Wigner analysis of three dimensional pupil with finite lateral aperture

Volume holographic optical element for light sheet fluorescence microscopy

Three-dimensional (3D) imaging of living organisms requires fine optical sectioning and high-speed image acquisition, which can be achieved by light sheet fluorescence microscopy (LSFM). However, orthogonal illumination and detection arms in the LSFM system make it bulky. Here, we propose and demonstrate the application of a volume holographic optical element (photopolymer-based volume holographic grating) for designing a compact LSFM system, called a volume holographic LSFM (VHLSFM). Using the VHLSFM, we performed in vivo imaging of Caenorhabditis elegans (C. elegans) and observed high-contrast optically sectioned fluorescence images of the oocytes and embryonic development in real time for 3D imaging.

Volume holographic spatial-spectral imaging systems [Invited]

In this paper, we present an overview of the recent developments in applications of volume holographic imaging techniques in microscopy. In these techniques, three-dimensional imaging incorporates multiplexed volume holographic gratings, which are formed in phenanthrenequinone poly(methyl methacrylate) (PQ-PMMA) photopolymer and act as spatial-spectral filters, to obtain multiplane images from a volumetric object without scanning. We introduce recent major roles of volume holography in different imaging modalities, including large-capacity spatial-spectral multiplane microscopy, digital holographic microscopy, and structured Talbot (or speckle) illumination fluorescence imaging. Among various imaging applications of volume holography, simultaneous multiplane fluorescence microscopy for collecting spatial-spectral information is distinct and has great potential for hyperspectral imaging. Depth selective spatial-spectral information from an object is particularly useful for designing a high-resolution microscope in real-time operation. We further discuss volume holography in particle trapping and beam shaping. In addition, we investigate future prospects of volume holography in microscopy as well as endoscopy.

Spatial mode multiplexing using volume holographic gratings

We experimentally demonstrate spatial mode multiplexing of optical beams using multiplexed volume holographic gratings (MVGHs) formed in phenanthrenquinone-poly (methyl methacrylate) (PQ-PMMA) photopolymer. Multiple spatial modes of Laguerre-Gaussian (LG) beams are recorded at the same pupil area of a volume hologram resulting in MVHGs, for simultaneous reconstruction of spatial modes. In addition, a helical phase beam, a non-diffracting beam with conical phase profile, and a parabolic non-diffracting beam with cubic phase profile have also been simultaneously recorded and reconstructed from MVHGs. Utilizing Bragg wavelength degeneracy property of volume hologram these multiplexed modes are reconstructed at multiple wavelengths ranging from blue (450nm) to red (635). Due to combined effect of three-dimensional pupil, Bragg wavelength degeneracy, angular selectivity, together with spatial mode properties these, MVHGs can act as spatial mode filter with spectral filtering property. Advantages of volume holography in beam shaping are discussed. Multiple first diffraction orders with desired beam shapes obtained from the single optical element (i.e. a volume hologram with MVHGs) may find important applications in optical communication experiments, and in volume holographic imaging and microscopy. Experimental results show solid evidence that MVGHs in beam shaping provide a simple, compact, single element, and direct way to multiplex spatial modes.

Reduction of blurring in broadband volume holographic imaging using a deconvolution method

Volume holographic imaging (VHI) is a promising biomedical imaging tool that can simultaneously provide multi-depth or multispectral information. When a VHI system is probed with a broadband source, the intensity spreads in the horizontal direction, causing degradation of the image contrast. We theoretically analyzed the reason of the horizontal intensity spread, and the analysis was validated by the simulation and experimental results of the broadband impulse response of the VHI system. We proposed a deconvolution method to reduce the horizontal intensity spread and increase the image contrast. Imaging experiments with three different objects, including bright field illuminated USAF test target and lung tissue specimen and fluorescent beads, were carried out to test the performance of the proposed method. The results demonstrated that the proposed method can significantly improve the horizontal contrast of the image acquire by broadband VHI system.