Search

Recently an ever-increasing activity in the area of coupling between optical waveguide and ring or micro resonator has been developed. Devices based on this coupling held the promise of a new modality of light switching, amplifications and modulation. In this paper, the feasibility of an all optical switch based on the integration of the potentiality of microcavity resonator and organic materials having large nonlinearities, i.e. liquid crystals (LC's), is discussed. The device is based on silicon technology with hybrid integration of liquid crystals as a nonlinear material.

Biosensors have by far moved from laboratories benches to the point of use, and, in some cases, their represent technical standards and commercial successes in applications of social interest, such as medical diagnostic or environmental monitoring. Based on biological molecules, but also on their bio-inspired synthetic counterparts, biosensors employ different transducers (optical, potentiometric, volt-amperometric, colorimetric, and so on) converting the molecular interaction information into a measurable electric signal. As the result of a real multi-disciplinary field of science and technology, biosensors can take advantage from each improvement and progress coming from other disciplines: new features and better performances have been reached in the last year due to simplified fabrication methodologies, deep integration of optical or electrical transducers, and, last but not least, microfluidic circuits. More recently, nanostructured components dramatically increased biosensors reliability especially in public health and environmental monitoring. Nevertheless, there is still a pressing demand of innovations which could lead to smaller, faster, and cheaper biosensors systems with ability to provide not only accurate information but also feedback actions to the real world. The fabrication of a new generation of hybrid biodevices, where biological, or bio-inspired, molecules are fully integrated with a micro or a nano technological platform, strongly depends on the bio-compatibilization treatments of the devices surfaces. The design and the realization of bio/non-bio interfaces with specific properties, such as chemical stability, wettability, and biomolecules immobilization ability, are key features in the miniaturization and optimization processes of biosensors. In particular, protein immobilization is a hot topic in biotechnology since commercial solutions, as in the case of DNA microarrays, are not still available. Proteins are, due to their composition, a class of very heterogeneous macromolecules with variable properties. For these reasons, it is extremely difficult to find a common surface suitable for different proteins with a broad range in molecular weight and physical-chemical properties such as charge and hydrophobicity. A further aspect is the orientation of the bound proteins, that could be of crucial relevance for quantitative analysis, interaction studies, and enzymatic reactions. Many different surfaces, and chemical treatments of these surfaces, have been investigated in the last years, but an universal solution for all the applications aforementioned could not be identified. Following this very actual theme, our main focus in this chapter is to discuss different applications in biosensing of a special class of amphiphilic proteins: the hydrophobins. These proteins self-assemble in a nanometric biofilm at the interfaces between water and air, or on the surfaces covered by water solution. New functionalities can be added to the biosensors surfaces without using any chemical or physical treatment, just covering them by a self-assembled protein biofilm. The main topics covered in the following paragraphs are: origin and properties of the hydrophobins; deposition methods of the hydrophobins biofilm on different surfaces and the characterizations techniques we use to determine the physical properties of these bio-interfaces; the features exhibited by the hydrophobins covered surfaces, and finally, the biosensors systems based on hydrophobins biofilms. We outline in this chapter how the peculiarities of these proteins can be of interest in the technological field, beyond their large utilization in biotechnology, nowadays at industrial level. Moreover, the experience matured on this subject can be the paradigm of a new kind of approach in design and realization of the next generation of biosensors.

We propose and demonstrate a sensing platform based on plasmonic metasurfaces for the detection of very low concentrations of deoxyribo-nucleic acid (DNA) fragments. The platform relies on surface-enhanced infrared absorption spectroscopy, implemented via a multispectral metasurface. Specifically, different regions (“pixels”) are engineered so as to separately cover the medium-infrared range of the electromagnetic spectrum extending from the functional-groups to the fingerprint region of a single analyte. In conjunction with a suitable bio-functionalization, this enables univocal and label-free recognition of specific molecules. For experimental validation, we fabricate a large-area gold metasurface on a silicon chip, and functionalize it with a recognition layer of peptide nucleic acid (PNA). Our experimental results indicate the possibility to detect complementary DNA fragments in concentrations as low as 50 fM, i.e., well below the value attained by standard methods, with additional advantages in terms of processing time, versatility and ease of implementation/operation.

