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We present here the implementation of an optoelectronic oscillator (OEO) that leverages the optical comb produced by a silicon add-drop ring resonator to directly convert signals from optical to microwave domain. The OEO comprises a CW laser, an intensity modulator, a silicon add-drop ring, a photodetector, and radiofrequency amplifier. By using millimeter-long silicon-on insulator micro-ring resonator, we generated an oscillation signal with a frequency determined by the free spectral range (FSR) of the ring. In this scheme, the sharp transmission peaks in the drop port of an add-drop silicon resonator are used as the optical comb. The optimised ring has a length of 5.8 mm with a measured FSR of 112 pm, an extinction ratio of 20 dB and an optical quality factor of 2.2 × 10 5 . The complete OEO loop yields a 14.12 GHz signal with a phase noise level of -100 dBc/Hz at an offset of 100 kHz from the carrier. This result shows that OEOs directly based on millimeters long silicon rings are a promising path for generating low-noise microwave signals.

Conductor-backed coplanar waveguide on 30-μm-thick BCB polymer is fabricated. In order to eliminate unwanted propagation modes for these lines designed for frequencies up to 1 THz, electroplated vias interconnect each coplanar ground to the backed conductor. Transmission line properties are extracted here up to 67 GHz, showing a characteristic impedance of about 50 Ω, but with high conduction losses for this frequency range due to the thin metal layer used. Thru-reflect-line correction and a de-embedding with electrical circuit of accesses are applied to extract line properties. The comparison with a coplanar waveguide model leads to a relative permittivity of 2.676 for the BCB in this low-frequency range.

Integrated silicon nanophotonics has progressed a lot over past decades with great promises for many surging applications in optoelectronics, information and communication technologies, sensing or health monitoring. Enabling low-cost, dense integration, and compatibility with modern semiconductor nanofabrication processes, silicon nanophotonics deliver compact and high-performance devices on single chips. A variety of nanophotonic functionalities, both passive and active, are nowadays available on semiconductor substrates, leveraging the maturity of open-access silicon foundries and epitaxial germanium integration. It encompasses essential functions such as light generation and amplification, fast electro-optical modulation, and reliable conversion of optical into electrical signals. Germaniumbased optical photodetectors are main building blocks within the library of integrated silicon nanophotonics, with performances that are nowadays on par with their III-V-based counterparts. Germanium photodetectors integrated at the end of waveguides are attractive for next-generation on-chip interconnections, because of their compactness, bandwidth and speed, energy consumption and cost. In this work, we present our latest advances on silicon-germanium p-i-n waveguide-integrated photodetectors based on lateral silicon-germanium-silicon heterojunctions. Our hetero-structured photodetectors were fabricated on top of 200-mm silicon-on-insulator substrates using industrial-scale fabrication processes compatible with complementary metal-oxide-semiconductor technology. Silicon-germanium p-i-n photodetectors operated under low bias voltages exhibited low dark-currents (~100 nA), cut-off frequencies beyond 50 GHz, and photo-responsivities of about 1.2 A/W. Photodetector sensitivities of -14 dBm and -11 dBm were achieved for communication data rates of 10 Gbps and 25 Gbps, respectively. P-i-n photodetectors with lateral heterojunction operated in an avalanche regime offered an additional degree of freedom to improve device performances. High-speed and low-noise characteristics were obtained in our p-i-n photodetectors upon avalanche operation, with a gain-bandwidth product of 210 GHz and a low carrier impact ionization ratio of about 0.25. The measured sensitivity of avalancheoperated devices was -11 dBm for 40 Gbps signal detection. As demonstrated in the reported achievements, heterostructured p-i-n photodetectors are thus suitable communication devices in future intra-data center links or high-speed optical interconnects.

Applications relying on mid-infrared radiation (λ ~ 3-30 μm) have progressed at a very rapid pace in recent years, stimulated by scientific and technological breakthroughs like mid-infrared cameras and quantum cascade lasers. On the other side, standalone and broadband devices allowing control of the beam amplitude and/or phase at ultra-fast rates (GHz or more) are still missing. Here we show a free-space amplitude modulator for mid-infrared radiation (λ ~ 10 μm) that can operate at room temperature up to at least 1.5 GHz (−3dB cutoff at ~750 MHz). The device relies on a semiconductor heterostructure enclosed in a judiciously designed metal–metal optical resonator. At zero bias, it operates in the strong light-matter coupling regime up to 300 K. By applying an appropriate bias, the device transitions towards the weak-coupling regime. The large change in reflectance is exploited to modulate the intensity of a mid-infrared continuous-wave laser up to 1.5 GHz., Broadband integrated electrical modulators are key components for photonic systems. Here, the authors present a room temperature mid-IR free-space amplitude modulator based on a semiconductor heterostructure that exploits the change in reflectance occurring at the change between weak and strong coupling.

