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International audience; La génération d’états de photon cohérents puissants dans le proche-IR et THz, présentant une structuration 3D spatio-temporelle, représente un défi physique et technologique. Elle est d’intérêt pour les applications : pinces optiques, capteurs, microscopie, LIDAR, télécoms, spectroscopie… Ces états originaux sont ici générés en exploitant les nanotechnologies à semi-conducteur III-V et les lasers à cavité externe verticale intégrant une métasurface : lumière VORTEX, bi-fréquences pour le THz, ou sans mode.

This article reports a novel 3-D imaging approach for remote, nondestructive material inspection at depth. The approach is based on a frequency-modulated continuous-wave (FMCW) radar system operating in the 75–110-GHz frequency band. Time-domain spectroscopy (TDS) measurements demonstrate that such a frequency band has manage-able attenuation levels in centimeter-long materials, thereby offering an advantageous resolution-versus-measurement-depth tradeoff compared with higher frequencies. The proposed setup includes a long delay on the reference signal in order to cancel redundant signals that would otherwise degrade the measurement. Furthermore, specific signal-processing techniques used to improve the performance of the system, which requires stringent component performances in terms of radio-frequency nonlinearity and return loss, are presented. Radio-frequency nonlinearity correction is based on a reference measurement, and the impact of deleterious reflections is reduced by averaging measurements conducted on a target at different longitudinal positions. As a result, an improvement of the signal-to-noise (S/N) ratio up to 20 dB is demonstrated. Tomography experiments were conducted on building materials showing 3-D imaging with theoretically limited longitudinal and transverse resolutions of 5 and 20 mm, respectively, thus opening the door to civil infrastructure monitoring applications.

In this work, we analyze the absorption spectra of silica fibers doped with erbium (Er) and usual codoping atoms such as aluminum (Al) and germanium (Ge). This study is performed in the 400 nm to 1000 nm wavelength range. We describe and identify relations between the optical fiber composition and the changes in their absorption spectra after two consecutive processes: a 300-Gy gamma irradiation and then after photobleaching obtained with a 980 nm laser light. Among the results we obtained, we want to emphasize that the creation of Al-related defects, known to be the main origin of radio-darkening in aluminosilicate fibers, depends also on the Al/Er ratio. We also identify a new Al originated trap, different from Al-OHC and not referenced in the existing scientific literature to our knowledge. Its contribution to the RIA seems to be really significant. Moreover, photobleaching appears to be a possible recovery mechanism as the Al-colored centers vanish under 980 nm laser light.

Spatially Localized States are individually addressable structures that may appear in large aspect-ratio optical resonators. They can be used as bits of information for all-optical buffering. We design and operate a modeless laser cavity based on a 1/2 VCSEL coupled to a distant mirror in self-imaging condition. Our study indicates how a VeCSEL can be specially designed to provide a robust system potentially capable of emitting Spatially Localized States and paves the way towards the observation of three dimensional - in space and time - confined states, the so-called light bullets.

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.

International audience

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.

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).

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.

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.

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.

We demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis.24 We use a first order phase perturbation to introduce a weak orbital anisotropy, based on a dielectric metasurface and non-linear laser dynamics, allowing selecting vortex handedness. Moreover, similarly to linear Doppler Shift, light carrying orbital angular momentum L, scattered by a rotating object at angular velocity, experiences a rotational Doppler shift L. We show that this fundamental light matter interaction can be detected exploiting self-mixing in a vortex laser under Doppler-shifted optical feedback, with quantum noise-limited light detection.25 This will allow us to combine a velocity sensor with optical tweezers for micro-manipulation applications, with high performances, simplicity and compactness. Such high performance laser opens the path to widespread new photonic applications.

The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here “orbital birefringence”, based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create “orbital gain dichroism” allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (mW output power in the near-IR at λ ≃ 1 μm, a charge l = ±1, … ±4 (>50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications.

We revisit and improve the optical heterodyne technique for the measurement of the laser coherence, by digital acquisition of the beat-note and numerical analysis of the resulting signal. Our main result is that with the same experimental setup we reach the very “short-time linewidth” with the highest accuracy as well as the frequency noise spectrum.

