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In neuroscience, optical techniques have become the leading method over electrophysiological techniques because of their ability to target defined populations upon tagging both for in vivo recordings using genetically encoded calcium or voltage indicators and stimulation using optogenetic opsins at the single neuronal level. Additionally, optical imaging has a smaller tissue displacement factor, the ratio of displaced neuronal tissue to field of view (FoV), thus accelerating the ability to simultaneously record from a larger volumes of neurons whereas electrophysiology arrays are limited in the total number of recordable neurons by the amount of sustained tissue damage. Conventional optical approaches, however, typically rely on microscopy techniques which require the subject to be head-fixed thus limiting the applicability especially at the chronic setting, raising the need for fully implantable optical interfaces. As a result, multiple lens-based miniature microscopes have been developed in academia and industry. Nevertheless, a truly implantable optical neurotechnology has remained intractable because traditional miniaturized fluorescence microscopes require an opening in the dura and skull that matches or exceeds the FoV and chronically extends outside the skull, resulting in a poor overall displacement factor. To overcome these limitations, I developed and characterized various implantable optoelectronic platforms designed to optically record from large neuronal FoVs in a minimally invasive implantable form factor. These works culminated in the SCOPe (Subdural CMOS Optical Probe) platform which was validated in multiple in vivo demonstrations involving mouse and nonhuman primate.

The development of digital technology permits the storage and processing of binary data at high rates, with high precision and density. Therefore, over the past few decades, Moore's law has pushed the development of scaling semiconductor devices for computing hardware. Although the current downward scaling trend has reached its scaling limits, a new "More-than-Moore" (MtM) trend has been emphasized as a diversified function of data collection, storage units, and processing devices. The function diversification defined in MtM can be viewed as an alternative form of "scaling down" for electronic systems, as it incorporates non-computing functions into digital ones, allowing digital devices to interact directly with the environment around them. Two-dimensional (2D) materials display promising potential for combining optical sensing and data storage with broadband photoresponse, outstanding photoresponsivity, rapid switching speed, multi-bit data storage, and high energy efficiency. In this work, in-solution 2D materials flakes (Hafnium Diselenide (HfSe2) and Germanium Selenide (GeSe) have been studied as a charge-trapping layer in non-volatile memory through the seamless fabrication process. Furthermore, the behavior of fabricated non-volatile memories under light illumination has been investigated towards in-memory light sensing. Atomic Force Microscopy, RAMAN spectroscopy, and X-ray Diffraction Spectroscopy characterized the charge-trapping materials. The electrical characterization of Metal Oxide Semiconductor (MOS) Capacitor memory revealed a memory window of 4V for the HfSe2 device under ±10V biasing. Intriguingly, the GeSe device exhibited an extraordinarily wide memory window of 11V under the same electrical biasing. Furthermore, the memory endurance for both materials as charge trapping layer (CTL) exceeds the standard threshold of electrical programming and erasing cycles. The accelerated retention test at different temperatures showed the memory device's stability and reliability for both materials. Under light stimuli with electrical readout voltage, the MOS memory exhibited wavelength and intensity-responsive behavior. The MOS memory of HfSe2 has demonstrated remarkable capabilities in storing the detected light signal, while also exhibiting a noteworthy increase in the memory window of approximately 1.8 V when subjected to a laser wavelength of 405 nm. Meanwhile, the GeSe device's CV measurement revealed a similar trend with the greatest memory window enhancements occurring in relation to 465 nm laser wavelength. Under ±6 V biasing in the absence of light, the memory window was found to be 8.3 V. However, following exposure to a 465 nm laser, this value increased significantly to 9.9 V, representing an increment of 1.6 V. In addition, both devices exhibited distinct sensing of various light intensities and an enhanced memory window as a result of the observable Vt shift caused by altering the levels of illumination. This memory enhancement suggests that photoexcited carriers in the CTL layer were responsible for the optical memory behavior. The 2D materials as CTL pave the way for a reconfigurable optical memory with multilevel optical data storage capacity. This research represents a significant step towards the development of a new generation of memory devices that can store and retrieve data using light signals.

