2 Electrooptic effect Pockels effect is the change

2차 비선형 광학효과 : 선형전기광학효과 Electro-optic effect, Pockels effect, is the change in refractive index of a material induced by the presence of a dc (or low frequency) electric field. 6

Index ellipsoid = The quantities rij are known as the electro- optic coefficient The linear electro-optic coefficients are related to the second order nonlinear optical susceptibility. 7

When we apply the external ac field to the poled polymer along the poling direction z, the index ellipsoid is, 8

2차 비선형 광학 고분자 Delocalization of π electron density of conjugated π systems induces a large dipole moment and increases optical nonlinearity of organic molecules. conjugated π systems Typical organic materials for NLO effect Donor N(CH 3)2 > NH 2 > OCH 3 > OH Acceptor NO > NO 2 > CHO > CN 15

Axis of rotation, Cn This is a line drawn such that rotating the molecule around it by steps of 360/n degrees will result in the same molecule. That is, rotating it n times brings you back to where you started, but at each of the intermediate steps it also looks the same. The point group C v This is a special case for linear molecules such as ICl and HCN, because it is possible to rotate the molecule about its principal axis to any desired degree and to draw an infinite number of vertical planes. Z=optic axis nz Z nx ny 16

Alignment of molecules : Electric field poling 17

Alignment of molecules : Langmuir-Blodgett Method 18

Alignment of molecules : Self assembled method 19

Self assembled thin film : POST 4 -amide polymer chemical structure Polymer backbone Benzenoid and Quinoid form Text Hemicyanine chromophore Text Jung-Hyuk Im, et. al. , Macromolacules, 33, 9606 -9611 (2000) N+ 20

POST 4 -amide self-assembled monolayer Ag Text Et. OH Text MPA(5 m. M, Dipping Time : 90 min) Base Layer (anion) Rinsing & Nitrogen gas dry 3 rd DI Water Rinsing & Nitrogen gas dry POST 4 -amide Monolayer(Cation) POST 4 -amide(5 m. M, Dipping Time : 30 min, p. H 9. 5) 21

강유전체 물질 Perovskite Structure (ABO 3) + Ex) PZT(Lead Zirconium Titanate : Pb(Zr, Ti)O 3) Ba. Ti. O 3 (Barium Titanate) Text SBT(Strontium Bismuth Tantalate : Sr. Bi 2 Ta 2 O 9 ) BLT (Lanthanum substituted Bismuth Titanate: Bi 3. 25 La 0. 75 Ti 3 O 12) Text SBT structure : two unit cells 22

3차 비선형 광학 고분자 Text Phthalocyanine Porphyrin array C 60 : Fullerene 23

Side chain polymer Text 24