An optofluidic constriction chip for monitoring metastatic potential and drug response of cancer cells.

Cellular mechanical properties constitute good markers to characterize tumor cells, to study cell population heterogeneity and to highlight the effect of drug treatments. In this work, we describe the fabrication and validation of an integrated optofluidic chip capable of analyzing cellular deformability on the basis of the pressure gradient needed to push a cell through a narrow constriction. We demonstrate the ability of the chip to discriminate between tumorigenic and metastatic breast cancer cells (MCF7 and MDA-MB231) and between human melanoma cells with different metastatic potential (A375P and A375MC2). Moreover, we show that this chip allows highlighting the effect of drugs interfering with microtubule organization (paclitaxel, combretastatin A-4 and nocodazole) on cancer cells, which leads to changes in the pressure-gradient required to push cells through the constriction. Our single-cell microfluidic device for mechanical evaluation is compact and easy to use, allowing for an extensive use in different laboratory environments.

An integrated optofluidic device for single-cell sorting driven by mechanical properties.

We present a novel optofluidic device for real-time sorting on the basis of cell mechanical properties, measured by optical stretching. The whole mechanism, based on optical forces, does not hamper the viability of the tested cells, which can be used for further analysis. The device effectiveness is demonstrated by extracting a sample population enriched with highly metastatic cells from a heterogeneous cell mixture.

Nonlinear properties of AlGaAs waveguides in continuous wave operation regime.

Aluminum Gallium Arsenide (AlGaAs) is an attractive platform for the development of integrated optical circuits for all-optical signal processing thanks to its large nonlinear coefficients in the 1.55-µm telecommunication spectral region. In this paper we discuss the results of the nonlinear continuous-wave optical characterization of AlGaAs waveguides at a wavelength of 1.55 µm. We also report the highest value ever reported in the literature for the real part of the nonlinear coefficient in this material (Re(γ) ≈521 W(-1)m(-1)).

Integrated nonlinear Mach Zehnder for 40 Gbit/s all-optical switching.

We report on the experimental demonstration of a novel silicon based fully integrated nonlinear Mach Zehnder device. A standard silicon waveguide is used as a nonlinear arm, conversely a large mode SU-8 waveguide acts as a purely linear arm. Given this asymmetry, an intensity dependent phase shift can be introduced between the two interferometric arms. Thanks to a fine tuning of the silicon arm optical properties, a low power, ultrafast, picosecond operation is demonstrated, allowing the use of this device for ultrafast all-optical signal processing in high density communication networks.

Integrated microfluidic device for single-cell trapping and spectroscopy.

Optofluidic microsystems are key components towards lab-on-a-chip devices for manipulation and analysis of biological specimens. In particular, the integration of optical tweezers (OT) in these devices allows stable sample trapping, while making available mechanical, chemical and spectroscopic analyses.

Low TPA and free-carrier effects in silicon nanocrystal-based horizontal slot waveguides.

We present the characterization of the ultrafast nonlinear dynamics of a CMOS-compatible horizontal-slot waveguide with silicon nanocrystals. Results are compared to strip silicon waveguides, and modeled with nonlinear split-step calculations. The extracted parameters show that the slot waveguide has weaker carrier effects and better nonlinear figure-of-merit than the strip waveguides.

Optofluidic integrated cell sorter fabricated by femtosecond lasers.

The main trend in optofluidics is currently towards full integration of the devices, thus improving automation, compactness and portability. In this respect femtosecond laser microfabrication is a very powerful technology given its capability of producing both optical waveguides and microfluidic channels. The current challenge in biology is the possibility to perform bioassays at the single cell level to unravel the hidden complexity in nominally homogeneous populations. Here we report on a new device implementing a fully integrated fluorescence-activated cell sorter. This non-invasive device is specifically designed to operate with a limited amount of cells but with a very high selectivity in the sorting process. Characterization of the device with beads and validation with human cells are presented.

Femtosecond laser fabricated monolithic chip for optical trapping and stretching of single cells.

We report on the fabrication by a femtosecond laser of an optofluidic device for optical trapping and stretching of single cells. Versatility and three-dimensional capabilities of this fabrication technology provide straightforward and extremely accurate alignment between the optical and fluidic components. Optical trapping and stretching of single red blood cells are demonstrated, thus proving the effectiveness of the proposed device as a monolithic optical stretcher. Our results pave the way for a new class of optofluidic devices for single cell analysis, in which, taking advantage of the flexibility of femtosecond laser micromachining, it is possible to further integrate sensing and sorting functions.

All-optical wavelength conversion of a 100-Gb/s polarization-multiplexed signal.

We present the results of an in-depth experimental investigation about all-optical wavelength conversion of a 100-Gb/s polarization-multiplexed (POLMUX) signal. Each polarization channel is modulated at 25 Gbaud by differential quadrature phase-shift keying (DQPSK). The conversion is realized exploiting the high nonlinear chi((2)) coefficient of a periodically poled lithium niobate waveguide, in a polarization-independent configuration. We find that slight non-idealities in the polarization independent setup of the wavelength converter can significantly impair the performance of POLMUX systems. We show that high-quality wavelength conversion can be nevertheless achieved for both the polarization channels, provided that an accurate optimization of the setup is performed. This is the first demonstration, to the best of our knowledge, of the possibility to obtain penalty-free all-optical wavelength conversion in a 100-Gb/s POLMUX transmission system using direct-detection.

Design and optimization of a reflection-based fiber-optic tweezers.

We present the numerical modelling of a novel all-fiber optical tweezers, whose efficacy has been recently demonstrated. The device, realized by properly shaping the end-face of a fiber bundle, exploits total internal reflection to enhance the trapping efficiency. In order to allow the optimization of the performance, the trapping efficiency is evaluated as a function of different geometrical parameters of the structure. Given the peculiar spatial and angular distribution of the optical field, a new figure of merit is adopted to assess tweezers performance.