Publications related to CMI - Comite de Direction

Fully self-contained turn-key soliton microcomb source

Jijun He, John David Jost, Tobias Kippenberg, Grigorii Likhachev, Junqiu Liu, Arslan Sajid Raja, Rui Ning Wang

We demonstrate a turn-key microcomb source based on 100 GHz Si3N4 ring microresonator. The device is fully optically and electronically integrated in a compact box, which runs by pushing one button.

IEEE2021

A Generalized Phase-Shift PWM Extension for Improved Natural and Active Balancing of Flying Capacitor Multilevel Inverters

Georgios Kampitsis, Elison de Nazareth Matioli

The emergence of wide bandgap power devices has brought the attention back to the flying capacitor (FC) multilevel inverters with a large number of stages, in an effort to increase the power density by minimizing the passive components. The main challenge that such systems face, particularly the ones based on high-frequency Gallium-Nitride devices and small-value ceramic capacitors, relate to the stringent requirements for precise and fast capacitor balancing. Conventional natural balancing techniques exhibit poor settling times, while most improved natural balancing methods are not easily scalable to more than five levels. The alternative of active balancing normally requires one isolated sensor per FC which increases the overall system cost and footprint, or a single ac-side sensor that is more compact but calls for sophisticated PWMs that again are not available for multiple levels. In this paper we introduce a generalized pulse width modulation (PWM) strategy based on the phase-shift and carrier swapping principles for an arbitrary number of levels. We provide an easy and intuitive method for the extraction of the PWM pattern, the switching states, and their sequence. Simulations were carried out in Matlab/Simulink and experimental tests were conducted on a single-phase 7-level GaN inverter prototype. Not only is the extended PWM advantageous in natural balancing, but it also provides the right zero switching states for ac-side FC sensing in active balancing.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

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Implantable devices for localized and controlled drug release are important, e.g., for therapies of cancer and chronic pain. However, most of the existing active implants are limited by the usage of nonbiodegradable materials; thus, surgery is needed to extract them after the treatment, which leads to secondary damage. Here, we show a fully biodegradable composite membrane made from silk fibroin and magnetic nanoparticles (MNPs). The membrane porosity can be remotely modified by an alternating magnetic field, which opens nanopores by local heating of MNPs in the composite allowing a liquid to diffuse through them. The stability of the silk membrane in water can be prolonged up to several months by increasing its beta-sheet content through ethanol annealing. We present the following original findings. (a) Nanopores can be generated inside the silk/MNP composite membrane by exposing it to an external alternating magnetic field. (b) A longer exposure time results in more nanopore sites. (c) The controllable release of rhodamine B dye is achieved by tuning the period of exposure to the magnetic field. The obtained results demonstrate the suitability of the investigated silk/MNP composite membrane as a potential functional material for implantable drug delivery.

AMER CHEMICAL SOC2022

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The science and engineering of two-dimensional materials (2DMs), in particular, of 2D semiconductors, is advancing at a thriving pace. It is well known that these delicate few-atoms thick materials can be damaged during the processing toward their integration into final devices. Thermal scanning probe lithography (t-SPL) is a gentle alternative to the typically used electron beam lithography to fabricate these devices avoiding the use of electrons, which are well known to deteriorate the 2DMs' properties. Here, t-SPL is used for the fabrication of MoS2-based field effect transistors (FETs). In particular, the use of t-SPL is demonstrated for the first time for the fabrication of edge-contact MoS2 FETs, combining the hot-tip patterning and Ar+ milling to etch the 2DM. To avoid contamination of the contact interface by atmospheric gas molecules, etching and metal deposition are performed without breaking the vacuum conditions in between. With this process, edge contact MoS2 FETs are successfully fabricated and characterized. On/off ratios up to 10(8) and 10(9) are obtained at room temperature in air and vacuum, respectively, i.e., comparable with the best values reported in the literature.

AMER CHEMICAL SOC2022

Electrically tunable optical resonator on a chip for fast tunable integrated lasers

Tobias Kippenberg, Grigorii Likhachev, Anat Siddharth

The present invention relates to an electrically tunable photonic resonator device for a component having a fast and flat actuation response, comprising: - At least one optical waveguide with an optical interface for coupling in laser light, - At least one optical resonator including a waveguide being made of an optical resonator material, particularly Si3N4, wherein laser light coupled via the at least one optical waveguide is coupled into the at least one optical resonator, - At least one piezo actuator to apply mechanical stress at least partially onto the at least one optical resonator; wherein the at least one optical resonator, the at least one piezo actuator and the at least one optical waveguide are monolithically integrated on a common substrate of the photonic resonator device; - a mechanical mode suppression means configured to attenuate one or more mechanical modes of oscillation caused by an AC operation of the at least one piezo actuator.

