Deepen your knowledge of new techniques for optical imaging from the micro/nano-scale to the macroscopic level, understanding the physical basis, discussing instrumental implementations and presenting examples of applications. The project session will improve the experimental, modelling, team working and soft-skill competencies required in research activity.

To provide the basic knowledge necessary for the understanding of the ultrashort light pulse generation mechanisms, their propagation in linear and nonlinear media, their characterization techniques. To give examples of the application of ultrashort pulses to the study of dynamical processes in physics, chemistry and biology. The acquired knowledge will enable the student to work in advanced research laboratories as well as in high tech companies developing laser sources or using them for applications in micromachining, telecommunications, sensing or biomedicine.

Part I: Nanoscopy and Optical Tomography

The key aim is to increase understanding on the application of photonics approaches to several imaging processes with particular emphasis on biological imaging both at the nanoscale (3D microscopy) up to optical tomography for clinical diagnostics. Further, methods related to wave physics, light-matter interaction, inverse problems will be exploited. The student will be able to apply this knowledge to different scenarios. Further, the authonomous study on scientific literature as well as the project activities will provide learning skills and soft skills.

Part II: Physics of Ultrafast processes

At the end of the course the student will acquire knowledge and understanding of the underlying physics and the technical working principles of ultrashort pulse laser systems. The student will be able to apply this knowledge and understanding to different scientific and industrial systems using ultrashort pulse lasers and to make judgements on the design of such systems for applications to spectroscopy, imaging or material processing. The student will acquire learning skills that will enable her/him to read advanced, graduate-level textbooks on nonlinear optics and photonics as well as papers on peer-reviewed scientific journals.

Part I: Nanoscopy and Optical Tomography

1. Diffuse Optical Tomography

• Brief overview on diffuse optics, time-resolved techniques, frequency-resolved techniques
• Theoretical models of photon migration
• photon density waves
• Diffuse Optical Tomography in the linear regime under Born approximation
• Reconstruction under non-linear regime
• Applications and new perspectives

2. Nanoscopy

• Recalls on far-field microscopy techniques, spatial resolution.
• diffraction limit is overcome by saturable transitions (RESOLFT): physical principles.
• possible implementations: STED, GSD, SPEM
• stochastic methods for optical nanoscopy: physical principles.
• possible implementations: PALM, STORM
• compare RESOLFT techniques and stochastic techniques
• Examples of application for optical nanoscopy

Project

There will be a project activity involving all students divided into groups. This activity foresee a laboratory session on advanced research instrumentation developed at the Department of Physics followed by a modelling and analysis session based on Matlab.

Part II: Physics of Ultrafast processes

1.   Properties of ultrashort laser pulses

• introduction to ultrafast optics;
• linear propagation equation for ultrashort pulses; dispersion and techniques for its compensation;
• nonlinear ultrashort  pulse propagation in second order media; three-fields coupled equations; second harmonic generation, sum and difference frequency generation;
• nonlinear ultrashort pulse propagation in third order media; Kerr effect, nonlinear Schrödinger equation, solitons, self-phase-modulation;
• ultrashort pulse characterization techniques: non-collinear and interferometric autocorrelation, FROG, SPIDER, 2DSI

2.   Ultrashort pulse generation techniques

• mode-locked lasers and passive mode-locking techniques;
• ultrashort pulse amplification, chirped pulse amplification technique;
• optical parametric amplifiers;
• carrier-envelope phase and frequency combs

3.   Applications of ultrashort pulses

• introduction to ultrafast spectroscopy techniques;
• degenerate, two-colour and broadband pump-probe;
• density matrix formalism for the decscription of light-matter interaction;
• four-wave mixing, photon echo and two-dimensional spectroscopy;
• ultrafast processes in metals and semiconductors;
• introduction to femtochemistry and femtobiology.

Part I: Nanoscopy and Optical Tomography

There are no binding prerequisites. The course on "Ottica Biomedica" provides some good basis for the section on Diffuse Optical Tomography, although these are not strictly needed.

Part II: Physics of Ultrafast Processes

The course requires basic knowledge of the foundations of classical electromagnetism, quantum electronics (light-matter interaction, principles of lasers) and quantum mechanics.

For both parts, a good understanding of the topics handled in the course of Photonics I is an important but not necessary prerequisite. 

The final assessment will be based on a written test which encompasses both lecture and project activities.

The exam will test the depth of understanding by the student of the handled topics, the developed critical skills and the capabilities to effectively organize the presented material, using a proper lexicon and efficiency and linearity of the discussion.

A collection of scientific papers will be provided at the starting of the course via the BEEP channel