A. R. N. Bastos

Integrated Optical Mach-Zehnder Interferometer Based on Organic-Inorganic Hybrids for Photonics-on-a-Chip Biosensing Applications

The development of portable low-cost integrated optics-based biosensors for photonics-on-a-chip devices for real-time diagnosis are of great interest, offering significant advantages over current analytical methods. We report the fabrication and characterization of an optical sensor based on a Mach-Zehnder interferometer to monitor the growing concentration of bacteria in a liquid medium. The device pattern was imprinted on transparent self-patternable organic-inorganic di-ureasil hybrid films by direct UV-laser, reducing the complexity and cost production compared with lithographic techniques or three-dimensional (3D) patterning using femtosecond lasers. The sensor performance was evaluated using, as an illustrative example, E. coli cell growth in an aqueous medium. The measured sensitivity (2 × 10−4 RIU) and limit of detection (LOD = 2 × 10−4) are among the best values known for low-refractive index contrast sensors. Furthermore, the di-ureasil hybrid used to produce this biosensor has additional advantages, such as mechanical flexibility, thermal stability, and low insertion losses due to fiber-device refractive index mismatch (~1.49). Therefore, the proposed sensor constitutes a direct, compact, fast, and cost-effective solution for monitoring the concentration of lived-cells.

Sustainable luminescent solar concentrators based on organic–inorganic hybrids modified with chlorophyll

Luminescent solar concentrators (LSCs) are luminescent waveguide layers that convert sunlight into specific wavelengths which are then guided by total internal reflection to a PV device located at the edges of the LSC. Their ability to concentrate sunlight onto small areas makes LSCs a useful complement to silicon-based PVs in a series of applications, such as urban integration and flexible fabrics towards mobile solar-energy. Challenges for the luminescent layer include the use of low-cost and sustainable nature-based organic molecules. We report novel chlorophyll-based LSCs with emission properties in the red/NIR spectral region. Here, chlorophyll molecules extracted from Spirulina maxima, an abundant cyanobacterium and an attractive natural source, are immobilized in organic–inorganic di- and tri-ureasil matrices enabling the production of sustainable LSCs. At low chlorophyll concentrations (<3 × 1017 molecules per cm3), the photophysical properties of the chlorophyll molecules after incorporation into the hybrids closely resemble those in ethanolic solution (with an absolute emission quantum yield of ∼0.16 and a fluorescence lifetime of ∼8 ns). The LSCs were coupled to a Si-based commercial PV device revealing optical conversion efficiency and power conversion efficiency values of ∼3.70% and 0.10%, respectively, illustrating the potential of this approach for the development of nature-based LSCs meeting the requirements of reliable, sustainable and competitive energy systems.

Flexible 90° hybrid coupler for coherent optical systems based on organic-inorganic hybrids

The next generation of optical networks requires the development of optical technology that supports high bandwidth, such as the coherent systems. The coherent detection allows the in-phase and quadrature components of a QPSK signal to be extracted as a result of the interference with a local oscillator. An integrated optics flexible 90° hybrid coupler device based on a single organic-inorganic di-ureasil hybrid layer was fabricated using direct UV-laser writing. The demodulator exhibits a single input - multiple output port transfer function depending on the optical signal phase. This example demonstrates that di-ureasils are potential low-cost solutions for the fabrication of polarization controlling devices.

Performance assessment of a QPSK coherent demodulator based on organic-inorganic hybrids

Coherent optical systems offer enhanced possibilities to increase data transmission capacity. To implement these systems, optical demodulators are required to decode the data. In this context, optical demodulators for a Quadrature Phase Shift Keying (QPSK) modulation based on 90° hybrid couplers are presented. The devices were produced by direct UV-laser patterning on sol-gel derived organic-inorganic hybrids, and the input-output ports transfer function revealed the dependence of the optical signal phase. Therefore, QPSK symbols were decoded, and the associated constellation diagram was analysed in real-time. To assess the device performance the error vector magnitude and phase deviations were obtained (5% and 1°, respectively) making the produced device a promising choice to replace current QPSK receivers.

Revisiting thermal-actuated integrated optics devices based on organic-inorganic hybrids

In this work, the contribution of organic-inorganic hybrids (di-ureasils) as integrated optics substrates for thermo-optical actuated devices is revisited. The hybrids are UV self-patterned without the need of photoinitiators and have a large thermo-optic coefficient, enabling the fabrication of IO devices using direct-UV lased writing. Examples include thermal actuated Mach-Zehnder (MZ) interferometers and tunable waveguide polarization controllers with for the new generation of optical communications.

Thermo-optical attenuator fabricated through direct UV laser writing in organic-inorganic hybrids

We report the fabrication of thermo-optic optical attenuators produced by direct UV laser writing in transparent, low surface roughness, and low-loss thin films of organic-inorganic hybrids, so called di-ureasils. The signal propagation and attenuation were demonstrated for propagation signals at 635.0 nm and 1550.0 nm, showing a power reduction up to 75% with a temperature gradient of -16.1 K·mm-1 and -7.6 K·mm-1 at 635.0 nm and 1550.0 nm, respectively.