[Show abstract][Hide abstract] ABSTRACT: This study concerns the modelling, in a dynamic regime of nonlinear operation, of a silicon on insulator (SOI) monomode waveguide with a grating coupler used as a photodiode. This model is made in the dynamic regime and is based on variations of the refractive index caused by both the photo generation of an electron hole pair and by thermal effects that are due to the recombination of carriers and the Joule effect. This model allows one to determine the operating range of the photodetector by adjusting key parameters, such as: the incident power density, the angular detuning relative to the resonance and the bias voltage.
[Show abstract][Hide abstract] ABSTRACT: The paper reports the design, fabrication and characterization of silicon-on-insulator (SOI) microring resonators using shallow etched rib waveguides. The variation of the Q-factor of microring resonators as a function of the ring diameter and coupling gap between the input waveguide and the ring is studied. Such structures are fabricated using e-beam lithography and reactive ion etching steps. Propagation loss of shallow etching rib waveguide has been evaluated to 0.8 dB/cm for wavelengths around 1550 nm. With a ring diameter of 100 mum and a coupling gap of 450 nm, the measured Q -factor is 35300. These results are matched by 3-D numerical optical modeling.
Full-text · Article · May 2009 · Journal of Lightwave Technology
[Show abstract][Hide abstract] ABSTRACT: We report the experimental demonstration of a germanium metal-semiconductor-metal (MSM) photodetector integrated in a SOI rib waveguide. Femtosecond pulse and frequency experiments have been used to characterize those MSM Ge photodetectors. The measured bandwidth under 6V bias is about 25 GHz at 1.55 microm wavelength with a responsivity as high as 1 A/W. The used technological processes are compatible with complementary-metal-oxide-semiconductor (CMOS) technology.
[Show abstract][Hide abstract] ABSTRACT: This paper reports on fabrication and characterization of two kinds of photodetectors: interdigited metal-germanium on silicon-metal photodetectors (Metal-Semiconductor-Metal or MSM) and pin germanium photodiodes for operation at optical telecommunication wavelengths. For both 1.31 micron and 1.55 micron wavelengths, the measured -3dB bandwidth of interdigited MSM photodetectors is 35 GHz under 2V bias for electrode spacing equal to 0.5 micron. For pin diodes at 1.55 micron wavelength, the measured -3dB bandwidth under -3V bias ranges from 9 to 29 GHz for mesa diameters from 20 to 7 microns, respectively.
No preview · Article · Mar 2007 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: Electrorefractive effect is experimentally demonstrated in an all-silicon optical structure. A highly doped Si P+ layer is embedded in the intrinsic region of a PIN diode integrated in a SOI waveguide. Holes are confined at equilibrium around the P+ layer. By applying a reverse bias to the diode, electrical field sweeps the carriers out of the active region. Free carrier concentration variations are responsible for local refractive index variations leading to an effective index variation of the waveguide optical mode and to an optical absorption variation. As a figure of merit, the product VπLπ, determined from the measured effective index variation, is equal to 3.1 V cm. Furthermore, the device performances have theoretically been investigated. Estimations show that VπLπ as small as 1 V cm are feasible using optimized structures. Response times lower than 2 ps are predicted, which gives the possibility to achieve very high-speed modulation. Furthermore, a temperature increases from 300 to 400 K does not change the index variation amplitude, and despite the carrier mobility reduction, response times are still lower than 2 ps.
No preview · Article · Dec 2006 · Journal of Luminescence
[Show abstract][Hide abstract] ABSTRACT: An experimental characterization of the grating couplers for sub-micrometer silicon-on-insulator (SOI) waveguides is presented. The grating couplers have been designed, realized, and characterized for the +1 diffraction order at an operating wavelength of 1.31 mum for TE polarization. At the resonant angle, a coupling efficiency higher than 55% has been measured. The angular coupling range and the wavelength tolerance have been evaluated to 3deg and 20 nm, respectively. The grating coupler is followed by a taper, and about 50% of the input power at 1.31 mum is coupled into sub-micrometer rib and strip SOI waveguides. The ration between light power decoupled toward the cladding and light power decoupled toward the substrate is about three
Full-text · Article · Nov 2006 · Journal of Lightwave Technology
[Show abstract][Hide abstract] ABSTRACT: Experimental results for refractive index variation induced by depletion in a silicon structure integrated in a PIN diode are reported. Thermal effect has been dissociated from the electrical contribution due to carrier density variation induced by a reverse bias voltage. A figure of merit V(pi)L(pi) of 3.1 V.cm has been obtained at 1.55mum. Numerical simulations show a good agreement between experimental and theoretical index variations.
[Show abstract][Hide abstract] ABSTRACT: Different technologies for the fabrication of Germanium photodetectors were developed. Germanium was grown by RPCVD in a silicon cavity in order to provide a direct coupling with a rib silicon waveguide. With direct deposition of Ti/TiN/AlCu on Ge, Metal-Schotkky-Metal (MSM) diodes were formed. PIN photodiode were fabricated either with in-situ doping during RP- CVD epitaxy of Ge, either by ion implantation. For vertical PIN photodiode, the germanium was successfully etched either in mesa either anisotropically with Cl2 gazes. Small footprint Ge photodiodes can lead to high speed operation on CMOS
No preview · Article · Oct 2006 · ECS Transactions
[Show abstract][Hide abstract] ABSTRACT: A structure based on the free-carrier-induced electrorefractive effect in Si/SiGe modulation-doped quantum wells, placed in the intrinsic region of a PIN diode has been proposed. Effective index variation produced by carrier depletion under a reverse bias leads to a phase modulation of a guided wave. The measured variation of the effective index is typically 2.10-4 for a 0V to 6V variation of the reverse bias voltage. This study is focused on the integration of modulation doped SiGe/Si quantum-well optical modulator in SOI submicron rib waveguides with optical losses lower than 0.4dB/cm. The influence of the geometrical parameters, of layer doping and of the metallic contacts has been determined through numerical simulations and optimized modulation structures are defined. The obtained factor of merit LchiVchi is then of 1.26 V.cm which can be favorably compared with the best published results obtained with other optimized modulators.