International audience; The strong evolution of silicon photonics towards very low power consumption circuits leads to the development of new strategies for photonic devices, especially for power-hungry components such as optical modulators. One strategy is to use Pockels effect in Si waveguides. However, bulk Si is a centrosymmetric semiconductor, which cannot exhibit any second order optical nonlinearities. Nonetheless, under a strain gradient, generated by depositing a stressed layer on Si waveguides, this restriction vanishes. In our work, we experimentally demonstrated a Pockels effect based electro-optic modulation at high frequency (> 5GHz) using a strained silicon Mach-Zehnder modulator.

We report on the first demonstration of high-speed optical modulation exploiting Pockels effect in strained silicon waveguides. Bandwidths larger than 20 GHz and low insertion loss have been achieved at a wavelength of 1550 nm.

Silicon photonics, considered as a major photonic platform for optical communications in data centers, is today also developed for others applications including quantum photonics and sensing. Advanced silicon functionalities based on optical nonlinearities are then required. As the presence of inversion symmetry in the Si crystal structure prevents the exploitation of second-order optical nonlinearities, the generation of strain gradients in Si by a stressed material can be considered. However, due to the semiconductor nature of silicon with the presence of carriers, no clear evidence of second-order nonlinearities have been reported yet. Here we report an experimental demonstration of high-speed Pockels effect in silicon waveguides at 1550 nm. Additionally, a theoretical model is developed to describe its frequency behavior. A second-order nonlinear susceptibility $$\chi _{xxy}^{(2)}$$ χ x x y ( 2 ) of −1.8 ± 0.2 pm V−1 is then experimentally determined. These results pave the way for the development of fast linear electro-optic effect for advanced silicon photonics devices.

A process for microelectronic technology is developed for integration of passive devices with existing active device technology for submillimeter wave and THz frequency range applications. Performances of a conductor-backed coplanar waveguide on BCB polymer and interconnecting via between ground planes are presented up to 67 GHz with a 50 Ω characteristic impedance and a BCB relative permittivity of 2.676.

International audience; Hetero-structured silicon-germanium-silicon photodetectors operating under low-reverse-voltages with high responsivity, fast response, and low dark-current levels are reported. A bit-error-rate of 10-9 is experimentally achieved for conventional data rates of 10, 20, and 25 Gbps, providing optical power sensitivities of-13.9,-12.7, and-11.3 dBm.

International audience; We present on experimental results of straininduced Pockels effect in silicon based on Mach-Zehnder interferometer modulators. We theoretically studied both Pockels effect and carrier parasitic effect in silicon under an electric field. We demonstrated high speed Pockels-based optical modulation up to 25 GHz.

In this work, a 25 Gb ps silicon push-pull Mach-Zehnder modulator operating in the O-Band (1260 nm – 1360 nm) of optical communications and fabricated on a 300 mm platform is presented. The measured modulation efficiency (VπLπ) was comprised between 0.95 V cm and 1.15 V cm, which is comparable to the state-of-the-art modulators in the C-Band, that enabled its use with a driving voltage of 3.3 Vpp, compatible with BiCMOS technology. An extinction ratio of 5 dB and an on-chip insertion losses of 3.6 dB were then demonstrated at 25 Gb ps.

Optical modulation in the O-Band using a Mach-Zehnder modulator in push-pull configuration is presented and experimentally demonstrated. Open eye diagrams at 25 GBps have been obtained with more than 8 dB extinction ratio with an active length of only 1 mm.

