We propose and experimentally demonstrate a technique, based on polarization modulation, for imaging of the polarization discriminating object hidden behind a scattering medium. This is realized by making use of the relation between the complex correlation function of the randomly scattered orthogonal polarization components in the far field and polarized source structure at the scattering plane. Full use of a polarimetric parameter at the scattering plane is realized in the object plane reconstruction behind the scattering medium using a backpropagation approach. To demonstrate application of the technique, imaging of two different objects lying behind the scattering media is presented.

Two-photon microscopy (TPM) offers deeper imaging depth inside the scattering medium, however, it suffers from limited resolution owing to the longer excitation wavelength. We demonstrate the use of a hollow Gaussian beam (HGB) at the therapeutic window to improve the resolution and signal-to-background ratio (SBR). The HGB was produced by omitting the azimuthal phase term from the vortex mode, and the excitation point spread function (PSF) can be readily tuned by the mode order. The performance of the TPM with HGB was evaluated by experimentally imaging 100 nm fluorescent beads to estimate the PSF. The HGB improved the lateral resolution of the TPM by 36% in contrast to the conventional TPM. The HGB also furnishes an improvement of SBR by eliminating the out-of-focus light owing to its ring shape. Furthermore, we have used a translating lens-based module for additional lateral resolution tuning and reduced the resolution further down to 44% with respect to conventional TPM. Finally, we have performed imaging with merely two-dimensional scanning of a 50 µm thick mouse brain slice (Thy-YFP H-line) using the developed TPM with HGB. Our compact, robust, and low-cost design of the HGB generation scheme can easily be integrated into the commercial TPM to accommodate the improvements.

We propose an experimental technique for two dimensional Jones matrix imaging of transparent and anisotropic sample using polarization interferometer. Employing this technique, the Jones matrix components are measured for polarizer and quarter wave plate and results are compared with theoretical results of the samples.

Phase sensitive two-photon microscopy is demonstrated using transport-of-intensity equation-based phase retrieval algorithm. Amplitude and phase information of the complex field of two-photon microscopy signal has been retrieved for fluorescence bead and presented.

We demonstrate two-photon microscopy based on hollow Gaussian beam illumination by leveraging an axially elongated central lobe, along with reduced central lobe width for increased mode order of the focused hollow Gaussian beam.