Design and fabrication of compound varifocal lens driven by polydimethylsiloxane film elastic deformation

A compound varifocal lens based on electromagnetic drive technology is designed and fabricated, where the polydimethylsiloxane(PDMS) film acts as a driving component, while the PDMS biconvex lens and the plane-concave lens form a coaxial compound lens system. The plane-concave lens equipped with driving coils is installed directly above the PDMS lens surrounded by the annular magnet. When different currents are applied, the annular magnet moves up and down, driving the PDMS film to undergo elastic deformation, and then resulting in longitudinal movement of the PDMS lens. The position change of the PDMS lens changes the focal length of the compound lens system. To verify the feasibility and practicability of this design, a prototype of our compound lens system is fabricated in experiment. Our proposed compound lens shows that its zoom ability reaches 9.28 mm when the current ranges from -0.20 A to 0.21 A.

One-year results for myopia control of orthokeratology with different back optic zone diameters: a randomized trial using a novel multispectral-based topographer

AIM:To present the 1-year results of a prospective cohort study investigating the efficacy,potential mechanism,and safety of orthokeratology(ortho-k)with different back optic zone diameters(BOZD)for myopia control in children.METHODS:This randomized clinical study was performed between Dec.2020 and Dec.2021.Participants were randomly assigned to three groups wearing ortho-k:5 mm BOZD(5-MM group),5.5 mm BOZD(5.5-MM group),and 6 mm BOZD(6-MM group).The 1-year data were recorded,including axial length,relative peripheral refraction(RPR,measured by multispectral refractive topography,MRT),and visual quality.The contrast sensitivity(CS)was evaluated by CSV-1000 instrument with spatial frequencies of 3,6,12,and 18 cycles/degree(c/d);the corneal higher-order aberrations(HOAs)were measured by iTrace aberration analyzer.The one-way ANOVA was performed to assess the differences between the three groups.The correlation between the change in AL and RPR was calculated by Pearson’s correlation coefficient.RESULTS:The 1-year results of 20,21,and 21 subjects in the 5-MM,5.5-MM,and 6-MM groups,respectively,were presented.There were no statistical differences in baseline age,sex,or ocular parameters between the three groups(all P>0.05).At the 1-year visit,the 5-MM group had lower axial elongation than the 6-MM group(0.07±0.09 vs 0.18±0.11 mm,P=0.001).The 5-MM group had more myopic total RPR(TRPR,P=0.014),with RPR in the 15°–30°(RPR 15–30,P=0.015),30°–45°(RPR 30–45,P=0.011),temporal(RPR-T,P=0.008),and nasal area(RPR-N,P<0.001)than the 6-MM group.RPR 15–30 in the 5.5-MM group was more myopic than that in the 6-MM group(P=0.002),and RPR-N in the 5-MM group was more myopic than that in the 5.5-MM group(P<0.001).There were positive correlations between the axial elongation and the change in TRPR(r=0.756,P<0.001),RPR 15–30(r=0.364,P=0.004),RPR 30–45(r=0.306,P=0.016),and RPR-N(r=0.253,P=0.047).The CS decreased at 3 c/d(P<0.001),and the corneal HOAs increased in the 5-MM group(P=0.030).CONCLUSION:Ortho-k with 5 mm BOZD can control myopia progression more effectively.The mechanism may be associated with greater myopic shifts in RPR.

High-Stability High-Energy Picosecond Optical Parametric Chirped Pulse Amplifier as a Preamplifier in Nd：Glass Petawatt System for Contrast Enhancement

We demonstrate a novel picosecond optical parametric preamplification to generate high-stability, high-energy and high-contrast seed pulses. The 5ps seed pulse is amplified from 60pJ to 300μJ with an 8.6ps/ 3mJ pump laser in a signal stage of short pulse non-collinear optical parametric chirped pulse amplification. The total gain is more than 106 and the rms energy stability is under 1.35%. The contrast ratio is higher than 10s within a scale of 20ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 106 outside the pump window.

