In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. F...In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. Firstly, the model of the GRIN fibre probe is presented, which is consisted of a single mode fibre （SMF）, a no-core fibre （NCF）, a GRIN fibre lens and an air path. Then, the software GLAD is adopted to numerically investigate how the lengths of the NCF and the GRIN fibre lens influence the performance of the Gaussian beam focusing through the GRIN fibre probe. The simulation results are well consistent with the experimental ones, showing that the GLAD based numerical simulation technique is an intuitive and effective tool for the verification of the properties of the light propagation. In this paper, we find that on the conditions of a constant GRIN fibre lens length of 0.1 mm and an NCF length of 0.36 mm, the working distance of the probe will be 0.75 mm and the focus spot size is 32 μm.展开更多
Photon spheres play a pivotal role in the imaging of luminous objects near black holes.In this paper,we examine observational appearances of a star freely falling in hairy black holes,which can possess one or two phot...Photon spheres play a pivotal role in the imaging of luminous objects near black holes.In this paper,we examine observational appearances of a star freely falling in hairy black holes,which can possess one or two photon spheres outside the event horizon.When there exists a single photon sphere,the total luminosity measured by distant observers decreases exponentially with time at late times.Due to successive arrivals of photons orbiting around the photon sphere different times,a specific observer would see a series of light flashes with decreasing intensity,which share a similar frequency content.Whereas in the case with two photon spheres,photons temporarily trapped between the photon spheres can cause a peak of the total luminosity,which is followed by a slow exponential decay,at late times.In addition,these photons lead to one more series of light flashes seen by the specific observer.展开更多
Fabrication method and device of ultra-small gradient-index （GRIN） fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography （OCT） imaging. The beam- ...Fabrication method and device of ultra-small gradient-index （GRIN） fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography （OCT） imaging. The beam- expanding effect of no-core fiber （NCF） and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber （SMF）, NCF and GRIN fiber lens. A stereo micro- scope based system was developed to fabricate the GRIN fiber probe. A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively. A con- focal microscopy was used to measure the dimensions of probe components. The results show that the sizes of probe components developed are at the level of millimeter. Therefore, the proposed experimental system meets the fabrication requirements of an ultra-small self-focusing GRIN fiber probe. This shows that this fabrication device and method can be employed in the fabrication of ultra- small self-focusing GRIN fiber probe and applied in the study of miniaturized optical probes and OCT systems.展开更多
A new device used to detect the low contrast target acquisition of photoelectric theodolite is designed and its reliability is experimentally demonstrated.The adjustable contrast optical target device,which can simula...A new device used to detect the low contrast target acquisition of photoelectric theodolite is designed and its reliability is experimentally demonstrated.The adjustable contrast optical target device,which can simulate the sky background luminance and a low contrast target,is established.It utilizes a big integrating sphere and a small one to simulate the luminance of the background and target respectively.Importantly,by controlling the luminous flux of the two integrating spheres,the targets and background radiance can be continuously adjustable under the condition of constant color temperature.Thus,the contrast can be controlled continuously in the range of 0%-90% and its stability is better than 1%.The biggest background luminance exceeds 60 W m-2str-1 in the spectral range of 400-800 nm.展开更多
基金supported by the International Cooperation Project of Shanghai Science and Technology Committee,China(Grant No.09530708700)
文摘In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. Firstly, the model of the GRIN fibre probe is presented, which is consisted of a single mode fibre （SMF）, a no-core fibre （NCF）, a GRIN fibre lens and an air path. Then, the software GLAD is adopted to numerically investigate how the lengths of the NCF and the GRIN fibre lens influence the performance of the Gaussian beam focusing through the GRIN fibre probe. The simulation results are well consistent with the experimental ones, showing that the GLAD based numerical simulation technique is an intuitive and effective tool for the verification of the properties of the light propagation. In this paper, we find that on the conditions of a constant GRIN fibre lens length of 0.1 mm and an NCF length of 0.36 mm, the working distance of the probe will be 0.75 mm and the focus spot size is 32 μm.
基金supported by the National Natural Science Foundation of China(Grant Nos.12105191,11947225,and 11875196)supported by the International Visiting Program for Excellent Young Scholars of Sichuan University。
文摘Photon spheres play a pivotal role in the imaging of luminous objects near black holes.In this paper,we examine observational appearances of a star freely falling in hairy black holes,which can possess one or two photon spheres outside the event horizon.When there exists a single photon sphere,the total luminosity measured by distant observers decreases exponentially with time at late times.Due to successive arrivals of photons orbiting around the photon sphere different times,a specific observer would see a series of light flashes with decreasing intensity,which share a similar frequency content.Whereas in the case with two photon spheres,photons temporarily trapped between the photon spheres can cause a peak of the total luminosity,which is followed by a slow exponential decay,at late times.In addition,these photons lead to one more series of light flashes seen by the specific observer.
基金supported by the National Natural Science Foundation of China(Grant No.41104065)the Dawn Planning Foundation of Shanghai Municipal Education Commission (Grant No.12CG047)by the Scientific Research Innovation Project of Shanghai Municipal Education Commission(Grant No. 13YZ022)
文摘Fabrication method and device of ultra-small gradient-index （GRIN） fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography （OCT） imaging. The beam- expanding effect of no-core fiber （NCF） and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber （SMF）, NCF and GRIN fiber lens. A stereo micro- scope based system was developed to fabricate the GRIN fiber probe. A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively. A con- focal microscopy was used to measure the dimensions of probe components. The results show that the sizes of probe components developed are at the level of millimeter. Therefore, the proposed experimental system meets the fabrication requirements of an ultra-small self-focusing GRIN fiber probe. This shows that this fabrication device and method can be employed in the fabrication of ultra- small self-focusing GRIN fiber probe and applied in the study of miniaturized optical probes and OCT systems.
基金supported by the Innovation Fund of Chinese Academy of Sciences (Grant No. YZ200904)
文摘A new device used to detect the low contrast target acquisition of photoelectric theodolite is designed and its reliability is experimentally demonstrated.The adjustable contrast optical target device,which can simulate the sky background luminance and a low contrast target,is established.It utilizes a big integrating sphere and a small one to simulate the luminance of the background and target respectively.Importantly,by controlling the luminous flux of the two integrating spheres,the targets and background radiance can be continuously adjustable under the condition of constant color temperature.Thus,the contrast can be controlled continuously in the range of 0%-90% and its stability is better than 1%.The biggest background luminance exceeds 60 W m-2str-1 in the spectral range of 400-800 nm.
