Loading...
4 results
Search Results
Now showing 1 - 4 of 4
- Silicon nitride based devices: lithographic mask roughness mitigationPublication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Vieira, ManuelaLithographic technology has been one of the main upholders to Moore's law in the semiconductor industry for the last decades. The underlying reason that enabled the evolution in semiconductor industry has been a steady silicon wafer printing cost, while being able to dramatically increase the number of nodes that can be printed per chip. Key developments in lithography such as wavelength decreasing, together with performance increase in lens and imaging technology, should be accounted for almost all the reduction of cost per function in integrated circuits technology. In this work, we will be presenting the simulation of two mitigation techniques for the impact of defects introduced by manufacturing processes. Namely, the lithographic mask limited resolution on the geometry of the representative device. These perturbations are a consequence of the lithographic mask limited resolution on the geometry of the representative device. For this purpose, the Beam Propagation and Finite Differences Time Domain methods will be used to simulate a multimode interference structure based on silicon nitride. The structure will be affected by previously mentioned perturbations and we expect results revealing a strong dependence between mask resolution, and imbalance and power loss. Two strategies will be followed concerning the mitigation of power loss and imbalance introduced by the limited resolution of lithographic mask: - Access waveguides tapering; - Adjustable power splitting ratios through the electro-optic effect. Through both strategies we aim to achieve an improvement on device’s performance but, in the latter are expected finer tuning capabilities, being enabled by dynamic compensation of power loss and imbalance when in a closed loop control architecture.
- Design and optimization of a waveguide/fibre coupler in the visible rangePublication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Fernandes, Miguel; Vieira, ManuelaWhen engineering photonic integrated structures, there will be a time that one must consider coupling out the electromagnetic field to an external device. Often, this coupling is made through a single mode optical fibre. Due to the mismatch in mode field diameters between waveguide and fibre modes, the propagating mode inside the dielectric waveguide must undertake a spot-size conversion. It requires to be radially expanded, often laterally by a tapered waveguide and longitudinally through other means, to match the radial profile of the optical fibre mode. Then, the energy must be coupled out of its propagating path into the plane of the optical fibre, through a structure that possesses such functional purpose. In this work, we describe the design steps and optimization of a silicon nitride waveguide/fibre coupler operating in the visible range. To this end, we start by designing an optimized 3D taper waveguide, using Beam Propagation method, that performs as the spot-size converter. Next, through the Eigen Mode Expansion method, a 2D subwavelength grating is designed and optimized regarding substrate leakage and propagating plane energy coupling out, thus vertically validating the energy distribution of the outgoing profile. The required subwavelength grating apodization is accomplished, once more through the Eigen Mode Expansion method, and by carefully engineering a metamaterial that performs accordingly. The obtained diffraction grating is then expanded horizontally to create a 3D structure and laterally validated through Beam Propagation method. Finally, the whole 3D structure is optimized and validated through Finite Differences Time Domain simulations regarding energy profile coupling out, and overlap integral matching is established with the fibre mode profile.
- Lithographic mask defects analysis on an MMI 3 dB splitterPublication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Vieira, ManuelaIn this paper, we present a simulation study that intends to characterize the influence of defects introduced by manufacturing processes on the geometry of a semiconductor structure suitable to be used as a multimode interference (MMI) 3 dB power splitter. Consequently, these defects will represent refractive index fluctuations which, on their turn, will drastically affect the propagation conditions within the structure. Our simulations were conducted on a software platform that implements the Beam Propagation numerical method. This work supports the development of a biomedical plasmonic sensor, which is based on the coupling between propagating modes in a dielectric waveguide and the surface plasmon mode that is generated on an overlaid metallic thin film, and where the output readout is achieved through an a-Si:H photodiode. By using a multimode interference 1 × 2 power splitter, this sensor device can utilize the non-sensing arm as a reference one, greatly facilitating its calibration and enhancing its performance. As the spectral sensitivity of amorphous silicon is restricted to the visible range, this sensing device should be operating on a wavelength not higher than 700 nm; thus, a-SiNx has been the material hereby proposed for both waveguides and MMI power splitter.
- Simulation analysis of a thin film semiconductor MMI 3dB splitter operating in the visible rangePublication . Lourenço, Paulo; Fantoni, Alessandro; Vieira, ManuelaIn this paper we present a simulation study that intends to characterize the influence of defects introduced by manufacturing processes on the geometry of a semiconductor structure suitable to be used as a multimode interference (MMI) 3 dB power splitter. Consequently, these defects will represent refractive index fluctuations which, on their turn, will drastically affect the propagation conditions within the structure. Our simulations were conducted on a software platform that implements both Beam Propagation and FDTD numerical methods. This work supports the development of a biomedical plasmonic sensor, which is based on the coupling between the propagating modes in a dielectric waveguide and the surface plasmon mode that is generated on an overlaid metallic thin film, and where the output readout is achieved through an a-Si:H photodiode. By using a multimode interference 1×2 power splitter, this sensor device can utilize the non-sensing arm as a reference one, greatly facilitating its calibration and enhanced performance. Amorphous silicon can be deposited by PECVD processes at temperatures lower than 300°C, an attractive characteristic which makes it back-end compatible to CMOS fabrication processes. As the spectral sensitivity of amorphous silicon is restricted to the visible range, this sensing device should be operating on a wavelength not higher than 700 nm, thus a-SiNx has been the material hereby proposed for both waveguides and MMI power splitter.