2022

Selective area epitaxy of GaAs: the unintuitive role of feature size and pitch

Akshay Balgarkashi, Elif Nur Dayi, Didem Dede, Anna Fontcuberta i Morral, Martin George Friedl, Lucas Güniat, Nicholas Paul Morgan, Valerio Piazza

Selective area epitaxy (SAE) provides the path for scalable fabrication of semiconductor nanostructures in a device-compatible configuration. In the current paradigm, SAE is understood as localized epitaxy, and is modelled by combining planar and self-assembled nanowire growth mechanisms. Here we use GaAs SAE as a model system to provide a different perspective. First, we provide evidence of the significant impact of the annealing stage in the calculation of the growth rates. Then, by elucidating the effect of geometrical constraints on the growth of the semiconductor crystal, we demonstrate the role of adatom desorption and resorption beyond the direct-impingement and diffusion-limited regime. Our theoretical model explains the effect of these constraints on the growth, and in particular why the SAE growth rate is highly sensitive to the pattern geometry. Finally, the disagreement of the model at the largest pitch points to non-negligible multiple adatom recycling between patterned features. Overall, our findings point out the importance of considering adatom diffusion, adsorption and desorption dynamics in designing the SAE pattern to create pre-determined nanoscale structures across a wafer. These results are fundamental for the SAE process to become viable in the semiconductor industry.

IOP Publishing Ltd2022

Comparison of electrical and optical transduction modes of DNA-wrapped SWCNT nanosensors for the reversible detection of neurotransmitters.

Giovanni Boero, Jürgen Brugger, Nergiz Sahin Solmaz

In this study, we compare the electrical and optical signal transduction of nanoscale biosensors based on single -walled carbon nanotubes (SWCNTs). Solution processable single-stranded (ss) DNA-wrapped SWCNTs were used for the fabrication of the distinct sensors. For electrical measurements, SWCNTs were assembled from solution onto pre-patterned electrodes by electric-field-assisted assembly in field-effect transistor (FET) configuration. A combination of micro-and nano-fabrication and microfluidics enabled the integration into a sensing platform that allowed real-time and reversible detection. For optical measurements, the near-infrared (NIR) fluorescence of the SWCNTs was acquired directly from solution. The detection of important biomolecules was investigated in high-ionic strength solution (0.5xPBS). Increase in fluorescence intensities correlated with a decrease in the SWCNTs electrical current and enabled detection of the important biomolecules dopamine, epinephrine, and ascorbic acid. For riboflavin, however, a decrease in the fluorescence intensity could not be associated with changes in the SWCNTs electrical current, which indicates a different sensing mechanism. The combination of SWCNT-based electrical and optical transduction holds great potential for selective detection of biomarkers in next generation portable diagnostic assays.

ELSEVIER ADVANCED TECHNOLOGY2022

Micro 3D printing of a functional MEMS accelerometer

Damien Maillard, Simone Pagliano, Göran Stemme, Luis Guillermo Villanueva Torrijo

Microelectromechanical system (MEMS) devices, such as accelerometers, are widely used across industries, including the automotive, consumer electronics, and medical industries. MEMS are efficiently produced at very high volumes using large-scale semiconductor manufacturing techniques. However, these techniques are not viable for the costefficient manufacturing of specialized MEMS devices at low- and medium-scale volumes. Thus, applications that require custom-designed MEMS devices for markets with low- and medium-scale volumes of below 5000-10,000 components per year are extremely difficult to address efficiently. The 3D printing of MEMS devices could enable the efficient realization and production of MEMS devices at these low- and medium-scale volumes. However, current micro-3D printing technologies have limited capabilities for printing functional MEMS. Herein, we demonstrate a functional 3D-printed MEMS accelerometer using 3D printing by two-photon polymerization in combination with the deposition of a strain gauge transducer by metal evaporation. We characterized the responsivity, resonance frequency, and stability over time of the MEMS accelerometer. Our results demonstrate that the 3D printing of functional MEMS is a viable approach that could enable the efficient realization of a variety of custom-designed MEMS devices, addressing new application areas that are difficult or impossible to address using conventional MEMS manufacturing.

SPRINGERNATURE2022

Experimental demonstration of dynamic spatiotemporal structured beams that simultaneously exhibit two orbital angular momenta by combining multiple frequency lines, each carrying multiple Laguerre-Gaussian modes

Maxim Karpov, Tobias Kippenberg, Hao Song, Xinzhou Su, Zhe Zhao

In general, there are different, relatively independent forms of orbital angular momenta at a given propagation distance, which might exhibit different dynamic spatial characteristics. One type involves a beam with a helical phase-front that rotates around its own beam center, such as a Laguerre-Gaussian (LG) beam with an azimuthal index not equal to zero. The other one is a Gaussian-like beam dot that revolves around a central axis. Here, we experimentally demonstrate the generation of a dynamic spatiotemporal (ST) structured beam that simultaneously exhibits both rotation and revolution at a given propagation distance. Nine Kerr frequency comb lines are coherently combined, each carrying a designed superposition of multiple LG modes containing one unique l value and multiple p values. Experimental results showthat the mode purity of the reconstructed revolving and rotating LG(30) beam is similar to 89% when both the beam waist and revolving radius (R) are 0.4 mm. Moreover, we explore the effects of the number of frequency comb lines and the R value on the mode purity of the generated ST beam. Consequently, we find that a higher mode purity can be achieved by involving more frequency comb lines or reducing the R. (C) 2022 Optica Publishing Group

Optica Publishing Group2022

Gain-switched semiconductor laser driven soliton microcombs

Jijun He, Tobias Kippenberg, Junqiu Liu, Erwan Guillaume Albert Lucas, Wenle Weng

Using phase-engineered coherent laser pulses produced by gain-switched semiconductor lasers, we generate low-power-threshold soliton microcombs whose repetition frequencies are in the X-band and K-band microwave ranges. (c) 2021TheAuthor(s)

IEEE2021