Self-linewidth-narrowing photonic oscillator.

We detail here the general principle of a self-adaptive oscillator in which the intertwined operation of a 100-m-long active optical resonator and a standard semiconductor laser mutually coupled by stimulated Brillouin scattering offers an ultimate high spectral purity. Single frequency operation of this self-adaptive photonic oscillator is achieved without any servo locking or stabilization electronics. In free running operation, this principle leads to a Lorentzian linewidth of 40 mHz and a Flicker noise linewidth of 200 Hz for 0.

Estimate of mode coupling in a spin-VECSEL.

We study experimentally the nonlinear mode coupling between circular polarizations in a vertical-cavity surface-emitting laser (VCSEL) device developed for spin injection. The specific experimental arrangement that includes a Faraday rotator enables laser oscillation on left-circular or right-circular polarization, by adjusting the cavity losses. We show the simultaneous oscillation of both polarizations never occurs, proving that the Lamb coupling constant is very close to 1 in this VCSEL device, a situation that is ideal for spintronic applications.

Reducing education inequalities through cloud-enabled live-cell biotechnology.

Biotechnology holds the potential to drive innovations across various fields from agriculture to medicine. However, despite numerous interventions, biotechnology education remains highly unequal worldwide. Historically, the high costs and potential exposure to hazardous materials have hindered biotechnology education.

Reconfigurable MIMO-based self-powered battery-less light communication system.

Simultaneous lightwave information and power transfer (SLIPT), co-existing with optical wireless communication, holds an enormous potential to provide continuous charging to remote Internet of Things (IoT) devices while ensuring connectivity. Combining SLIPT with an omnidirectional receiver, we can leverage a higher power budget while maintaining a stable connection, a major challenge for optical wireless communication systems. Here, we design a multiplexed SLIPT-based system comprising an array of photodetectors (PDs) arranged in a 3 × 3 configuration.

Spin injection enhancement in CW VECSEL at room temperature using push-pull optical pumping.

We report the enhancement of spin injection efficiency in an external-cavity VCSEL based on a non-resonant pumping coupled with a polarized optical resonant illumination. This double pumping scheme allows both the injection of spin polarized electrons in the conduction band and the selection of the spin orientation for the electron/hole recombination laser process. Experimentally, a flip of the polarization state of the laser is achieved with an ellipticity of +31° (spin down) and -33° (spin up), so an increase of about 50% of the ellipticity is achieved in comparison to an optical non-resonant pumping alone.

Dynamic charging as a complementary approach in modern EV charging infrastructure.

Whether the future of transportation is going to be electric or not is no longer a question. Electric vehicles (EVs) offer several benefits toward global sustainability. However, without a variety of charging infrastructures that cover diverse forthcoming charging needs, the speed of vehicle electrification may be slow and limited.

Beam wander prediction with recurrent neural networks.

Among the problems that prevent free-space optical communication systems from becoming a truly mainstream technology is beam wander, which is especially important for structured light beams since beam misalignment introduces additional crosstalk at the receiver. The paper suggests a recurrent neural network-based (RNN) solution to predict beam wander in free space optics (FSO). The approach uses past beam center of mass positions to predict future movement, significantly outperforming various prediction types.

Impact of Evanescence Process on Three-Dimensional Sub-Diffusion-Based Molecular Communication Channel.

In most of the existing works of molecular communication (MC), the standard diffusion environment is taken into account where the mean square displacement (MSD) of an information molecule (IM) scales linearly with time. On the contrary, this work considers the sub-diffusion motion that appears in crowded and complex (porous or fractal) environments (movement of the particles in the living cells) where the particle's MSD scales as a fractional order power law in time. Moreover, we examine an additional evanescence process resulting from which the molecules can degrade before hitting the boundary of the receiver (RX).

Self-powered weather station for remote areas and difficult-access locations.

Monitoring climate change can be accomplished by deploying Internet of Things (IoT) sensor devices to collect data on various climate variables. Providing continuous power or replacing batteries for these devices is not always available, particularly in difficult-access locations and harsh environments. Here, we propose a design for a self-powered weather station that can harvest energy, decode information using solar cells, and is controlled by a programmable system-on-chip.

Dual-wavelength luminescent fibers receiver for wide field-of-view, Gb/s underwater optical wireless communication.

Extending the field-of-view (FoV) of underwater wireless optical communication (UWOC) receivers can significantly ease the need for active positioning and tracking mechanisms. Two bundle of scintillating fibers emitting at 430- and 488-nm were used to detect two independent signals from ultraviolet and visible laser sources. A zero-forcing approach to minimize inter-channel crosstalk was further implemented.

ECG-based machine-learning algorithms for heartbeat classification.

Electrocardiogram (ECG) signals represent the electrical activity of the human hearts and consist of several waveforms (P, QRS, and T). The duration and shape of each waveform and the distances between different peaks are used to diagnose heart diseases. In this work, to better analyze ECG signals, a new algorithm that exploits two-event related moving-averages (TERMA) and fractional-Fourier-transform (FrFT) algorithms is proposed.

Electrically pumped shot-noise limited class A VECSEL at telecom wavelength.

