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We propose obtaining TiO

We present an electro-optic dual-comb spectrometer operating in the mid- infrared for carbon dioxide sensing. Isotopic ratio measurements of 13CO2/12CO2 are per- formed and the results show good agreements with the expectations.

We propose obtaining TiO2 films by ICPCVD for the fabrication of low-loss waveguides. The challenge is to produce a dense and homogeneous layer with a high refractive index and low absorption in the visible range. Crystallized layers with features such as grains and amorphous layers have a rather low index for the application targeted, so we aimed for an intermediate state. We investigated the influence of plasma power, pressure, deposition time and annealing temperature on the structural, crystalline, and optical properties in order to tailor them. We showed that crystallization into rutile at the nanoscale occurred during deposition and under wisely chosen conditions, we reached a refractive index of 2.5 at 630 nm without creating interfaces or inhomogeneity in the layer depth. Annealing permits one to further increase the index, up to 2.6. TEM analysis on one sample before and after annealing confirmed the nano-polycrystallization and presence of both anatase and rutile phases and we considered that this intermediate state of crystallization was the best compromise for guided optics.

We demonstrate a dual-comb spectrometer based on the direct electro-optic modulation of a continuous-wave laser operating in the thulium amplification band. We show that the emergent two-micrometer technology is already suitable for developing all-fibered dual-comb setups employed here for gas sensing applications. By performing spectroscopic measurements around two micrometers on carbon dioxide, we obtain very good agreement between the experimental results and calculations provided by the HITRAN database. These results pave the way to the extension of electro-optic dual-comb spectrometry in the mid-infrared region.

Mid-infrared (2−20 μm) gas sensing allows the detection of strong molecular absorptions with rather small absorption lengths (≤1 m). Various techniques can perform spectroscopic measurements in the mid-infrared but dual-comb spectroscopy (DCS) is one of the most powerful knowing its precision and real-time abilities [1]. However, setups used to perform DCS are in general complex since they require the phase locking of two independent femtosecond lasers at the known state of the art stability. This particular drawback can be bypassed if the combs are generated with electro-optic modulators (EOM) [2]. However, these equipments operate in the telecommunication wavelengths, generally near 1.55 μm where molecular absorptions are not very intense. Here, we experimentally demonstrate two different techniques of generating frequency combs with EOMs around 2 μm.

We show that subwavelength silicon-rich nitride waveguides efficiently sustain high-speed transmissions at 2 $\mu$m. We report the transmission of a 10 Gbit/s signal over 3.5 cm with negligible power penalty. Parametric conversion in the pulsed pump regime is also demonstrated using the same waveguide structure with an efficiency as high as -18 dB., Comment: arXiv admin note: text overlap with arXiv:1811.04717

We report the first demonstration of a single-pass dual-orthogonal-pump four-wave mixing-based wavelength conversion scheme in a silicon-based waveguide. The silicon germanium waveguide used was designed to exhibit strong TE/TM mode similarity across a broad wavelength range as well as a large nonlinear coefficient. A polarization-dependent loss of just 0.42 dB was measured, and the conversion of 40-Gb/s differential phase-shift keying signals was demonstrated with 1.5-dB power penalty at a bit error ratio of $10^{-9}$ .

We operate micron-sized CdSe/CdS core–shell quantum dot (QD) clusters deposited onto gold patches as integrated light sources for the excitation of photonic waveguides. The surface plasmon mode launched by the QD fluorescence at the top interface of the gold patches are efficiently coupled to photonic modes sustained by titanium dioxide ridge waveguides. We show that, despite a large effective index difference, the plasmonic and the photonic modes can couple with a very high efficiency provided the vertical offset between the two kinds of waveguides is carefully controlled. Based on the effective index contrast of the plasmonic and the photonic modes, we engineer in-plane integrated hybrid lenses. The hybrid lenses are obtained by shaping the contact interface between the plasmonic and the photonic waveguides. We demonstrate a 2-fold enhancement of the coupling efficiency for tapers equipped with a hybrid lens. Our results are expected to be useful for the development of low-cost, integrated light sources...