We demonstrate coherent THz emission based on the stable operation of a dual-frequency vertical-external-cavity surface-emitting laser. The laser operates on two Laguerre-Gauss transverse modes in a single-axis cavity, thanks to sub-wavelength thick metallic transverse mask deposit on the surface emitting semiconductor structure. A beat note at frequencies from 50 GHz to 3 THz has been demonstrated and coherent THz emission was demonstrated at 190 GHz by excitation of a uni-travelling-carrier photodiode emitter.

Single frequency and low linewidth (

We report on the highly coherent modeless broadband continuous wave operation of a semiconductor vertical-external-cavity-surface-emitting laser. The laser design is based on a frequency-shifted-feedback scheme provided by an acousto-optic frequency shifter inserted in a linear or a ring traveling wave cavity. The gain mirror is a GaAs-based multiple quantum well structure providing large gain at 1.07 μm. This laser exhibits a coherent optical spectrum over 1.27 nm (330 GHz) bandwidth, with 70 mW output power and a high beam quality. The light polarization is linear (>30 dB extinction ratio). The laser dynamics exhibits a low intensity noise close to class A regime, with a ∼1.5 MHz cutoff frequency. The frequency noise spectral density shows a first-order low-pass like shape (130 kHz cutoff) leading to a Gaussian shape for homodyne interferometric signals. The measured beat width is ≃54 kHz and the coherence time of ∼19 μs. No nonlinear effects are observed, showing dynamics very close to theory.

International audience; Light carrying orbital angular momentum (L) over right arrow, scattered by a rotating object at angular velocity (Omega) over right arrow, experiences a rotational Doppler shift (Omega) over right arrow.(L) over right arrow. We show that this fundamental light-matter interaction can be detected exploiting self-mixing in a vortex laser under Doppler-shifted optical feedback, with quantum noise-limited light detection. We used a low-noise relaxation oscillation-free (class-A) vortex laser, based on III-V semiconductor vertical-external-cavity-surface-emitting laser technology to generate coherent Laguerre-Gauss beams carrying L = hl (l = +/- 1,...+/- 4). Linear and rotational Doppler effects were studied experimentally and theoretically. This will allow us to combine a velocity sensor with optical tweezers for micro-manipulation applications, with high performances: compact, powerful >> 10 mW, high-quality beam, auto-aligned, linear response up to > 10(8) rad/s or > 300 km/h, low back-scattered light detection limit < 10(-16)/Hz.

We report on electrical noise measurements on both Hg/sub 0.7/Cd/sub 0.3/Te test patterns and hybrid 320 /spl times/ 256 focal plane array in order to explain the low-frequency pixel flickering physical origin. Dark and under infrared illumination test patterns characterization highlights that the detector chip is not responsible for the flickering phenomenon. Taking into account the silicon readout chip influence when the full infrared complementary metal-oxyd semiconductor (IRCMOS) infrared detector is investigated, the indium bump based interconnecting system is finally pointed out as a potential excess noise source.

International audience; Linewidth determination by self-heterodyne or self-homodyne methods may lead to mistaken interpretation, because these measurements often include significant broadening due to low-frequency FM noise. The effects of FM noise on these linewidth measurement schemes are investigated. An analytical formulation of the photocurrent autocorrelation function is given for different frequency noise signatures, the lineshape being extracted from numerical implementation. We apply these results to linewidth prediction for 850-nm commercial vertical-cavity surface-emitting lasers and get almost perfect agreement between the theoretical and the experimental approaches.

The frequency noise of a laser has a direct influence on the lineshape and the linewidth. We present here the frequency-noise spectrum we obtained with selectively-oxidized Vertical-Cavity Surface-Emitting Lasers (VCSELs) emitting in the range of 850nm. We noticed different parts in the spectrum: a 1/fn part in the low-frequency range, independent of the output power, and a white-noise part in the high-frequency range, inversely dependent of the output power. The link with the laser lineshape is theoretically performed.

