• 096059 - MICRO AND NANOOPTICS [1]

The Aim of the course is threefold: (i) to introduce the student to the theoretical foundations and main applications of Integrated Optics; (ii) to provide the student with a set of advanced tools and methods for the design and quantitative description of optical components and devices at the microscale; (iii) to give the student the theoretical basis for the understanding of highly innovative topics in modern Photonics.

• The student understands the physical basis of the optical phenomena taking place at the micro and nanoscale.
• The student knows the guidelines for the modelling and design of integrated devices.
• The student is aware of the key functionalities implemented in micro and integrated optics.

The student is able to apply the basic knowledge described above for:

• explaining the operating principles of some prototypal optical devices at the microscale, with particular attention to their quantitative description and to the validity limits of the models under consideration;
• solving simple problems in integrated and telecom optics and guided-wave photonics;
• understanding new trends in the high-tech market (from IT highways to lab-on-chip) dealing with advanced photonic structures.

1. Introduction to optical communication systems.

Historical evolution. Introductory concepts: analog and digital transmission, multiplexing techniques, modulation formats. Layout of an optical communication system: topology, design criteria, integrated optical devices. Analysis of the bit-error-rate as a function of the main noise system sources. Communication systems limited by attenuation and dispersion.

2. Integrated optical devices. Couplers and power splitters in integrated optics.

Coupled mode theory. Transfer matrix of the directional coupler. Functional analysis of the directional coupler as a 3-dB coupler, as a frequency filter and as an optical switch. Other types of couplers and beam splitters: the bifurcation, the multimode interference coupler, the star coupler.

3. Optical filters in integrated optics.

FIR (Finite Impulse Response) and IIR (Infinite Impulse Response) filters. General spectral properties of filters. Mach-Zehnder interferometer: spectral response and engineering guidelines. The Arrayed Waveguide Grating (AWG): operation principle, transfer function, engineering guidelines. Functional analysis of the AWG as a de/multiplexer, as a router and as a reconfigurable add-drop filter. Ring resonant filter: transfer function and main features.

4. Electro-optic intensity modulators.

The electro-optic effect: basic principles. X-cut and Z-cut lithium niobate modulators. Lumped and travelling electrodes. Bandwidth limitations. Integrated optical intensity modulators: architectures (Mach-Zehnder interferometer, directional coupler, deltabeta-reversed directional coupler) and performance. Comparison with bulk modulators.

5. Recent advances in the field of optical communications.

DPSK modulation formats: signal to noise ratio and architecture of transmitters and receivers. Coherent detection and digital signal processing for multi-level transmission formats and dispersion compensation. Concluding seminar on fabrication techniques, packaging issues and new technological perspectives.

Concluding seminar on Silicon Photonics.

No pre-requisites, but the teaching makes use of the basic concepts of Optics and Electromagnetism.

Written examination, optionally followed by an oral examination.

The written exam consists of open questions: 3 questions to be solved in 2 hours and 15 minutes for students signed up for the full course of Micro and Nanooptics, 2 questions to be solved in 1 hour and 45 minutes for students signed up only for the course of Integrated Optics (which corresponds to the first part of Micro and Nanooptics). At the discretion of the student, the written text is followed by an oral test. The aim is to ascertain:

• the understanding of the physical basis of the optical phenomena at the microscale;
• the knowledge of the definitions, theorems and general concepts dealing with optical waveguides and integrated optics telecom components;
• the capability to discuss, both qualitatively and quantitatively, the performance of prototypal microoptical devices as a function of their key parameters.