OVERVIEW

It is a course on the optical properties of  materials and the basic experimental methods to study them. Empahsis is placed on the applications of spectroscopic ellipsometry. A basic knowledge of electromagnetism in dielectrics, wave, solid-state physics. The course is mainly aimed at students in condensed matter physics, materials science and chemistry.

AIMS AND CONTENT

AIMS AND LEARNING OUTCOMES

Students will gain up-to-date skills on the application of spectroscopic methods to the study of optical properties of composite nano-materials of interest in the field of photonics. Through laboratory, demonstration and experiential activities, students will acquire basic skills in optical spectroscopy and spectroscopic ellipsometry.

PREREQUISITES

The attendance of bsic courses in electromegnetism and quantum mechanics is recommended

TEACHING METHODS

Traditional lectures. Laboratory demonstrations. Laboratory experiences.

SYLLABUS/CONTENT

A. Light & materials (I): fundamental optical processes.

1. Absorption&Dispersion

1.1 Dielectric function and complex refractive index in linear response regime of homogeneous and isotropic materials (OI)
Lorentz oscillator for bound electrons. Dielectric function and complex refractive index.  Multiple resonances.  Kramers- Kronig relations.  Phenomenological models for normal dispersion (Sellmeyer, Cauchy).  Clausius-Mossotti formula for dense dielectrics.  Optical properties of glasses and other amorphous insulators. Consequences of dispersion.

1.2 Beyond OI materials
Inhomogeneity: effective medium models and modifications to the Clausius-Mossotti relation. Anisotropy: dielectric tensor and birefringence.

2. Free carriers
Drude's model. Dielectric function of simple metals.  Plasma oscillations of electron gas.  Low frequency limit. Optical properties of aluminum.  Nonmetallic conducting materials.

B.   Light & structures: interfaces.

3. Reflection and refraction. Ellipsometry.
Interfaces. Plane of incidence and the polarization s and p. Fresnel coefficients.  Brewster angle. Critical angle. Jones representation of polarization states. Jones matrix of a non-depolarizing sample. Fundamental relation of ellipsometry: Ψ and Δ.

4. Multiple interfaces.
Reflectivity and ellipsometry from an isotropic thin-film system. Calculation of reflection and transmission coefficient for isotropic multilayers. Interferential mirrors and optical filters. Perfect mirrors.   

5.  Instrumentation and measurement methods (with laboratory demonstrations). 
Optical components for experiments (sources, monochromators, polarizers, compensators). Matrix description of the main optical components.  Single wavelength zero ellipsometry. Magneto-optical Kerr effect. Spectroscopic ellipsometry. Transfer function of optical systems by Jones' method.   Kretschmann configuration and surface plasmon resonance (SPR). Spatially resolved optical spectroscopies. Time-resolved ultrafast optical spectroscopies.

C.   Light & Materials (II). Quantum models: absorption, emission, and scattering.

6.  Interband Transitions.
Band structure of semiconductors. Absorption threshold. Direct gap: probability of transition near threshold.  Semiconductor color. Indirect gap: phonon-assisted transitions.  Comparison with experimental data.  Low temperature effects. Transitions away from threshold: effects of band parallelism.  Effect of defects and doping. Absorption threshold in amorphous oxides.  Band structure of noble metals. Interband transitions and color effects.

7.  Excitons and luminescence.
Excitons in pure semiconductors.  Strongly and weakly bound excitons.    Luminescence processes and measurements.  Materials for LED and photovoltaic applications. Molecular semiconductors.

8. Raman Scattering

Principles. Basic instrumentation. Raman spectrometers and micro-spectrometers (with laboratory demonstration).

D.    Light & Materials (III). Introduction to nano-photonics (with invited seminars).

9.  Nano-metals
Metal nanoparticles. Absorption and scattering. Plasmonic resonances.  Particle aggregates. Materials, methods and models for plasmonics in the visible and UV. Organized 2D systems of nanoparticles. Plasmonic sensors for gases and bio-molecules.

10. Nano-semiconductors
Ultra-thin heterostructures and new 2D semiconductors.  Quantum dots.  New materials for quantum dots.

11.  Ultra-thin films
Metamaterials. Photonic crystals and natural Bragg reflectors (hints). Langmuir-Blodgett films and self-assembled organic monolayers.

RECOMMENDED READING/BIBLIOGRAPHY

Textbook M. Fox, Optical properties of Solids, Oxford University press

B. Culshaw - Introducing Photonics (SPIE - Cambridge)

Lecture Notes ( slides, in English available on dedicated repositories

Other texts available at the DIFI's library

H. Arwin, Thin Film Optics and Polarized Light

O. Stenzel The Physics of Thin Film Optical Spectra, Springer

E. Hecht, Optics, Addison Wesley

H. Tompkins, W.A. Mc Gahan, Spectroscopic Ellipsometry and Reflectometry, Wiley,

TEACHERS AND EXAM BOARD

Exam Board

MAURIZIO CANEPA (President)

SILVANA TERRENI

FRANCESCO BISIO (President Substitute)

LESSONS

LESSONS START

March 2022, date to be decided

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

The final exam deals with a seminar of the student on a broad topic. The topics are assigned by the lecturer at least three weeks in advance to the exam.

ASSESSMENT METHODS

Frequent and active presence to the lectures and laboratory activities.  Evaluation of the seminar presented for the exam: coherence with course contents, validity and degree of analysis of presented contents. Ability of critical analysis  of treated arguments.

FURTHER INFORMATION

https://dida.fisica.unige.it/dida/