Digital holographic microscopy investigation of second harmonic generated at a glass/air interface

Abstract

Optical second-harmonic generation, thanks to its coherent nature, is a suitable signal for interferometric measurements such as digital holography, a well-established imaging technique that allows recovery of complex diffraction wave fields from which it is possible to extract both amplitude-contrast and quantitative phase images. Here, we report on a multifunctional form of microscopy, namely, second-harmonic generation digital holographic microscopy. As a proof of concept, we have investigated the second-harmonic signal generated at the glass/air interface of a microscope slide under focused femtosecond laser illumination, and we propose, for the first time to our knowledge, a representation and interpretation of the recovered phase. In this simple yet educative case study, we observe that the second harmonic is generated by the axial component of the incident field polarization.

Principles and techniques of digital holographic microscopy

“…In Ref. 196, the second-harmonic generation at the glass-air surface was studied by setting up an interference between the second harmonic of the reference wave and the SHG signal from the interface using focused femtosecond laser illumination. Imaging through a nonlinear medium was demonstrated in Ref.…”

Multimodal label-free microscopy

“…96 Due to the coherent nature of the detection of imaging modes such as QPM and OCT, several applications have been reported to combine coherent processes such as SHG and interferometric approaches. Combined SHG-QPM was¯rst reported for nanocrystals, 97 before being applied to polarization-resolved measurements, 98,99 and biological specimens.…”

Quantitative phase imaging of live cells with near on-axis digital holographic microscopy using constrained optimization approach

“…These QPI techniques have been explored in different biological applications. [9][10][11][12] Ikeda et al developed the Hilbert phase microscopy and demonstrated its application in studying the morphology of red blood cells (RBCs), quantifying the RBC volume, observing the thermal fluctuations in RBCs, and imaging tissue slices of mouse brain, spleen, and liver. 4,13,14 DHM has been demonstrated in various applications such as quantifying the thickness of living neuron cells, 15 imaging the remodeling of synaptic network in neurons, 11 sperm imaging, 16,17 and so on.…”