• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.429-434
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• 2010

A novel T-type polyester 7 containing 1-(2,5-dioxyphenyl)-2-{5-(1,2,2-tricyanovinyl)-2-thienyl}ethenes as nonlinear optical (NLO) chromophores, which are part of the polymer backbone, was prepared and characterized. Polyester 7 is soluble in common organic solvents such as dimethylsulfoxide and N,N-dimethylformamide. It showed a thermal stability up to $300^{\circ}C$ in thermogravimetric analysis thermogram and the glass-transition temperature ($T_g$) obtained from differential scanning calorimetry thermogram was around $113^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer films at 1,560 nm fundamental wavelength was around 1.85 pm/V. The dipole alignment exhibits a greater thermal stability even at $10^{\circ}C$ higher than $T_g$, and there is no SHG decay below $125^{\circ}C$ due to the partial mainchain character of the polymer structure, which is acceptable for nonlinear optical device applications.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3361-3366
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• 2011

New Y-type polyester (3) containing nitrophenylazoresorcinoxy groups as NLO chromophores, which are components of the polymer backbone, was prepared and characterized. Polyester 3 is soluble in common organic solvents such as N,N-dimethylformamide and acetone. It shows a thermal stability up to $240^{\circ}C$ in thermogravimetric analysis with glass-transition temperature ($T_g$) obtained from differential scanning calorimetry near $116^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer film at the 1064 nm fundamental wavelength is around $4.63{\times}10^{-9}$ esu. The dipole alignment exhibits a thermal stability even at $4^{\circ}C$ higher than $T_g$, and there is no SHG decay below $120^{\circ}C$ due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.933-938
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• 2008

2,4-Di-(2'-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and polymerized with terephthaloyl chloride and adipoyl chloride to yield novel Y-type polyesters 4 and 5 containing dioxybenzylidenemalononitrile groups as NLO-chromophores, which constituted parts of the polymer backbone. The resulting polymers 4 and 5 are soluble in common organic solvents such as acetone and N,N-dimethylformamide. Polymers 4 and 5 showed thermal stability up to 300 ${^{\circ}C}$ in thermogravimetric analysis with glass-transition temperatures obtained from differential scanning calorimetry in the range 83-94 ${^{\circ}C}$. The second harmonic generation (SHG) coefficients ($d_{33}$) of poled polymer films at the 1064 nm fundamental wavelength were around $6.48\;{\times}\;10^{-9}$ esu. The dipole alignment exhibited high thermal stability even at 10 ${^{\circ}C}$ higher than $T_g$ and no significant SHG decay was observed below 105 ${^{\circ}C}$ partially due to the main-chain character of polymer structure, which is acceptable for NLO device applications.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1080-1084
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• 2009

Methyl 2,4-di-(2'-hydroxyethoxy)benzylidenecyanoacetate (3) was prepared and polymerized with terephthaloyl chloride to yield a novel Y-type polyester 4 containing 2,4-dioxybenzylidenecyanoacetate groups as NLOchromophores, which constituted parts of the polymer backbone. The resulting polymer 4 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. Polymer 4 showed thermal stability up to 280 ${^{\circ}C}$ in thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry near 108 ${^{\circ}C}$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer films at the 1064 nm fundamental wavelength was around $3.54\;{\time}\;10^{-9}$ esu. The dipole alignment exhibited a thermal stability up to near $T_g$ and no significant SHG decay was observed below 100 ${^{\circ}C}$ due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.198-203
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• 1997

Two different carbazolylnitrostilbene chromophores with second-order nonlinear optical (NLO) activity were newly synthesized by the reaction of 9-(2-hydroxyethyl)-9H-carbazol-3-carbaldehyde with 4-nitrophenylacetonitrile or 4-nitrophenylacetic acid. The NLO monomers were obtained by reaction of these chromophores with methacryloyl chloride. The side-chain nonlinear optical polymers were synthesized by the copolymerization of NLO monomer with methylmethacrylate using a free radical initiator. The chemical structures of the polymers were identified by spectroscopic means and the polymer properties such as molecular weight, Tg, solubility, UV-visible absorption, and second-harmonic generation (SHG) coefficients were investigated.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.79-79
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• 2003

SHG (Second harmonic generation) can be used to probe the surface of centrosymmetric particles suspended in bulk isotropic solution, because it is forbidden in centrosymmetric media under the dipole approximation. Using this technique, we can study the transport dynamics of small organic dye molecules across liposome bilayers. Because molecules adsorbed on the outer layer are in opposite direction with that on the inner layer by symmetry, the SH field is proportional to the difference between the number density of dye molecules on both sides of the bilayer, and the time dependence of the SH intensity is related to the time constant of the molecular transportation of dye molecules across liposome bilayers.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.251-259
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• 1996

Two-Photon Fluorescence (TPF) experiment measures temporal width of an amplified short laser pulse which has passed through a four-pass Nd: glass amplifier, after selecting a single pulse from pulse train Q-switched and mode-locked(QSML) in Nd:YLF master oscillator. Determination of pulsewidth and pulseshape was also made with detection of autocorrelation trace of CW mode-locked pulse train by using noncollinear type I Second Harmonic Generation (SHG) method. The observed TPF track showed various patterns, depending on pulse-selecting position in QSML pulse train. That is, autocorrelation of a pulse extracted at front of the train displayed smooth pulse shape, while one from the trailing part of the train created many sharp spikes and substructure in the pulse. By TPF method, pulsewidth was measured to be 44.4 ps with contrast ratio of 2.86 which enabled us to find out energy fraction of a pulse to total energy, (sum of pulse and background); we obtain the value of 0.62. Pulsewidth of 46.6ps was also acquired in another SHG experiment with the help of only mode-locked pulse train. On the other hand, we confirmed that shape of the pulse is close to $sech^2$ one as a result of fitting the SHG autocorrelation signal with various functions. With simulation using this $sech^2$ type of pulse, pulsewidth reduction of the beam, having passed through four-pass amplifier, was also verified.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.605-606
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• 2004

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.491-496
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• 2010

The relaxation behavior of aligned electric dipoles in a mixed polymer of P2ANS with P(VDF-TrFE) is studied with optical second harmonic generation (SHG). In this work, a macroscopic noncentrosymmetry of the spin coated film was achieved by an electrical poling. The relaxation of induced polar order of nonlinear optic(NLO) chromophores after poling leads to an insufficient long-term stability of NLO properties. In this work, we develop a new technique to suppress such kind of dipole relaxation in a poled polymer. We found that the poled dipoles in a NLO polymer were effectively immobilized by the internal electric field created by a thermally annealed ferroelectric polymer. The long-term stability in a mixed system of NLO polymer/ferroelectric polymer was successively accomplished by a series of thermal treatments applied to the mixed polymer system at a temperature of $140^{\circ}C$ for at least 1hour after poling.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.224-225
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• 2003

Since group velocity (GV) mismatch significantly limits the efficiency of nonlinear interactions such as second harmonic generation (SHG), several techniques have been developed to compensate GV mismatch. The simplest way to avoid the GV mismatch problem is to reduce the device length. However, it results in a poor trade-off between the SHG spectral bandwidth and the conversion efficiency. (omitted)