Large-area and transparent all-dielectric metasurfaces sustaining photonic bound states in the continuum (BICs) provide a set of fundamental advantages for ultrasensitive biosensing. BICs bridge the gap of large effective mode volume with large experimental quality factor. Relying on the transduction mechanism of reactive sensing principle, herein, we first numerically study the potential of subwavelength confinement driven by topological decoupling from free space radiation for BIC-based biosensing. Then, we experimentally combine this capability with minimal and low-cost optical setup, applying the devised quasi-BIC resonator for PNA/DNA selective biosensing with real-time monitoring of the binding event. A sensitivity of 20 molecules per micron squared is achieved, i.e. ≃0.01 pg. Further enhancement can easily be envisaged, pointing out the possibility of single-molecule regime. This work aims at a precise and ultrasensitive approach for developing low-cost point-of-care tools suitable for routine disease prescreening analyses in laboratory, also adaptable to industrial production control.

In this work, we employed the Raman microscopy to study the internalization kinetics and spatial distribution of small interfering RNA (siRNA)-diatomite nanoparticles (DNPs) complex in human lung epidermoid carcinoma cell line (H1355) up to 72 h. Raman images are compared with confocal fluorescence microscopy results. The Raman analysis provides that the siRNA-DNPs are internalized and co-localized in lipid vesicles within 18 h, after that equilibrium is achieved.

In this article, the realization and characterization of a new kind of resonant cavity enhanced photo-detector, fully compatible with silicon microelectronic technologies and working at 1.55 μm, are reported. The detector is a resonant cavity enhanced structure incorporating a Schottky diode, and its working principle is based on the internal photo-emission effect. A comparison between a Schottky diode (Al/Si or Cu/Si) and the Schottky diode fed on a high-reflectivity Bragg mirror is carried out. Considering Al as Schottky metal, no difference in responsivity is obtained; considering Cu as Schottky metal, a three-fold responsivity improvement is experimentally demonstrated.

article i nfo Development of non-volatile memories based on organic soft materials is one of two main trends in industry for flash-memories. The electrical bistability of such materials makes them ideal candidates for cost-effective, fast programming switching devices. SiO2-Rose Bengal (bis-triethylammonium) hybrid thin films are reported here together with their characterizations. The technology yields well reproducible films with good current-voltage switching characteristics. Owing to their physical and chemical stability the films are suited to standard micro-photolitography technology, rendering their fabrication cost-effective.

The performances of a digital optical switch, based on the thermo-optic effect in amorphous silicon, are investigated for the first time to our knowledge. Numerical simulations shows that the strong thermo-optic effect of amorphous silicon combined with the possibility of realizing micrometric integrated structures, allow the realization of efficient waveguide devices capable of microsecond switching times. The switch, operating at the infrared communications wavelength of 1550 nm, can be easily integrated in silicon optoelectronic circuits and is thought for low-cost photonic applications.

Department of Physical Sciences, University of Naples “Federico II”, Via Cinthia, 80126 Naples, Italy * Author to whom correspondence should be addressed. E-mail: luca.destefano@na.imm.cnr.it Received: 15 February 2007 / Accepted: 26 February 2007 / Published: 28 February 2007 Abstract: A photochemical functionalization process which passivates the porous silicon surface of optical biosensors has been optimized as a function of the thickness and the porosity of the devices. The surface modification has been characterized by contact angle measurements. Fluorescence measurements have been used to investigate the stability of the DNA single strands bound to the nanostructured material. A dose-response curve for an optical label-free biosensor in the 6-80 µM range has been realized. Keywords: Optical Biosensors, Porous Silicon, Biochip. 1. Introduction Biosensors are nowadays technological hot topics due to the possible applications in social interest fields such as medical diagnostic and health care, monitoring of environmental pollutants, home and defence security [1]. Besides the signal generated by the sensing device, the biosensor is constituted by the molecular recognition element and the transducer material. The molecular recognition element can be a biological molecule, such as DNA single strand, proteins, enzymes, or a biological system, such as

Nanostructured materials, due to their peculiar physical and chemical properties, constitute the new class of functional supports for specific innovative applications. There is a strong competition between synthetic, man-made nanostructured materials and those coming directly from nature: the first ones can be precisely tailored by properly design and fabrication; the second ones are directly available without any cost of production. In this paper, we report our latest achievements on different materials, porous silicon, zinc oxide nanowires and diatomite powders, which belong to these categories.