Full-text · Article · Jan 2006 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: SOI microwaveguides and associated devices (splitters, turns,...) are used for light distribution. Rib SOI geometries obtained by shallow etching of the silicon film offer definite advantages for the integration of active devices while fulfilling efficiency and compactness. Propagation losses of such waveguides are one order of magnitude smaller than for single mode strip waveguides. Rib-based compact and low loss optical signal distribution from one input to up to 1024 output points has been demonstrated. Light injection in submicron SOI waveguides is discussed. The indirect bandgap of silicon is not in favor of light emission and modulation. Realization of silicon sources and efficient high speed silicon-based modulators is a real challenge. For light detection, germanium can be grown on silicon and Ge photodetectors with -3dB bandwidths up to 30 GHz have been demonstrated.
No preview · Article · Jan 2006 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: An overview of integrated silicon-based optical modulators and germanium on silicon photodetectors for optical interconnects in CMOS circuits and high frequency integrated transceivers are presented.
[Show abstract][Hide abstract] ABSTRACT: Modulation-doped SiGe-Si multiple quantum well and all-silicon modulators embedded in reverse biased PIN junctions and integrated in SOI waveguides are described. Experimental evidence for electrorefractive effect is presented, and frequency operation is investigated
[Show abstract][Hide abstract] ABSTRACT: 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 1.55 mum. Femtosecond impulse and frequency experiments have been carried out to characterize those MSM Ge photodetectors. For both wavelengths, the measured 3 dB bandwidth under 2 V bias are close to 10, 18, 20, and 35 GHz for electrode spacings equal to 2000, 1000, 700, and 500 nm, respectively.
No preview · Article · Dec 2005 · Applied Physics Letters
[Show abstract][Hide abstract] ABSTRACT: The low excess loss experimental demonstration of ten successive light divisions is presented. This distribution is realized by using shallow-etched rib silicon-on-insulator waveguides with compact beam splitters and 90° turns based on total internal reflection corner mirrors. The measured excess optical loss is only 0.7 dB per division. This result is an important step in a 1 to 1024 optical distribution demonstration.
Full-text · Article · Dec 2005 · Applied Physics Letters
[Show abstract][Hide abstract] ABSTRACT: A modulation-doped SiGe/Si multiple quantum well modulator (MD-MQW) embedded in a reverse biased PIN junction and integrated in a SOI waveguide is described. Experimental evidence of electrorefractive effect is reported and frequency operation is investigated.
[Show abstract][Hide abstract] ABSTRACT: A 3 dB bandwidth of 35 GHz at 1.31 μm and 1.55 μm wavelengths is reported for inter-digited germanium on silicon-on-insulator metal-semiconductor-metal photodetector with finger spacing of 500 nm.
[Show abstract][Hide abstract] ABSTRACT: Experimental demonstration of successive optical divisions from one input to 1024 output points is presented using slightly etched submicron rib SOI waveguides. Excess loss per division of 0.7 dB has been measured.
[Show abstract][Hide abstract] ABSTRACT: A SiGe/Si optical modulator based on the free-carrier plasma dispersion effect is presented. A SiGe/Si multilayer structure is included in a p-i-n diode and integrated in a submicrometric silicon-on-insulator (SOI) rib waveguide. A P+ Si layer inserted in the Si barriers provide holes that are confined in the SiGe wells at the equilibrium and can be depleted by applying a reverse bias. This structure offers high-speed phase modulation properties. Numerical simulations are used to design the optical modulator. An optimal structure is defined comprising three 10-nm-thick SiGe layers and four 5-nm-thick P+ Si layers. The predicted refractive index variation is 1.7 x 10(-4) under a -6-V bias voltage, and the associated absorption variation is 3 dB/cm. Intensity modulation is obtained by embedding the active region inside a microinterferometric structure. Using resonant cavities a few hundred micrometers long, a modulation depth larger than 60% is achieved with insertion losses of 12 dB, whereas Mach-Zehnder interferometers of a few millimeters length lead to modulation depths larger than 95% with insertion losses lower than 8 dB. (c) 2005 Society of Photo-Optical Instrumentation Engineers.
No preview · Article · Aug 2005 · Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: The main characteristics of germanium photodetectors integrated in silicon-on-insulator optical waveguides for intrachip optical interconnects are presented. The epitaxial Ge layers are grown on Si(001) by reduced-pressure chemical vapor deposition. The optical absorption of Ge layers is recorded from 1.2 to 1.7 µm and linked to the layer strain. The responsivity of an interdigitated metal-semiconductor-metal Ge photodetector has been measured. Light coupling from a slightly etched submicron rib silicon-on-insulator waveguide to a Ge photodetector is studied for two configurations: butt coupling and vertical coupling.