arXiv subjects

Marc Jofre

Publications and source records attributed to Marc Jofre.

7 recordsLinked to original sources

arXiv2023

Optically Pumped Magnetometer with High Spatial Resolution Magnetic Guide for the Detection of Magnetic Droplets in a Microfluidic Channel

Quantum sensors provide unprecedented magnetic field detection sensitivities, enabling these to extend the common magnetometry range of applications and environments of operation. In this framework, many applications also require high spatial resolution magnetic measurements for biomedical research, environmental monitoring and industrial production. In this regard, Optically Pumped Magnetometers (OPMs) are considered as prominent candidates, but are impaired in size with micrometer scale magnetic particles, e.g. magnetic droplets. In order to address this limitation, here we study the effects of adding a micrometer-to-millimeter magnetic guide to a miniature OPM. This device is applied to detect Fe3O4 magnetic droplets flowing at rates up to $25$ drop./s in a microfluidic channel. The computed spatial resolution is $300$ $\mu$m and the measured SNR is larger than $15$ dB for the different sizes of considered magnetic droplets.

physics.app-ph↗

arXiv2022

Superheterodyne Microwave System for the Detection of Bioparticles with Coplanar Electrodes on a Microfluidic Platform

The combination of microwave and microfluidic technologies has the potential to enable wireless monitoring and interaction with bioparticles, facilitating in this way the exploration of a still largely uncharted territory at the intersection of biology, communication engineering and microscale physics. Opportunely, the scientific and technical requirements of microfluidics and microwave techniques converge to the need of system miniaturization to achieve the required sensitivity levels. This work, therefore, presents the design and optimization of a measurement system for the detection of bioparticles over the frequency range $0.01$ to $10$ $\mathrm{GHz}$, with different coplanar electrodes configurations on a microfluidic platform. The design of the measurement signal-chain setup is optimized for a novel real-time superheterodyne microwave detection system. In particular, signal integrity is achieved by means of a microwave-shielded chamber, which is protected from external electromagnetic interference that may potentially impact the coplanar electrodes mounted on the microfluidic device. Additionally, analytical expressions and experimental validation of the system-level performance are provided and discussed for the different designs of the coplanar electrodes. This technique is applied to measure the electrical field perturbation produced by $10$ $\mathrm{μm}$ polystyrene beads with a concentration of $10^5$ $\mathrm{beads/mL}$, and flowing at a rate of $10$ $\mathrm{μL/m}$. The achieved SNR is in the order of $40$ $\mathrm{dB}$ for the three coplanar electrodes considered.

eess.SY↗

arXiv2015

An image cytometer based on angular spatial frequency processing and its validation for rapid detection and quantification of waterborne microorganisms

We introduce a new image cytometer design for detection of very small particulate and demonstrate its capability in water analysis. The device is a compact microscope composed of off the shelf components, such as a light emitting diode (LED) source, a complementary metal oxide semiconductor (CMOS) image sensor, and a specific combination of optical lenses that allow, through an appropriate software, Fourier transform processing of the sample volume. Waterborne microorganisms, such as Escherichia coli (E. coli), Legionella pneumophila (L. pneumophila) and Phytoplankton, are detected by interrogating the volume sample either in a fluorescent or label-free mode, i.e. with or without fluorescein isothiocyanate (FITC) molecules attached to the micro-organisms, respectively. We achieve a sensitivity of 50 cells/ml, which can be further increased to 0.2 cells/ml by preconcentrating an initial sample volume of 500 ml with an adhoc fluidic system. We also prove the capability of the proposed image cytometer of differentiating microbiological populations by size with a resolution of 3 um and of operating in real contaminated water.

physics.optics↗

arXiv2013

Phase-stable source of polarization-entangled photons in a linear double-pass configuration

We demonstrate a compact, robust, and highly efficient source of polarization-entangled photons, based on linear bi-directional down-conversion in a novel 'folded sandwich' configuration. Bi-directionally pumping a single periodically poled KTiOPO$_4$ (ppKTP) crystal with a 405-nm laser diode, we generate entangled photon pairs at the non-degenerate wavelengths 784 nm (signal) and 839 nm (idler), and achieve an unprecedented detection rate of 11.8 kcps for 10.4 $μ$W of pump power (1.1 million pairs / mW), in a 2.9-nm bandwidth, while maintaining a very high two-photon entanglement quality, with a Bell-state fidelity of $99.3\pm0.3$%.

quant-ph↗

arXiv2012

A high-brightness source of polarization-entangled photons optimized for applications in free space

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.

quant-ph↗

arXiv2011

A passive transmitter for quantum key distribution with coherent light

Signal state preparation in quantum key distribution schemes can be realized using either an active or a passive source. Passive sources might be valuable in some scenarios; for instance, in those experimental setups operating at high transmission rates, since no externally driven element is required. Typical passive transmitters involve parametric down-conversion. More recently, it has been shown that phase-randomized coherent pulses also allow passive generation of decoy states and Bennett-Brassard 1984 (BB84) polarization signals, though the combination of both setups in a single passive source is cumbersome. In this paper, we present a complete passive transmitter that prepares decoy-state BB84 signals using coherent light. Our method employs sum-frequency generation together with linear optical components and classical photodetectors. In the asymptotic limit of an infinite long experiment, the resulting secret key rate (per pulse) is comparable to the one delivered by an active decoy-state BB84 setup with an infinite number of decoy settings.

quant-ph↗

arXiv2010

Polarization change induced by a galvanometric optical scanner

We study the optical properties of a two-axis galvanometric optical scanner constituted by a pair of rotating planar mirrors, focusing our attention on the transformation induced on the polarization state of the input beam. We obtain the matrix that defines the transformation of the propagation direction of the beam and the Jones matrix that defines the transformation of the polarization state. Both matrices are expressed in terms of the rotation angles of two mirrors. Finally, we calculate the parameters of the general rotation in the Poincare' sphere that describes the change of polarization state for each mutual orientation of the mirrors.

physics.optics↗