Chapter 1

Question 1

Second harmonic generation

Answer 1

2 photons of w (same freq) are destroyedm one photon of 2w created

Question 2

What is 3 wave mixing

Answer 2

3 photons involved, i.e. second harm generation, 2nd order process

Question 3

Common use of 2nd harminic generation

Answer 3

Convert output of fixed freq laser to diff spectral region e.g. ND YAG to 530nm by w (1000nm) to 2w (500nm)

Question 4

What are the possibilities when you have two incident field with two different frequencies

Answer 4

Second harmonic generation
X(2w1,w1,w1) same for w2

Sum freq generation
X(w1+w2,w1,w2)

Difference freq gen
X(w1-w2,w1,-w2)

Optical rectification
X(0,w1,-w1)

Question 5

Since 4 processes are possible with an incident E field with 2 freq components which will occur

Answer 5

Only 1 will dominate in intensity due to phase matching conditions which tend to select only one of these. IRL you decide which by deciding the incident polarisation and thus choose which of SFG, SHG, DFG OR you want

Question 6

Application of sum freq generation

Answer 6

X(w1+w2,w1+w2)
make w1 fixed and w2 tunable and you can gneerate high freq (UV) but utnable

Question 7

Application of difference freq gen

Answer 7

Produce tunable IR with one freq tunable VIS laser and one fixed frew VIS laser

Question 8

Difference between DFG and SFG

Answer 8

DFG one frequence is destroyed and one is created so that one of the input light is actually amplified.

DFG known as optical parametric amplification

Question 9

Third harmonic generation

Answer 9

3 photons of w are destroyed one photon of 3w is created
X(3w,w,w,w)

Question 10

What can amplification in 2nd harm diff freq generation be used for

Answer 10

Optical parmateric oscillation and down conversion

Question 11

What does parametric mean

Answer 11

Initial and final QM states are identical
No transfer of population between real levels, only virtual levels

Real X
Photon energy conserved

Question 12

What does non parmatric processes mean

Answer 12

Involce tranfer of population from one real level to another

Always complex X
Photon energy not always conserved

Question 13

Real vs imaginary part of linear index of refraction

Answer 13

Real part : parametric processes
Imaginary: due to non parametric porcesses (Asosciated with real levels and population transfer and thus with the absorption fo radiation)

Question 14

What does dispersion mean in terms of X dependence

Answer 14

X changes with the light frequency (depends on w)

Question 15

Intrinsic perm

Answer 15

Can swap the order of the generaTING freq as long as you also swap E fields with them and the generATED freq stays the same

X(w3,w1,w2) = X(w3,w2,w1) so long as you change it so that the correct E field stays with its starting frequence

Question 16

Types of symmetry and validity

Answer 16

Reality of the fileds
- can replace things with 0 and cc always vaid

Intrinsic perm symm
- can swap wn,m if you swap jk so that the correct E stays with its freq

Full permutation sym
- valid for lossless media
ALL (incl gen.) freq args can be swiotched so long as you also change the ijk (and put minuses etc)

Question 17

What is the meaning of full perm symm

Answer 17

Valid for lossless media
X suceptibility has the same value irrespective of which fields are incident and which are generated

X has the same value for different processes (since diff gen freq_> diff process)