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We demonstrate coherent and tunable THz emission by excitation of a unitraveling-carrier photodiode by a dual-frequency III–V semiconductor laser emitting up to 80 mW of optical power around 1 $\mu$ m. The laser is an optically-pumped vertical-external-cavity surface-emitting laser that operates simultaneously on two transverse Laguerre–Gauss modes. Modes frequency difference is driven by thermal effects, band-filling effects and/or phase masks, allowing THz emission from 50 GHz to few THz. To reach THz emission from a pigtailed photodiode, we detail quantitatively how orthogonal transverse modes can be coupled within a single-mode fiber, leading to more than 20% beat efficiency. Coherent THz emission spectrum is presented with a linewidth of about 150 kHz for 3-ms acquisition time, and an output power limited by the photodiode (typically 1 $\mu$ W at 300 GHz). Frequency noise is measured for the optical transverse modes along with the THz signal. The latter presents a frequency noise that is about 20-dB lower than the optical ones, thus proving that the dual-frequency concept allows frequency noise reduction by correlating part of the technical noise of the two modes.

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Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based Vertical External Cavity Surface Emitting Laser (VeCSEL) technologies [1] seem to be a well suited path to meet the required specifications of demanding applications. Here, we report on the realization of industry ready packaged low noise single frequency VeCSEL devices emitting in the 0.8-1.1 µm and 2-2.5 µm spectral range with high performances thanks to a combination of power-coherence-wavelength tunability and compactness. A fundamental study of the non-linear multimode laser dynamics was carried out to avoid dynamic phase-amplitude instability. We demonstrate both experimentally and theoretically the existence of a deterministic dynamics of the laser field, with either a regular multimode non-stationary regime, or a route to robust single frequency operation. Integration of flat photonics technology allows the realization of devices emitting new coherent light states (VORTEX or dual frequency lasers) for applications to optical tweezers or THz emission, for instance.

Dual frequency comb generation is a field which has seen considerable interest in recent years, with notable implementations such as dual wavelength operation of a Mode-locked Integrated External-cavity Surface Emit- ting Laser (MIXSEL), CW pumping of orthogonal polarisation states in a microring resonator, and optical phase-locking of discrete frequency combs. Dual frequency operation of CW Vertical External Cavity Surface Emitting Lasers (VECSEL) has been demonstrated in a particularly well controlled way using sub-wavelength metallic masks fabricated onto the surface of the laser gain structure. We present a variation of this technique in which patterned loss masks are machined onto a VECSEL cavity mirror using a Digital Micromirror Device (DMD)-enabled femtosecond-laser ablation system, where the DMD is used as an intensity spatial light mod- ulator. Interaction of the loss mask with the laser mode area results in the VECSEL oscillating preferentially on the spatial modes that observe the least loss within the aperture, and modulation of pump power enables control of the oscillating mode frequency separation. We describe the characteristics of the masks and the properties of the laser operation as progress towards eventual pulsed emission. Our technique has the advan- tages of discrete gain and Semiconductor Saturable Absorber Mirror (SESAM) structures, very fast fabrication times and the ability to fabricate multiple apertures on a single mirror.

The use of photo-mixing techniques for THz emission offers attractive performances such as tunability and modulation bandwidth, that are suitable for bio-medical sensing and imaging, communications, or security. We will present the state-of-the-art performances of a vertical-external-cavity surface-emitting laser that operates on two transverse modes to ensure a stable continuous-wave and coherent (longitudinal, transverse and polarization) dual-frequency operation. THz emission is subsequently obtained by excitation of an uni-traveling-carrier photodiode (UTC-PD). The stability of the dual-frequency operation is achieved thanks to different types of functionalized surfaces involving the micro-fabrication of integrated III-V absorbing metallic masks or metamaterial phase masks by e-beam lithography. These functionalized surfaces allow to shape the optical and THz performances in terms of power, tunability and coherence. The latter will be specifically detailed in terms of longitudinal coherence, showing a THz frequency noise that is orders of magnitude lower than the optical one thanks to a significant correlation of technical noise. Tunable emission will be demonstrated from 50 GHz up to few THz with a linewidth of 150 kHz (during 3-ms), for a power of 1 W at 260 GHz that is limited by the UTC-PD for an optical excitation at 1064 nm at room temperature. We will discuss on the possibility to improve such a power significantly by taking advantage of the involved high-order transverse mode, offering possible intrinsically coherent networks of photo-emitters, thus paving the way to compact and agile coherent THz sources offering an output power over few mWs at frequencies of 100s of GHz.