International audience

We demonstrate a high reflectivity (99%), low-loss (0.1%) and aberrations-free (2% of λ rms phase fluctuations) concave Bragg mirror (20mm radius of curvature) integrating a photonic crystal with engineered spherical phase and amplitude transfer functions, based on a III-V semiconductors flat photonics technology. This mirror design is of high interest for highly coherent high power stable external cavity semiconductor lasers, exhibiting very low noise. We design the photonic crystal for operation in the pass band. The approach incorporates spatial, spectral (filter bandwidth= 5nm) and polarization filtering capabilities. Thanks to the mirror, a compact single mode TEM(00) 2mm-long air gap high finesse (cold cavity Q-factor 10(6) - 10(7)) stable laser cavity is demonstrated with a GaAs-based quantum-wells 1/2-VCSEL gain structure at 1μm. Excellent laser performances are obtained in single frequency operation: low threshold density of 2kW/cm(2) with high differential efficiency (21%). And high spatial, temporal and polarization coherence: TEM(00) beam close to diffraction limit, linear light polarization (60dB), Side Mode Suppression Ratio46dB, relative intensity noise at quantum limit (-150dB) in 1MHz-84GHz radio frequency range, and a theoretical linewidth fundamental limit at 10 Hz (Q-factor ∼ 3.10(13)).

Demanding applications such as LIDAR, velocimetry, gas analysis or atomic clock rely on a highly coherent laser. Offering high coherence at high power and flexible wavelength, the GaAs- and Sb-based VECSEL technologies seem to be a well suited path to fulfill the required specifications of demanding applications. Till now, technical and physical knowledge of high power high coherence single frequency compact diode-pumped VECSELs have been developed at IES [1], with low intensity and frequency noise, but this promising technology is still at laboratory stage. The expertise built up in this field allows considering the realization of user-friendly marketable products, with performances that do not exist on the market today at 1 μm and 2.3 μm. Our goal is to develop a single frequency diode-pumped VECSEL, intracavity element free, achieving the desired performances, and to integrate this component into a compact module. The VECSEL prototypes developed in the frame of this work exhibit exciting features compared to diode-pumped solidstate lasers; they combine high power high coherence in a single TEM00 mode emission, free running narrow linewidth with high SMSR, a linear polarization, broadband continuous tunability, and compact design without any movable intracavity elements. All these specifications can be reached thanks to the high finesse cavity of VECSEL technology, associated to ideal homogeneous laser QW gain behavior.

This work consists in an in-depth analysis of the VeCSELs beam coherence thanks to the physical study of the noise properties for both the frequency and the intensity of the optical beam.

We report linewidth and lineshape measurements on 1.55-/spl mu/m distributed Bragg reflector tunable laser diodes using the heterodyne method. We measure Lorentzian linewidths ranging from 3.5 to 25 MHz without any passive section injection. Biasing the Bragg section enhances the residual linewidth up to 6.2 MHz, changes the linewidth-power product, and brings an additional Gaussian lineshape. The feedback sensitivity of the overall setup is also demonstrated.

We report a continuous-wave highly-coherent and tunable dual-frequency laser emitting at two frequencies separated by 30 GHz to 3 THz, based on compact III–V diode- pumped quantum-well surface-emitting semiconductor laser technology. The concept is based on the stable simul- taneous operation of two Laguerre–Gauss transverse modes in a single-axis short cavity, using an integrated sub- wavelength-thick metallic mask. Simultaneous operation is demonstrated theoretically and experimentally by recording intensity noises and beat frequency, and time- resolved optical spectra. We demonstrated a >80 mW out- put power, diffraction-limited beam, narrow linewidth of 45 dB), and low in- tensity noise class-A dynamics of

The integration of an industry ready packaged Sb-based Vertical-External-Cavity Surface-Emitting-Laser (VECSEL) into a Cavity Ring Down Spectrometer (CRDS) is presented. The instrument operates in the important 2.3 μm atmospheric transparency window and provides a high sensitivity (minimum detectable absorption of 9 × 10(-11) cm(-1)) over a wide spectra range. The VECSEL performances combine a large continuous tunability over 120 cm(-1) around 4300 cm(-1) together with a powerful (∼5 mW) TEM00 diffraction limited beam and linewidth at MHz level (for 1 ms of integration time). The achieved performances are illustrated by high sensitivity recordings of the very weak absorption spectrum of water vapor in the region. The developed method gives potential access to the 2-2.7 μm range for CRDS.

