Nonlinear optical microscopy methods

Microscopy methods based on nonlinear optical phenomena that provide chemical information are a recent development. Infrared snm-frequency microscopy has been demonstrated for LB films of arachidic acid, allowing for surface-specific imaging of the lateral distribution of a selected vibrational mode, the asymmetric methyl stretch [60]. The method is sensitive to the snrface distribntion of the functional gronp as well as to lateral variations in the gronp environmental and conformation. Second-harmonic generation (SHG) microscopy has also been demonstrated for both spread monolayers and LB films of dye molecules [61,62]. The method images the molecular density and orientation field with optical resolution, and local qnantitative information can be extracted. 

In terms of beam delivery, the DLW method is based on optical microscopy, confocal microscopy [4,6,13] and laser tweezers [14] (for reviews on laser tweezers see [ 15,16]). These techniques allow for a high spatial 3D resolution of a tightly focused laser beam with optical exposure of micrometric-sized volumes via linear and nonlinear absorption. In addition, mechanical and thermal forces can be exerted upon objects as small as 10 nm molecular dipolar alignment can be controlled by polarization of light in volumes of with submicrometric cross-sections. This circumstance widens the field of applications for laser nano- and microfabrication in liquid and solid materials [17-22]. 

Fortunately, the success of surface science, optical and x-ray techniques in the last few decades has provided access for electrochemists to structural information of electrode/electrolyte interfaces. The optical and X-ray spectroscopic techniques have mainly been used in situ, i.e., in the presence of the bulk electrolyte. These techniques include EXAFS (extended x-ray absorption fine structure), SXS (surface x-ray scattering), XSff (x-ray standing wave technique, SERS (surface enhanced Raman scattering), NOM (nonlinear optical methods) IRS (infrared spectroscopy), MS (Mossbauer spectroscopy), RLS (radioactive labelling spectroscopy), STM (scanning tunneling microscopy), and... 

Micron- and submicron-scale lateral structures of optically nonlinear organic films comprised of substituted trons-stilbene derivatives (Ri = OCH3, R2 = CN) was characterized [45]. Second harmonic generation (SHG), optical microscopy, and atomic force microscopy (AFM) were used in this investigation. The third-order nonlinear optical properties and two-photon absorption ofdifferent types of stilbene derivatives (D-tt-D, A-7t-A, D-7t-A) were investigated [46]. Using the INDO/CI method, the UV-vis spectra were explored and the position and strength of the two-photon absorption were predicted by sum-over-states expression. Relationships of the structures, spectra, and nonlinear optical properties have been examined. Two-photon absorption spectra (650-1000 nm) of a series of asymmetrically substituted stilbenoid chromophores... 

In this chapter we describe advances in the femtosecond time-resolved multiphoton photoemission spectroscopy (TR-MPP) as a method for probing electronic structure and ultrafast interfacial charge transfer dynamics of adsorbate-covered solid surfaces. The focus is on surface science-based approaches that combine ultrafast optical pump probe excitation to induce nonlinear multi-photon photoemission (MPP) from clean or adsorbate covered single crystal surfaces. The photoemitted electrons transmit spectroscopic and dynamical information, which is captured by their energy analysis in real or reciprocal space. We examine how photoelectron spectroscopy and microscopy yield information on the unoccupied molecular structure, electron transfer and relaxation processes, light induced chemical and physical transformations and the evolution of coherent single particle and collective excitations at solid surfaces. 

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