Photonic technologies have since long dreamed of non-invasive monitoring tools to inspect the light inside optical waveguides. By exploiting photon interaction with intra-gap energy states localized at the waveguide surface, we demonstrate that light intensity can be monitored by measuring the electric conductance of the silicon waveguide through a capacitive access to the waveguide via the SiO cladding.
This approach realizes a ContactLess Integrated Photonic Probe (CLIPP), that is simple, inherently CMOS compatible, noninvasive and scalable to hundreds of probing points per chip.
Light monitoring with a sensitivity of -30 dBm and a dynamic range of 40 dB is demonstrated in waveguides and high-Q resonators, and for the tuning of coupled-resonator optical filters.
The CLIPP concept has been demonstrated on both silicon (Si) and indium phosphide (InP) photonic platforms, and has been utilized in several different applications, including for instance automatic fiber-to-waveguide alignment, wavelength tuning and stabilization of micro-ring resonators (MRRs) , light-path tracking and feedback-control of switch fabrics.
The group is now involved in the European Project STREAMS (http://ict-streams.eu/ ) having the overall objective to develop the necessary Silicon Photonics Transceiver and Routing technologies towards a new, power efficient, WDM-based, Tb/s, optical on-board interconnection paradigm that enables multiple high bandwidth, point-to-point direct links on the board level, as a step forward to the realization of multi-socket server blades technology.
The group will develop all the electronics to read the CLIPP sensors and to feedback control the operating point of the many optical devices in the Photonic chip.

Click here for a Video on the STREAMS project

S. Grillanda, M. Carminati, F. Morichetti, P. Ciccarella, A. Annoni, G. Ferrari, M. Strain, M. Sorel, M. Sampietro, A. Melloni
"Noninvasive monitoring and control in silicon photonics using CMOS integrated electronics"
Optica, vol. 1, no. 3, pp. 129-135, 2014, doi: 10.1364/OPTICA.1.000129.

F. Morichetti, S. Grillanda, M. Carminati, G. Ferrari, M. Sampietro, M.J. Strain, M. Sorel, A. Melloni
"Non-invasive on-chip light observation by contactless waveguide conductivity monitoring"
IEEE J. Sel. Top. Quant. Electron., v.20, n.4, pp.292-301, 2014,
doi:10.1109/JSTQE.2014.2300046.

Integrated circuits for high sensitivity impedance measurements

By means of a CMOS ultra-low-noise and wide-bandwidth current sensing circuit, the experimental detection of capacitance variations with a resolution as low as few zeptoFarads (10-21 F) has been achieved. The mm-sized chip can be easily integrated in extremely compact sensing setups. The adoption of an integrated implementation provides miniaturization, state-of-art performance, multi-sensor capability and implantable possibility.
The experimental results match the theoretical expectation down to a resolution of 5 zF rms with 6V across the sample at 100 kHz and 100 ms time constant. The achieved current resolution of 15 fA rms (at ms time scale) and the tracking of 40 zF capacitance steps demonstrate how the read-out circuit can serve as a versatile tool for the development of nano-biosensors.

M. Carminati , G. Ferrari, F. Guagliardo, M. Sampietro
"ZeptoFarad capacitance detection with a miniaturized CMOS current front-end for nanoscale sensors"
Sensors and Actuators A, Vol.172 (2011) pp. 117-123. doi:http://dx.doi.org/10.1016/j.sna.2011.02.052

CMOS for electrochemistry with nanoelectrodes

Nano-electrochemical and bio-sensing applications require the reading of the few electrons that are exchanged at the interface, either since the electrode area is nanometric or since the concentration of the redox species is extremely low. To this aim an integrated CMOS current preamplifier used as an add-on for standard bench-top electrochemical instrumentation has been made, providing a current amplification of 1000 over the wide frequency range DC-2MHz and can be placed at the input of a current-to-voltage converter.
Thanks to its millimetric size it drastically reduces the input stray capacitance of the connection cables to the electrode, offering superior noise performance such as 0.55fA (rms) current resolution with 1Hz bandwidth demonstrated in the detection of 1.5fA current steps, allowing to increase the largest measurable impedance by two orders of magnitude (up to 100GOhm with only 10mV applied and 0.125s averaging time) and the impedance noise in time tracking is reduced 35 times.

M. Carminati, G. Ferrari, D. Bianchi, M. Sampietro,
"FemtoAmpere Integrated Current Preamplifier for Low Noise and Wide Bandwidth Electrochemistry with Nanoelectrodes"
Electrochimica Acta (2013), http://dx.doi.org/10.1016/j.electacta.2013.03.093

Fully Ink-Jet printed organic-based image sensor on a large area plastic foil

By making use of Drop-On-Demand inkjet printing, that allows the definition of structures with a lateral resolution down to few tens of micrometer, we are developing organic-based photodetectors and transistors with a completely additive approach, where both the electrodes and the photoactive layer are printed. Aiming at large area applications in the field of visible light or X-ray digital imagers, we are focusing on devices with an active area of about 100x100 um and we are having obtained excellent optoelectronic performances for the fully printed devices, with good yield and reproducibility.
This work is made in collaboration with IIT, the Italian Institute of Technology under the financial support of "Fondazione Cariplo", grant n. 2011-0368.

G. Azzellino. A. Grimoldi, M. Binda, M. Caironi, D. Natali, and M. Sampietro
"Fully inkjet printed organic photodetector with high quantum yield"
Advanced Material, Vol.25, Issue 47, pp. 6829-6833, (2013)
DOI: 10.1002/adma.201303473

On-fiber photodetector for in-situ sensing

We have demonstrated an integrated fiber/receiver system made by direct deposition of an Organic Photodetector (OPD) onto a plastic optical fiber (POF) output facet.
Fundamental to this achievement has been the exploitation of spray coating technique for the deposition of the solution processible OPD organic layers onto the highly non-planar and unconventional substrate.
The obtained figures of merits, such as the almost flat EQE over a wide light intensity range of more than two orders of magnitude and the capability of detecting light pulses with response time as low as about 10 us, certify the first example of successful deposition of functional layers onto an optical fiber.

Maddalena Binda, Dario Natali, Antonio Iacchetti and Marco Sampietro
"Integration of an organic photodetector onto a plastic optical fiber by means of spray coating technique"
Advanced Material, Vol.25, Issue 31, pp. 4335-4339, August 21, 2013
DOI: 10.1002/adma.201301285

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Politecnico di Milano Dipartimento di Elettronica, Informazione e Bioingegneria Piazza L. da Vinci 32  20133 Milano,  Italy

Tel. (+39) 0223996188  Fax (+39) 022367604  Email:    Marco.Sampietro@polimi.it