We present the design, technology and performances of a tunable Sb-based diode-pumped type-I quantum-well vertical-external-cavity surface-emitting lasers emitting at 2.7μm. The half VCSEL structure was grown by MBE with quantum-well growth temperature of 440 °C. The sample was thermally annealed to optimize the QW gain design. We report on room-temperature continuous-wave laser with 0.17mW output power and low threshold incident pump intensity of 0.7kW/cm2 while pumping at 830nm with a commercial diode laser. The external cavity provides a circular TEM00 beam with a low divergence of 3.6°. The short mm-long optical cavity laser exhibits tunable single frequency operation, with a side mode suppression ratio 23 dB, a linewidth 4GHz and a linear light polarization. Thermal and optical properties are studied.

We demonstrate broadband (THz) cw operation of a modeless external-cavity quantum-dot semiconductor diode laser. The laser cavity design is based on a frequency-shifted-feedback laser design using an intracavity acoustooptic frequency shifter. The rms intensity fluctuations are < 0.5% and the coherence time is 1 μs. The spectral optical power density is (see manuscript) 0.2 μW/MHz.

We present the design, technology, and performances of a tunable Sb-based diode-pumped type-I quantum-well (QW) vertical-external-cavity surface-emitting lasers emitting at 2.7 μm. The half vertical-cavity surface-emitting laser (VCSEL) structure was grown by molecular beam epitaxy with quantum-well growth temperature of 440 °C. The sample was thermally annealed to optimize the QW gain design. We report on room-temperature continuous-wave laser with 0.17-mW output power and low threshold incident pump intensity of 0.7 kW/cm2 while pumping at 830 nm with a commercial diode laser. The external cavity provides a circular TEM00 beam with a low divergence of 3.6°. The short mm-long optical cavity laser exhibits tunable single frequency operation, with a sidemode suppression ratio >;>; 23dB, a linewidth

In the last decade, there has been increased interest in photonic technology for new satellite applications. One critical issue is the high sensitivity to radiative environments of the Erbium Doped Fiber (EDF). It leads to a radiation-induced absorption (RIA) that is not due to erbium content but mainly to the aluminium that ensures the erbium inclusion in glass. As the radiation induced losses grow as an exponential function of fiber length, the principal way so far to reduce EDFA degradation has consisted in increasing erbium concentration using conventional doping techniques. However, this is limited by the quenching effect, which impacts the fiber length needed to reach high gain, but also by the Aluminium-induced RIA. It has been recently proposed an original nanoparticle (NP) doping approach, which allows codopant content decrease with reduced quenching impact, while keeping EDF amplifying performances. A radiation-resistant amplifier can thus be designed as a "quenching-free", heavily-erbium-doped amplifier with low RIA. We demonstrate for the first time an aluminium-free EDF, exhibiting low quenching and low RIA. Despite the lack of aluminium, using silica NPs allows an erbium concentration close to the one of standard EDFs (200 ppm). This fiber is compared to a 1400 ppm Erbium-doped optical fiber with a strong aluminium concentration. Whereas the two fibers exhibit similar initial optical gain (15 dB under saturation conditions), the NP doped Al-free EDF shows only 2 dB gain reduction after a 600 Gy gamma deposit, while the Al/Er EDF incurs more than 10 dB gain degradation.

