INTRODUCTION In recent years optical second-harmonic generation (SHG) has developed into a useful probe of adsorbate molecules on surfaces.", 2 It has been applied to a wide variety of adsorbate-covered surfaces, ranging from single crystals under ultrahigh vacuum conditions3'4 to liquids and amorphous solids under ambient conditions.5-1" From these experiments it is possible to deduce concentr...

Second-harmonic-generation (SHG) microscopy is an interesting new tool for observing dermal collagen fiber in skin. However, conventional SHG microscopy using a mode-locked Ti:sapphire laser suffers from low penetration depth and a slow image acquisition rate caused by scattering and absorption in tissue, making it difficult to use for in vivo applications on human skin. We develop an SHG micro...

We present experimental demonstration and analysis of enhanced surface second harmonic generation (SHG) from hexagonal arrays of silicon pillars. Three sets of Si pillar samples with truncated cone-shaped pillar arrays having periods of 500, 1000, and 2000 nm, and corresponding average diameters of 200, 585 and 1550 nm, respectively, are fabricated by colloidal lithography and plasma dry etchin...

A spectroscopy system is developed for studying the two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) of epithelial tissue in backscattering geometry. Our findings show that TPEF signals from epithelial and underlying stromal layers exhibit different spectral characteristics, providing information on the biomorphology and biochemistry of tissue. The SHG signal serves a...

We demonstrate the ability of single-subwavelength-size nanoapertures fabricated in a gold metal thin film to enhance second-harmonic generation (SHG) as compared to a bare metal film. Nonlinear microscopy imaging with polarization resolution is used to quantify the SHG enhancement in circular and triangular nanoaperture shapes. The dependence of the measured SHG enhancement on circular apertur...

We describe a novel second harmonic generation (SHG) microscope that employs heterodyne detection by interfering the epi directed SHG from a sample with SHG from a reference crystal. In addition, the microscope provides complementary reflectance information based on optical coherence microscopy (OCM). The instrument features dual balanced detection to minimize the effect of source fluctuations,...

Second-harmonic generation (SHG) is a direct measure of the strength second-order nonlinear optical effects, which also include frequency mixing and parametric oscillations. Natural artificial materials with broken center-of-inversion symmetry in their unit cell display high SHG efficiency, however, silicon-foundry compatible group IV semiconductors (Si, Ge) are centrosymmetric, thereby prevent...

Microtubule (MT) ensemble polarity is a diagnostic determinant of the structure and function of neuronal processes. Here, polarized MT structures are selectively imaged with second-harmonic generation (SHG) microscopy in native brain tissue. This SHG is found to colocalize with axons in both brain slices and cultured neurons. Because SHG arises only from noninversion symmetric structures, the u...

Second Harmonic Generation (SHG) has been used in combination with a near-field scanning optical microscope (NSOM) to image biological samples for the first time. Near-field SHG images of azure B stained mouse natural killer (NK) cells were recorded at four different wavelengths using a tunable near-infrared femtosecond laser. The surface specificity of SHG allows membrane structures to be sele...

We report a direct observation on the laterally emitted surface second harmonic generation (SHG) in a single ZnTe nanowire. The highly directional surface SHG radiates vertically to the nanowire growth-axis with a high conversion efficiency of 5 × 10(-6) and a low divergence angle of 4°. Polarization state, emission intensity, and direction of the surface SHG are found to be dependent on the po...