A Novel Optical Control Plane for Switching an Electro-Optical Hybrid Node in Translucent WDM Optical Networks

In a translucent network scenario, development of an optical control plane (OCP) that is aware of the location and number of available regenerators and all-optical wavelength converters (AOWCs) is of paramount importance. However, current generalized multiprotocol label switching (GMPLS) protocol suite does not consider the distribution of regenerator and AOWC availability information to all the network nodes. In this paper, we propose a novel optical control plane (OCP) architecture that 1) disseminates information about network components (i.e. regenerators and AOWCs) to all the network nodes, and 2) evaluates candidate routes which use fewest amounts of network components. Performance of the proposed OCP is compared with a recently proposed hybrid OCP approach in terms of blocking performance, number of deployed components and lightpath establishment setup times. The obtained simulation results show that the proposed OCP approach demonstrates low connection blocking and establishes lightpaths by 1) minimizing the overall network cost owing to the deployment of minimum total number of network components, and 2) demonstrating acceptable lightpath establishment setup times at all traffic loads. Further, the proposed OCP methodology is compatible and suitable for controlling the operations of a novel electro-optical hybrid translucent node which is a latency efficient technology capable of delivering a cost effective implementation suitable for large scale deployment.

Influences of Atmospheric Turbulence on Image Resolution of Airborne and Space-Borne Optical Remote Sensing System

A new way is proposed to evaluate the influence of atmospheric turbulence on image resolution of airborne and space-borne optical remote sensing system, which is called as arrival angle-method. Applying this method, some engineering examples are selected to analyze the turbulence influences on image resolution based on three different atmospheric turbulence models quantificationally, for the airborne remote sensing system, the resolution errors caused by the atmospheric turbulence are less than 1 cm, and for the space-borne remote sensing system, the errors are around 1 cm. The results are similar to that obtained by the previous Friedmethod. Compared with the Fried-method, the arrival angle-method is rather simple and can be easily used in engineering fields.

Changes of retinal vessel density in low to moderate myopic eyes with orthokeratology evaluated by optical coherence tomography angiography

AIM:To explore the effect of orthokeratology(OK)fitting on retinal vessel density in low to moderate myopia adolescents by using optical coherence tomography angiography.METHODS:Children aged 10 to 14y with a cycloplegic spherical equivalent refraction of−0.50 diopter(D)to−5.00 D and astigmatism with more than−1.50 D were recruited.The enrolled adolescents were divided into OK group and spectacle group.During regular followup,adolescents were measured respectively at pre-wear,1,3,and 6mo after treatment.The follow-up included uncorrected distance visual acuity(UDVA),axial length(AL),superficial capillary plexus density(SCPD),deep capillary plexus density(DCPD),central retinal thickness(CRT),foveal avascular zone area(FAZ-A),foveal avascular zone perimeter(FAZ-P)and foveal vessel density in a 300-μmwide region around foveal avascular zone(FD-300).The collected data were analyzed using statistical methods.RESULTS:By one month,SCPD significantly increased in the fovea and superior retina,and DCPD significantly increased inferiorly in OK group compared to spectacle group(P<0.05).By three months,there were significant increases in SCPD in the fovea and inferior retina,and DCPD in the parafovea,superior,and inferior retina in OK group(P<0.05),while the increase in SCPD and DCPD in the fovea were observed by six months(P<0.05).The FD-300 significantly increased at every follow-up in OK group compared to spectacle group(P<0.05).No significant differences in the CRT,FAZ-A and FAZ-P and FD-300 were observed between two groups(P>0.05).OK group showed a significant improvement in UDVA after wearing OK,compared to spectacle group(P<0.01),while the AL did not show a significant difference between two groups(P>0.05).CONCLUSION:Short-term OK worn can increase local retinal vessel density in adolescents with low-to-moderate myopia.

Refractive Plasmonic Sensor Based on Fano Resonances in an Optical System

A symmetric plasmonie structure consisting of metal-insulator metal waveguide, groove studied, which supports double Fano resonances deriving from two different mechanisms and slot cavities is One of the Fano resonances originates from the interference between the resonances of groove and slot cavities, and the other comes from the interference between slot cavities. The spectral line shapes and the peaks of the double Fano resonances can be modulated by changing the length of the slot cavities and the height of the groove. Furthermore, the wavelength of the resonance peak has a linear relationship with the length of the slot cavities. The proposed plasmonic nanosensor possesses a sensitivity of 800nm/RIU and a figure of merit of 3150, which may have important applications in switches, sensors, and nonlinear devices.