International audience; In the last decade, there has been increased interest in photonic technology for new satellite applications. One critical issue is the high sensitivity to radiative environments of the Erbium Doped Fiber (EDF). It leads to a radiation-induced absorption (RIA) that is not due to erbium content but mainly to the aluminium that ensures the erbium inclusion in glass. As the radiation induced losses grow as an exponential function of fiber length, the principal way so far to reduce EDFA degradation has consisted in increasing erbium concentration using conventional doping techniques. However, this is limited by the quenching effect, which impacts the fiber length needed to reach high gain, but also by the Aluminium-induced RIA. It has been recently proposed an original nanoparticle (NP) doping approach, which allows codopant content decrease with reduced quenching impact, while keeping EDF amplifying performances. A radiation-resistant amplifier can thus be designed as a "quenching-free", heavily-erbium-doped amplifier with low RIA. We demonstrate for the first time an aluminium-free EDF, exhibiting low quenching and low RIA. Despite the lack of aluminium, using silica NPs allows an erbium concentration close to the one of standard EDFs (200 ppm). This fiber is compared to a 1400 ppm Erbium-doped optical fiber with a strong aluminium concentration. Whereas the two fibers exhibit similar initial optical gain (15 dB under saturation conditions), the NP doped Al-free EDF shows only 2 dB gain reduction after a 600 Gy gamma deposit, while the Al/Er EDF incurs more than 10 dB gain degradation.

We demonstrate for the first time a radiationresistant Erbium-Doped Fiber exhibiting performances that can fill the requirements of Erbium-Doped Fiber Amplifiers for space applications. This is based on an Aluminum co-doping atom reduction enabled by Nanoparticules Doping-Process. For this purpose, we developed several fibers containing very different erbium and aluminum concentrations, and tested them in the same optical amplifier configuration. This work allows to bring to the fore a highly radiation resistant Erbium-doped pure silica optical fiber exhibiting a low quenching level. This result is an important step as the EDFA is increasingly recognized as an enabling technology for the extensive use of photonic sub-systems in future satellites.

The qualification of erbium-doped fibers for space applications is made complex because they exhibit enhanced low-dose-rate sensitivity. We demonstrate a new assessment method that allows these optical fibers to be tested over a short time, which can be extended to any photonic device.

International audience; We demonstrate high power (multiwatt) low noise single frequency operation of tunable compact verical-external- cavity surface-emitting-lasers exhibiting a low divergence high beam quality, of great interest for photonics applications. The quantum-well based lasers are operating in CW at RT at 1μm and 2.3μm exploiting GaAs and Sb technologies. For heat management purpose the VECSEL membranes were bonded on a SiC substrate. Both high power diode pumping (using GaAs commercial diode) at large incidence angle and electrical pumping are developed. The design and physical properties of the coherent wave are presented. We took advantage of thermal lens-based stability to develop a short (0.5 < 5mm) external cavity without any intracavity filter. We measured a low divergence circular TEM00 beam (M2 = 1.2) close to diffraction limit, with a linear light polarization (> 30 dB). The side mode suppression ratio is > 45 dB. The free running laser linewidth is 37 kHz limited by pump induced thermal fluctuations. Thanks to this high-Q external cavity approach, the frequency noise is low and the dynamics is in the relaxation-oscillation-free regime, exhibiting low intensity noise (< 0.1%), with a cutoff frequency > 41MHz above which the shot noise level is reached. The key parameters limiting the laser power and coherence will be discussed. These design/properties can be extended to other wavelengths.

Laser technology is maturing rapidly and is finding applications in areas such as high resolution spectroscopy, optical telecoms, metrology, where highly coherent, low noise, compact and high power tunable sources are required. For this purpose, a compact design can be achieved, using a simple extended-cavity semiconductor surface emitting laser (VeCSEL), that outclasses the performances reached by traditional laser technologies (laser diode, DPSSL, …). These lasers offer continuous wave operation at 300K at high output power with a circular, diffraction limited, low divergence beam.

We demonstrate high power (2.1W) low noise single frequency operation of a tunable compact verical-external-cavity surface-emitting- laser exhibiting a high beam quality. We took advantage of thermal lens-based stability to develop a short (3-10 mm) plano-plano external cavity without any intracavity filter. The semiconductor structure emitting at 1microm is optically pumped by a 8W commercial 808 nm multimode diode laser at large incidence angle. For heat management purpose the GaAs-based VECSEL membrane was bonded on a SiC substrate. We measured a low divergence quasi-circular TEM00 beam (M2 = 1.2) close to diffraction limit, with a linear light polarization (30 dB).We simulated the steady state laser beam of this unstable cavity using Fresnel diffraction. The side mode suppression ratio is45 dB. The free running laser linewidth is 37 kHz limited by pump induced thermal fluctuations. Thanks to this high-Q external cavity approach, the frequency noise is low and the dynamics is in the relaxation-oscillation-free regime, exhibiting low intensity noise (0.1%), with a cutoff frequency approximately 41MHz above which the shot noise level is reached. The key parameters limiting the laser power and coherence are studied. This design/properties can be extended to other wavelengths.

