NON LINEAR OPTICS

Degree course: 
Corso di Second cycle degree in PHYSICS
Academic year when starting the degree: 
2020/2021
Year: 
1
Academic year in which the course will be held: 
2020/2021
Course type: 
Compulsory subjects, characteristic of the class
Credits: 
6
Period: 
Second semester
Standard lectures hours: 
48
Detail of lecture’s hours: 
Lesson (48 hours)
Requirements: 

For a better understanding of the topics covered in the course, it is required that students have already attended courses of Electromagnetism and Physics of Matter. In addition, it is advisable that students have inserted the course of Optics in their learning program and that they have already attended it.

Final Examination: 
Orale

The exam is in English, it is oral and it is essentially divided into two parts:
First of all, students are asked to choose and talk about a topic among those mentioned in the course. This part of the exam is aimed at verifying:
- the knowledge of a specific nonlinear process
- the understanding of its features
- the capability of deeply analyzing its nature.
In the second part of the exam, some questions about the remaining topics are asked, through which the teacher will check if the students
- have acquired a sufficient knowledge of nonlinear optical phenomena
- have also learnt skills in recognizing and fully understanding them
- are able to identify the main applications of nonlinear optics to science and technology
- properly use the technical language to explain the nonlinear processes
To pass the exam, a satisfactory presentation of the first part is required.
To successfully pass the exam students should know all the topics presented in the course. The deeper the knowledge the better the evaluation.
Full mark with laude is assigned only to students that accomplish all the aims and outcomes discussed above are able to re-elaborate the different topics, to establish connections and comparisons, and to make practical examples are able to make connections between the theoretical presentation of the non-linear processes and their experimental realization in the lab.

Assessment: 
Voto Finale

The course is aimed at providing students with concepts and methods to recognize and understand the different nonlinear optical phenomena. Indeed, Nonlinear Optics still represents a current research topic in Physics. Thus, the course could be of great interest for students who intend to undertake a research career in the Optics field.
To achieve this goal, the theoretical approach is supported by some experimental activities in the optics Labs of the Department, in which students will observe the most part of nonlinear optical phenomena and test their main applications.

At the end of the course, students will be able to:
- describe the fundamental nonlinear optical phenomena (parametric and non-parametric ones)
- explain the requirements and conditions to be met to achieve these processes
- evaluate the different nonlinear processes, by understanding their origin and distinguishing between linear and nonlinear phenomena
- critically evaluate the main applications of nonlinear optics to science and technology
- discuss the different topics by means of a proper technical language and by making comparisons among them
- make connections between the theoretical part and the experimental activities.

INTRODUCTORY PART
- Historical background and introduction to the main nonlinear optical phenomena;
- Passive mode-locking techniques obtained by means of nonlinear processes;
- Linear optical systems and Kramers-Kronig relations in linear and nonlinear optics;
SECOND-ORDER NONLINEAR PROCESSES
- Symmetry properties of the second-order nonlinear susceptibility;
- Second-order nonlinear processes under plane-wave approximation: second-harmonic generation, sum-frequency generation, parametric amplification, spontaneous parametric down conversion, optical parametric oscillator;
- Phase-matching conditions and generation in phase-mismatch conditions;
- Generation of nonlinear processes by means of focused Gaussian beams;
THIRD-ORDER NONLINEAR PROCESSES
- Symmetry properties of third-order nonlinear susceptibility;
- Description of the intensity-dependent refractive index of the non-linear medium;
- Processes resulting from the intensity-dependent refractive index: self-phase modulation, self-focusing, filamentation, temporal solitons, phase conjugation;
- Optically induced damage and multiphoton absorption;
ULTRAFAST OPTICS
- Ultrafast and ultra-intense optics: nonlinear Schrödinger equation, white-light continuum and high-harmonic generation.
LABORATORY ACTIVITIES
The laboratory activities aim at directly observing and investigating some nonlinear optical phenomena, especially those related to second-order nonlinearity, already presented from the theoretical point of view.
In fact, on the basis of the available laser sources and instruments, at least the following processes can be studied:
- second-harmonic generation in collinear and non-collinear geometry: application to the measurement of short-pulse duration using the autocorrelation technique;
- quantitative analysis of second-harmonic generation in phase-mismatch condition:
- sum- and difference-frequency generation: study of the processes as functions of the polarization of the input optical fields;
- spontaneous parametric down conversion (SPDC): observation of SPDC cones and quantitative analysis of their spatial and spectral properties;
- passive mode-locking technique: use of a laser source in which such a technique can be easily obtained and observed.

Lectures are based on the following textbooks:
- R. W. Boyd, “Nonlinear Optics”, Academic Press (2008);
- B. E. A. Saleh and M. C. Teich, “Fundamentals of Photonics”, John Wiley & Sons, Inc. (1991);
- V. G. Dmitriev, G. G. Gurzadyan, and D. N. Nikogosyan, “Handbook of Nonline-ar Optical Crystals”, Springer (1999).
Moreover, when it is the case, copies of some articles are provided during les-sons.

The course is essentially based on lectures, during which the teacher presents the topics by making calculations and supporting all the statements with prac-tical examples (38 hours). When it is advisable, the teacher will provide students with additional materials, such as articles and reviews. In order to improve the quality of teaching and to make the content of theoretical lessons much more understandable, the remaining 10 hours will be devoted to the experimental observation and characterization of nonlinear optical processes in the laboratory.

For questions/comments students are invited to directly contact the teacher by e-mail at the following address: alessia.allevi@uninsubria.it.

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