Z-type Langmuir–Blodgett film structures: surface plasmon resonance, second harmonic generation and fibre optic devices

Abstract

Second harmonic generation (SHG) from Langmuir-Blodgett (LB) films of the iodide (I) and octadecylsulfate (11) salts of E-Noctadecyl-4-[ 2-(4-dibutylaminophenyl)ethenyl] quinolinium and from films of a related pyridinium dye (111) increases with the number of layers. The LB film structures are non-centrosymmetric (Z-type) and have high second-order susceptibilities, x(')zzz, of 120 pm V-' for dye 1(20 layers), 80 pm V-' for dye I1 (100 layers) and 30 pm V-' for dye I11 (160 layers) at Am= 1.064 pm. The values are resonantly enhanced but for dye I11 the absorbance is very weak at the harmonic wavelength. The real and imaginary parts of the dielectric permittivity of dye I, derived from the surface plasmon resonance (SPR), are 3.14 f 0.06 and 0.66 f 0.03, respectively, at 532 nm and, with the exception of the monolayer, the thickness is 3.0 f 0.3 nm layer-'. Waveguiding overlays of dye I, evanescently coupled to side-polished optical fibres, have resulted in useful in-line wavelength-selective elements. The LB technique allows the necessary control of film thickness for such devices.Langmuir-Blodgett (LB) films have been extensively studied for second harmonic generation (SHG) in thr~ugh-planel-~ and guided-wave configuration^.'-^ Pitt and Walpita' first Paper 5/05257B;

Quantitative measurement and interpretation of optical second harmonic generation from molecular interfaces

“…[8][9][10][11][12][13][14][15][16][17] SSHG has also become one of the most important tools for liquid and material surface characterizations. [15][16][17][18][19][20][21][22][23][24][25][26][27] SSHG has also been used to probe molecular electronic spectroscopy of molecular interfaces. 3,[28][29][30][31] There have been a number of books or book chapters, 32,33 and review articles [9][10][11][12][13][14][15][16][17] on the fundamental theory and different aspects of the applications for surface studies with SSHG over the past twenty years.…”

“…50 This is simply because, unlike in SFG-VS, 8 most SHG measurements are not right on the electronic resonance, and that there is no simple way to separate the contributions to the measured SHG signal from the symmetric and asymmetric polarizability tensor elements in the analysis. In the SHG literatures, simplification of the molecular polarizability tensor elements with uniaxial or rodlike assumption was generally used, [21][22][23][24][25] except for a few cases. 16,43,[51][52][53] Nevertheless, a systematic and unified treatment of the molecular tensor elements can be very helpful in understanding and application of the SHG for surface and thin film studies.…”

Natural Formation of Nanostructures: From Fundamentals in Metal Heteroepitaxy to Applications in Optics and Biomaterials Science

“…If surface and interface effects are negligible, and the degree of ordering within the film remains constant with the film thickness, the SHG intensity detected for Θ = 0 and ϕ = 0 related to the largest nonlinear optical coefficient d 333 should increase quadratically with film thickness. [195][196][197] This dependence is proven for films of the selected molecules on glass substrates in Fig. 54.…”

Structural and optical properties of Langmuir—Blodgett films of a Schiff base coordination polymer: A material for hydrocarbon vapor sensing

“…Another possibility is that the molecules of MBSH/TA are oriented so that one of the hydrophobic groups is adjacent to the subphase. This model has been suggested previously for second harmonic generation in LB films [11,12]. In both cases the structure, as deposited, would have a layer thickness of ca.…”