Frequency combs are optical spectra composed of a set of discrete equally spaced lines. Such spectra can be generated by diverse sources such as mode-locked lasers, resonators, or electro-optic modulators. This last possibility has shown a growing interest in the recent years for its advantageous features in providing high repetition rates, intrinsic mutual coherence, or high power per comb lines. Moreover, applications of electro-optic modulator-based combs have flourished in fundamental physics, spectroscopy, or instrumental calibrations. In this paper, we present the most recent progresses made on frequency combs generated by electro-optic modulators, along with the applications where these combs have shown a particular interest.

Background: Electrically controlled optical metal antennas are an emerging class of nanodevices enabling a bilateral transduction between electrons and photons. At the heart of the device is a tunnel junction that may either emit light upon injection of electrons or generate an electrical current when excited by a light wave. The current study explores a technological route for producing these functional units based upon the electromigration of metal constrictions.Results: We combine multiple nanofabrication steps to realize in-plane tunneling junctions made of two gold electrodes, separated by a sub-nanometer gap acting as the feedgap of an optical antenna. We electrically characterize the transport properties of the junctions in the light of the Fowler–Nordheim representation and the Simmons model for electron tunneling. We demonstrate light emission from the feedgap upon electron injection and show examples of how this nanoscale light source can be coupled to waveguiding structures.Conclusion: Electromigrated in-plane tunneling optical antennas feature interesting properties with their unique functionality enabling interfacing electrons and photons at the atomic scale and with the same device. This technology may open new routes for device-to-device communication and for interconnecting an electronic control layer to a photonic architecture.

We report the transmission of a 10 Gbps telecommunication signal at 2 μm in waveguides made of three different materials: Si, SiGe and TiO2. Bit error rates below 10−9 can be achieved after transmission in the devices with subwavelength dimensions.

We experimentally demonstrate a novel approach of generating frequency combs in a highly nonlinear fiber. Using fourth-order modulation instability, we converted around 2 µm two mutually coherent frequency combs to perform CO2 spectroscopy.

Exploring new spectral bands for optical transmission is one of the solutions to support the increasingly demand of data traffic. The recent development of dedicated hollow-core photonic bandgap fibers [1], associated to the emergence of thulium doped fiber amplifiers [2] has recently focused the attention further in the infrared, and more specifically around 2 μm. Regarding integrated photonics, it becomes therefore interesting to find a suitable platform to operate at 2 μm as well as in the other more conventional spectral bands (going from 800 nm to 1550 nm). Here, we propose titanium dioxide (TiO 2 ) as a good candidate for integrated waveguide photonics and demonstrate, for the first time, high bit rate transmissions at 1550 nm and 1980 nm.

