OPTICAL SUM FREQUENCY GENERATION STUDY OF ORGANIC MATERIALS

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OPTICAL SUM FREQUENCY GENERATION STUDY OF ORGANIC MATERIALS Student : Le Thi Kim Anh K56 Talented Program in Physics Supervisor : Dr.Hoang Chi Hieu 1 *Nonlinear Optics *Sum frequency generation (SFG) spectroscopy *Organic materials *Experiment - Samples - Experimental setup - Results * Conclusion Contents 2 Nonlinear Optics  Linear optics - ‘Optics of weak light’: Light is deflected or delayed but its frequency is unchanged.  Non-Linear optics- ‘Optics of intense light’: Describes the behavior of light in nonlinear media, in which the dielectric polarization P responds nonlinearly to the electric field E of the light. 3 Nonlinear Optics Linear Optics Light intensity does not affect optical phenomenon. Nonlinear Optics - The refractive index ( velocity of light) in the optical media depends on light intensity. - Superposition principle is violated. - Light can interact with light - Light frequency can be changed in the nonlinear media 4 Polarizaon  Linear  Nonlinear P: the polarization of medium ε 0 : the permittivity of free space E: electric field χ (i) : susceptibilities of ‘i’ order nonlinear 5 The second order polarization generates SFG P( ω 1 + ω 2 )= ε 0 χ (2) E 1 E 2 Sum frequency generaon (SFG)  - Sum Frequency Generation (SFG)is a non-linear optical process in which 2 photons of angular frequencies ω 1 and ω 2 annihilate, simultaneously, one photon of ω 3 =ω 1 +ω 2 is generated . ћ ω 2 ћ ω 1 ћ ω 1 + ћ ω 2 Vib. level Energy DiagramSchematic view χ (2) χ (2) ω 1 ω 2 ω SFG =ω 1 + ω 2 6 SFG Spectroscopy: The output intensity is given by (χ (2) is the second-order susceptibility A useful technique to analyze surfaces, interfaces and biomaterial - The peaks appear when ω 2 matches ω q - SFG is forbidden in centrosymmetric media. Analyze and selectively detect molecule vibrational modes with orientation 7 Why SFG is forbidden in centrosymetric media 8 The 2 nd nonlinear polarization component that generates SFG: Organic materials  Almost organic materials belongs to molecule chirality.  Chiral structure which break centrosymmetric and generates SFG signal  SFG can provide the chemical selectivity,interface specificity,chemical indentification based on the changes of the vibrational spectrum . 9 Figure: Chirality in the amino-acid alanine. Structures of the two mirror-image forms. The image is part of the information on the 2001 Nobel Prize in Chemistry. EXPERIMENTAL  Experimental Setup 10 SFG system optical layout 532 nm 3333 nm 458 nm Pulse lazer: 30 ps Pulse energy ∼ 200 mJ Repeatation rate 50Hz Eskpla company [...]...Recent studies  Both experiment SFG study of Si (112) and Hydrated cellose show advantages of SFG method and have succeeded in carrying out the experiment to measure SFG spectra,using the first in Vietnam  Mr Khien gets initial achievement to explain crystal tructures of Si (112) PSP polarization Configuration 11 Recent studies 50 Mr Long study dependence SFG spectra of cellulose (HC) on the hydration... spectra of HC using pure water and NaOH 30% 12 Conclusion    SFG is a very new technology in the world with very high accuracy at monolayer level SFG is powerful to study on surface / interface and biological and biomedicalmaterials SFG has potential development for studying in Biology take 3D images, orientation biological molecule by using SFG microscope  Future works: we will study SFG spectra of. .. and biomedicalmaterials SFG has potential development for studying in Biology take 3D images, orientation biological molecule by using SFG microscope  Future works: we will study SFG spectra of some biomaterials like DNA and protein, 13 THANK YOU FOR YOUR ATTENTION 14 15 16 . OPTICAL SUM FREQUENCY GENERATION STUDY OF ORGANIC MATERIALS Student : Le Thi Kim Anh K56 Talented Program in Physics Supervisor : Dr.Hoang Chi Hieu 1 *Nonlinear Optics *Sum frequency generation. susceptibilities of ‘i’ order nonlinear 5 The second order polarization generates SFG P( ω 1 + ω 2 )= ε 0 χ (2) E 1 E 2 Sum frequency generaon (SFG)  - Sum Frequency Generation (SFG)is a non-linear optical. electric field E of the light. 3 Nonlinear Optics Linear Optics Light intensity does not affect optical phenomenon. Nonlinear Optics - The refractive index ( velocity of light) in the optical media