infrared (SWIR) light offers several advantages over visible light, including high eye-safety threshold, reduced atmospheric transmission attenuation, and lower solar background interference. These properties make SWIR light valuable in various applications, such as in optical communications, imaging technologies and automotive industry. Avalanche photodiodes (APDs) are particularly suited for detecting low levels of light due to their internal avalanche gain. Silicon (Si) is favoured as an avalanche material because of its low excess avalanche noise, while germanium (Ge) is an excellent candidate for detecting SWIR light. The use of cost-effective CMOS process technology and the potential for integration with existing Si photonics further enhance the appeal of this material system. Our previous work demonstrated a 50μm-diameter Ge-on-Si linear-mode APD with high avalanche gain and low excess noise at 1550nm wavelength and at room temperature. However, a high dark current still remains one of the main challenges. In this paper, we will present the ongoing development of SWIR Ge-on-Si APDs, focusing on reducing the device dark current by reducing device active area and extending device operating wavelength by employing GeSn as photon absorption region. A 10μm-diameter Ge-on-Si APD shows 8 times dark current reduction at room temperature c.f. the 50μm-diameter Ge-on-Si APD. Furthermore, we designed and fabricated GeSn-on-Si photodiodes with a GeSn thickness of 1μm to investigate device spectrum response at different temperatures
Effects of annealing silicon ion irradiated rib waveguides with respect to free carrier lifetime
No full textPreviously we have reported the effects of silicon ion irradiation on free carrier lifetime and propagation loss in silicon rib waveguides, and simulated net Raman gain based on experimental results. We further extend this work by reporting the effects of thermally treating a silicon irradiated sample with a higher dose and energy than previously reported, which produced a poor trade-off between free carrier lifetime and excess optical absorption prior to thermal treatment. Excess losses greater than 80dB/cm were recorded prior to annealing. After thermal treatment, the sample demonstrated characteristics of excess loss and free carrier lifetime recorded previously in much lower energy and dose silicon ion irradiated samples, suggesting that thermally treating samples could enhance the trade-off between free carrier lifetime and excess loss introduced to the rib waveguides. Raman gain simulations based on the new experimental data are reported and show an increase in net gain over previously reported data, suggesting that higher dose, shallow silicon ion implantation is the most efficient way of optimising the trade-off between lifetime reduction and excess optical absorption in silicon rib waveguides, a proposal in our earlier work. The effects of thermally treating low temperature oxide clad waveguides with respect to free carrier lifetime are also reported. Results show that thermally treating a low temperature oxide clad waveguide can vary the intrinsic lifetime. The results of this investigation as well as a discussion into the possible origin of the lifetime change are given.</p
SOI ring resonators with controllable MMI coupler sections
No full textA ring resonator using a single 2×2 MMI as the coupler section has the distinct advantages of low sensitivity to fabrication error, temperature, wavelength and polarisation. However, the coupling coefficient of the 2×2 MMI coupler is fixed; hence, the performance of this type of device is limited, e.g. transmission spectrum with high extinction ratio is difficult to achieve. We have designed and simulated ring resonators with coupler sections consisting of two 2×2 MMIs and phase shifters, so that the coupling efficiency can be varied from 0% to 100% with relative ease. For a single ring resonator, the transmission spectrum can be controlled to achieve an extinction ratio of >20dB and a spectral bandwidth of <1nm. For a multiple ring filter, the transmission spectrum can be controlled to achieve an extinction ratio of >30dB and a bandwidth of <1nm; in addition, a flat-top transmission spectrum is also achievable. The whole device has a footprint of approximately 200μm by 100μm.</p
Next generation device grade silicon-germanium on insulator
No full textHigh quality single crystal silicon-germanium-on-insulator has the potential to facilitate the next generation of photonic and electronic devices. Using a rapid melt growth technique we engineer tailored single crystal silicon-germanium-on-insulator structures with near constant composition over large areas. The proposed structures avoid the problem of laterally graded SiGe compositions, caused by preferential Si rich solid formation, encountered in straight SiGe wires by providing radiating elements distributed along the structures. This method enables the fabrication of multiple single crystal silicon-germanium-on-insulator layers of different compositions, on the same Si wafer, using only a single deposition process and a single anneal process, simply by modifying the structural design and/or the anneal temperature. This facilitates a host of device designs, within a relatively simple growth environment, as compared to the complexities of other methods, and also offers flexibility in device designs within that growth environment
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