We report on short optical pulse generation by gain-switching (GS) a low-cost commercial vertical-cavity surface-emitting laser emitting at 1.55 μm. The dependence of pulse characteristics on GS ...parameters is investigated and analyzed. Pulses with duration of 55 ps and time-bandwidth product between 0.91 and 2.2 are obtained at repetition rates between 1 and 3 GHz.
Mutually coupled random lasers in complex photonic networks Consoli, Antonio; Caselli, Niccolo; Lopez, Cefe
2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC),
2021-June-21
Conference Proceeding
Coupled optical resonators show a rich dynamical behaviour that can be exploited in different applications, e.g. chaos based communication and sensing, information processing and mimicking of neural ...networks 1 . Random lasers (RLs) are light sources in which optical feedback is provided by scattering elements, resulting in multi-mode emission with narrow resonances randomly distributed in frequency 2 . Our group has previously demonstrated that RLs can be implemented by placing the active medium between two scattering surfaces 3 . Here, we apply this fabrication approach to the realization of in-plane networks in which the nodes are made of disordered scattering media, acting as coupling elements between different resonators 4 . The active medium employed is a dye doped polymer film and the single RL consists of a stripe shaped pumped area, placed between two scattering elements. Each scattering element, obtained by pulsed laser ablation of the polymer film, consists of random surface defects at the polymer/air interface able to provide feedback for lasing. We first consider a network formed by two RLs which share one scattering node. In Fig. 1(a) , RL1 (RL2) consists of the pumped stripe labelled 1 (2) and the two scattering nodes A and B (B and C). Independent spectral signatures are detected at node B, when one laser at a time is turned on, see Fig. 1(b) . In Fig. 1(c) , we compare the compound cavity emission, when both lasers are turned on (RL1&RL2), with the sum of the emissions of each laser turned on, one at a time (RL1+RL2). A rearrangement of lasing peaks is observed with respect to the sum of spectral profiles that would result only from the scattering of each independent laser from node B.
Random lasers (RLs) are intriguing devices with promising applications as light sources for imaging, sensing, super resolution spectral analysis or complex networks engineering. RLs can be obtained ...from optically pumped dyes, optical fibers and crystals, or electrically pumped semiconductor heterostructures. Semicon-ductor RLs are usually fabricated by introducing scattering defects into the active layer, adding a degree of complexity to the fabrication process and losing the ease of realization potentially offered by disordered structures. Ready availability of electrically pumped RLs, avoiding costly fabrication approach, would boost the use of these devices in research and applications. Here, we realize an incoherent semiconductor RL by simply processing the output mirror of an off-the-shelf Fabry-Perot laser diode via controlled laser ablation. Optical feedback provided by the intact back mirror and the ablated front mirror results in multi-mode ran-dom lasing with low spatial coherence and speckled output emission profile.
This paper presents a novel network slicing management and orchestration architectural framework. A brief description of business scenarios and potential customers of network slicing is provided, ...illustrating the need for ordering network services with very different requirements. Based on specific customer goals (of ordering and building an end-to-end network slice instance) and other requirements gathered from industry and standardization associations, a solution is proposed enabling the automation of end-to-end network slice management and orchestration in multiple resource domains. This architecture distinguishes between two main design time and runtime components: Network Slice Design and Multi-Domain Orchestrator, belonging to different competence service areas with different players in these domains, and proposes the required interfaces and data structures between these components.
The ability to accurately observe the Earth's carbon cycles from space gives scientists an important tool to analyze climate change. Current space-borne Integrated-Path Differential Absorption (IPDA) ...lidar concepts have the potential to meet this need. They are mainly based on the pulsed time-of-flight principle, in which two high energy pulses of different wavelengths interrogate the atmosphere for its transmission properties and are backscattered by the ground. In this paper, feasibility study results of a Pseudo-Random Single Photon Counting (PRSPC) IPDA lidar are reported. The proposed approach replaces the high energy pulsed source (e.g. a solid-state laser), with a semiconductor laser in CW operation with a similar average power of a few Watts, benefiting from better efficiency and reliability. The auto-correlation property of Pseudo-Random Binary Sequence (PRBS) and temporal shifting of the codes can be utilized to transmit both wavelengths simultaneously, avoiding the beam misalignment problem experienced by pulsed techniques. The envelope signal to noise ratio has been analyzed, and various system parameters have been selected. By restricting the telescopes field-of-view, the dominant noise source of ambient light can be suppressed, and in addition with a low noise single photon counting detector, a retrieval precision of 1.5 ppm over 50 km along-track averaging could be attained. We also describe preliminary experimental results involving a negative feedback Indium Gallium Arsenide (InGaAs) single photon avalanche photodiode and a low power Distributed Feedback laser diode modulated with PRBS driven acoustic optical modulator. The results demonstrate that higher detector saturation count rates will be needed for use in future spacebourne missions but measurement linearity and precision should meet the stringent requirements set out by future Earth-observing missions.
It is now well known that peripheral nerves are a target for the action of neuroactive steroids. This review summarizes observations obtained so far, indicating that through the interaction with ...classical and nonclassical steroid receptors, neuroactive steroids (e.g., progesterone, testosterone and their derivatives, estrogens, etc.) are able to influence several parameters of the peripheral nervous system, particularly its glial compartment (i.e., Schwann cells). Interestingly, some of these neuroactive steroids might be considered as promising neuroprotective agents. They are able to counteract neurodegenerative events of rat peripheral nerves occurring after experimental physical trauma, during the aging process, or in hereditary demyelinating diseases. On this basis, the hypothesis that neuroactive steroids might represent a new therapeutic strategy for peripheral neuropathy is proposed.
Light interference in strongly disordered photonic media can generate lasers where random modes are amplified in unpredictable way. The ease of fabrication, along with their low coherence caused by ...multiple small-linewidth peaks, made random lasers (RL) emerging, efficient, speckle-free light sources and a means to achieve spectral super-resolution. With potential to become a mature and accessible technology, their complex system's nature furnishes endless opportunities to unveil fundamental physics, since they can act as elements of optical network architectures. To date no experimental studies have analyzed the optical interaction between independent resonators in networks of RLs. Realizing RLs with a pumped strip joining two rough mirrors, we experimentally investigate and numerically simulate the emergence of networks when, by sharing scattering centers, RLs become coupled. We prove that the emission of a single RL can be manipulated by the action of others in the network, giving rise to substantial peak rearrangements and energy redistribution, fingerprint of mode coupling. Our findings, involving a few coupled RLs, firmly set the basis for the study of full-grown photonic networks. Oddly, both their deep understanding and their deployment as hardware clearly point in the direction of a novel disruptive technology: artificial intelligence on photonic random neural networks.
Emerging evidence implicates γ-aminobutyric acid type B (GABA
B) receptors in peripheral nervous system (PNS) functions. In order to elucidate which biochemical, morphological and functional ...parameters of peripheral nerve fibers depend on GABA
B receptors we studied GABA
B1-deficient mice, which are devoid of functional GABA
B receptors. Here, we show that GABA
B1-deficient mice exhibit morphological and molecular changes in peripheral myelin, including an increase in the number of irregular fibers and increases in the expression levels of the myelin proteins PMP22 and P0. Moreover, the number of small myelinated fibers and small neurons of the lumbar dorsal root ganglia is higher in GABA
B1-deficient mice than in wild-type littermates. We further show that GABA
B1-deficient mice exhibit gait alterations and reduced allodynia. In summary, our findings implicate GABA
B receptors in the PNS myelination process and raise the possibility that PNS alterations contribute to the sensory phenotypes of GABA
B1-deficient mice.
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