Ana Maria Gutierrez

Ring-Assisted Mach–Zehnder Interferometer Silicon Modulator for Enhanced Performance

A high-speed ring-assisted Mach-Zehnder interferometer (RAMZI) silicon modulator is reported and experimentally demonstrated. The RAMZI optical structure relaxes the optimum coupling condition of the ring without degrading the modulator performance, which therefore improves the modulator robustness against fabrication deviations and could eventually lead to an enhanced modulation bandwidth. Hence, our RAMZI silicon modulator, based on carrier depletion in a pipin active structure, exhibits a 3 dB electro-optical bandwidth of 19 GHz, enabling up to 20 Gbit/s data transmission over a RF/optical interaction length of only ~200 μm.

CMOS Compatible Silicon-on-Insulator Polarization Rotator Based on Symmetry Breaking of the Waveguide Cross Section

A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25- μm-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 & dB with insertion losses ranging from -1 to -2.5 & dB over a wavelength range of 30 nm is demonstrated.

Slow-Light-Enhanced Silicon Optical Modulators Under Low-Drive-Voltage Operation

The integration of nanophotonics components with advanced complementary metal-oxide-semiconductor (CMOS) electronics requires drive voltages as low as 1 V for enabling next-generation CMOS electrophotonics transceivers. Slow-light propagation has been recently demonstrated as an effective mechanism to enhance the modulation efficiency in free-carrier-based electrooptical silicon modulators. Here, we exploit the use of slow light to reduce the driving voltage of carrier-depletion-based Mach-Zehnder modulators. The slow-light phase shifter consists of a p-n junction positioned in the middle of a corrugated waveguide. A modulation efficiency as high as VπLπ ~ 0.6 V·cm is achieved, thus allowing data transmission rates up to 10 Gb/s with a 1.5-Vpp drive voltage and an insertion loss of ~12 dB. The influence of the drive voltage on the modulation speed as well as the variation of the insertion losses with a group index is also analyzed and discussed.

Influence of BaTiO3 ferroelectric orientation for electro-optic modulation on silicon.

The influence of BaTiO(3) ferroelectric domain orientations for high efficiency electro-optic modulation has been thoroughly analyzed. The Mach-Zehnder modulator structure is based on a CMOS compatible silicon/BaTiO(3)/silicon slot waveguide that supports both TE and TM polarizations whereas the Pockels effect is exploited by the application of a horizontal electric field with lateral electrodes placed on top of the BaTiO(3) layer. The influence of the waveguide parameters has been optimized for each configuration and the lowest V(π) voltage combined with low losses has been determined. A V(π)L as low as 0.27 V·cm has been obtained for a-axis oriented BaTiO(3) and TE polarization by rotating the waveguide structure to an optimum angle.

High linear ring-assisted MZI electro-optic silicon modulators suitable for radio-over-fiber applications

The linearity properties of ring-assisted MZI (RAMZI) electro-optic silicon modulators are investigated. When quadrature biased the RAMZI silicon modulator with Vbias,DC=1 V and applied a 1 GHz RF tone frequency, it is obtained a Spurious-Free Dynamic Range (SFDR) of 71.65 dB·Hz2/3, and an input intercept point IIP3=67 dBm. Measurements on QPSK and 16-QAM electrical modulated signals on a 1 GHz carrier also show an experimental error vector magnitude (EVM) lower than 10% and 14% for 20 Msymbol/s and 50 Msymbol/s modulation rates respectively, which corroborates their potential for RoF applications.

Increased sensitivity through maximizing the extinction ratio of SOI delay-interferometer receiver for 10G DPSK

We present an optimized design for a 10G- differential-phase-shift-keyed (DPSK) receiver based on a silicon-on-insulator (SOI) unbalanced tunable Mach-Zehnder interferometer (MZI) switch in sequence with a Mach-Zehnder delay interferometer (MZDI). The proposed design eliminates the limitation in sensitivity of the device produced by the waveguide propagation losses in the delay line. A 2.3 dB increase in receiver sensitivity at a bit-error-rate (BER) of 10(-9) is experimentally measured over a standard implementation. The enhanced sensitivity is achieved with zero power consumption by tuning the operating wavelength or with less than 5 mW for a fixed wavelength using microheaters. Also the foot-print of the device is minimized to 0.11 mm(2) by the use of compact spirals.

