2018 Session – RF & THz photonics

Analysis of the Operation of an Integrated Unidirectional Phase Modulator

T. T. M. van Schaijk, D. Lenstra, K. A. Williams and E. A. J. M. Bente Eindhoven University of Technology, Den Dolech 2, 5612AZ Eindhoven, The Netherlands Tel: +31402473728, Email: p.v.schaijk@tue.nl

In this paper we present a model and experimental verification of a unidirectional phase modulator realised in InP. We show that non-linearity in the phase-voltage dependance of the electro-refractive modulators has to be takenintoaccount.Itlimitstheisolationthatcanbeobtainedusingthedeviceanditintroducesmodulationonthe forward propagating wave. Finally we derive minimum requirements for the electrical driving signals that allow operation of the unidirectional phase modulator close to this optimal performance such that its performance is limited by non-linearity only. In this way, we find for our device a maximum tolerable imbalance in modulation amplitude of 2%, a phase error of 0.18◦ and an error in the summed modulation amplitude of the two driving signals of 2.8%. These values are feasible with current electronics.

Keywords: integrated isolator, optical isolator, unidirectional phase modulator, photonic integration

Fr.1.B.1 66-Regular Paper, Analysis of the Operation of an Integrated Unidirectional Phase Modulator

Low loss transmission lines in COBRA generic photonic integration platform

Marija Trajkovic, Fabrice Blache, Helene Debregeas, Xaveer Leijtens, Kevin Williams
Eindhoven University of Technology, Institute for Photonic Integration (previously COBRA research center)
5600 MB Eindhoven, the Netherlands
Tel: +33182720455, e-mail: m.trajkovic@tue.nl
III-V Lab, joint laboratory between Nokia Bell Labs, Thales Research and Technology, and CEA Leti
Campus de Polytechnique, 1 avenue Augustin Fresnel, 91767 Palaiseau-Cedex, France

Delivering unperturbed radio-frequency signal to the components on densely packed photonic integrated chip is an important aspect for circuits needed to operate at high bit rates. Efficient, low-loss routing of a high-speed electrical signal from the driver to the photonic chip can be a challenge. Therefore, the design of transmission lines for intra-chip connection, with low microwave loss and matched characteristic impedance to the rest of the circuit is important. We have characterized transmission lines on two different substrates, n-InP doped and semiinsulating. Low-loss transmission lines in the COBRA generic integration platform are fabricated and measured up to 65 GHz.

Keywords: transmission line, radio-frequency, n-doped substrate, semi-insulating substrate, microwave loss, characteristic impedance

Fr.1.B.2 67-Regular Paper, Low loss transmission lines in COBRA generic photonic integration platform

The heterogeneous future of integrated Millimeter- and Terahertz-wave photonics

Guillermo Carpintero, Robinson C. Guzmán, Mu Chieh Lo, Muhsin Ali, Alberto Zarzuelo, Luis Enrique García-Muñoz, Daniel Segovia, Elliott Brown, David de Felipe, Norbert Keil
Universidad Carlos III de Madrid, Av. de la Universidad, 30 – 28911, Leganés
Madrid – Spain Tel: +34916249427, Fax: +34 916249430
E-mail: guiller@ing.uc3m.es
Wright State University, 3821 Colonel Glenn Hwy, Room 109, Dayton, OH 45435-0001 USA
E-mail elliott.brown@wright.edu
Fraunhofer Heinrich Hertz Institute, Photonics Components Department
Einsteinufer 37 – 10587 Berlin, Germany
E-mail: david.felipe@hhi.fraunhofer.de

High frequency generation using photonic techniques combines the best of two worlds, photonics with RF electronics. Photonic integration technology has been shown effective in order to reduce size and cost of this approach. More recently, heterogeneous integration is bringing the advantage of choosing the integration substrate material to optimize the performance of each components for the function that performs, instead of having to compromise the epitaxial structure of different components with different function.

