Search

Surface current patterns in single patch antennas are imaged by means of photoexpansion nanospectroscopy performed with an atomic force microscopy probe and a broadly tunable quantum cascade laser system. The local ohmic losses lead to temperature increase of a thin polymer layer positioned in the cavity, which then expands.

A thin layer of a mid-IR transparent polymer is inserted inside a metallic optical nano-resonator, where a photonic mode and an intersubband transition are strongly coupled together. Acting as a non-perturbative transducer, and without modifying the optical response, the polymer allows the detection of absorbed optical power in the form of thermal expansion due to heat dissipation. This innovative approach permits to identify - even at the single nano-resonator level - the typical anti crossing characteristic of the polaritonic system, and to perform direct imaging of the electromagnetic fields buried within the inside of an otherwise inaccessible optical nanocavity.

The strong light-matter coupling is an exotic phenomenon of interest not only for basic physics, but also because it has potential for improving optoelectronic devices. When dealing with conduction band electrons in semiconductor quantum wells (QWs), intersubband (ISB) transitions can couple to the optical resonances of plasmonic antennas. In the case of strong light-matter coupling, a characteristic anticrossing of the "light" and "matter" excitations is observed. It stems from the appearance of new eigenmodes, called cavity polaritons.

We resolve the dispersion of multiple vibro-polariton modes issued from the coupling of several vibrational bands of the methylene group with a resonant modes of a mid-infrared micro-cavity. The experimental results are in excellent agreement with numerical simulations.

Exploiting the coupling of laser beams to atomic force microscopy probes, both scattering and absorption of mid-infrared radiation (wavelengths of 5 to $11\ \mu \mathrm{m}$ ) have been measured in the near field region of single patch-antennas, strongly coupled to the intersubband transition of an InGaAs/AlInAs quantum well.

Understanding the interplay among the spectrum of electrophysiological signals in the brain, distributed over broad spatial and temporal scales, is fundamental to decipher how brain circuits operate and might dysfunction in disease. Here, we present a multiscale recording system for simultaneous and synchronous acquisitions from a new generation of im-plantable CMOS active probes (single-shaft, 512 microelectrodes, 25 kHz/electrode full-array sampling) as well as from implantable conventional electrode array probes interfaced with a custom-designed CMOS-based headstage. The platform can manage highresolution recordings from up to 4 differently located probes, and one 36-channels low-resolution passive electrode array. As presented here, and prior to complete in-vivo validation, the design and recording performance of high- and low-density electrode array ICs were experimentally tested ex-vivo on retinal whole-mounts.

The optical properties of metallic nano-structures are intimately related to their temperature variation, characteristics which can be exploited for applications such as photocatalysis [1], nanochemistry [2] or sensor devices [3]. Here we show how the geometrical characteristics of the nano-structure, which are related to the structure optical response [4, 5], can in fact be used to modulate the temperature response. The idea is that when metallic structures interact with an electromagnetic field they heat up due to Joule effect. The corresponding temperature increase modifies the optical response of the structure and thus its heating process. The key finding is that, depending on the structures geometry, absorption efficiency can either increase or decrease with temperature. Since absorption relates to the thermal energy dissipation and thus to temperature increase, the mechanism leads to positive or negative loops. Consequently, not only an error would be made by neglecting the role of temperature, but it would be not even possible to know, a priori, if the error is towards higher or lower absorption values. The model, which does not require any fitting parameter, can be utilized to study opto-thermal phenomena when high temperature or high intensity sources are employed.

The integration of implantable CMOS neural probes with thousands of simultaneously recording microelectrodes is a promising approach for neuroscience and might allow to literally image electrophysiological neuronal activity in multiple brain circuits as we have previously shown in vitro. Here, we present a complete system based on a fully multiplexed CMOS neural probe that was designed for in-vivo acute recordings with a scalable circuit architecture. In particular, a first prototype of a single-shaft probe with 512 electrodes was realized in a standard CMOS 0.18μm technology and post-processed to structure the shaft with a wedge-like geometry of 30μm in thickness at the tip and 80μm at the base. The design of the system and of the probe as well as the post-processing techniques are discussed. Finally, preliminary results on electrical, mechanical and implantation tests are presented to demonstrate the feasibility of our approach.