Since the invention of Zernike phase contrast method in 1930,it has been widely used in optical microscopy and more recently in X-ray microscopy.Considering the image contrast is a mixture of absorption and phase info...Since the invention of Zernike phase contrast method in 1930,it has been widely used in optical microscopy and more recently in X-ray microscopy.Considering the image contrast is a mixture of absorption and phase information,we recently have proposed and demonstrated a method for quantitative phase retrieval in Zernike phase contrast X-ray microscopy.In this contribution,we analyze the performance of this method at different photon energies.Intensity images of PMMA samples are simulated at 2.5 keV and 6.2 keV,respectively,and phase retrieval is performed using the proposed method.The results demonstrate that the proposed phase retrieval method is applicable over a wide energy range.For weakly absorbing features,the optimal photon energy is 2.5 keV,from the point of view of image contrast and accuracy of phase retrieval.On the other hand,in the case of strong absorption objects,a higher photon energy is preferred to reduce the error of phase retrieval.These results can be used as guidelines to perform quantitative phase retrieval in Zernike phase contrast X-ray microscopy with the proposed method.展开更多
It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incohe...It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incoherence in nonlinear interactions.In this work,we study the synthesis of optical spatial coherence in second harmonic generation using quadratic nonlinear photonic crystals.We demonstrate a method where the second harmonic coherence is customized by employing quantitative phase retrieval and a complex square-root filter sequentially on fundamental frequency speckles.As a proof-of-concept,we experimentally show incoherent imaging of a smiley face transitioning from infrared to visible light.Moreover,we apply this method to produce two representative types of structured light beams in second harmonic generation:incoherent vortex and Airy beams.During the nonlinear synthesis of incoherent vortex beams,we have,for the first time,experimentally verified the conservation of orbital angular momentum in the nonlinear frequency conversion process of a low-coherence source.Furthermore,the generated second-harmonic incoherent Airy beam preserves the self-acceleration characteristics of its fundamental frequency counterpart,remaining unaffected by reductions in coherence.Our results not only deepen the fundamental understanding of optical coherence but also unlock exciting possibilities for applications in infrared imaging and fluorescence microscopy where optical nonlinear interactions play an important role.展开更多
基金Supported by the State Key Project for Fundamental Research(2012CB825801)National Natural Science Foundation of China(11475170,11205157 and 11179004)Anhui Provincial Natural Science Foundation(1508085MA20)
文摘Since the invention of Zernike phase contrast method in 1930,it has been widely used in optical microscopy and more recently in X-ray microscopy.Considering the image contrast is a mixture of absorption and phase information,we recently have proposed and demonstrated a method for quantitative phase retrieval in Zernike phase contrast X-ray microscopy.In this contribution,we analyze the performance of this method at different photon energies.Intensity images of PMMA samples are simulated at 2.5 keV and 6.2 keV,respectively,and phase retrieval is performed using the proposed method.The results demonstrate that the proposed phase retrieval method is applicable over a wide energy range.For weakly absorbing features,the optimal photon energy is 2.5 keV,from the point of view of image contrast and accuracy of phase retrieval.On the other hand,in the case of strong absorption objects,a higher photon energy is preferred to reduce the error of phase retrieval.These results can be used as guidelines to perform quantitative phase retrieval in Zernike phase contrast X-ray microscopy with the proposed method.
基金support provided by Israel Science Foundation,grants 969/22 and 3117/23.
文摘It is commonly assumed that nonlinear frequency conversion requires lasers with high coherence;however,this assumption has constrained our broader understanding of coherence and overlooked the potential role of incoherence in nonlinear interactions.In this work,we study the synthesis of optical spatial coherence in second harmonic generation using quadratic nonlinear photonic crystals.We demonstrate a method where the second harmonic coherence is customized by employing quantitative phase retrieval and a complex square-root filter sequentially on fundamental frequency speckles.As a proof-of-concept,we experimentally show incoherent imaging of a smiley face transitioning from infrared to visible light.Moreover,we apply this method to produce two representative types of structured light beams in second harmonic generation:incoherent vortex and Airy beams.During the nonlinear synthesis of incoherent vortex beams,we have,for the first time,experimentally verified the conservation of orbital angular momentum in the nonlinear frequency conversion process of a low-coherence source.Furthermore,the generated second-harmonic incoherent Airy beam preserves the self-acceleration characteristics of its fundamental frequency counterpart,remaining unaffected by reductions in coherence.Our results not only deepen the fundamental understanding of optical coherence but also unlock exciting possibilities for applications in infrared imaging and fluorescence microscopy where optical nonlinear interactions play an important role.