Silicon photonics has generated a strong interest in recent years, mainly for optical communications and optical interconnects in CMOS circuits. The main motivations for silicon photonics are the reduction of photonic system costs and the increase of the number of functionalities on the same integrated chip by combining photonics and electronics, along with a strong reduction of power consumption. However, one of the constraints of silicon as an active photonic material is its vanishing second order optical susceptibility, the so called χ(2) , due to the centrosymmety of the silicon crystal. To overcome this limitation, strain has been used as a way to deform the crystal and destroy the centrosymmetry which inhibits χ(2). The paper presents the recent advances in the development of second-order nonlinearities including discussions from fundamental origin of Pockels effect in silicon until its implementation in a real device. Carrier effects induced by an electric field leading to an electro-optics behavior will also be discussed.

International audience; A new Si/Ge/Si heterojunction based waveguide photodetector has been demonstrated in order to reduce the fabrication cost, increase the responsivity, and improve process robustness. State of the art characteristics in terms of dark current, responsivity and bandwidth have been obtained. Furthermore, such photodetectors were characterized in avalanche mode in order to improve the sensitivity and reduce the overall power consumption of the optical circuit

The evolution of silicon optical modulators is recalled, from the first effect demonstrations to the characterization of high-performance devices integrated in optical waveguides. Among possibilities to achieve optical modulation in silicon-based materials, the carrier depletion effect has demonstrated good capacities. Carrier depletion in Si and SiGe/Si structures has been theoretically and experimentally investigated. Large phase modulation efficiency, low optical loss, and large cutoff frequency are obtained by considering simultaneously optical and electrical structure performances. Integrated Mach-Zehnder interferometers and resonators are compared to convert phase modulation into intensity modulation. Finally, recent results on high-speed and low-loss silicon optical modulator using an asymmetric Mach-Zehnder interferometer are presented. It is based on a p-doped slit embedded in the intrinsic region of a lateral pin diode integrated in a silicon-on-insulator waveguide. This design allows a good overlap between the optical mode and carrier density variations. An insertion loss of 5 dB has been measured with a -3 dB bandwidth of 15 GHz.

Silicon-based photonics has generated a strong interest in the last years, mainly for optical telecommunications and optical interconnects in microelectronic circuits and industrial breakthroughs have been even performed by companies like IBM, Luxtera, INTEL, and ST Microelectronics. The main future rationales are the reduction of photonic system costs, the increase of the number of functionalities on the same integrated chip by combining photonics and electronics, and the decrease of power consumption. During the DACINCT workshop, we will present recent results on ultrafast optical modulators based on carrier depletion effect and germanium photodetectors integrated in silicon on insulator (SOI) waveguides. Both optoelectronic devices have been fabricated on a CMOS 300mm platform. The achieved performances constitute a new milestone towards new generations of several Tb/s chips merging electronics and photonics.

We present the state of the art of microwave performances of silicon heterostructures FETs (hetero-FETs). Recent advances are illustrated on using DaimlerChrysler (DC) technologies. fMAX as high as 188 and 135 GHz with minimum noise figure, NFmin as low as 0.3 and 0.5 dB at 2.5 GHz are reported, respectively, for n- and p-MODFET with gatelength from 100 to 130 nm. Experimental data and physical simulations of optimized structures show that fMAX of 70 nm gatelength n-MODFET could reach 360 GHz.

In order to show the potential interest of SrBi 2 Nb 2 O 9 (SBN) ferroelectric films to develop microwave agile devices, we have undertaken the radiofrequency characterization of structures patterned in Au/SBN bilayers deposited on LaAlO 3 and MgO single-crystals. Both coplanar waveguide transmission lines and 10 GHz half-wavelength resonators were characterized in the 100 kHz to 10 GHz frequency range and in the 300 K to 100 K temperature range.

Properties of YBaCuO thin films are evaluated in two distinct frequency ranges using different patterns made during the same process on LaAlO/sub 3/ substrate. Microwave superconducting properties in the range 1-45 GHz are determined by S-parameters measurement of a superconducting coplanar waveguide in the range 53-95 K. We obtain a surface resistance of 0.4 m/spl Omega/ at 10.8 GHz and 77 K. Radio-frequency properties are obtained by measuring the Q-factor of a superconducting resonator (YBCO multiturn transmission lines separated by a sapphire sheet) dedicated to surface magnetic resonance imaging. At 52 MHz and 77 K we measure a Q-factor of 33180. The extraction of the radio-frequency surface resistance from Q-factor measurements in the 64-95 K range takes into account external loss mechanisms and nonuniform normal current distribution and leads to a 0.0093-/spl mu//spl Omega/ surface resistance at 52 MHz and 77 K, in good agreement with the value extrapolated from microwave measurements assuming an /spl omega//sup 2/ frequency dependence. The evaluation of /spl lambda//sub 0/ is carried out by using several models for X/sub L/(t). Least squares fits to data in the microwave and radio-frequency domain are performed using the Gorter-Casimir expression for X/sub L/(t) and give the same /spl lambda//sub 0/ value for both devices.

