Imaging with third harmonic generation (THG) provides a powerful label-free approach to probing biological systems, particularly looking at structures formed by lipids. We present the first demonstration of THG widefield holographic microscopy. Holographic microscopy preserves the amplitude and phase of the measured field, which enables us to construct a synthetic spatial aperture with expanded field of view for complex valued THG images. Additionally, we implement a matrix approach postprocessing algorithm to reconstruct aberration-free THG holographic images by estimating and correcting for phase aberrations and scattering distortions.
Non-invasive imaging with high resolution deep within biological materials without the use of harmful ionizing radiation is of great interest in the field of medical imaging. Second harmonic generation is an excellent mechanism to circumvent this issue by providing outstanding contrast and optical sectioning. In general, these signals are weak and prone to scattering which introduce great challenges when imaging deep within turbid media. We will discuss recently demonstrated Epi-SHG holography, which can detect very weak backscattered SHG signals and enables the application of recently developed techniques which utilize the phase information to allow diffraction limited imaging within deep tissue.
In recent years, new super resolution imaging methods based on the anti-bunching properties of photons emitted by single quantum emitters have emerged. Thus far, these methods have been extremely limited in speed as they rely on very low repetition lasers to match the speed of cameras or use high-speed photon counting at individual points scanned across the surface of the object. Here, we study the use of spatio-temporally modulated illumination light to acquire photon counts from an extended region of the object. Thus, we combine high speed photon detection with extended illumination to enhance the imaging speed of anti-bunching super resolution microscopy.
Imaging of the interior of object with light has long been a challenge for optical imaging. Optical diffraction tomography (ODT) is able to obtain three-dimensional (3D) object information through object rotation. We will discuss harmonic optical tomography (HOT) that exploits a defocused illumination beam for nonlinear optical tomography. We will also discuss our demonstration of coherent ODT with incoherent light emission in a new optical tomography technique called fluorescent diffraction tomography (FDT) and the use of spatial frequency imaging for high speed nonlinear optical microscopy.
Plasma-based soft x-ray lasers (SXRL) enable experiments requiring bright, high energy, soft x-ray laser pulses to be conducted in compact facilities. Recent advances in high energy, high repetition rate, ultrashort pulse solid state lasers now make it possible to extend their wavelenght range, increase their repetition rates, and improve their efficiency. Recently we extended the operation of gain-saturated compact repetitive x-ray lasers down to λ=6.85 nm in Ni-like Gd [1]. Isoelectronic scaling of these collisionally excited laser transitions produced strong lasing at 6.67 nm and 6.11 nm in Ni-like Tb and amplification at 6.41 nm and 5.85 nm in Ni-like Dy [1]. This recent progress will be summarized, and efforts to further extend laser operation to shorter wavelengths will be reviewed. We will also discuss the possibility of increasing the efficiency of plasma-based soft x-ray lasers by controlling the pulse shape of the pump pulses. Prospects of these SXRL will be discussed.
Work supported by the US Department of Energy Basic Energy Sciences and by the National Science Foundation
[1] A. Rockwood, Y. Wang, S. Wang, M. Berrill, V.N. Shlyaptsev, and J.J. Rocca, "Compact gain-saturated x-ray lasers down to 6.85 nm and amplification down to 5.85 nm". Optica. 5, 257, (2018).
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