Three-Dimensional Profiling of Refractive Index Distribution inside Transparent Materials by Use of Nonresonant Four-Wave Mixing Microscopy

Abstract

We propose that four-wave mixing (FWM) microscopy can be applied to three-dimensional mapping of refractive index (RI) structure inside transparent samples. We derive an analytical relationship between the RI and the intensity of the FWM signal that is due to nonresonant optical nonlinearity. By using the relationship, the RI profile can be directly and quantitatively obtained from the intensity distribution of the FWM signal. We experimentally demonstrate the RI profiling of a phase grating fabricated in a non-alkali glass.

Four-wave mixing microscopy of nanostructures

“…The spatially varying nonlinear susceptibility is the source of the vibrationally nonresonant contrast in biological CARS imaging. While often an undesirable signal contribution in vibrational imaging studies, this nonresonant component is nonetheless a material characteristic and can be used to generate images based on contrast derived from the electronic polarizability [93]. This nonresonant FWM imaging approach has been used to obtain structural and morphological information of biological samples [94].…”

Background-free deep imaging by spatial overlap modulation nonlinear optical microscopy

“…A series of nonlinear optical techniques, such as two-photon excitation fluorescence (TPEF) [ 1 – 3 ], second-harmonic generation (SHG) [ 4 , 5 ], third-harmonic generation (THG) [ 6 , 7 ], coherent anti-Stokes Raman scattering (CARS) [ 8 , 9 ], stimulated parametric emission (SPE) [ 10 ], nonresonant four-wave mixing (NFWM) [ 11 ], two-photon absorption (TPA) [ 12 ] and stimulated Raman scattering (SRS) [ 13 – 15 ], has been developed in the field of high spatial resolution microscopy, opening up a wide range of applications in physics, chemistry, and biology. Nonlinear optical microscopy (NLOM) offers several advantages over linear optical microscopy.…”

“…SHG microscopy [ 4 , 5 ] has been used to image oriented and organized structures. THG [ 6 , 7 ] and NFWM [ 11 ] microscopies can produce images based on refractive index variations. CARS [ 8 , 9 ] and SRS [ 13 – 15 ] microscopies, which employ two-color fields, provide image contrast derived from vibrations of the chemical components or the thermodynamic state of the sample.…”

Implementation of spatial overlap modulation nonlinear optical microscopy using an electro-optic deflector

“…Nonlinear optical microscopy based on a variety of nonlinear optical techniques, such as twophoton excitation fluorescence (TPEF) [1][2][3], second-harmonic generation (SHG) [4], thirdharmonic generation [5,6], four-wave mixing [7][8][9][10], two-photon absorption (TPA) [11,12], stimulated Raman scattering (SRS) [13][14][15] and cross-phase modulation [16,17], has been developed for applications in physics, chemistry, and biology. Nonlinear optical microscopy offers several advantages over linear optical microscopy, which include three-dimensional resolution without a confocal pinhole, high penetration depth with near-infrared light excitation, less out-of-focus photon-induced damage and photobleaching.…”