We demonstrate a reduction of loss and group velocity dispersion (GVD) of THz plasmonic waveguides by using a low-loss thin flexible substrate. We present a numerical calculation of the effect of the substrate thickness on the GVD. We show experimentally low absorption and weak distortion of the propagated THz pulses along a THz plasmonic waveguide on a flexible 58μm-thick polyimide substrate.

The ac electrical impedance of a 400-nm-thick La0.67Sr0.33MnO3 thin film (on MgO) has been measured in the frequency range from 30 MHz up to 6 GHz using etched strips. The impedance is found to be nearly a constant resistance that is equal to the dc resistance. The only deviations, in the order of their magnitude, are: (i) the contact pad impedance at low frequency, (ii) a small inductive part in the impedance of the material, and (iii) a low decrease of the resistance above 3 GHz.

The bias dependence of the single-port microwave reflection gain of 15 /spl mu/m-diameter Si Esaki tunnel diodes, grown by molecular beam epitaxy, was studied as a function of frequency. A simple equivalent circuit accurately modeled the data and yielded the forward-bias junction capacitance, which cannot be obtained by conventional low frequency capacitance-voltage techniques. The diodes were highly-doped step p-i-n junctions and exhibited a peak current density of 16 kA/cm/sup 2/. The microwave reflection gain and cut-off frequency were 12 dB land 1.6 GHz, respectively, with a speed index (slew rate) of 7.1 V/ns.

High Tc structures have raised a great interest for microelectronics applications. We have investigated two layer coplanar structures made of an Ag layer (200nm) sputtered on YBaCuO (300nm). The typical structures are 50Ω coplanar lines and resonator bandpass filters (24 GHz) analyzed from 45MHz to 30GHz. Coplanar lines are studied in the normal and superconducting states whereas filter shows transmitted signals only in the superconducting state. We propose a phenomenologic model taking into account the two layers and their interface. At 60K and 10GHz, the Rs of our YBaCuO layer is roughly 1.5mΩ. A good consistency is observed among the different lines and resonating measurements.

High performance ?-doped double recess 0.1-0.4?m AlGaAs-GaAs S-HEMTs[1] and ?-doped single-recess 0.1-0.7?m AlGaAs/GaInAs/GaAs PM-HEMTs [2-3] are studied from 300K down to 60K. DC and 0.1-40GHz HF measurements followed by electric parameter extractions give extensive evolutions of HEMT electric parameters versus temperature T, gatelength 1 g . The results are interpreted in terms of the transition regime from diffusive to strong overshoot/near ballistic carrier transport under the gate. In the longer devices (1 g =0.4-0.7?m), the latter effects become important at low temperatures and bring frequency intrinsic performance improvement mainly in terms of an increase of maximum intrinsic transconductance g mo . The shorter devices (0.1-0.2?m) appear to be already well in the overshoot regime at 300K due to the high quality epitaxial layers, and their frequency performance improvement upon cooling comes mainly from a reduction of intrinsic capacitance C gsint . The relative increase of intrinsic unity current gain cut-off frequency f tint upon cooling rates at a similar value of 30-40% for all investigated gatelengths(0.1-0.7?m).

We present a coordinated experimental and theoretical investigation of the parameter evolution of ultra-short gate HEMTs down to 0.1?m gate-length, and of the physical and electrical limitations to performance improvements. The study encompasses a broad range of well qualified situations allowing comparisons with previous investigations[1-4]. The main features are,- the exploitation of two reliable technological processes namely planar-doped double- recessed AlGaAs/GaAs HEMT (S-HEMT) and planar-doped pseudomorphic AlGaAs/GaInAs/GaAs HEMT with T-shaped and rectangular gate (PM-HEMT), represented in Fig. 1 and 2), - coherent evolutions of full electrical parameter extractions from dc and 0.1- 40GHz HF coplanar probe on-chip measurements, including capacitances versus gate length down to 0.1?m, - physical modeling based on a quasibidimensional hydrodynamic approach (Q-2D), allowing systematic parametrisation of HEMTs, completed with electromagnetic finite element 2-D modeling of electrostatic parasitic capacitances, - physical modeling based on Monte Carlo simulations (MC) for the investigation of short l g transistors. For the gate width lg?0,1 ?m this analysis shows that the optimization of S- and PM-HEMT depends on three parameters: - a weak influence of V ds on the diffusion under the gate, - a low parasitic electrostatic capacitance, - a high carrier velocity.