[pt] A integração monolítica de um modulador com um guia de onda é de muito interesse para aplicação em comunicações ópticas pelo fato de que podemos diminuir as perdas por acoplamento óptico entre os dois dispositivos e usar moduladores curtos que operem em altas taxas de transmissão de dados. O crescimento epitaxial seletivo é uma das técnicas mais promissoras na atualidade para aplicação na integração monolítica de dispositivos semicondutores. Esta técnica permite controlar a espessura e a tensão das camadas crescidas seletivamente permitindo otimizar a integração e as características das estruturas dos dispositivos. A tese trata da implementação, do estudo e da aplicação do crescimento epitaxial seletivo por MOCVD de estruturas casadas e tensionadas de poços quânticos múltiplos de InGaAs/InAlAs para a fabricação de moduladores de amplitude baseados no efeito Stark e sua integração com guias de onda. O desempenho dos moduladores, baseados em estruturas de poços quânticos múltiplos de InGaAs/InAlAs que operam em 1,55 ym, é notavelmente melhorado quando é introduzida uma composição de 52% de Ga na liga e se tem um poço de ~100 A de espessura. Nesse caso, os moduladores possuem uma elevada figura de mérito e podem ser insensíveis à polarização. Nesse estudo foram crescidas várias amostras onde foi analisado o aumento na taxa de crescimento e a variação na composição das ligas de InGaAs e InAlAs em material bulk e em poços quânticos de InGaAs/InAlAs em função da geometria da máscara utilizada, i.e. diferentes larguras do dielétrico e largura da janela onde ocorre o crescimento fixo. Finalmente foram processados guias de onda cujas estruturas foram crescidas com a técnica de crescimento seletivo. Esses guias foram caracterizados por técnicas de campo próximo. / [en] The monolithic integration of a modulator with a waveguide is a lot of interest for application in optical communications for the fact in that can decrease the losses for optical joining between the two devices and to use short modulators that operate in high rates of transmission data. The selective growth is at the present time, one the more promising technique for application in the monolithic integration of semiconductors device. This technique allows to control the thickness and the stress of the grown layers allowing to improve the integration and the characteristics of the devices structures. These thesis is about the implementation, study and application of the selectuve growth by MOCVD of both match and tensile structures of multi quantum wells of inGaAs/InAlAs for the production of the amplitude modulators based on the Stark effect and its integration with waveguide. The performance of the modulators based on structures of multi quantum wells of InGaAs/InAlAs operating in 1,55 um, is notably improved whena Ga composition of 52% is used and the thickness of a quantum well is near to ~100 A. In that case, the modulators have a high figured of merit and they can be insensitive to the polarization. In this study, several samples was grown and the growing rate increase was analyzed and the variation of the composition in InGaAs and InAlAs in bulk alloys and in quantum wells of InGaAs/InAlAs in function of the window where the growth is spent. Finally, waveguides were processed whose structures were grown with the technique of selective growth. Those guides were characterized by the near field technique.

Current major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic functionality poses requirements to the senor head; the sensor head needs to have reasonably small size while it should have reasonable sensitivity and fabrication tolerance. This research proposes a novel type of SPR sensor head and demonstrates a fabricated device with an array of integrated optical SPR sensor heads endowed with optoelectronic functionality. The novel integrated optical SPR sensor head relies on mode conversion efficiency for its operational principle. The beauty of this type of sensor head is it can produce clear contrast in SPR spectrum with a highly miniaturized and simple structure, in contrast to several-millimeter-scale conventional absorption type or interferometer type sensor heads. The integrated optical SPR sensor with optoelectronic functionality has been realized by structuring a dielectric waveguide based SPR sensor head on a photodetector-integrated semiconductor substrate. A large number of unit sensors have been fabricated on a substrate with a batch fabrication process, which promises a high throughput SPR sensor system or low-priced disposable sensors.