Versatile and easy to implement methods to generate arbitrary optical waveforms at high repetition rates are of considerable interest with applications in optical communications, all-optical signal processing, instrumentation systems and microwave signal manipulation. While shaping sinusoidal, Gaussian or hyperbolic secant intensity profiles is commonly achieved by means of modulators or mode-locked lasers, other pulse profiles such as parabolic, triangular or flat-top shapes still remain challenging to synthesize. In this context, several strategies were already explored. First, the linear pulse shaping is a common method to carve an initial ultrashort pulse train into the desired shape. The line-by-line shaping of a coherent frequency comb made of tens of spectral components was also investigated to generate more complex structures whereas Fourier synthesis of a few discrete frequencies spectrum was exploited to efficiently generate high-fidelity ultrafast periodic intensity profiles. Besides linear shaping techniques, several nonlinear methods were implemented to benefit from the adiabatic evolution of the intensity pulse profile upon propagation in optical fibers. Other examples of efficient methods are based on the photonic generation involving specific Mach-Zehnder modulators, microwave photonic filters as well as frequency-to-time conversion. In this contribution, we theoretically and experimentally demonstrate a new approach enabling the synthesis of periodic high-repetition rate pulses with various intensity profiles ranging from parabola to triangular and flat-top pulses. More precisely by linear phase and amplitude shaping of only four spectral lines is it possible to reach the targeted temporal profile. Indeed, tailoring the input symmetric spectrum only requires the determination of two physical parameters: the phase difference between the inner and outer spectral sidebands and the ratio between the amplitude of these sidebands. Therefore, a systematic bidimensional analysis provides the optimum parameters and also highlights that switching between the different waveforms is achieved by simply changing the spectral phase between the inner and outer sidebands. We successfully validate this concept with the generation of high-fidelity ultrafast periodic waveforms at 40 GHz by shaping with a liquid cristal on insulator a four sideband comb resulting from a phase-modulated continuous wave. In order to reach higher repetition rates, we also describe a new scenario to obtain the required initial spectrum by taking advantage of the four-wave mixing process occurring in a highly nonlinear fiber. This approach is experimentally implemented at a repetition rate of 80-GHz by use of intensity and phase measurements that stress that full-duty cycle, high-quality, triangular, parabolic or flat-top profiles are obtained in full agreement with numerical simulations. The reconfigurable property of this photonic waveform generator is confirmed. Finally, the generation of bunch of shaped pulses is investigated, as well as the impact of Brillouin backscattering.

International audience; In this work, we experimentally investigate several temporal and spectral methods to highlight extreme fluctuations which can develop during the Raman amplification of an ultrashort pulse train. Forward and backward pumping schemes are compared to dual pass configurations.

We demonstrate error-free transmission of 10 Gbit/s non-return to zero optical signals along 2.5 cm long SiGe waveguides at a wavelength of 1.98 μm. Bit error rate measurements confirm the absence of penalty during the transmission through a subwavelength 1.3 μm-wide waveguide as well as through a 2.2 μm wide waveguide.

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicon-germanium waveguide. The 3 cm long waveguide is pumped by femtosecond pulses at 2.4 μm, and the generated supercontinuum extends from 1.45 to 2.79 μm (at the −30 dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5–1.8 μm region and soliton fission. The SCG was modeled numerically, and excellent agreement with the experimental results was obtained.

We demonstrate a polarization-assisted PSA-based phase regenerator in a passive low-birefringence SiGe waveguide at low CW pump power. A PSER of 28.6-dB enables a six-fold reduction in phase-error and BER improvement of approximately 2-dB in the regenerated signal.

This talk presents recent progress in optical signal processing based on compact waveguides fabricated mainly using silicon germanium alloys. Applications include supercontinuum generation, wavelength conversion and signal regeneration.

A binary step-like phase response and phase-sensitive extinction ratio in excess of 28dB under CW pump operation was demonstrated in a 20mm-long low birefringence SiGe waveguide, using a polarization-assisted phase sensitive amplifier scheme.

International audience; Embedded metal grating couplers into titanium dioxide layer are proposed. A coupling efficiency better than 20 % is experimentally demonstrated with a 3-dB bandwidth of 86 nm in agreement with simulation results. This allowed us to perform error-free transmissions of 10 Gbit/s wavelength multiplexed signals in the C-band.

This paper presents the potential of silicon germanium waveguides in the nonlinear conversion of light from mid-infrared wavelengths to the telecom band utilizing four-wave mixing. Design aspects and first characterization results of fabricated devices are presented.

We demonstrate the design, fabrication and characterization of a highly nonlinear graded-index SiGe waveguide for the conversion of mid-infrared signals to the near-infrared. Using phase-matched four-wave mixing, we report the conversion of a signal at 2.65 µm to 1.77 µm using a pump at 2.12 µm.