Research on Measuring Method of Optical Focal Plane

The mathematic model and the characteristic curve of three kinds of focus measures are given in this article. The experimental devices of optical focal plane measurement erected by the use of three kinds of focus measures are introduced. The experimental results are discussed and analyzed.

An Optical Path Length Modulator for Laser Diode Self-Mixing Interference

Transparent liquid flattening or stretching realizes optical path length modulation. A flat thin seal transparent cavity, one flank is an electromagnetic driving membrane and is filled over with transparent liquid. Vibration of the membrane makes the liquid compressing or stretching, changes the liquid layer thickness, i.e. the optical path length of light through the liquid layer. The liquid layer compressed is equivalent to increase membrane tension. The membrane has higher resonant frequency. The cavity diameter 10 mm modulation frequency is about 18 kHz.

Advanced optical microscopy methods for in vivo imaging of sub-cellular structures in thick biological tissuesl

Optical microscopy has become an indispensable tool for visualizing sub-cellular structures andbiological processes.However,scattering in biological tissues is a major obstacle that preventshigh-resolution images from being obtained from deep regions of tissue.We review commontechniques,such as multiphoton microscopy(MPM)and optical coherence microscopy(OCM),for diffraction limited imaging beyond an imaging depth of 0.5 mm.Novel implementations havebeen emerging in recent years giving higher imaging speed,deeper penetration,and better imagequality.Focal modulation microscopy(FMM)is a novel method that combines confocal spatialfltering with focal modulation to reject out-of-focus background.FMM has demonstrated animaging depth comparable to those of MPM and OCM,near-real-time image acquisition,and thecapability for multiple contrast mechanisms.

Optical Gain Coefficient Measurements for 1-(4’-(Diphenylamino)-[1,1’-biphenyl]-4-yl)ethanone

In this study, the optical gain coefficient due to spontaneous emission for the conjugated compound 1-(4’-(diphenylamino)-[1,1’-biphenyl]-4-yl)ethanone (DBE) in two solvents, Tetrahydrofuran (THF) and Dichloromethane (DCM) was investigated using the variable stripe length method. The solutions were placed in 10 mm cuvettes and pumped optically with N2 laser (337 nm) with pulse duration of 1.2 ns and repetition rate of 10 Hz. A maximum net gain of 12 cm&minus;1 for the compound in THF, and 7 cm&minus;1 for the compound in DCM were recorded at the input energy of 162 &mu;J. The fluorescence quantum yields (&empty;f) of the compound were determined at the excitation wavelength of 337 nm using coumarin as a standard. The values of (&empty;f) for the samples in DCM and THF solvents were found to be 0.68 and 0.61, respectively. The high values of quantum yields suggest the possibility of using this material as an active media for lasing and for LED.

Transmittance Measurement of the Nonplanar Optical Based on Focal-Plane-Array Camera

Aiming to solve the problem that it is difficult to accurately measure UV cut-off transmittance of xenon quartz glass by using present spectrophotometer in China SG III project. Through the analysis, we believe that its reason was that the xenon quartz glass was nonplanar so the outgoing beam geometry from under-test was different from that from standard sample. A method of transmittance measurement based on focal-plane-array camera was proposed in this article. The effects of camera uniformity and spot sampling on transmittance measurement were analyzed theoretically. This method, which can reduce the effect of beam geometry on transmittance measurement and eliminate the cutting error occurring during light transmission by monitoring the completeness of incident beam in real-time, is verified from experiments. The random standard uncertainty of this method here is 0.035% or less. It is particularly useful in the transmittance measurement of nonplanar optical.

Two-year longitudinal change in choroidal and retinal thickness in school-aged myopic children:exploratory analysis of clinical trials for myopia progression