We offer here an accurate quantitative model of the RIA (radiation-induced absorption) at low dose-rate (below 1 kGy) that experience the most common erbium-doped fibers (Ge-Al-Er–doped silica) under radiations. It addresses the degradation mechanisms of the glass fiber, especially the influence of its doping elements versus its sensitivity to radiations. Moreover, it depends mainly on macroscopic quantities coming from literature or experiments. For these two reasons, it is a reliable and efficient tool for the engineering of erbium-doped fibers (erbium-free fibers too) exposed to ionizing radiations and is validated in this paper by comparing the modelisation results to RIA experiments on 14 Er-doped optical fiber samples, in which composition changes a lot from one sample to another (in the range 0–25%wt for Ge, 0–10%wt for Al and 0–1500ppm for Er).

Toward the treatment of osteoarthritis (OA), the authors have been investigating self-complementary adeno-associated virus (scAAV) for intra-articular delivery of therapeutic gene products. As OA frequently affects weight-bearing joints, pharmacokinetic studies of scAAV gene delivery were performed in the joints of the equine forelimb to identify parameters relevant to clinical translation in humans. Using interleukin-1 receptor antagonist (IL-1Ra) as a secreted therapeutic reporter, scAAV vector plasmids containing codon-optimized cDNA for equine IL-1Ra (eqIL-1Ra) were generated, which produced eqIL-1Ra at levels 30- to 50-fold higher than the native sequence. The most efficient cDNA was packaged in AAV2.5 capsid, and following characterization in vitro, the virus was injected into the carpal and metacarpophalangeal joints of horses over a 100-fold dose range. A putative ceiling dose of 5 × 10(12) viral genomes was identified that elevated the steady-state eqIL-1Ra in the synovial fluids of injected joints by >40-fold over endogenous levels and was sustained for at least 6 months. No adverse effects were seen, and eqIL-1Ra in serum and urine remained at background levels throughout. Using the 5 × 10(12) viral genome dose of scAAV, and green fluorescent protein as a cytologic marker, the local and systemic distribution of vector and transduced cells following intra-articular injection scAAV.GFP were compared in healthy equine joints and in those with late-stage, naturally occurring OA. In both cases, 99.7% of the vector remained within the injected joint. Strikingly, the pathologies characteristic of OA (synovitis, osteophyte formation, and cartilage erosion) were associated with a substantial increase in transgenic expression relative to tissues in healthy joints. This was most notable in regions of articular cartilage with visible damage, where foci of brilliantly fluorescent chondrocytes were observed. Overall, these data suggest that AAV-mediated gene transfer can provide relatively safe, sustained protein drug delivery to joints of human proportions.

International audience; Increasing the data rates of wireless communicationsrequires to increase the carrier frequency to hundred’s of GHz,thus emitters and detectors that can operate at high data ratesare required. We review a possible source and receiver that canbeen used for THz communications. We present a photonic-basedemitter that provides a coherent THz signal in the 50–700+ GHz,based on the excitation of a uni-travelling carrier photodiodeby a two-frequency semiconductor laser that operates on twotransverse modes. The performance of THz detectors basedon GaAs field-effect transistors are also presented, along withcommunications using direct amplitude modulation at 8.3 Gbpsand an heterodyne communication at 1.5 Gbps.

The state of the art and the perspectives of THz emission driven by a dual-frequency laser that operates simultaneously on two transverse modes around 1064 nm are presented. The reported THz performances in terms of tunability (50-700-GHz), coherence (150-kHz for 3-ms acquisition time), and power ( $1\ \mu\text{W}$ at 260 GHz) are presented while using a uni-travelling-carrier photodiode for photo-mixing. Novel photo-mixers specifically designed to match the transverse modes of the laser are discussed in terms of transverse beam characteristics and power.

Actes du colloque international, 7-10 mars 2012, INHA, Centre allemand d’histoire de l’art.; International audience

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International audience; Tout comme les récits de voyage peuplaient les contrées lointaines de créatures monstrueuses vivant aux côtés de peuplades exotiques, une certaine représentation des origines de l'humanité à la Renaissance associe la figure du monstre, mi-homme, mi-animal, à l'être primitif, livrant une autre version de l'évolution humaine. Cette démarche commune dans l'évocation de l'ailleurs et de l'antan fait du monstrueux un marqueur fort de l'altérité, l'inconnu ou le méconnu laissant place à l' "invenzione".

