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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.

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.

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; Silicon is the mainstream material in the electronic industry and it is rapidly expanding its dominance into the field of photonics. Indeed, silicon photonics has been the subject of intense research activities to pave the way for next generation of energy-efficient high-speed computing, information processing and communications systems. The trend is to use optics in intimate proximity to the electronic circuit, which implies a high level of optoelectronic integration. Over the last decade, the field of silicon photonics has advanced at a remarkable pace. Recent advances in integrated germanium receiver will be presented including the developments of a new Ge-based detector integration and avalanche Ge structures.

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.

A system dynamics model was created to simulate fuel cycle interactions between two separate nuclear entities, and this model was employed to investigate fuel leasing arrangements. The model was also adapted to evaluate proliferation and economic implications of an international leasing regime. For a nuclear growth scenario, an open fuel cycle results in extensive spent-fuel accumulation. For a closed fuel cycle, the leasing fuel cycle shows potential to reduce proliferation concern, especially if coupled with improved security and safeguard technology.

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 conjunction with a remote-controlled smart-sensors project (Villegas M, Bildstein P and Nicole P 1997 Translateur de frequence micro-ondes pour capteur intelligent autonome Proc. 10eme Journees Nationales Microondes (St Malo, 21-23 May 1997) pp 270-1), this study concerns the validation of a radio-frequency microelectromechanical system combining micromechanical capacitive functions and microwave data communication functions. In this project, we have focused on the back-modulation function used for data re-emission. We decided to develop this function with a microelectromechanical mixer made as a passive microwave frequency shifter using an integrated silicon micromechanical capacitive structure. The principles, together with electromechanical considerations, the technology of the silicon implantation, and some first experimental results are described in this paper. The main interest lies in the characterization of the device: both electrical and mechanical properties are tested in parallel to assist us in improving the system and defining a new micromechanical frequency-translator prototype.

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 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).

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.

High frequency small-signal measurements provide information for time-domain device characterisation. Parasitic phenomena associated with probe and interconnect-metal lines surrounding the device, have an impact on measurements during wafer test. The aim of this work was to subtract the small-signal high-frequency access path effects, using an equivalent model in the 45 MHz-10 GHz range. We propose to apply to bipolar silicon technology a de-embedding GaAs-MESFET method for which the effect of access path are considerably lowered and therefore can be neglected. This correction can then be taken into account for each frequency value during a time domain modelisation.

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.

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.

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 direct detection of emitted radiation from variable thickness niobium bridges shows the existence of self-coherence giving rise to a Josephson type current in microbridges operated in the single row vortex flow regime. Their high frequency properties such as emitted radiation level, ac current related to mixing experiments and induced steps are discussed.