Class A shot-noise limited operation is achieved in an electrically pumped vertical external cavity surface emitting laser (VECSEL), opening the way for integration of such peculiar noiseless laser oscillation in applications where low power consumption and footprint are mandatory. The quantum well active medium is grown on an InP substrate to enable laser oscillation at telecom wavelengths. Single frequency class A operation is obtained by proper optimization of the cavity dimensions, ensuring at the same time a sufficiently long and high-finesse cavity without any intracavity filtering components.

Wide-field-of-view optical detectors using fused fiber-optic tapers.

Photodetectors used in wireless applications suffer from a trade-off between their response speeds and their active areas, which limits the received signal-to-noise ratio (SNR). Conventional light-focusing elements used to improve the SNR narrow the field of view (FOV). Herein, we demonstrate a versatile imaging light-focusing element featuring a wide FOV and high optical gain using fused fiber-optic tapers.

Modeling the Lamb mode-coupling constant of quantum well semiconductor lasers.

We theoretically compute the coupling constant C between two emission modes of an extended cavity laser with a multiple quantum-well active layer. We use an optimized Monte Carlo model based on the Markov chain that describes the elementary events of carriers and photons over time. This model allows us to evaluate the influence on C of the transition from a class A laser to a class B laser and illustrates that the best stability of dual-mode lasers is obtained with the former.

Identifying structured light modes in a desert environment using machine learning algorithms.

The unique orthogonal shapes of structured light beams have attracted researchers to use as information carriers. Structured light-based free space optical communication is subject to atmospheric propagation effects such as rain, fog, and rain, which complicate the mode demultiplexing process using conventional technology. In this context, we experimentally investigate the detection of Laguerre Gaussian and Hermite Gaussian beams under dust storm conditions using machine learning algorithms.

Orthogonality-breaking polarimetric sensing modalities for selective polarization imaging.

Polarimetric sensing/imaging by orthogonality breaking is a microwave-photonics-inspired optical remote sensing technique that was shown to be particularly suited to characterize dichroic samples in a direct and single-shot way. In this work, we expand the scope of this approach in order to gain sensitivity on birefringent and/or purely depolarizing materials by respectively introducing a circular or a linear polarization analyzer in the detection module. We experimentally validate the interest of these two new, to the best of our knowledge, induced orthogonality-breaking modalities in the context of infrared active imaging.

An all-optical technique enables instantaneous single-shot demodulation of images at high frequency.

High-frequency demodulation of wide area optical signals in a snapshot manner remains a technological challenge. If solved, it could open tremendous perspectives in 3D imaging, vibrometry, free-space communications, automated vision, or ballistic photon imaging in scattering media with numerous applications in smart autonomous vehicles and medical diagnosis. We present here a snapshot quadrature demodulation imaging technique, capable of estimating the amplitude and phase from a single acquisition, without synchronization of emitter and receiver, and with the added capability of continuous frequency tuning.

Ultraviolet-to-blue color-converting scintillating-fibers photoreceiver for 375-nm laser-based underwater wireless optical communication.

Underwater wireless optical communication (UWOC) can offer reliable and secure connectivity for enabling future internet-of-underwater-things (IoUT), owing to its unlicensed spectrum and high transmission speed. However, a critical bottleneck lies in the strict requirement of pointing, acquisition, and tracking (PAT), for effective recovery of modulated optical signals at the receiver end. A large-area, high bandwidth, and wide-angle-of-view photoreceiver is therefore crucial for establishing a high-speed yet reliable communication link under non-directional pointing in a turbulent underwater environment.

Direct measurement of the spectral dependence of Lamb coupling constant in a dual frequency quantum well-based VECSEL.

Spectral dependence of Lamb coupling constant C is experimentally investigated in an InGaAlAs Quantum Wells active medium. An Optically-Pumped Vertical-External-Cavity Surface-Emitting Laser is designed to sustain the oscillation of two orthogonally polarized modes sharing the same active region while separated in the rest of the cavity. This laser design enables to tune independently the two wavelengths and, at the same time, to apply differential losses in order to extract without any extrapolation the actual coupling constant.

Microwave signal switching on a silicon photonic chip.

Microwave photonics uses light to carry and process microwave signals over a photonic link. However, light can instead be used as a stimulus to microwave devices that directly control microwave signals. Such optically controlled amplitude and phase-shift switches are investigated for use in reconfigurable microwave systems, but they suffer from large footprint, high optical power level required for switching, lack of scalability and complex integration requirements, restricting their implementation in practical microwave systems.

Primary User Localization and Its Error Analysis in 5G Cognitive Radio Networks.

It is crucial to estimate the location of primary users (PUs) for the development of cognitive radio networks (CRNs). Great efforts have been made in the past to develop localization algorithms with better accuracy but low computation. In CRNs, PUs do not cooperate with secondary users (SUs), which makes the localization task challenging.

Liquid crystal-based tunable photodetector operating in the telecom C-band.

Liquid crystal (LC) microcells monolithically integrated on the surface of InGaAs based photodiodes (PDs) are demonstrated. These LC microcells acting as tunable Fabry-Perot filters exhibit a wavelength tunability of more than 100 nm around 1550 nm with less than 10V applied voltage. Using a tunable laser operating in the S and C bands, photocurrent measurements are performed.