The noise performances of a new base-collector self-aligned technology of double-heterojunction single-finger InGaAs-InP bipolar transistor are investigated at 300 K. Noise parameter variations are studied versus frequency in the 2-18 GHz range, versus collector current and emitter area. A low minimum noise figure F/sub min/=0.6 dB is demonstrated at 2 GHz with a 4.8-/spl mu/m/sup 2/ emitter. Variations of F/sub min/ show a minimum versus collector current. The high cutoff frequencies of the devices limit the increase of F/sub min/ versus frequency.

We report the generation of continuous terahertz waves from microwave frequencies up to 2 THz obtained by photomixing two optical waves at 1.55-mum wavelengths in an optimized ion-irradiated In0.53Ga0.47As interdigitated photomixers. Output powers greater than 40 nW at 0.5 THz and 10 nW at 1 THz have been achieved. The optimum excitation conditions regarding optical power and bias voltage are discussed.

Here, we report the gigahertz-rate modulation of a tunable terahertz carrier. Terahertz radiation, tunable from 300 GHz to 1.2 THz, is generated by mixing two telecom lasers with an offset frequency in an ultrafast In0.53Ga0.47As photoconductive device coupled to a broadband antenna. The microwave modulation applied to the telecom lasers is directly transferred to the terahertz carrier. A maximum modulation rate of 20 GHz has been achieved, and the bandwidth is independent of the carrier frequency.

Using high bandwidth resistance measurements, we study the single-shot response of tunnel junctions subjected to spin torque pulses. After the pulse onset, the switching proceeds by a ns-scale incubation delay during which the resistance is quiet, followed by a 400 ps transition terminated by a large ringing that is damped progressively. While the incubation delay fluctuates significantly, the resistance traces are reproducible once this delay is passed. After switching, the time-resolved resistance traces indicate micromagnetic configurations that are rather spatially coherent.

We report the generation of continuous terahertz waves from microwave frequencies of up to 2THz obtained by photomixing two optical waves at 1.55μm wavelengths in ion-irradiated In0.53Ga0.47As interdigitated photomixers. A 200nm thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than 40nW at 0.5THz and 10nW at 1THz have been achieved. Considering the observed saturation of the output power with the increase of bias voltage, the optimum excitation conditions regarding optical power and bias voltage are discussed.

We measured the terahertz (THz) emission from heavy-ion irradiated In/sub 0.35/Ga/sub 0.47/As photoconductive (PC) antennas excited at 1550 nm. The In/sub 0.35/Ga/sub 0.47/As layer irradiated at 10/sup 12/ cm/sup -2/ shows a carrier lifetime shorter than 200 fs, a steady-state mobility of 490 cm/sup 2/V/sup -1/s/sup -1/, and a dark resistivity of 3.1 /spl Omega/cm. The spectrum of the electric field radiated from the heavy-ion irradiated In/sub 0.35/Ga/sub 0.47/As antenna extends beyond 2 THz. Comparative measurements performed on In/sub 0.35/Ga/sub 0.47/As PC antennas irradiated at 10/sup 11/ cm/sup -2/ and 10/sup 12/ cm/sup -2/ demonstrate the impact of the defect center scattering on the photo-excited carrier mobility.

Microwave and low frequency noise performance of buried channel SiGe HFETs fabricated on several strain relieved buffer (SRB) are presented. The impact of such SRB on microwave device noise performance is estimated by a proper noise de-embedding technique. The influence of device gate length on high microwave noise parameters is also discussed. High frequency noise properties measured in the 2.5-18 GHz frequency range are simulated means of the small signal equivalent circuit. Good agreement between measurement and modeling is obtained Furthermore, the low frequency noise properties for devices with different gate dimensions are discussed in order to predict further improvements on noise performance when shrinking the gate length below 100 nm.

