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Electrostatic Self Assembled Films For Photonics Ph D Defense
- 1. Second-Order Nonlinear Optical Characteristics of Nanoscale Self-Assembled Multilayer Films J. R. Heflin R. M. Davis H. W. Gibson G. Indebetouw H. Marand Ph. D. Thesis Defense by Patrick J. Neyman June 16, 2004 © Patrick Neyman: patrickneyman.com
- 12. Experimental Apparatus © Patrick Neyman: patrickneyman.com
- 13. Beam Propagation in Sample © Patrick Neyman: patrickneyman.com
- 18. Tilt Angle Measurements © Patrick Neyman: patrickneyman.com 0 100 200 300 400 500 600 700 -100 -80 -60 -40 -20 0 20 40 60 80 100 Polarizer Angle I(2 )
- 36. Thermal Stability © Patrick Neyman: patrickneyman.com Heat to Hold for 150 °C 18 hours Cool to room temp
- 37. Thermal Stability © Patrick Neyman: patrickneyman.com
Notas del editor
- Many issues at films must be considered: Refraction is big one These will be addressed further in Defense
- Fringe envelope flattens when consider angle-dependent Optical Path Length in films
- First Pi-electron excited state dominant in determining Beta (HOMO-LUMO shift) donor charge transferred to acceptor
- Helical nature of PS119 FIRST APPROXIMATION
- Competitive Orientation Random Orientation
- This is one of two methods of determining the relative chi(2)
- From earlier work (although I did dip the films) Altering parameters of cation solution has same results (inverse by pH) (M.S.)
- Non-Zero intercept indicates INTERFACE EFFECTS
- Problems with current method: accounting for index makes method fail. chi(2)zzz were 1.0 and 2.1 for 10, 7
- Best to calculate chi(2) from slope of SRSHG vs. bilayers
- bl = BILAYERS Introduce thick film controversy: disbelief that films may be made greater than tens of bilayers Poly S-119 tested also, Must first consider absorption of the Second Harmonic
- These approximations lead to approximation to convert SHG-absorbing data to non-SHG-absorbing data for establishment of chi(2)
- Poly S-119 tested also, Must first consider absorption of the Second Harmonic SHG-absorbing film approaches asymptotic value, dependent on coherence length and absorption coefficient
- Fit to curve using calculated absorption allows estimation of coherence length Excel-friendly approximation uses measured quantities: A(SHG), I2w [thickness is hidden in A=l*alpha, shifts data up] May determine SRSHG SLOPE from the LINEAR REGION -- FIRST 3 POINTS SHG at 532 nm – CLEARLY absorbing, (600 relatively non-absorbing)
- Now can determine chi(2) for both wavelengths 1064 > 1200 due to Resonant enhancement
- For CHISAM: optimization of pH and NaCl, structure issues
- Competitive Orientation Random Orientation Selective polar order
- pH control allows orientational control Note the conjugation IS NOT ALONG bonding axis and conjugation is broken by benzyl group, REGARDLESS of ISOMER
- PR used to demonstrate method and find best pH conditions ABS: linear growth REGARDLESS of pH vs. pKa SHG: IGNORE 10.5 / 10 (nonrepeatable due to precipitation, possibly) pH 7, 4.5 BEST pH7 gives thickest film => best conditions
- Conjugation is broken REGARDLESS of isomer Trans configuration is planar FIRST APPROXIMATION
- Increased conjugation ~single conjugation axis FIRST APPROXIMATION
- 0.50 NaCl: best COMBINATION of thickness and chi(2)zzz A/nm = [(extinction coefficient) * concentration] / ln(10) Drop in concentration and increase in chi(2) suggests significantly improved orientation
- Rough model of surface (sinx)(cosy)
- For CHISAM: optimization of pH and NaCl, structure issues
- LEAD IN: Poly S-119 Results: stable at 150 C for 18 hours temperature-dependent reduction of SHG PROCION RED did not exhibit thermal stability PB 30 bilayers
- Similar experimental conditions PB 30 bilayers
- pH 10.5 / 10, 20 bilayers No NaCl
- Point out axis assignments Monitoring of Absorbance with Temp in attempt to understand decrease in SHG
- For CHISAM: optimization of pH and NaCl, structure issues
- PS 119 is a continuation Red circles are comparison with quartz
- For CHISAM: optimization of pH and NaCl, structure issues
- Polarized light passes through substrate – ITO electrode – film reflects off of Aluminum electrode Babinet-Soleil provides precise polarization control Modulating voltage applied to electrodes modulates the birefringence of the film causing modulating phase shift in light exiting the film causing modulating intensity due to Babinet-Soleil birefringence of material acts as wave plate causing a rotation in the polarization state, which then translates as intensity modulation due to presence of analyzer. without the birefringence change, the B-S is adjusted so that no light passes through the analyzer.