Keywords: microwave photonics, THz signal generation, photonic integration

Fr.1.B.3 29-Invited Paper, Guillermo Carpintero (Universidad Carlos III), “The future of THz integrated photonics”

Integrated Passband Optical Filter with High-Order Phase-Shifted Bragg Grating in Silicon-on-Insulator Technology

Claudio Porzi, Antonella Bogoni
TeCIP – Scuola Superiore Sant’Anna, Via Moruzzi 1 – 56124, Pisa – Italy
E-mail: claudio.porzi@sssup.it
CNIT – National Photonics Labs, Via Moruzzi 1 – 56124 Pisa – Italy
E-mail: antonella.bogoni@cnit.it

An integrated passband optical filter based on a high-order phase-shifted Bragg grating (BG) realized in siliconon-insulator technology is presented. Five half-wave cavities are placed between six BG mirrors defined by laterally corrugating a strip silicon waveguide through electron-beam lithographic process. The BG mirrors are dimensioned in order to provide the proper reflectivity at Bragg wavelength such to tailor the spectral transmission of the multi-cavity filter. A passband window within a 1 THz stopband region having nearly-Gaussian transfer function with a -3dB bandwidth of ~25 GHz, low insertion loss of less than 1 dB, minimum stopband attenuation of ~35 dB, and a passband-to-stopband transition bandwidth of ~30 GHz is observed. These features, which are unreported for such class of structures, illustrate the potentials of this approach for realizing FSR-free bandpass optical filters with arbitrary bandwidth, strong out-of-band rejection, and fast roll-off. Effects of waveguide corrugation depth on the stopband width has also been investigated.

Keywords: Integrated optical filters, silicon photonics, Bragg gratings, Fabry-Perot filters.

Fr.1.B.4 91-Regular Paper, Integrated Passband Optical Filter with High-Order Phase-Shifted Bragg Grating in Silicon-on-Insulator Technology

Silicon Micro-ring Resonator Integrated in an Optoelectronic Oscillator System

Phuong T. Do, Carlos Alosno-Ramos, Diego Pérez-Galacho, Xavier Le Roux, Pascal Landais, Laurent Vivienn, Isabelle Ledoux-Rak, Bernard Journet and Eric Cassan
LPQM (CNRS UMR-8537) École Normale Supérieure de Cachan, Centrale Supelec, Université ParisSaclay, 61 avenue du Président Wilson, 94235 Cachan Cedex, France 2 C2N (CNRS UMR-9001), Univ. Paris-Sud, Université Paris-Saclay, Bât 220, rue André Ampère, 91405 Orsay Cedex, France
Tel: +33758866710, e-mail: tdo01@ens-paris-saclay.fr

In this paper, we present our recent results on the integration of an add-drop silicon micro-ring resonator in an optoelectronic oscillator (OEO) system for the generation of low phase noise RF signal at around 16 GHz. The add-drop ring serves as a selective band pass microwave filter in the OEO, being the frequency operation of the loop defined by the resonator free spectral range (FSR). The investigated micro-ring resonators have been fabricated using a standard silicon-on-insulator (SOI) substrate with 450-nm-wide Si waveguides and an unfolded physical length of 4.7 mm. To reduce the footprint of the device, a spiral arrangement was chosen with a total footprint of 500 µm by 500 µm. After fabrication, samples were tested using input and output grating couplers. The measured micro-ring resonators exhibited typical loaded qualities factors of around 120 000 at 1.55 µm wavelength. Optimized resonators were then introduced in the OEO system, to generate a RF signal around 16.2 GHz matching well the designed resonator FSR. These results constitute the first demonstration of an OEO RF oscillator integrating such a long SOI add-drop silicon ring resonator, paving the way for the future integration of an OEO system on a single chip.

Keywords: Function integration, silicon micro-ring resonator, microwave photonic filter, optoelectronic oscillator.

Fr.1.B.5 101-Regular Paper, Silicon Micro-ring Resonator Integrated in an Optoelectronic Oscillator System