A 3 dB bandwidth of 35 GHz at 1.31 /spl mu/m and 1.55 /spl mu/m wavelengths is reported for inter-digited germanium on silicon-on-insulator metal-semiconductor-metal photodetector with finger spacing of 500 nm.

Ion-irradiated InGaAs lattice-matched to InP has been explored in this work and used as the active layer of new photoconductors. Photoconductors with an ion-irradiated InGaAs layer of 0.3 /spl mu/m thickness have been fabricated and the samples were grown by metal organic vapor phase epitaxy lattice-matched to InP substrate. The InGaAs layers were irradiated either by 200 MeV heavy-ion (Au/sup +/) at fluences from 1/spl times/10/sup 10/ to 1/spl times/10/sup 12/ ions/cm/sup 2/ or by 1MeV light ion (H/sup +/) at fluences from 1/spl times/10/sup 13/ to 1/spl times/10/sup 15/ cm/sup 2/. Hall measurements have also been performed on ion irradiated InGaAs layers. We have shown that the ion irradiation of InGaAs layers provides subpicosecond carrier lifetime while preserving good electrical properties of the material. Ion-irradiated InGaAs is very promising for the fabrication of 1.55 /spl mu/m ultrafast sensitive photoconductors.

The high frequency and noise performances of n- and p-SiGe based MODFETs are reviewed. Their excellent HF and low noise behavior makes them well suited for RF mobile communications. We discuss their physical modeling, design optimization and self-heating effects.

We report on ultrafast GaN/AlGaN waveguide quantum cascade detectors with a peak detection wavelength of 1.5 μm. Mesa devices with a size of 7 × 7 and 10 × 10 μm2 have been fabricated with radio-frequency impedance-matched access lines. A strong enhancement of the responsivity is reported by illuminating the waveguide facet, with respect to illumination of the top surface. The room temperature responsivity is estimated to be higher than 9.5 ± 2 and 7.8 ± 2 mA/W, while the −3dB frequency response is extracted to be 42 and 37.4 GHz for 7 × 7 and 10 × 10 μm2 devices, respectively.

We have measured the distribution of switching times in spin-transfer switching induced by fast current pulses in two pillar-shaped systems: (i) spin valves and (ii) MgO-based magnetic tunnel junctions. (i) Spin valves can sustain high currents, such that the application of pulsed currents of amplitude a few times that of the static switching threshold is possible. This makes subnanosecond switching within reach. In that limit, the pulse durations leading to switching follow a multiply stepped distribution at 300K and a regular distribution at 40K. At 300K, this reflects the precessional nature of the switching, which proceeds through a small number of precession cycles. The switching time distribution can be modeled from the thermal variance of the initial magnetization orientations. At 40K, nonuniform magnetization switching occurs. (ii) In MgO-based tunnel junctions, we could follow individual time-resolved switching events with a 13GHz bandwidth. The switching proceeds through a nanosecond-scale rando...

We report the fabrication and the characterization of interdigited metal-germanium on silicon metal photodetectors (metal-semiconductor-metal or MSM) for operation at both optical telecommunication wavelengths: 1.31 and 1.55μm. Femtosecond impulse and frequency experiments have been carried out to characterize those MSM Ge photodetectors. For both wavelengths, the measured 3dB bandwidth under 2V bias are close to 10, 18, 20, and 35GHz for electrode spacings equal to 2000, 1000, 700, and 500nm, respectively.

De-embedded high frequency (HF) noise parameters of Ge p-channel modulation doped field effect transistors (MODFETs) on a Si0.4Ge0.6 virtual substrate have been determined for the first time. The 0.1 × 100 µm devices have a minimum noise figure NFmin = 0.3 dB (0.5 dB) ± 0.2 dB, a noise resistance Rn = 95 Ω (90 Ω) ± 5 Ω, an optimum reflection coefficient Γopt = 0.7∠6° and an associated gain Gass = 14 dB (13 dB) at 1.2 GHz (2.5 GHz), at a bias corresponding to the optimum unity current-gain frequency fT = 55 GHz and the maximum oscillation frequency fMAX = 135 GHz. Noise results are given in the 1.2–12 GHz frequency range and 20–160 mA/mm current range.