In this paper, a new strategy for highly selective and sensitive direct detection of lymphoma cells by exploiting the interaction between a peptide and its B-cell receptor, has been evaluated. In particular, an idiotype peptide, able to specifically bind the B-cell receptor of A20 cells in mice engrafted with A20 lymphoma, has been used as molecular probe. The new detection technique has been demonstrated on a planar crystalline silicon chip. Coverage of 85% of silicon surface and detection efficiency of 8.5 × 10(-3) cells/μm(2) were obtained. The recognition strategy promises to extend its application in studying the interaction between ligands and their cell-surface receptors.

The thermo-optic coefficient (TOC) of hydrogenated amorphous silicon (a-Si:H) has been measured in the temperature range 30–200 °C, at the communication wavelength of 1.55 μm . The experimental data have been fitted using a single oscillator model that takes into account the shape of e2-spectrum of the amorphous semiconductor. The extracted parameters significantly extend, and are consistent with, the few data reported in the literature. An interesting analogy with crystalline silicon (c-Si) is also found and discussed.

A novel 2-bit nano-silicon based non-volatile memory is proposed to double memory density. The thin film structure exhibits two conduction states (ON and OFF) at different voltages and has a cost-effective structure. The structure utilizes the good electrical properties of fluorinated SiO"2 thin films, together with the bi-stable properties conferred by the nano-silicon particles therein embedded. A polymeric layer of 8-hydroxyquinoline aluminum salt (Alq3) further deposited on the top of the nano-particle layer through chemical evaporation and a silver paste contact determines the final structure. The positive 0-15V scan reveals two discontinuities with an ON/OFF ratio of 10^4-10^5 (2-4V) and OFF/ON of 10^3 (12.5-13.0V). The reverse scan displays again two distinct thresholds, range of 10.5-11.0V (ON/OFF ratio 10^-^3), respectively, 0.5V (OFF/ON ratio 10^-^5-10^-^4).

Starting from an a-Si:H/a-SiC:H stack deposited by glow discharge on a crystal silicon wafer, we have fabricated and measured the properties of rib waveguides suitable for infrared optical communication purposes. Propagation losses as small as 0.7 dB/cm have been measured. The same waveguiding structure has been utilised for the construction of Fabry–Perot interferometers. As the process is compatible with the standard microelectronic technologies, the integration of optical and electronic functions on the same chip becomes possible.

Hydrophobins are small proteins secreted by fungi, which self-assemble into amphipathic membranes at air–liquid or liquid–solid interfaces. The physical and chemical properties of some hydrophobins, both in solution and as a biofilm, are affected by poly or oligosaccharides. We have studied the interaction between glucose and the hydrophobin Vmh2 from Pleurotus ostreatus by spectroscopic ellipsometry (SE), atomic force microscopy (AFM) and water contact angle (WCA). We have found that Vmh2–glucose complexes forms a chemically stable biofilm, obtained by drop deposition on silicon, 1.6 nm thick and containing 35 per cent of glucose, quantified by SE. AFM highlighted the presence of nanometric rodlet-like aggregates (average height, width and length being equal to 3.6, 23.8 and 40 nm, respectively) on the biofilm surface, slightly different from those obtained in the absence of glucose (4.11, 23.9 and 64 nm). The wettability of a silicon surface, covered by the organic layer of Vmh2–glucose, strongly changed: WCA decreased from 90° down to 17°.

A crystalline silicon surface can be made biocompatible and chemically stable by a self-assembled biofilm of proteins, the hydrophobins (HFBs) purified from the fungus Pleurotus ostreatus. The protein modified silicon surface shows an improvement in wettability and is suitable for immobilization of other proteins. Two different proteins were successfully immobilized on the HFBs coated chips: the bovine serum albumin and an enzyme, a laccase, which retains its catalytic activity even when bound on the chip. Variable angle spectroscopic ellipsometry (VASE), water contact angle (WCA), and fluorescence measurements demonstrated that the proposed approach in silicon surface bioactivation is a feasible strategy for the fabrication of a new class of hybrid biodevices

A new class of silicon electro-optical modulators for λ = 1.3 and 1.55 μm is proposed and analyzed. The devices, based on single- and multi-pass Fabry-Perot interferometry, can be built by standard microelectronic tecniques.

