Gian-Luca Bona

SiON high-refractive-index waveguide and planar lightwave circuits

The rapidly growing optical communication market requires photonic components with ever-increasing functionality and complexity that can be fabricated reliably at low cost. Of the various approaches used to fabricate photonic components, those based on planar waveguides have achieved high performance and represent a promising path toward compact integration of optical functions. We present an overview of an approach used to produce an optical single-mode waveguide. Through its strong mode confinement, the approach makes it possible to integrate optical filter functions with higher functionality, as required for high-data-rate communication networks. The waveguide is based on the use of a silicon oxynitride (SiON) core and silicon oxide cladding layers, and can be fabricated using conventional chip fabrication techniques. Using the new approach, conventional passive optical components such as arrayed waveguide gratings for wavelength-division-multiplexed transmission systems can be fabricated in a more compact way than using standard silica-on-silicon waveguide methods. Moreover, the realization of more enhanced, adaptive optical functions such as finite- impulse-response as well as infinite-impulse-response filters is possible. Reconfiguration is achieved through the thermo-optic effect. A reconfigurable gain-flattening filter and an adaptive dispersion compensator are presented as examples.

Lasing in organic circular grating structures

Optically pumped organic polymer lasers are fabricated by spin coating a thin polymer film onto a nanopatterned SiO2 circular-grating surface-emitting distributed Bragg reflector. For certain grating parameters, we observe a peak inside the stop band that leads to lasing with a reduced threshold. An analytical model, based on the transfer-matrix method, has been developed to investigate the origin of this peak. The theoretical results are in good agreement with the experimental findings.

Wavelength division multiplexed add/drop ring technology in corporate backbone networks

The Corporate Optical Backbone Network (COBNET) project is a joint research project within the ACTS program of the European Commission. The COBNET consortium is considering the use of advanced optical networking technologies for the backbones of future corporate networks. In particular, multichannel add/drop ring networks based on wavelength division multiplexing (WDM) as well as on optical space-division multiplexing (SDM) technologies are being pursued. An overview is given of the system concept, the device technology, and the demonstration network that was developed within COBNET. The WDM ring option and specifically the related add/drop devices are focused on in more detail. These devices are fabricated in a newly developed highrefractive- index contrast planar silica-on-silicon technology by using silicon-oxynitride (SiON) as the core waveguide material. Compact add/ drop components based on the resonant coupler concept are realized. The filter characteristic can be tailored and tuned by thermo-optic heaters, which enables the selection of any given wavelength out of a series of wavelengths from the WDM ring using the same device.

Add–drop filter based on apodized surface-corrugated gratings

We report on the fabrication of a grating-based add–drop filter in SiON planar waveguide technology. We achieved apodization of the Bragg grating by concatenating subgratings with various duty cycles. We present the theoretical and experimental dependence of the coupling coefficient on the duty cycle, which leads to a minimum coupling coefficient of 30%. With a breeder genetic algorithm we were able to find optimal apodization profiles within this limited coupling coefficient range. The final device is compatible with a 100-GHz channel spacing and has a bandwidth utilization factor of 36%.

Design and implementation of an optical interconnect demonstrator with board-integrated waveguides and microlens coupling

We discuss some of the trade-offs that we are facing when choosing design parameters for future optical backplane interconnects. We present some of our current choices, along with experimental module- and system-level results.

Optical links for printed circuit boards

We identify applications for optics-enabled printed circuit boards, together with a list of requirements that have to be met for real-world products. We draw conclusions for the technology choices, and present our approaches and experiments.

Efficient coupling into and out of high-Q resonators

The temporal-coupled-mode theory is directly applied to the design of devices that feature a resonator with a high quality factor. For the temporal-coupled-mode theory we calculate the decay rate of the resonator to determine the transmission properties of the device. The analysis using the decay rates requires little computational effort, and therefore the optimum device properties can be determined quickly. Two examples, a wavelength filter and a resonator crossing, are presented to illustrate the use of the analysis.

Integrated Optical Fir-filters for Adaptive Equalization of Fiber Channel Impairments at 40 Gbit/s

In high bitrate optical transmission systems the dynamic changes of the transmission channel easily exceed the system tolerances for an error free operation. To meet the tolerances an adaptive equalizer is necessary. We demonstrate the capabilities of planar lightwave circuit integrated optical FIR-filters for an adaptive compensation of optical fiber channel impairments with electrical spectrum monitoring as feedback in simulations and measurements at 40 Gb/s.

Birefringence control and manipulation in silicon-oxynitride

This paper describes methods to control and manipulate birefringence in SiliconOxyNitride waveguides and devices. Each method is demonstrated by measurements on example devices. The methods and devices that will be covered are: Reduction of heater induced birefringence in a dynamic gain equalizer by heater design or etched trenches. Reduction of polarization mode dispersion in a tunable dispersion compensator by UV trimming of residual waveguide birefringence. Polarization conversion using integrated optical half-wave-plates, fabricated by etching trenches at one side of a waveguide. Polarization splitting using waveguide sections with specified birefringence, obtained by etched trenches at both sides of the waveguide.

Lasing in a 2D photonic bandgap structure

Organic two-dimensional photonic bandgap structures (2D PBG) have been fabricated by spin-coating a thin polymer film onto a nano-patterned SiO2 circular-grating surface-emitting distributed Bragg reflectors (CG-SE-DBR). When optically pumped and for certain grating parameters, these structures exhibit a peak inside the stop band that leads to lasing with a reduced threshold. An analytical model based on the transfer-matrix method has been developed to investigate the origin of this peak. The theoretical results are in excellent agreement with the experimental findings.