PhotoAKI: Photonic Biosensor for point of care and Early Diagnostics of Acute Kidney Injury

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Publications

Design and optimization of a waveguide/fibre coupler in the visible range

Publication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Fernandes, Miguel; Vieira, Manuela

When 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.

2021-03-05Conference object

Restricted access

Thin film refractive index and thickness

Publication . Lourenço, Paulo; Vieira, Manuela; Fantoni, Alessandro

Integrated optics are a contemporaneous reality in which thin-film technology and methods utilized in the development of integrated circuitry, are applied to both optical circuits and devices. This provides systems that show improved characteristics when compared to their electronic counterparts. Optical systems enable wider bandwidth operation, less power consumption, more immunity to interference and higher cost-efficiency. These features definitely represent a huge improvement in our daily lives when completely embedded in Information and Communications Technologies, replacing a large percentage of contemporaneous electronic based systems. The building blocks of these optical systems consist on waveguides and structures formed by deposited thin films. Two characteristics of utmost importance for these structures are the height and refractive index of the deposited film. In this work and by using a prism coupler, we will be presenting an optical setup and the experimental method that is used to determine both refractive index and thickness of the wave guiding structure.

2020-04Book part

Open access

Silicon nitride based devices: lithographic mask roughness mitigation

Publication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Vieira, Manuela

Lithographic 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.

2020-04Other

Open access

Cross-section mismatch: metamaterials to the rescue

Publication . Lourenço, Paulo; Fantoni, Alessandro; Costa, João; Vieira, Manuela

Coupling light into and/or out of a photonic integrated circuit is often accomplished by establishing a vertical link between a single-mode optical fiber and a resonant waveguide grating, which is then followed by a tapered and a single-mode waveguides. The tapered waveguide operates as a spot-size converter, laterally expanding or contracting the light beam between the single-mode waveguide and the resonant waveguide grating. In this work, we propose using subwavelength structures to achieve tapering functionalities. To this end, we designed a metamaterial structure that enables the modulation of the refractive index necessary to either expand or focus a beam of light. Furthermore, we simulated the metamaterial structure through adequate numerical methods and the expanding, and focusing performances were analyzed in terms of efficiency and mode profile matching. We achieved over 43 % and 48 % for the integral overlap with the transverse magnetic fundamental mode for the focusing and expanding configurations, respectively, out of 49 % and 51 % of power transferred.

2022-12Journal article

Open access

Optimisation of a plasmonic parallel waveguide sensor based on amorphous silicon compounds

Publication . Costa, João; Fantoni, Alessandro; Lourenço, Paulo; Vieira, Manuela

This work reports the simulation of a plasmonic waveguide sensor working in the visible range based on amorphous silicon compounds. Typical plasmonic sensor interrogation schemes are based on scanning over the wavelength or the incident angle to search for the resonance condition. These solutions usually require expensive or bulky components, such as prisms, motor-driven rotation stages or tunable lasers. In this work we propose an amorphous silicon nitride waveguide structure consisting of an array of parallel surface plasmon interferometers of different lengths, each one comprising a thin layer of aluminium embedded into the waveguide. Using modal decomposition simulations, we show that the variation of the output power at the end of each waveguide array element provides a convenient interrogation scheme. By exploring amorphous silicon compounds that can be deposited by Pressure Enhanced Chemical Vapor Deposition (PECVD) at low temperatures, we aim to achieve a low-cost fabrication process that is compatible with backend CMOS processing and wavelengths in the visible range.

2020-04Conference object

Open access