Introduction to Nonlinear Optics

1
Introduction to Nonlinear Optics

• H. R. Khalesifard
• Institute for Advanced Studies in Basic Sciences
• Email khalesi_at_iasbs.ac.ir

2
Contents

1. Introduction
2. The essence of nonlinear optics
3. Second order nonlinear phenomena
4. Third order nonlinear phenomena
5. Nonlinear optical materials
6. Applications of nonlinear optics

3
Introduction

• Question
• Is it possible to change the color of a
  monochromatic light?
• Answer
• Not without a laser light

4
Stimulated emission, The MASER and The LASER

• (1916) The concept of stimulated emission Albert
  Einstein
• (1928) Observation of negative absorption or
  stimulated emission near to resonant wavelengths,
  Rudolf Walther Ladenburg
• (1930) There is no need for a physical system to
  always be in thermal equilibrium, Artur L.
  Schawlow

5
(No Transcript)
6
LASER (MASER)
7
The Maser

• Two groups were working on Maser in 50s
• Alexander M. Prokhorov and Nikolai G. Bassov
  (Lebedev institute of Moscow)
• Charles H. Townes, James P. Gordon and Herbert J.
  Zeiger (Colombia University)

8

• Left to right Prokhorov, Townes and Basov at
  the Lebede institute (1964 Nobel prize in Physics
  for developing the Maser-Laser principle)

9

• Townes (left) and Gordon (right) and the
  ammonia maser they had built at Colombia
  University

10
The LASER

• (1951) V. A. Fabrikant A method for the
  application of electromagnetic radiation
  (ultraviolet, visible, infrared, and radio
  waves) patented in Soviet Union.
• (1958) Townes and Arthur L. Schawlow, Infrared
  and Optical Masers, Physical Review
• (1958) Gordon Gould definition of Laser as
  Light Amplification by Stimulated Emission of
  Radiation
• (1960) Schawlow and Townes
  U. S. Patent
  No. 2,929,922
• (1960) Theodore Maiman Invention of the first
  Ruby Laser
• (1960) Ali Javan The first He-Ne Laser

11

• Maiman and the first ruby laser

12

• Ali Javan and the first He-Ne Laser

13
Properties of Laser Beam

• A laser beam
• Is intense
• Is Coherent
• Has a very low divergence
• Can be compressed in time up to few femto second
  

14
Applications of Laser

• (1960s) A solution looking for a problem
• (Present time) Medicine, Research, Supermarkets,
  Entertainment, Industry, Military, Communication,
  Art, Information technology,

15
Start of Nonlinear Optics

• Nonlinear optics started by the discovery of
  Second Harmonic generation shortly after
  demonstration of the first laser.
• (Peter Franken et al 1961)

16
2. The Essence of Nonlinear Optics

• When the intensity of the incident light to a
  material system increases the response of medium
  is no longer linear

17
Response of an optical Medium

• The response of an optical medium to the incident
  electro magnetic field is the induced dipole
  moments inside the medium

18
Nonlinear Susceptibility
Dipole moment per unit volume or polarization

• The general form of polarization

19
Nonlinear Polarization

• Permanent Polarization
• First order polarization
• Second order Polarization
• Third Order Polarization

20
How does optical nonlinearity appear

• The strength of the electric field of the
  light wave should be in the range of atomic fields

21
Nonlinear Optical Interactions

• The E-field of a laser beam
• 2nd order nonlinear polarization

22
2nd Order Nonlinearities

• The incident optical field
• Nonlinear polarization contains the following
  terms

23
Sum Frequency Generation
Application Tunable radiation in the UV
Spectral region.
24
Difference Frequency Generation
25
Phase Matching

• Since the optical (NLO) media are dispersive,
• The fundamental and the harmonic signals have
• different propagation speeds inside the media.
• The harmonic signals generated at different
  points
• interfere destructively with each other.

26
SHG Experiments

• We can use a resonator to increase the efficiency
  of SHG.

27
(No Transcript)
28
What is the phase conjugation
The signal wave
The phase conjugated wave