A wide variety of nanomaterials ranging from polymer assemblies to organic and inorganic nanostructures (particles, wires, rods etc) have been actively pursued in recent years for various applications. The synthesis route of these nanomaterials had been driven through two fundamental approaches - 'Top down' and 'Bottom up'. The key aspect of their application remained in the ability to make the nanomaterials suitable for targeted location by manipulating their structure and functionalizing with active target groups. Functional nanomaterials like polyelectrolyte based multilayered thin films, nanofibres and graphene based composite materials are highlighted in the current research. Multilayer thin films were fabricated by conventional dip coating and newly developed spray coating techniques. Spray coating technique has an advantage of being applied for large scale production as compared to the dip coating technique. Conformal hydrophobic/hydrophilic and superhydrophobic/hydrophilic thermal switchable surfaces were fabricated with multilayer films of poly(allylaminehydrochloride) (PAH) and silica nanoparticles by the dip coating technique, followed by the functionalization with thermosensitive polymer-poly(N-isopropylacrylamide)(PNIPAAM) and perfluorosilane. The thermally switchable superhydrophobic/ hydrophilic polymer patch was integrated in a microfluidic channel to act as a stop valve. At 70 degree centigrade, the valve was superhydrophobic and stopped the water flow (close status) while at room temperature, the patch became hydrophilic, and allowed the flow (open status). Spray-coated multilayered film of poly(allylaminehydrochloride) (PAH) and silica nanoparticles was fabricated on polycarbonate substrate as an anti-reflection (AR) coating. The adhesion between the substrate and the coating was enhanced by treating the polycarbonate surface with aminopropyltrimethoxylsilane (APTS) and sol-gel. The coating was finally made abrasion-resistant with a further sol-gel treatment on top of AR coating, which formed a hard thin scratch-resistant film on the coating. The resultant AR coating could reduce the reflection from 5 to 0.3% on plastic. Besides multilayered films, the fabrication of polyelectrolyte based electrospun nanofibers was also explored. Ultrathin nanofibers comprising 2-weak polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylaminehydrochloride) (PAH) were fabricated using the electrospinning technique and methylene blue (MB) was used as a model drug to evaluate the potential application of the fibers for drug delivery. The release of MB was controlled in a nonbuffered medium by changing the pH of the solution. Temperature controlled release of MB was obtained by depositing temperature sensitive PAA/poly(N-isopropylacrylamide) (PNIPAAM) multilayers onto the fiber surfaces. The sustained release of MB in a phosphate buffered saline (PBS) solution was achieved by constructing perfluorosilane networks on the fiber surfaces as capping layers. The fiber was also loaded with a real life anti-depressant drug (2,3-tertbutyl-4-methoxyphenol) and fiber surface was made superhydrophobic. The drug loaded superhydrophobic nanofiber mat was immersed under water, phosphate buffer saline and surfactant solutions in three separated experiments. The rate of release of durg was monitored from the fiber surface as a result of wetting with different solutions. Time dependent wetting of the superhydrophobic surface and consequently the release of drug was studied with different concentrations of surfactant solutions. The results provided important information about the underwater superhydrophobicity and retention time of drug in the nanofibers. The nanostructured polymers like nanowires, nanoribbons and nanorods had several other applications too, based on their structure. Different self-assembled structures of semiconducting polymers showed improved properties based on their architectures. Poly(3-hexylthiophene) (P3HT) supramolecular structures were fabricated on P3HT-dispersed reduced graphene oxide (RGO) nanosheets. P3HT was used to disperse RGO in hot anisole/N, N-dimethylformamide solvents, and the polymer formed nanowires on RGO surfaces through a RGO induced crystallization process. The Raman spectroscopy confirmed the interaction between P3HT and RGO, which allowed the manipulation of the composite's electrical properties. Such a bottom-up approach provided interesting information about graphene-based composites and inspired to study the interaction between RGO and the molecular semiconductor-tetrasulphonate salt of copper phthalocyanine (TSCuPc) for nanometer-scale electronics. The reduction of graphene oxide in presence of TSCuPc produced a highly stabilized aqueous composite ink with monodispersed graphene sheets. To demonstrate the potential application of the donor (TSCuPc)'acceptor (graphene) composite, the RGO/TSCuPc suspension was successfully incorporated in a thin film device and the optoelectronic property was measured. The conductivity (dark current) of the composite film decreased compared to that of pure graphene due to the donor molecule incorporation, but the photoconductivity and photoresponsivity increased to an appreciable extent. The property of the composite film overall improved with thermal annealing and optimum loading of TSCuPc molecules.