Using fresh water diatom, identified as Melosira variance which is growing faster than other algae in the ponds, we characterized the ultrastructure of its silica frustule by electron microscopic observations. On hypothesizing that the ultrastructure has some meanings in photosynthesis, behaviors of a single frustule toward light irradiation were analyzed using an optical fiber. We found that the frustule absorbed light mainly in the blue wavelength region. The theoretical analyses of optical properties supported experimental results and suggested a strong interaction between blue light and inner silica materials. It is speculated that the interaction served for partial extinction of excessive irradiation of blue light and for enhancing photosynthesis of the diatom. © 2008 American Institute of Physics.

The authors have compared the sensitivities of resonant optical biochemical sensors, based on both periodic and aperiodic porous silicon structures, such as the Bragg and the Thue-Morse multilayer. The shifts of the reflectivity spectra of these devices on exposure to several chemical compounds have been measured: the aperiodic multilayer is more sensitive than the periodic one. Adopting a simple theoretical model of the optical response of devices, they inferred that the aperiodic structure provide a higher filling capability with respect to the periodic one, due to the lower number of interfaces.

The anisotropic wet micromachining of silicon, based on a water solution of potassium hydroxide (KOH), is a standard fabrication process that is extensively exploited in the realization of very complex microsystems, which comprise cantilevers, membranes, and bridges. A nanostructured self-assembled biofilm of amphiphilic proteins, the hydrophobins, was deposited on crystalline silicon by solution deposition and characterized by variable-angle spectroscopic ellipsometry (VASE). This procedure formed chemically and mechanically stable mono- and multilayers of self-assembled proteins. The biomolecular membrane has been tested as masking material in the KOH wet etch of the crystalline silicon. The process has been monitored by VASE and atomic force microscopy measurements. Because of the high persistence of the protein biofilm, the hydrophobin-coated silicon surface is perfectly protected during the standard KOH micromachining process.

In this communication, the design and the fabrication of a silicon-glass microsystem for lab-on-chip sensing applications have been reported. Each component has been realised using wet etch process and the porous silicon (PSi) technology, while the final device has been obtained intimately joining all elements by the Anodic Bonding (AB) process. The flow injection analysis (FIA) principle has been adopted in the microfluidic manipulation of the analyte samples: very small volume of the substances can be quickly and repeatedly monitored. The transducer element of the sensor device is a PSi Fabry-Perot monolayer which allows a very effective interaction with several chemicals and biological molecules. Time resolved measurements revealed very rapid response times in detecting some volatile substances.

Lithium batteries have found a wide range of applications due to their very compact energy packing and effective cost. Theoretically Li-cells can hold up to 5V, however to date no mass-produced rechargeable battery surpasses 4 V. The structure here analyzed consists of: lithium porous cathode, solid electrolyte and silver anode. A spinel LiNi0.4X0.1Mn1.5O4 sol-gel layer was deposited on a porous substrate in order to obtain higher specific surface for single chips. The anode was thermally evaporated Ag. The electrolyte used was a sol-gel hybrid layer containing Li ions. The devices, fabricated on ceramic wafers, displayed high capacities.

In this paper, the design of a resonant cavity enhanced photodetector, working at 1.55 µm and based on silicon technology, is reported. The photon absorption is due to the internal photoemission effect over the Schottky barrier at the metal–silicon interface. The photodetector is composed of a silicon layer in between multiple layers of Si–SiO2, as a bottom mirror, and a thin Au film and dielectric coating, as a top mirror. In order to estimate the quantum efficiency, we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory) and its extension for thin films, while for the optical analysis of the device, used to calculate mirror reflectivities and active layer absorptance, a numerical method based on the transfer matrix method has been implemented. Our numerical results prove a significant enhancement of the efficiency obtained at resonant wavelengths by a very thin absorbing layer.

In this paper, the design of a resonant cavity-enhanced (RCE) Schottky photodetector, based on internal photoemission effect and working at 1.55 μm, is presented. In order to estimate the theoretical quantum efficiency we take the advantage of analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films, while for the optical analysis of device a numerical method, based on the transfer matrix method, has been implemented. Finally, we complete our design calculating bandwidth and bandwidth-efficiency product. Our numerical results prove that a quantum efficiency of 0.1% is obtained at resonant wavelength (1.55 μm) with a very thin absorbing metal layer (30 nm). Theoretical values of 100 GHz and 100 MHz were obtained, respectively, for the carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency. The proposed photodetector can work at room temperature and its fabrication is completely compatible with standard silicon technology.

