Andrzej Gajda

Phase regeneration of DPSK signals in a silicon waveguide with reverse-biased p-i-n junction

Phase regeneration of differential phase-shift keying (DPSK) signals is demonstrated using a silicon waveguide as nonlinear medium for the first time. A p-i-n junction across the waveguide enables decreasing the nonlinear losses introduced by free-carrier absorption (FCA), thus allowing phase-sensitive extinction ratios as high as 20 dB to be reached under continuous-wave (CW) pumping operation. Furthermore the regeneration properties are investigated under dynamic operation for a 10-Gb/s DPSK signal degraded by phase noise, showing receiver sensitivity improvements above 14 dB. Different phase noise frequencies and amplitudes are examined, resulting in an improvement of the performance of the regenerated signal in all the considered cases.

Tunable Bragg reflectors on silicon-on-insulator rib waveguides.

We present the design, fabrication and characterization of Bragg reflectors on silicon-on-insulator rib waveguides. The fabrication is based on a new double lithographic process, combining electron-beam lithography for the grating and photolithography for the waveguides. This process allows the realization of low loss reflectors, which were fully characterized. The influence of the etching depth and of the waveguide geometry on the reflector performance is considered. We demonstrate a reflectivity larger than 80% over a bandwidth of 0.8 nm with an insertion loss of only 0.5 dB. A thermal tunability of the device is also considered, showing that a shift of the reflected wavelength of 77 pm/K is possible.

Highly efficient CW parametric conversion at 1550 nm in SOI waveguides by reverse biased p-i-n junction.

In this paper we present four-wave mixing (FWM) based parametric conversion experiments in p-i-n diode assisted silicon-on-insulator (SOI) nano-rib waveguides using continuous-wave (CW) light around 1550 nm wavelength. Using a reverse biased p-i-n waveguide diode we observe an increase of the wavelength conversion efficiency of more than 4.5 dB compared to low loss nano-rib waveguides without p-i-n junction, achieving a peak efficiency of -1 dB. Conversion efficiency improves also by more than 7 dB compared to previously reported experiments deploying 1.5 µm SOI waveguides with p-i-n structure. To the best of our knowledge, the observed peak conversion efficiency of -1dB is the highest CW efficiency in SOI reported so far.

Deep-UV Technology for the Fabrication of Bragg Gratings on SOI Rib Waveguides

In this letter, we present a wafer level technology based on deep-ultraviolet lithography to fabricate Bragg gratings on silicon-on-insulator rib waveguides. The principle of the used double-patterning technique is presented, as well the influence of the process variation on the device performances. The fabricated Bragg gratings were characterized and compared to analogue structures patterned with electron-beam lithography.

Design rules for p-i-n diode carriers sweeping in nano-rib waveguides on SOI

In this paper we present a detailed analysis of the carrier lifetime for a p-i-n junction on silicon nano-rib waveguides. Several factors determining efficiency of carriers removal from the waveguiding region will be discussed. We compare different structure geometries and spacings between p and n doped regions to show the way to optimize electrons and holes sweeping for CW nonlinear optical devices.

Analysis of Optical and Electrical Tradeoffs of Traveling-Wave Depletion-Type Si Mach–Zehnder Modulators for High-Speed Operation

Fundamental limiting factors regarding high-speed performance of broadband depletion-type silicon (Si) Mach-Zehnder modulators (MZMs) are studied. Optical and electrical measurements of MZMs with traveling wave electrodes (TWE) reveal significant dependences between optoelectrical bandwidth and design parameters. An equivalent circuit model is implemented to fit measured modulator characteristics. Using the model, the limits of TWE depletion-type Si MZM systems are studied under the requirement of specific driving voltage. By comparing phase shifters with different doping concentration or junction position, we explore the fundamental optical and electrical tradeoffs which are limiting high-speed operation.

Numerical survey on Bragg reflectors in silicon-on-insulator waveguides

We present a numerical survey of wavelength-selective Bragg reflectors in silicon-on-insulator waveguides. By an appropriate choice of grating period, duty cycle, etch depth and grating length, usable gratings can be designed.

1.024 Tb/s wavelength conversion in a silicon waveguide with reverse-biased p-i-n junction

We experimentally show an all-optical wavelength conversion of 8 × 32-GBd single-polarization 16QAM signals using a silicon nano-rib waveguide. The application of reverse biasing of the p-i-n junction of the waveguide allows a conversion efficiency of -8.5 dB with a measured 3-dB optical bandwidth of about 40 nm. Using digital coherent reception, it is shown that the receiver optical signal-to-noise ratio penalty, at a bit-error ratio of 1 × 10-3, of the wavelength-converted signals over all eight channels was less than 0.6 dB with reference to their respective back-to-back signal channels.

Chirped Gratings on Tapered SOI Rib Waveguides For Dispersion Compensation

The fabrication and characterization of chirped Bragg gratings on tapered SOI rib waveguides is presented. A dispersion of 250 ps/nm over a bandwidth of 1 nm is demonstrated with 1 cm long gratings.

Performance Evaluation of a Silicon Waveguide for Phase Regeneration of a QPSK Signal

In this paper a silicon-on-insulator nanorib waveguide with reverse-biased p-i-n-junction is used to experimentally demonstrate phase-sensitive amplification based on four-wave mixing for the realization of an in-line four-level phase-regenerator. Phase regeneration of a 14-GBd quadrature phase-shift keying signal is demonstrated for the first time employing a silicon waveguide as phase sensitive amplifier. The regenerator is placed in a 1040-km dispersion-managed link and it is shown that phase noise accumulation in the transmission link can be reduced by the use of the in-line silicon-based phase-regeneration.