- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Geometric representation of polarization for a general three-dimensional optical field
摘要： On the basis of previous work in this area, we propose a new geometric representation of polarization for a general three-dimensional (3D) optical field. This representation is based on the characteristic and eigenvalue decompositions of the 3 × 3 coherency matrix, which is appropriate for all 3D polarized optical fields, including totally polarized, partially polarized and totally un-polarized optical fields. Based on this representation method, the degree of polarization (DoP) for an arbitrary 3D optical field can be characterized by a unique point located on a spatial equilateral triangle. Correspondingly, the 3D state of polarization (SoP) can be illustrated by the 3D distribution maps of polarization ellipse quantitatively.
关键词： Coherence,Polarimetry,Polarization
更新于2025-09-04 15:30:14
-
Detuning-induced stimulated Raman adiabatic passage in two-level systems with permanent dipole moments
摘要： The detuning-induced stimulated Raman adiabatic passage (D-STIRAP) in two-level systems with permanent dipole moments (PDMs) is investigated. Based on a transformed Schr?dinger equation, we discuss the coherence generation under the one- and two-photon excitations, respectively. In the one-photon excitation, our analysis shows that the envelope of the pump pulse gets modulated in presence of the PDMs. The modulation becomes stronger while the difference between the PDMs of the two levels becomes larger. Gradually, the adiabatic process of the D-STIRAP fails to complete and the robustness of the technique disappears. Therefore, parameters have to be chosen with care if maximum coherence is desired in systems with large or giant difference between the PDMs. Similar results can also be found in the two-photon excitation, although the influence of the PDMs on the D-STIRAP seems weaker compared with that in the one-photon excitation case. Finally, we point out that the negative role of the PDMs can be effectively avoided by simply choosing longer pulses instead and the D-STIRAP can be safely applied in two-level systems with PDMs.
关键词： D-STIRAP,one-photon excitation,two-level systems,coherence generation,two-photon excitation,permanent dipole moments
更新于2025-09-04 15:30:14
-
Estimation of refractive index for biological tissue using micro-optical coherence tomography
摘要： The refractive index of biological tissue is required for investigating the tissue’s optical properties. Efforts have been made to characterize refractive indices of biological tissues at a single wavelength, but it is more convenient to know the Cauchy’s coefficients, which provide refractive index over a wide range of wavelengths. We demonstrate a method to noninvasively provide the Cauchy’s dispersion coefficients of biological tissues using micro-optical coherence tomography. Using short-frequency Fourier transforms, the relative optical thickness of the sample in the wavelength range of the broadband source was obtained from interferograms. The coefficients of Cauchy’s equation were estimated based on the wavelength-dependent sample thickness. We validated the proposed method using distilled water and fresh rat cornea ex vivo, and the experimental results were consistent with the reference data.
关键词： Cauchy’s formula,Refractive index,Optical coherence tomography,Cauchy’s dispersion coefficients
更新于2025-09-04 15:30:14
-
Impact of image averaging on wide-field choroidal thickness measurements using enhanced-depth imaging optical coherence tomography
摘要： Background: The aim of this study was to examine the influence of B-scan averaging on choroidal thickness using wide-field enhanced-depth imaging optical coherence tomography. Methods: Six high-resolution trans-foveal horizontal enhanced-depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B-scans, using the automated real-time image averaging and follow-up features of a Spectralis device. The impact of B-scan averaging on regional measures of wide-field choroidal thickness (across macular and peripheral regions) and their accuracy was investigated, assuming that averaging 100 B-scans would provide the most accurate estimate of choroidal thickness. Results: Regional estimates of wide-field choroidal thickness did not vary across the different B-scan averaging conditions (all p > 0.05). The mean choroidal thickness averaged across the full wide-field area exhibited the closest agreement to measures obtained with 100 averaged B-scans, when frame averaging exceeded 30 B-scans (95 per cent limits of agreement +10 to ?7, +7 to ?7 and +6 to ?3 μm for 30, 40 and 50 averaged B-scans, respectively), compared to 10 and 20 averaged B-scans (95 per cent limits of agreement +13 to ?8 and +13 to ?6 μm, respectively; p < 0.01 and p < 0.02 compared to the accuracy of 50 averaged B-scans). Conclusion: Averaging 30 B-scans for an individual enhanced-depth imaging optical coherence tomography line scan provided accurate measures of choroidal thickness across a wide-field (60°) area in young healthy eyes. This information can assist in designing the volumetric scan protocols required for detailed examination of the macular and peripheral choroid.
关键词： wide-field imaging,choroidal thickness,optical coherence tomography,enhanced-depth imaging,B-scan averaging
更新于2025-09-04 15:30:14
-
Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology
摘要： The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections. In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU pro?les were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE and choroid. Fundus pigmentation maps were extracted from histologic serial sections. Pigmentation pro?les were correlated to DOPU pro?les of the same eyes. Strong depolarization was found in the RPE/choroid complex of pigmented rats, whereas the same structures exhibited uniform polarization in albino rats. The difference between the depolarization characteristics between albino and pigmented animals was statistically signi?cant. In the fundus pigmentation maps, optical pigment density was zero in albino rat eyes. In pigmented rat eyes, a strong negative correlation between optical pigment density and DOPU was observed. This in vivo and ex vivo investigation of posterior rat eyes indicates that melanin is the cause of depolarization in retinal PS-OCT images. It further demonstrates that melanin pigmentation in the RPE and choroid can be quanti?ed via depolarization imaging and therefore suggests that PS-OCT is a useful tool for the noninvasive quantitative assessment of pigmentary changes in vision-threatening diseases such as age-related macular degeneration.