Superconducting microbridges of hard superconductors can be realized reproducibly using an ion bombardment technique. The micromachining is obtained directly by focussing onto the superconducting film a reduced ionic image which represents the structure to be machined. We describe and discuss the superconducting properties of niobium Josephson microbridges fabricated using this technique : critical temperature, normal resistance, I-V characteristic, dc magnetic field effect and microwave field effect. Microbridges with an operating temperature of 4.2 K have been realized.

On présente une technique reproductible de fabrication de microponts supraconducteurs applicable aux supraconducteurs « durs » (Ta, V, Nb) par bombardement ionique. L'usinage de microponts est obtenu globalement en formant sur un film mince une image ionique représentant la structure à usiner. Les propriétés de microponts de niobium ainsi réalisés sont ensuite décrites : température critique, résistance normale, caractéristique (I, V), action d'un champ magnétique continu et d'un champ hyperfréquence.

International audience; On-chip light detection is universally regarded as a key functionality that enables myriad of applications, including optical communications, sensing, health monitoring or object recognition, to name a few. Silicon is widely used in the microelectronics industry. However, its electronics bandgap precludes the fabrication of high-performance photodetectors that operate at wavelengths longer that 1.1 µm, a spectral range harnessed by optical communication windows of low fiber attenuation and dispersion. Conversely, Germanium, a group-IV semiconductor as Silicon, with a cutoff wavelength of ~1.8 µm, yields efficient light detection at near-infrared wavelengths. Germanium-based photodetectors are mature building blocks in the library of silicon nanophotonic devices, with a low dark-current, a fast response, a high responsivity and low power consumption with an established fabrication flow. In this work, we report on the design, fabrication and operation of waveguide pin photodetectors that advantageously exploit lateral Silicon/Germanium/Silicon heterojunctions. Devices were fabricated on 200 mm silicon-on-insulator substrates using standard microelectronics production tools and processes. This photodetector architecture takes advantage of the compatibility with contact process steps of silicon modulators, thereby offering substantially reduced fabrication complexity for transmitters and receivers, while providing improved optical characteristics. More specifically, at a low-bias reverse voltage of-1 V, we experimentally achieved dark-currents lower that 10 nA, a device photo-responsivity up to 1.1 A/W, and large 3-dB opto-electrical bandwidths over 50 GHz. In addition, high-speed data rate transmission measurements via eye diagram inspection have been conducted, with pin photodetector operation at the conventional 10 Gbps up to the future 40 Gbps link speeds.

The evolution of the density of states in ion implanted Nb films is investigated from experimental measurements of T c , ρ, dBc 2 /dt. It is shown to interpret fairly well the correlated reduction of T c .

Photodetectors are cornerstone components in integrated optical circuits and are essential for applications underlying modern science and engineering. Structures harnessing conventional crystalline materials are typically at the heart of such devices. In particular, group-IV semiconductors such as silicon and germanium open up more possibilities for high-performing on-chip photodetection thanks to their favorable electrical and optical properties at near-infrared wavelengths and processing compatibility with modern chip manufacturing. However, scaling the performance of silicon-germanium photodetectors to technologically relevant levels and benefiting from improved speed, reduced driving bias, enhanced sensitivity, and lowered power consumption arguably remains key for densely integrated photonic links in mainstream shortwave infrared optical communications. Here we report on a reliable 40 Gbps direct detection of chip-integrated silicon-germanium avalanche p-i-n photo receiver driven with low-bias supplies at 1.55 µm wavelength. The avalanche photodetection scheme calls upon fabrication steps commonly used in complementary metal-oxide-semiconductor foundries, alleviating the need for complex epitaxial wafer structures and/or multiple ion implantation schemes. The photo receiver exhibits an internal multiplication gain of 120, a high gain-bandwidth product up to 210 GHz, and a low effective ionization coefficient of ∼ 0.25 . Robust and stable photodetection at 40 Gbps of on–off keying modulation is achieved at low optical input powers, without any need for receiver electronic stages. Simultaneously, compact avalanche p-i-n photodetectors with submicrometric heterostructures promote error-free operation at transmission bit rates of 32 Gbps and 40 Gbps, with power sensitivities of − 12.8 d B m and − 11.2 d B m , respectively (for 10 − 9 error rate and without error correction coding during use). Such a performance in an on-chip avalanche photodetector is a significant step toward large-scale integrated optoelectronic systems. These achievements are promising for use in data center networks, optical interconnects, or quantum information technologies.