A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a ...A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a zeroth-order vortex beam,and the diffracted intensity ratio of two beams is adjustable between 0 and 1.The coherent superposition of the two diffracted beams generates a brighter Airy spot(or Poisson spot)in the middle of the spiral pattern,where the singularity for typical vortex beam is located.Experiments employing circular,triangular,and rectangular phase apertures with topological charges from 3 to 16 demonstrate a stable,compact,and flexible apparatus for vortex beam conversion.By adjusting the parameters of the phase aperture,the proposed method can realize the optical Gaussian tweezer function and the optical vortex tweezer function simultaneously along the same axis or switch the experimental setup between the two functions.It also has potential applications in light communication through turbulent air by transmitting an orbital angular momentum-coded signal with a concentric beacon laser.展开更多
To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz det...To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz detection with a single chirped pulse as the probe for THz electro-optic(EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show that this interferometer can effectively suppress the noise usually suffered in a non-common-path interferometer. The measured single-shot SNR is up to 88.85, and the measured THz waveforms are independent of the orientation of the used Zn Te EO sensor, so it is easy to operate and the results are more reliable. These features mean that the interferometer is quite qualified for applications where strong THz pulses, usually with single-shot or low repetition rate, are indispensable.展开更多
In this study,an innovative technique is introduced to significantly enhance the sensitivity of electronic speckle pattern interferometry(ESPI)for the dynamic assessment of specular(mirrorlike)object deformations.By u...In this study,an innovative technique is introduced to significantly enhance the sensitivity of electronic speckle pattern interferometry(ESPI)for the dynamic assessment of specular(mirrorlike)object deformations.By utilizing a common-path illumination strategy,wherein illumination and observation beams are precisely aligned,this method effectively doubles the optical path difference,leading to a twofold increase in measurement sensitivity.In addition,this method mitigates the effects of speckle noise on the measurement of minor deformations,expanding the applications of ESPI.Theoretical and experimental evaluations corroborate the efficacy of this approach.展开更多
We demonstrate the subsurface imaging of an articular cartilage using Fourier-domain common-path optical coherence tomography. The bare fiber probe integrated with a hypodermic needle provides the rigidness required t...We demonstrate the subsurface imaging of an articular cartilage using Fourier-domain common-path optical coherence tomography. The bare fiber probe integrated with a hypodermic needle provides the rigidness required to perform lateral scanning with less microscale bending. By submerging both the probe and the specimen into saline solution, we not only reduce the beam divergence, but also increase the signal-to-noise ratio compared with the measurement in free space. Our system can differentiate the characteristic cartilage zones and identity various micro-structured defects in an ex vivo chicken knee cartilage, thus demonstrating that it could be used to conduct early arthritis diagnosis and intraoperative endo-microscopy.展开更多
This study shows that the principle of a recently proposed connnon-path laser interferometer containing a planar grating is nonexistent and apparently caused by a mathematical derivation error. Both p- and s-polarized...This study shows that the principle of a recently proposed connnon-path laser interferometer containing a planar grating is nonexistent and apparently caused by a mathematical derivation error. Both p- and s-polarized beams ill the proposed setup experience once the ＋lst-order diffraction and once the lst-order diffraction by tile grating. As a result, the phase of each beam remains unchanged and the interference fringes formed by the two beams are not expected to move when the grating is translated in the grating vector direction. We perform an experiment to confirm this prediction. Both our analysis and experimental observation cast doubt on the experimental results of the authors who proposed the interferometer.展开更多
The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with...The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with an external contact reference. The unique design of the common-path OCT is utilized to set up an imaging system in which a chicken eye is placed adjacent to a glass plate serving as the external reference plane for the imaging system. As the force is applied to the chicken eye, it presses against the reference glass plate. The modified OCT image obtained is used to calculate the size of contact area, which is then used to derive the tensile stress on the cornea. The drop in signal levels upon contact of reference glass plate with the tissue are extremely sharp because of the sharp decline in reference power levels itself, thus providing us with an accurate measurement of contact area. The experimental results were in good agreement with the numerical predictions. The results of this study might be useful in providing new insights and ideas to improve the precision and safety of currently used ophthalmic surgical techniques. This research outlines a method which could be used to provide high resolution OCT images and a precise feedback of the forces applied to the cornea simultaneously.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.T2293753 and T2293750)the Major Science and Technology Project in Hainan Province of China(Grant No.ZDKJ2019012).