Actes du colloque international organisé par la Bibliothèque Hertziana - Institut Max-Planck pour l'histoire de l'art et l'Académie de France à Rome - Villa Médicis, en collaboration avec l'université Paris-Sorbonne (Labex EHNE), le Centre André Chastel et Telemme de l'université Aix-Marseille. Rome, Villa Médicis, 12-13 juin 2014 et Marseille, Mucem, 9-10 octobre 2014.; International audience

We present a highly coherent semiconductor laser device formed by a ½-VCSEL structure and an external concave mirror in a millimetre high finesse stable cavity. The quantum well structure is diode-pumped by a commercial single mode GaAs laser diode system. This free running low noise tunable single-frequency laser exhibits >50mW output power in a low divergent circular TEM00 beam with a spectral linewidth below 1kHz and a relative intensity noise close to the quantum limit. This approach ensures, with a compact design, homogeneous gain behaviour and a sufficiently long photon lifetime to reach the oscillation-relaxation-free class-A regime, with a cut off frequency around 10MHz.

Since years, the VeCSEL concept is pointed out as a technology of choice for beyond-state-of-the-art laser light sources. The targeted coherent state in CW is typically the common gaussian TEM 00 , single frequency, linearly polarized lightstate. In this work, we take advantage of the VeCSEL technology for the generation of other kinds of coherent states, thanks to the insertion of intracavity functions, such as low-loss intensity and phase filters integrated on a semiconductor chip. This technological development permitted to demonstrate very pure high-order Laguerre-Gauss mode, both degenerate and non-degenerate(vortex)modes, preserving the coherence properties of usual TEM 00 VeCSELs. This technology paves the way for the generation of other coherences (Bessel beams) or new functionnalities (wavelength filtering, etc.). We also explore new time domain coherence : owing to a high gain semiconductor chip design and the insertion of intracavity AOM, we demonstrated the first Frequecy-Shifted-Feedback VeCSEL, with a broadband coherence state as wide as 300 GHz.

We introduce a methodology for efficient monitoring of processes running on hosts in a corporate network. The methodology is based on collecting streams of system calls produced by all or selected processes on the hosts, and sending them over the network to a monitoring server, where machine learning algorithms are used to identify changes in process behavior due to malicious activity, hardware failures, or software errors. The methodology uses a sequence of system call count vectors as the data format which can handle large and varying volumes of data. Unlike previous approaches, the methodology introduced in this paper is suitable for distributed collection and processing of data in large corporate networks. We evaluate the methodology both in a laboratory setting on a real-life setup and provide statistics characterizing performance and accuracy of the methodology., 5 pages, 4 figures, ICCST 2017

We explore how radiation-resistant broadband erbium-doped fibers (EDFs) can be achieved by using a carefully selected chemical composition, without specific coating or specific packaging. In this framework, we define a factor of merit, an appropriate and effective tool to design a radiation-hardened EDF amplifier (EDFA) based on a mature technology. We focus on specialty fibers, with a finely tuned composition in aluminum and erbium, guaranteeing the optimal operation of an EDFA (a 20-nm bandwidth and an optical output power level of at least 18 dBm) in the classical booster configuration throughout the entire geostationary mission. These performances are estimated thanks to a standard accelerated test, with a 300-Gy dose deposition at a dose rate of 0.4 Gy/h. We also confirmed, based on experiments and modeling, the importance of the radiation-induced absorption at pump wavelength on the EDFA degradation under irradiation.

We report on the highly coherent modeless broadband continuous wave operation of a semiconductor vertical-external cavity-surface-emitting laser. Its design is based on a frequency-shifted-feedback scheme provided by an acousto-optic frequency shifter inserted into the cavity. Chirping the optical wave inside the cavity leads to the elimination of the traditional spectral resonances occurring in usual laser cavities, leading to a wideband (>330GHz here) continuous spectrum. The light is of high coherence concerning the transverse mode and the polarisation state, as well as in the time domain (time coherence ≈ 19μs, like a 1MHz DFB) in spite of its wideband emission.

Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8-1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency laser micro-chip, intracavity element free, based on a patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high temporal coherence together with a low divergence diffraction limited TEM00 beam. They exhibit a class-A dynamics with a Relative Intensity Noise as low as -140dB/Hz and at shot noise level reached above 200MHz RF frequency (up to 160GHz), a free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), a linear polarization (>50dB suppression ratio), and broadband continuous tunability greater than 400GHz ( Those devices surpass the state of the art commercial technologies thanks to a combination of power-coherence-wavelength tunability performances and integration.

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