A non-perturbing, fast, low-cost probe for near-field measurements is presented in this paper. The new sensing technique's capabilities in antenna fault diagnosis and direct measurement of field intensity distribution at subwavelength distance from the sources are demonstrated by test measurement on different microwave antennas and applicators. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 95–98, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10981

A novel amorphous-silicon-based photonic micromodulator is proposed which can be easily integrated into silicon low-cost optoelectronic appliances. The device is designed to operate at the two infrared communication wavelengths of 1300 and 1550 nm, either on broad or narrow spectrum sources, and is activated by visible light pulses controlling the infrared light absorption coefficient through the generation of free carriers. A planar waveguide integrated prototype has been fabricated on a silicon wafer by plasma enhanced chemical vapour deposition, and tested at bit rates up to 200 kbit/s.

A new non-disturbing photonic probe for measuring electromagnetic (EM) power is presented. The sensing element is made of a silicon Fabry–Perot optical microcavity connected to an optical fiber for remote interrogation. Preliminary measurements have been carried out in a non-optimized prototype in the frequency range 2–18 GHz. They have shown the capability to detect minimum EM power densities of ∼1.4 mW/cm 2 , and a flat response at frequencies greater than 10 GHz. A proper calibration makes the sensor useful as an E-field probe. In this case, resolutions as low as 8 V/m have been measured. A simple theoretical analysis giving results in fair agreement with the experiments is also reported. Simulations show that wide margins of optimizations of the sensor exist.

The present work reports on our recent achievements in the exploitation of a simple technology for the fabrication of hydrogenated amorphous silicon (a-Si:H) based low-loss rib waveguides. In particular, waveguides with various widths have been fabricated out of an a-SiC:H/a-Si:H stack deposited by plasma enhanced chemical vapor deposition at the relatively low temperature of 220 degrees C. The ribs were defined by an anisotropic, CH4-based, reactive ion etching process. The devices have been subsequently characterized by cut-back technique. Even though a dependence of attenuation parameter on the waveguide width was observed, propagation losses as low as 0.7 dB/cm could be measured at λ=1.3 μm, in good agreement with he theoretical estimations based on the intrinsic absorption of the material. Starting from the same structure, a Fabry- Perot thermo optical modulator has been also fabricated and tested at the communication wavelength of 1.3 μm.

Waveguides and interferometric light amplitude modulators for application at the 1.3- and 1.55-/spl mu/m fiber communication wavelengths have been fabricated with thin-film hydrogenated amorphous silicon and its related alloys. The technique adopted for the thin-film growth is the plasma- enhanced chemical vapor deposition, which has been shown to give the lowest defect concentration in the film. Consequently the proposed waveguiding structures take advantage of the low optical absorption shown by a-Si:H at photon energies below the energy gap. In addition a good radiation confinement can be obtained thanks to the bandgap tailoring opportunity offered by this simple and inexpensive technology. In particular rib waveguides, based on a a-SiC:H/a-Si:H stack, have been realized on crystal silicon, showing low propagation losses. Recently, however, a new interest as low as 0.7 dB/cm. The same structure has been utilized for the fabrication of thermooptic Fabry-Perot modulators with switching times of 10 /spl mu/s. Modulators based on the alternative waveguiding configuration ZnO/a-Si:H, giving comparable results, are also presented.

The realization of single-mode rib waveguides in standard epitaxial silicon layer on lightly doped silicon substrate, using ion implantation to form the lower cladding, is reported. The implanted buffer layer enhances' the vertical confinement and improves the propagation characteristics. Respect to similar standard all-silicon waveguides a propagation loss reduction of about 7 dB/cm, in the single-mode regime, has been measured. A numerical analysis has been performed to evaluate the theoretical attenuation and the transverse optical field profiles. As a result of the presence of the ion implanted buffer layer, an increase of the fundamental mode confinement factor from 0.3 to 0.85 has been calculated. This results in a great enhancement of the coupling efficiency with standard single-mode optical fibers. Moreover, the proposed technique is low cost, fully compatible with standard VLSI processes, and allows a great flexibility in the integration of guided-wave devices and electronic circuits. Finally, the very high thermal conductivity characterizing these waveguides makes them attractive host-structures for electrically and thermally controlled active optical devices.