Computing as a service is rapidly becoming the new normal for many sectors of the economy. The widespread availability of broadband internet has allowed an extensive range of services to be delivered on-demand from centralized computing systems known as ‘data centers’. These systems have evolved to be enormously complex. Optical-based communication is desired to increase data center capability and efficiency, however traditional optical technologies are not feasible due to cost and size. Silicon photonics aims to deliver optical communications on an integrated and affordable platform for use in data centers by leveraging the existing capabilities of complementary metal-oxide semiconductor manufacturing. This thesis contains a description of the development of monolithic silicon photodiodes for use in photonic integrated circuits in, and beyond, the current telecommunications wavelength windows. The focus is on methods which are compatible with standard silicon processing techniques. This is in contrast to the current approaches which rely on hybrid material systems that increase fabrication complexity. Chapter 1 and 2 provide background information to place this work into context. Chapter 3 presents an experimental study of resonant devices with lattice defects which determines the refractive index change in silicon-on-insulator waveguides. High-speed operation of resonant photodiodes is demonstrated and is found to be limited by resonance instability. Chapter 4 demonstrates high responsivity avalanche photodetectors using lattice defects. The detectors are shown to operate error-free at 10 Gbit/s, thus confirming their capability for optical interconnects. Chapter 5 presents photodiodes operating with absorption through surface-state defects. These detectors show fast operation (10 Gbit/s) and have an extremely simple fabrication process. Chapter 6 demonstrates photodiodes operating beyond the traditional telecommunications window. Operation at 20 Gbit/s, at a wavelength of 1.96 µm is demonstrated, offering potential for their use in the next generation of optical communication systems which will exploit the thulium doped fiber amplifier. / Thesis / Doctor of Philosophy (PhD) / This thesis describes photodiodes constructed on silicon optical waveguides. The photodiodes are notable for their high-speed performance and simple fabrication methods. Such devices may find use within chip-integrated optical transceivers, which are desired for optical interconnects within large-scale computing systems such as data centers.

An efficient numerical method to simulate a subpicosecond semiconductor optical switch is developed in this research. The problem under studying involves both electromagnetic wave propagation and semiconductor dynamic transport, which is a nonlinear phenomenon. Finite difference time domain (FDTD) technique is used to approximate the time dependent Maxwell's equations for full-wave analysis of the wave propagation. The dynamic transport is handled by solving the balance equations using the energy and momentum relaxation time approximation. Based on the structure of the device, a physical semi-analytical model is also developed for preliminary analysis. Simulation results in the device's subpicosecond responses including nonlinearity and overshoot. The validity of the method is verified by comparing the simulation with the published experimental results. The method can be extended to other devices as well. / Ph. D.

Due to the complex nature of jaw movements, three-dimensional (3D) movement recording provide information about the jaw movement capacity. The aim of the present report was to test the reliability of measuring lower jaw movements using a 3D movement recording system and to calculate the lower jaw movement volume. Lower jaw movements, recorded by 3D optoelectronic movement analysis system (MacReflex®) was compared with reference values from a digital caliper. Pre-tests were performed to develop a software to calculate the lower jaw movements in separate dimensions and its volume. Pilot tests with two test persons followed to register the lower jaw movements and calculate lower jaw movement volume. The results indicate low reliability of lower jaw movements measured by movement recording system compared with reference values from digital caliper, reflected by delta values (D = max-min). The values from the movement recording system indicate high variability reflected by higher levels of standard deviation for movement recorded values compared with digital caliper and by percentage values calculated from the differences between mean values of movement recording and digital caliper. The calculated lower jaw movement volume was 10.3 cm3 and 17.2 cm3 for the test persons, respectively. Conclusively, the results imply that further testing of the method is needed with larger series and test-retest reliability analysis to evaluate the possibility to improve accuracy of tracing jaw movements with recording device. The 3D-movement recording system together with the software could be used for calculation of lower jaw movement volume but its accuracy could not be validated.