We demonstrate four wave mixing (FWM) based wavelength conversion of 40 Gbaud differential phase shift keyed (DPSK) and quadrature phase shift keyed (QPSK) signals in a 2.5 cm long silicon germanium waveguide. For a 290 mW pump power, bit error ratio (BER) measurements show approximately a 2-dB power penalty in both cases of DPSK (measured at a BER of 10-9) and QPSK (at a BER of 10-3) signals that we examined.

We report on analytical, numerical and experimental studies of higher-order modulation instability in fiber optics. This new form of instability arises from the nonlinear superposition of elementary instabilities and manifests as complex, yet deterministic temporal pulse break-up dynamics. We use the Darboux transformation to analytically describe the process and compare with experiments. In particular, we show how suitably low frequency modulation on a continuous wave field allows for the excitation of higher-order modulation instability through cascaded four-wave mixing.

By combining real time characterization with cut-back measurements, we provide the first direct observation of Peregrine-like soliton longitudinal evolution dynamics and report a new effect associated with the breakup of a Peregrine soliton into two subpulses, each providing similar characteristics of localization upon finite background. Experimental results are in good agreement with simulations.

Several promising applications demonstrate all the benefits expected from the interaction of dispersive and nonlinear effects in single mode optical fibers: pulse shaping, ultra-short pulse source conception, rogue wave generation and high bit-rate optical communications.

We review our experimental and theoretical results showing the emergence of rogue events during light propagation in fiber-based nonlinear systems. Distinct statistical properties are underlined through parametric and Raman amplifications, supercontinuum generation and optical turbulence.

In the article entitled "Research on the nonlinear pulse propagation by numerical analysis" , Li Li and Aihan Yin summarize the key elements affecting the nonlinear propagation of an optical pulse in an optical fiber. We comment these results.

We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

International audience; We propose a new method for the generation of both triangular-shaped optical pulses and flat-top, coherent supercontinuum spectra using the effect of fourth-order dispersion on parabolic pulses in a passive, normally dispersive highly nonlinear fiber. The pulse re-shaping process is described qualitatively and is compared to numerical simulations.

We show that rogue waves can emerge from optical turbulence and that their coherent deterministic description provided by the rational solutions is compatible with the statistical description provided by the wave turbulence theory.

Summary form only given. Modulation instability (MI) is a ubiquitous process in which a weak field is exponentially amplified through a balance between dispersive and nonlinear effects. In single-mode scalar optical fibers, the positive Kerr nonlinearity phase-mismatch can be compensated by anomalous second-order dispersion, a process known as MI2. But phase-matched solutions can also exist in normal second-order dispersion region, thanks to negative even higher-order terms [1]. This process, that we label MI4, gives rise to a pair of narrow sidebands widely detuned far from the pump. MI may grow spontaneously from broadband noise and is usually the main process involved in the early stages of most supercontinuum (SC) generation. Because of its stochastic nature, MI creates strong fluctuations of spectral power, especially near the SC edges. In the time domain, these fluctuations manifest as so-called optical rogue waves, both in the MI2 [2] and MI4 [3] cases. Active methods based on stimulating the MI2 process have already been proposed [4]. However, in the configuration based on MI4, no experiments or numerical works have focused on the study of fluctuations and their reduction.For the first time, the large fluctuations of an SC generated from MI4 are highlighted and a method to mitigate them is proposed and validated. The experimental setup is sketched in Fig. 1(a) and relies on a Q-switch Nd-YAG laser emitting sub-nanosecond pulses. Pump pulses are combined with one or two continuous-wave seeds in the C-band corresponding to the Stokes MI-4 gain bandwidth of a 2 m long photonic crystal fiber. Output spectra as well as the statistical fluctuations after a narrowband filter are experimentally recorded and summarized in Fig. 1(b-c). Contrary to the MI2 case, stimulating the MI4 process with a single seed does not allow to significantly reduce fluctuations. We have found that this can be explained by the spontaneous cascaded MI2 process arising from the amplified seed in the vicinity of the MI4 gain band [5]. Therefore, two seeds are required to stimulate both the MI4 and the subsequent MI2, which results in an overall stabilization of the SC. This concept is validated from both experiments and numerical simulations. Fig 1(d) demonstrates that the spontaneous MI2-induced sideband (Fig. 1d2) can be efficiently mitigated by the double seeding scheme (Fig. 1d3). Consequently, the level of fluctuations affecting shot-to-shot records is drastically reduced (Figs. 1e) and numerical simulations based on the extended nonlinear Schrodinger equation reproduce the experimental stability improvement of the continuum source.