A new class of temperature silicon micro-sensors, based on an interferometric optical technique, is presented. The sensing element consists of a planar Fabry-Perot cavity defined on a silicon wafer by highly anisotropic reactive ion etching, and is therefore suitable for full integration with other standard opto- and micro-electronic devices. Preliminary temperature measurements have been performed with the temperature resolutions predicted by the theory. The limit performances, in terms of resolution, speed of operation and energy dissipation of this class of sensors are discussed in detail. In particular, a final temperature resolution of 0.064/spl deg/C is expected for a low loss interferometric cavity, with a settling time of 150 ns and a 0.2% readout error. An energy resolution as low as 30 nJ is also estimated.

Complex micro- and nanostructured materials for optical sensing purposes are designed and fabricated using top technologies. A completely different approach to engineering systems at the nanoscale consists in recognizing the nanostructures and morphologies that nature has optimized during life's history on earth. We have found that the photoluminescence emission from silica skeleton of marine diatoms Thalassiosira rotula Meunier is strongly dependent on the surrounding environment. Both the optical intensity and the peaks positions are affected by gases and organic vapors. Depending on the electronegativity and polarizing ability, some substances quench the luminescence, while others effectively enhance it. These phenomena allow the discrimination between different substances. These naturally occurring organisms are thus good candidates as optical sensing materials. © 2005 American Institute of Physics.

A new non-disturbing optically interrogated silicon sensor for measuring electromagnetic power in the microwave and millimetre-wave range is presented. A prototype was realised and then tested in the microwave frequency range 2.5-18 GHz. A minimum detectable electromagnetic power density of /spl sim/1.4 mW/cm/sup 2/ was measured. Higher performances are expected, according to simulations, in optimised devices.

A theoretical study aimed at the optimum design of thermo- optic guided-wave switches realized in silicon-on-oxide technology is reported. The heat transfer processes occurring inside such devices are analyzed by means of a 3D finite element thermal simulator. In particular, in rib waveguiding structures, we demonstrate that the optimum values of the oxide layer thickness and of the outer rib height are a function of the heating pulse power used to drive the device. The theoretical results carried out are consistent with the experiments reported in literature.

An integrated interferometric temperature sensor, realized on a silicon substrate, is presented. The device consists of an array of planar Fabry-Pe´rot waveguiding cavities realized by plasma etching and standard microelectronic techniques. Experimental data demonstrating the monitoring of temperature variation both in modulus and sign, with a resolution of approximately I°C, are reported. The influence of the cavity losses and size on the sensor performance is discussed. The realization of amorphous silicon-based guided-wave sensors is then suggested to obtain better temperature resolution.

The temperature dependence of the thermo-optic coefficient for crystalline silicon has been measured in the temperature range between room temperature and 550 K at the wavelength of 1523 nm by means of an interferometric technique. This technique, which requires a very simple experimental setup, is based on the observation of the fringe pattern produced by temperature changes in a Fabry–Perot resonator. Measurement results indicate that the thermo-optic coefficient is independent on the sample doping and crystal plane orientation. The experimental data appear to be in agreement with the few values reported to date at this important wavelength. The temperature dependence of the excitonic band gap is also calculated by fitting these data with a recently introduced model of ∂n/∂T.

The thermo-optic coefficient ∂n/∂T has been measured from room temperature to 600 K at the wavelength of 1523 nm in three important semiconductors for fiber-optic device fabrication, namely, InP, GaAs, and 6H–SiC. The adopted technique is very simple and is based on the observation of the periodicity of the signal transmitted, at the desired wavelength, by an etalon made of the material under test, when it experiences a temperature variation. The values of ∂n/∂T measured in InP and GaAs at room temperature are in agreement with previously reported ones, but increase with temperature with a weak quadratic dependence. SiC conversely shows a lower thermo-optic coefficient (2.77×10−5 K−1) at 300 K, which, however, doubles for a 300 K temperature increase.

The strong thermo-optic effect in silicon has been exploited for the fabrication of new sensing and communication devices. A temperature sensor, an electromagnetic energy sensor and an optical modulator are in particular presented. These devices, all working on interferometric principles, have been realized by means of the silicon standard microelectronic technologies, and are therefore suitable for full integration with on-chip circuitry. New thermo-optical materials are finally proposed with superior characteriztics, which still maintain the compatibility with VLSI technology.