文摘A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a zeroth-order vortex beam,and the diffracted intensity ratio of two beams is adjustable between 0 and 1.The coherent superposition of the two diffracted beams generates a brighter Airy spot(or Poisson spot)in the middle of the spiral pattern,where the singularity for typical vortex beam is located.Experiments employing circular,triangular,and rectangular phase apertures with topological charges from 3 to 16 demonstrate a stable,compact,and flexible apparatus for vortex beam conversion.By adjusting the parameters of the phase aperture,the proposed method can realize the optical Gaussian tweezer function and the optical vortex tweezer function simultaneously along the same axis or switch the experimental setup between the two functions.It also has potential applications in light communication through turbulent air by transmitting an orbital angular momentum-coded signal with a concentric beacon laser.
基金National Natural Science Foundation of China(NSFC)(61490710,61775142,61705132)Science and Technology Planning Project of Guangdong Province(2016B050501005)Specialized Research Fund for the Shenzhen Strategic Emerging Industries Development(JCYJ20150324141711651,JCYJ20150525092941064,JCYJ20170412105812811)
文摘To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz detection with a single chirped pulse as the probe for THz electro-optic(EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show that this interferometer can effectively suppress the noise usually suffered in a non-common-path interferometer. The measured single-shot SNR is up to 88.85, and the measured THz waveforms are independent of the orientation of the used Zn Te EO sensor, so it is easy to operate and the results are more reliable. These features mean that the interferometer is quite qualified for applications where strong THz pulses, usually with single-shot or low repetition rate, are indispensable.
基金supported by the National Natural Science Foundation of China(Nos.52375536 and 52375535)the Key Research and Development Program of Jiangxi Province(No.20223BBE51010)。
文摘In this study,an innovative technique is introduced to significantly enhance the sensitivity of electronic speckle pattern interferometry(ESPI)for the dynamic assessment of specular(mirrorlike)object deformations.By utilizing a common-path illumination strategy,wherein illumination and observation beams are precisely aligned,this method effectively doubles the optical path difference,leading to a twofold increase in measurement sensitivity.In addition,this method mitigates the effects of speckle noise on the measurement of minor deformations,expanding the applications of ESPI.Theoretical and experimental evaluations corroborate the efficacy of this approach.
基金supported by the second stage of the Brain Korea 21 Project in 2009a Korean Science and Engineering Foundation(KOSEF) grant funded by the Korea Government(MEST)(No.R01-2008-000-20089-0).
文摘We demonstrate the subsurface imaging of an articular cartilage using Fourier-domain common-path optical coherence tomography. The bare fiber probe integrated with a hypodermic needle provides the rigidness required to perform lateral scanning with less microscale bending. By submerging both the probe and the specimen into saline solution, we not only reduce the beam divergence, but also increase the signal-to-noise ratio compared with the measurement in free space. Our system can differentiate the characteristic cartilage zones and identity various micro-structured defects in an ex vivo chicken knee cartilage, thus demonstrating that it could be used to conduct early arthritis diagnosis and intraoperative endo-microscopy.
文摘This study shows that the principle of a recently proposed connnon-path laser interferometer containing a planar grating is nonexistent and apparently caused by a mathematical derivation error. Both p- and s-polarized beams ill the proposed setup experience once the ＋lst-order diffraction and once the lst-order diffraction by tile grating. As a result, the phase of each beam remains unchanged and the interference fringes formed by the two beams are not expected to move when the grating is translated in the grating vector direction. We perform an experiment to confirm this prediction. Both our analysis and experimental observation cast doubt on the experimental results of the authors who proposed the interferometer.
文摘The objective of this study is to demonstrate that tensile stress resulting due to applied force on cornea can be accurately measured by using a time-domain common-path optical coherence tomography （OCT） system with an external contact reference. The unique design of the common-path OCT is utilized to set up an imaging system in which a chicken eye is placed adjacent to a glass plate serving as the external reference plane for the imaging system. As the force is applied to the chicken eye, it presses against the reference glass plate. The modified OCT image obtained is used to calculate the size of contact area, which is then used to derive the tensile stress on the cornea. The drop in signal levels upon contact of reference glass plate with the tissue are extremely sharp because of the sharp decline in reference power levels itself, thus providing us with an accurate measurement of contact area. The experimental results were in good agreement with the numerical predictions. The results of this study might be useful in providing new insights and ideas to improve the precision and safety of currently used ophthalmic surgical techniques. This research outlines a method which could be used to provide high resolution OCT images and a precise feedback of the forces applied to the cornea simultaneously.