We present the operation of a passively mode-locked Erbium (Er)-doped fiber ring laser that incorporates a fully programmable filter, allowing control of the cavity net dispersion.

International audience; We report on the dynamics of the higher-order modulation instability in optical fibers and show that it is the very same phenomenon that underpins the emergence of rogue waves in the early stage of supercontinuum generation.

International audience; We report on theoretical, numerical and experimental study of a new form of instability in a nonlinear fiber. This process of higher-order modulation instability arises from the nonlinear superposition of elementary instability dynamics.

Recent investigations in nonlinear fiber optics have shown a renewed interest in certain classes of analytical solutions of the Nonlinear Schrodinger equation which, although present in the mathematical literature for 25 years, have been largely overlooked in studies of nonlinear fiber propagation. In this paper we review recent experiments that have shown the power of this analytic approach.

International audience; We numerically study the dynamics of ultra-broadband wavelength converters based on fourth-order scalar modulation instability. We report the spontaneous emergence of solitons and trapped radiation waves as well as L-shaped associated statistical signatures.

We report the characterization of the optical properties of Silicon-Germanium (SiGe) waveguides. The evolution of these properties is presented as a function of the Ge concentration and the waveguide width.

We demonstrate polarization insensitive FWM-based wavelength conversion of 40Gb/s DPSK signals in a SiGe waveguide, with 0.42-dB polarization-dependent loss. A 1.5-dB Dower nenaltv was measured at a BER of 10−9.

International audience; We report the first observation in optics of the Peregrine soliton, a novel class of nonlinear localized structure. Two experimental configurations are explored and the impact of non-ideal initial conditions is discussed.

We report the first demonstration of broadband supercontinuum generation in silicon-germanium waveguides. Upon propagation of ultra-short femtosecond pulses in a 3-cm-long waveguide, the broadening extended from 1.455µm to 2.788µm (at the −30-dB point).

We report the characterization of loss and nonlinearity of a broadband tellurite glass fiber both at 1.55µm and 2µm wavelengths. The study is accompanied by a demonstration of wavelength conversion at both of these wavelengths.

International audience; The Akhmediev breather formalism of modulation instability is extended to describe the spectral dynamics of induced multiple sideband generation from a modulated continuous wave field. Exact theoretical results describing the frequency domain evolution are compared with experiments performed using single mode fiber around 1550 nm. The spectral theory is shown to reproduce the depletion dynamics of an injected modulated continuous wave pump and to describe the Fermi-Pasta Ulam recurrence and recovery towards the initial state. Realistic simulations including higher-order dispersion, loss and Raman scattering are used to identify that the primary physical factors that preclude perfect recurrence are related to imperfect initial conditions.

International audience; We report experimental observation and characterization of rogue wave-like extreme value statistics arising from pump-signal noise transfer in a fiber Raman amplifier. Specifically, by exploiting Raman amplification with an incoherent pump, the amplified signal is shown to develop a series of temporal intensity spikes whose peak power follows a power-law probability distribution. The results are interpreted using a numerical model of the Raman gain process using coupled nonlinear Schrödinger equations, and the numerical model predicts results in good agreement with experiment.

We demonstrate four-wave mixing based wavelength conversion of 40 Gbaud DPSK and QPSK signals in a 2.5-cm long silicon germanium waveguide with a nonlinearity coefficient of 25.8/W/m.