High performace silicon 2x2 optical switch based on a thermo-optically tunable multimode interference coupler and efficient electrodes.

Optical switches based on tunable multimode interference (MMI) couplers can simultaneously reduce the footprint and increase the tolerance against fabrication deviations. Here, a compact 2x2 silicon switch based on a thermo-optically tunable MMI structure with a footprint of only 0.005 mm(2) is proposed and demonstrated. The MMI structure has been optimized using a silica trench acting as a thermal isolator without introducing any substantial loss penalty or crosstalk degradation. Furthermore, the electrodes performance have significantly been improved via engineering the heater geometry and using two metallization steps. Thereby, a drastic power consumption reduction of around 90% has been demonstrated yielding to values as low as 24.9 mW. Furthermore, very fast switching times of only 1.19 µs have also been achieved.

Luminescence properties of Ce3+ and Tb3+ co-doped SiOxNy thin films: Prospects for color tunability in silicon-based hosts

In this work, the role of the nitrogen content, the annealing temperature, and the sample morphology on the luminescence properties of Ce3+ and Tb3+ co-doped SiOxNy thin films has been investigated. An increasing nitrogen atomic percentage has been incorporated in the host matrix by gradually replacing oxygen with nitrogen during fabrication while maintaining the Si content unaltered, obtaining a sequential variation in the film composition from nearly stoichiometric SiO2 to SiOxNy. The study of rare earth doped single layers has allowed us to identify the parameters that yield an optimum optical performance from Ce3+ and Tb3+ ions. Ce3+ ions proved to be highly sensitive to the annealing temperature and the nitrogen content, showing strong PL emission for relatively low nitrogen contents (from 0 to 20%) and moderate annealing temperatures (800–1000 °C) or under high temperature annealing (1180 °C). Tb3+ ions, on the other hand, displayed a mild dependence on those film parameters. Rare earth co-doping ha...

Analytical Model for Calculating the Nonlinear Distortion in Silicon-Based Electro-Optic Mach–Zehnder Modulators

In this study, an analytical model for calculating the nonlinear harmonic/intermodulation distortion for RF signals in silicon-based electro-optic modulators is investigated by considering the nonlinearity on the effective index change curve with the operation point and the device structure simultaneously. Distortion expressions are obtained and theoretical results are presented showing that optimal modulator parameters can be found to linearize it. Moreover, the harmonic distortion of a 1 mm silicon-based asymmetric MZI is RF characterized and used to corroborate the theoretical results. Based on the present model, the nonlinear distortion in terms of bias voltage or operating wavelength is calculated and validated by comparing with the experimental data, showing a good agreement between measurements and theory. Analog photonic link quality parameter like carrier-to-distortion is one of the parameters that can be found with that model. Finally, the modulation depth is measured to assure that no over-modulation is produced.

Electro-Optical Modulation Based on Pockels Effect in BaTiO 3 With a Multi-Domain Structure

The influence of an in-plane multi-domain structure in BaTiO₃ films grown on SrTiO₃/Si buffers for highly efficient electro-optic modulation has been analyzed. The modulation performance can be significantly enhanced by rotating a certain angle, the optical waveguide, with respect to the BaTiO₃ crystallographic axes. A robust electro-optical performance against variations in the domain structure as well as the lowest V_π voltage can be achieved by using the rotation angles between 35° and 55°. Our calculations show that V_π voltages below 1.7 V for a modulation length of 2 mm can be obtained by means of a CMOS compatible hybrid silicon/BaTiO₃ waveguide structure.