International audience; Diffraction-limited sources around 976 nm are attractive to build sources around 488 nm, or to pump rare-earth-doped materials. Continuous wave efficient lasers have been obtained with single-mode fibres, in which we demonstrate pulsed laser diode amplification with gains higher than 30 dB. Theoretical studies can predict the amplifier performances versus the input signal characteristics and show the pulse width influence on excited state population. We used a classical timespace two-level model that we solved thanks to a Finite-Difference Time-Domain method. These simulations taking into account both time and space evolutions and a parasitic laser effect describe correctly the experimental results.

International audience; We report on a diode-pumped vertical external-cavity surface-emitting laser emitting around 852 nm for Cesium atomic clocks experiments. We have designed a 7-quantum-well semiconductor structure optimized for low laser threshold. An output power of 330 mW was achieved for 1.1 W of incident pump power. Furthermore a compact setup was built for low-power single-requency emission. We obtained an output power of 17 mW in a single longitudinal mode, exhibiting both broad (9 nm) and continuous (14 GHz) tunability around the Cesium D2 line. The laser frequency has been stabilized on an atomic transition with residual frequency fluctuations ~ 300 kHz. Through a beatnote experiment the -3 dB laser linewidth has been measured to < 500 kHz over 10 ms.

We demonstrate high power high efficiency (0:3 W) low noise single frequency operation of a compact extended-cavity surface-emitting-semiconductor-laser exhibiting a continuous tunability over 0:84 THz with high beam quality. We took advantage of thermal lens-based stability to develop a short (3 mm) plano-plano external cavity without any intracavity filter. The structure is optically pumped by a 1 W commercial 830 nm multimode diode laser. No heat management was required. We measured a low divergence circular TEM(00) beam at the diffraction limit (M(2)1:05) with a linear light polarization (37 dB). The side mode suppression ratio is 60 dB. The free running laser linewidth is 850 kHz limited by pump induced thermal fluctuations. Thanks to this high-Q external cavity approach, the frequency noise is low and the dynamics is in the relaxation-oscillation-free regime, exhibiting a low intensity noise, with a cutoff frequency approximately 250 MHz above which the shot noise level is reached. We show that pump properties define the cavity design and laser coherence.

This paper deals with noise and noise correlation experimental results in copropagative distributed Raman Amplifiers. Each stage of the whole amplifier is studied, focusing on the pumping system influence. This work finally leads to the background ASE noise excess noise due to pumping system RIN.

This paper deals with the study of the various excess noises in copropagative distributed Raman Amplifiers. We study the influence of the biasing system on the laser sources through three simple home-made curent sources. A second step consists in studying the polarization multiplexer noise contribution. Finally, the impact of these noise exces on the amplifier background noise is studied.

This paper deals with photodetected noise processes occuring in co-propagative DRA (Distributed Raman Amplifiers) such as beat noises. We develop here numerical modelisations and experimental set-ups in order to confront theory and measurements for each excess noise source. Our measurements demonstrate that the Raman ASE process, which gives rise to the DRA "background" noise, is poissonian, in spite of a super-poissonian pumping power, and how this statistics is disturbed by pump excess noise.

International audience; Tunable Lasers are key-components for Wavelength Division Multiplexing optical communication applications at 1.55μm. In this paper, we compare a rate equation model with measurements performed in order to study the Bragg section contribution in the 1/f-optical-beam noise power spectral density.

We report on electrical noise measurements on both Hg0.7Cd0.3Te test patterns and hybrid 320 × 256 focal plane array in order to explain the low frequency pixel flickering physical origin. Dark and under infrared illumination test patterns characterization highlights that the detector chip isn’t responsible for the flickering phenomenon. Taking into account the silicon readout chip influence when the full IRCMOS infrared detector is investigated, the indium bump based interconnecting system is finally pointed out as a potential excess noise source.