Ivano Giuntoni

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.

Continuously tunable delay line based on SOI tapered Bragg gratings.

The realization of an integrated delay line using tapered Bragg gratings in a drop-filter configuration is presented. The device is fabricated on silicon-on-insulator (SOI) rib waveguides using a Deep-UV 248 nm lithography. The continuous delay tunability is achieved using the thermo-optical effect, showing experimentally that a tuning range of 450 ps can be obtained with a tuning coefficient of -51 ps/°C. Furthermore the system performance is considered, showing that an operation at a bit rate of 25 Gbit/s can be achieved, and could be extended to 80 Gbit/s with the addition of a proper dispersion compensation.

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.

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.

Integrated Dispersion Compensator Based on Apodized SOI Bragg Gratings

In this letter, we present the design and realization of an integrated drop filter with optimized tapered Bragg gratings for the compensation of the optical chromatic dispersion. An apodization profile for the gratings has been determined for an optimal reduction of the group delay ripple and the enhancement of the system performance. The apodization has been carried out varying the width of the grating trenches at the two ends with a sine profile and the principle has been experimentally demonstrated. The device permits a dispersion compensation of 480 ps/nm and an error-free detection of a DQPSK signal up to 30 Gbaud.

Light coupling between vertical III-As nanowires and planar Si photonic waveguides for the monolithic integration of active optoelectronic devices on a Si platform.

We present a new concept for the optical interfacing between vertical III-As nanowires and planar Si waveguides. The nanowires are arranged in a two-dimensional array which forms a grating structure on top of the waveguide. This grating enables light coupling in both directions between the components made from the two different material classes. Numerical simulations show that this concept permits a light extraction efficiency from the waveguide larger than 45% and a light insertion efficiency larger than 35%. This new approach would allow the monolithic integration of nanowire-based active optoelectronics devices, like photodetectors and light sources, on the Si photonics platform.

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.

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

In this Paper we present a deep ultra-violet lithography (248nm) based double patterning technique for the fabrication of Bragg gratings on SOI 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 influence of the overlay error was identified as a possibly limiting factor for the application of this technique. Usable structures were realized, in spite of small overlay error and non-rectangular grating profile. The optical characterization showed that the presented technique is capable to provide high performance Si waveguides and Bragg gratings.