关键词： choroid,melanin,optical coherence tomography,depolarization,retinal pigment epithelium,polarization sensitive devices
更新于2025-09-04 15:30:14
-
Choroidal Thickness at the Outside of Fovea in Diabetic Retinopathy Using Spectral-Domain Optical Coherence Tomography
摘要： Purpose: To evaluate choroidal thickness at the outside of the fovea in patients with diabetic retinopathy using spectral-domain optical coherence tomography. Methods: We examined 87 eyes of 87 patients with diabetic retinopathy and 40 eyes of 40 normal patients. Patients with diabetic retinopathy were divided into 3 groups according to the grade of diabetic retinopathy and macular edema. The choroidal thickness was obtained at the fovea and outside of the fovea using enhanced depth imaging of Spectralis optical coherence tomography. One foveal and 8 peripheral images were selected and choroidal thickness was measured from the outer border of the retinal pigment epithelium to the inner scleral border. Results: Subfoveal choroidal thickness was thinner with increasing severity of diabetic retinopathy. However, there was no significant difference between groups without the nasal side of the fovea. A statistically significant difference was observed over the fovea at the superotemporal area. Conclusions: The choroidal thickness outside of the fovea was thinner with the severity of diabetic retinopathy and was more pronounced in the superotemporal area.
关键词： Optical coherence tomography,Diabetic retinopathy,Choroidal thickness,Enhanced depth imaging
更新于2025-09-04 15:30:14
-
A Case of Acute Bilateral Solar Retinopathy Diagnosed with Spectral Domain Optical Coherence Tomography
摘要： To report a case of acute bilateral solar retinopathy diagnosed using spectral domain optical coherence tomography (SD-OCT). Case summary: A 74-year-old female patient consulted for amblyopia and metamorphopsia at a local hospital. On the patient’s first visit, there were no abnormal findings based on slit lamp microscope. Additional examinations were conducted since the patient complained of metamorphopsia with visual acuity and corrected vision. Fundus photography and SD-OCT examination showed symmetrical lesions near the bilateral macula. Several evaluations of the patient’s medical history confirmed that the patient was exposed directly to the sun for 30 minutes. One month after the first visit, visual acuity improved but metamorphopsia remained unchanged. Lesion status could not be confirmed by fundus photography. There was no abnormal finding on fluorescence angiography. SD-OCT examination still showed bilateral symmetric disruption of the outer retina but with no significant interval change. Conclusions: In the present case, the patient with bilateral intraocular lenses who complained of acute binocular amblyopia was diagnosed accurately through SD-OCT tests for bilateral symmetric disruption on the outer retina and repetitive evaluations of patient’s medical history.
关键词： Spectral domain optical coherence tomography (SD-OCT),Acute bilateral solar retinopathy,Patient’s medical history,Disruption
更新于2025-09-04 15:30:14
-
Retinal and Macular Ganglion Cell Count Estimated With Optical Coherence Tomography RTVUE-100 as a Candidate Biomarker for Glaucoma
摘要： To evaluate the ability of total and macular estimated retinal ganglion cell (RGC) counts to discriminate between healthy and glaucomatous eyes. To determine threshold markers of the estimated RGCs taking into account age dependence.
关键词： ganglion cells,optical coherence tomography,glaucoma
更新于2025-09-04 15:30:14
-
Spectral domain optical coherence tomography imaging of subretinal bands associated with chronic retinal detachments
摘要： We report three patients with subretinal bands associated with retinal detachment in chronic retinal detachments who underwent successful retinal reattachment. Subretinal bands before and after surgery can be identified on clinical examination and spectral domain optical coherence tomography. Removal of subretinal bands is not mandatory to achieve retinal reattachment.
关键词： optical coherence tomography,retinal detachment,subretinal bands
更新于2025-09-04 15:30:14
-
Is Vibrational Coherence a Byproduct of Singlet Exciton Fission?
摘要： A phenomenological wavefunction-based model of vibrationally coherent absorption modulation is proposed and applied to reproduce the triplet-triplet absorption spectra of bis-triisopropylsilylethynyl (TIPS)-pentacene, with the objective of testing whether the singlet fission process in that system spontaneously generates coherent vibrational packets, as recently suggested for TIPS-tetracene. The model is parametrized by a complete set of Franck-Condon parameters obtained from methodologically consistent DFT calculations for all relevant normal modes in all relevant electronic states. The results strongly depend on inhomogeneous broadening of absorption bands, which is explicitly included. They very well agree with the recently published experimental coherence spectra of the pertinent system, validating our underlying principal assumption that the singlet fission process, which generates the observed triplet states, is neutral with respect to vibrational coherences. Experimental confirmation of this interpretational posit demonstrates that in the pentacene derivative, apparently in contrast to the case of its tetracene analogue, fission is not a source of vibrational coherence. Our finding suggests that although the singlet fission process may possibly in individual cases induce vibrational coherence, this feature is not a constitutive characteristic of the fission phenomenon.
关键词： DFT calculations,singlet exciton fission,Franck-Condon parameters,TIPS-pentacene,vibrational coherence
更新于2025-09-04 15:30:14