2019 Passive integrated photonic structures and design methodologies

Machine-assisted design and stochastic analysis in integrated photonics
(Invited paper)

Daniele Melati1, Yuri Grinberg2, Mohsen Kamandar Dezfouli1, Abi Waqas3, Paolo Manfredi4, Pavel Cheben1, Jens H. Schmid1, Siegfried Janz1, Alejandro Sánchez-Postigo5, and Dan-Xia Xu1
1Advanced Electronics and Photonics Research Center, National Research Council Canada, 1200 Montreal Rd., Ottawa, ON K1A 0R6, Canada
2Digital Technologies Research Center, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
3Departement of Telecommunication Engineering, Mehran University of Engineering and Technology, Jamshoro, 76062 Sindh, Pakistan
4Department of Electronics and Telecommunications, Politecnico di Torino, 10129 Torino, Italy
5Universidad de Málaga, Departamento de Ingeniería de Comunicaciones, ETSI Telecomunicación, Campus de Teatinos s/n, 29071 Málaga, Spain
e-mail: daniele.melati@nrc-cnrc.gc.ca

ABSTRACT
Integrated photonic devices are steadily making their way into many application fields including modern optical communication networks and advanced sensors. On the other hand, the design of photonic devices and circuits mostly remains a time-consuming process largely based on the designer experience. This limits the size and complexity of the parameter space that can be handled. Moreover, addressing the effect of manufacturing variability remains a fundamental challenge since small fabrication errors can have a significant impact on light propagation, especially in high-index-contrast platforms such as silicon-on-insulator. The analysis of this variability with conventional approaches (e.g. Monte Carlo) can become prohibitive due to the large number of required simulations. Recent advances in machine-assisted design methods are opening the possibility to vastly expand the number of design parameters, exploring novel functionalities and non-intuitive geometries. In this invited talk we discuss the use of machine learning methods for the design of integrated photonic devices. We show the existence of a large number of possible designs that are all equivalent with respect to a given primary design objective but with distinct properties in other performance criteria. We use pattern recognition to reveal their relationship and to reduce the dimensionality of the large design space by properly defining new design variables. Likewise, we show how efficient stochastic techniques allow a quick assessment of the performance robustness and the expected fabrication yield for each tentative device. We focus in particular on stochastic spectral methods that have been regarded as a promising alternative to the classical Monte Carlo method, achieving a considerable reduction of the simulation time. Together, the reduction in the design space dimensionality and efficient stochastic techniques allow for the integration of the fabrication tolerance considerations into the design process.
Keywords: photonic devices, silicon photonics, machine learning, stochastic processes, pattern recognition, uncertainty analysis.

Machine-assisted design and stochastic analysis in integrated photonics


Ultracompact 40-Channels Arrayed Waveguide Grating on Silicon Nitride Platform at 850nm (Student Paper)
Zunyue Zhang1, Yi Wang1, Hon Ki Tsang1
1 Dept. of Electronic Engineering, The Chinese University of Hong Kong, Shatin NT, Hong Kong SAR, China
e-mail: hktsang@ee.cuhk.edu.hk

ABSTRACT
We propose and demonstrate a 40-channels arrayed waveguide grating (AWG) on silicon nitride platform at 850nm. The total size of the AWG is 910×680 𝜇𝑚2. The transmission spectrum is measured. The AWG has an operating bandwidth of 60nm and has a measured insertion loss of 0.6dB. The channel crosstalk is 20dB.
Keywords: Arrayed waveguide grating, ultracompact, very near infrared, silicon nitride platform.

Ultracompact 40-Channels Arrayed Waveguide Grating on Silicon Nitride Platform at 850nm


Interleaved Silicon Nitride AWG Spectrometers
B. Imran Akca1, Christopher R. Doerr 2
1 VU University Amsterdam, Department of Physics and Astronomy, De Boelelaan 1081, 1081 HV Amsterdam,
The Netherlands
2 Acacia Communications, 1301 Route 36, Hazlet, NJ, USA 07730
e-mail: b.i.avci@vu.nl

ABSTRACT
Interleaved arrayed waveguide gratings (AWGs) have a great potential in providing large channel counts and narrower channel spacings for many applications, including optical communication, spectroscopy, and imaging.
Here, a 75-channel silicon nitride based interleaved AWG was experimentally demonstrated. The design is comprised of a 3-channel primary AWG with 1 nm of resolution and three 25-channel secondary AWGs each with 3 nm of resolution. The final device has a spectral resolution of 1 nm over 75 nm bandwidth centered at 1550 nm.
Its performance is compared with a conventional AWG spectrometer with 75 nm of bandwidth and 1 nm of resolution. The interleaved AWG demultiplexer showed lower crosstalk and better uniformity in addition to being two times smaller than the conventional design.
Keywords: AWG spectrometers, compact, interleaved, better uniformity

Interleaved Silicon Nitride AWG Spectrometers


Efficient Mode Multiplexer for Few-Mode Fibres Using Integrated Silicon-on-Insulator Grating Coupler Student Paper
Yeyu Tong, Wen Zhou, Xinru Wu and Hon Ki Tsang*
Centre for Advanced Research in Photonics, Department of Electronic Engineering
The Chinese University of Hong Kong, Shatin, Hong Kong
e-mail: hktsang@ee.cuhk.edu.hk

ABSTRACT
A novel high-efficiency mode multiplexer is proposed to launch four channels including two polarizations of the LP01 mode and LP11 mode into step-index few-mode fibres (FMFs). Simulations predicted the coupling efficiency to be −4.3 dB for LP01 mode and −5.0 dB for the LP11 mode. Back reflections less than −11 dB is obtained within the C band. The design was fabricated in a multi-project wafer (MPW) run for silicon photonics.
Experimental coupling efficiency of −4.9 dB and −6.1 dB was obtained for LP01 and LP11, respectively. The proposed mode multiplexer is suitable for future applications with FMFs in space-division-multiplexing networks.
Keywords: Integrated optics, diffraction gratings, few-mode fibres, space-division multiplexing.

Efficient Mode Multiplexer for Few-Mode Fibres Using Integrated Silicon-on-Insulator Grating Coupler


High-Performance Silicon Photonics Optical Filters with High-Order Distributed Feedback Resonators
Claudio Porzi1, Graham J. Sharp2, Marc Sorel2, Antonella Bogoni1
1 TeCIP Institute, Scuola Superiore Sant’Anna, 56124 Pisa – Italy
2 School of Engineering, University of Glasgow, Glasgow, G12 8LP – United Kingdom
e-mail: c.porzi@santannapisa.it

ABSTRACT
Silicon photonics tunable passband optical filters with flat-top feature, large out-of-band rejection in excess of 40 dB, ultra-fast roll-off up to 1,000 dB/nm, and unprecedented passband-to-stopband ratio for high-index-contrast technology have been fabricated and characterized. The integrated filters are based on high-order distributedfeedback resonators implemented with cascaded phase-shifted Bragg gratings in silicon strip waveguides. Local micro-heaters are used for finely controlling the phases of the individual cavities of the coupled resonators and for
providing additional tuning mechanism. Two different coupled-cavity resonators with passband widths of 25 GHz and 2 GHz, realized with 6th- and 5th- order filter designs, respectively, are exemplarily reported.
Keywords: Silicon photonics, integrated optical filters, waveguide Bragg gratings, Fabry-Perot filters.

High-Performance Silicon Photonics Optical Filters with High-Order Distributed Feedback Resonators