Background:With increasing axial length(AL)and myopia progression,the micro-structure of the retina and choroid gradually changes.Our study describes the longitudinal changes in retinal and choroidal thickness in school-aged children with myopia and explores the relationship between changes in choroidal thickness and myopia progression.Methods:An exploratory analysis of a randomized trial was performed.Children(n=168,aged 7 to 12 years)with myopia from-0.75 diopter(D)to-4.00 D were enrolled in this prospective longitudinal study.Cycloplegic refraction,AL,retinal and choroidal thicknesses were measured at baseline and at 1-and 2-year follow-ups."Rapid progression myopia"was defined as increasing in myopia>1.00 D and'"stable progression myopia"was≤1.00 D during the 2-year follow-up.Factors affecting the changes in choroidal thickness were analysed using linear mixed models.Results:AL significantly increased by 0.67±0.24 mm with a myopic shift of-1.50±0.64 D over the 2 years.The overall retinal thickness increased from 251.12±15.91μm at baseline to 253.47±15.74μm at the 2-year followup(F=23.785,P<0.001).The subfoveal choroidal thickness decreased from 231.03±54.04μm at baseline to 206.53±59.71μm at the 2-year follow-up(F=73.358,P<0.001).Choroidal thinning was significantly associated with AL elongation(β=-43.579μm/mm,P=0.002)and sex(β=-17.258,P=0.001).Choroidal thickness continued to decrease in subjects with rapid progression(F=92.06,P<0.001)but not in those with steady progression(F=2.23,P=0.119).Conclusion:Significant choroidal thinning was observed and was associated with rapid progression and sex.These findings indicate a need to understand the role of the choroid in eye growth and myopia development.Synopsis/Precis:The macular choroidal thickness of myopic children is relevant to different degrees of myopic progression in this 2-year longitudinal study.These findings suggest that control of choroidal thickness might work to regulate human ocular growth.

Focal choroidal excavation complicated with choroidal neovascularization in young and middle aged patients

AIM: To investigate the clinical and optical coherence tomography(OCT) features of focal choroidal excavation(FCE) complicated with choroidal neovascularization(CNV) in young and middle aged patients. METHODS: We performed a retrospective review of 26 patients with FCE accompanied by CNV. All patients underwent a complete ophthalmic examination. We analyzed the clinical characteristics of patients, focusing on the spectral-domain OCT features. All patients received intravitreal injection of anti-vascular endothelial growth factor(anti-VEGF) agents. And we assessed the changes of central retinal thickness and best-corrected visual acuity(BCVA) after anti-VEGF therapy. RESULTS: The mean age of 26 patients was 35.5±7.3 y(range, 21-48 y). Of the 26 FCE lesions, 11 were located subfoveal, 6 were parafoveal, and 9 were extrafoveal. The mean FCE depth was 129.8±50.3 μm, and the mean width was 901.3±306.0 μm. The FCE depth was correlated positively with the width, but not correlated with age or refractive error. CNV was located within the excavation(19 eyes) or adjacent to the excavation(7 eyes). After anti-VEGF therapy, the central retinal thickness was significantly reduced and the BCVA was significantly improved. In the absorption process of subretinal fluid, we found that the fluid in the excavations needed to be absorbed at the last. A small amount of residual fluid could still be seen in a few deep excavations even after a longterm follow-up.CONCLUSION: FCE may be an important reason to cause CNV. Especially in young patients with idiopathic CNV, we should pay attention to the use of OCT to check the presence of FCE. Anti-VEGF therapy is generally effective for CNV associated with FCE.

Focal choroidal excavation: a preliminary interpretation based on clinic and review

AIM: To describe the clinical and imaging characteristics associated with focal choroidal excavation(FCE), analyze the possible complication, and interpret its probable etiopathogenesis.METHODS: Retrospective descriptive case series of 37 eyes of 32 patients with FCE. Findings of spectral-domain optical coherence tomography(SD-OCT),fluorescein angiography, indocyanine green angiography,and clinical features were analyzed. RESULTS: All patients were Chinese. Five patients(15.6%) were bilaterally involved. Patients’ ages ranged from 7 to 66 y. Refractive error ranged between +2.0 D and 11.0 D. Mean best-corrected visual acuity was 0.6(range, 0.1 to 1.2). Fundus examinations exhibited mild-moderate localized pigmentary disturbances in the corresponding area of 17 eyes. Fluorescein angiography performed in 18 patients showed varying degrees of hyperfluorescence and hypofluorescence related to a range of retinal pigment epithelium(RPE) alterations.Indocyanine green angiography performed in 7 patients showed hypofluorescence at the excavation. SD-OCT demonstrated choroidal excavation in all 37 eyes.Twenty-nine eyes showed a single lesion of FCE, and three eyes showed 2-3 separated lesions. Fifteen eyes showed separation between the photoreceptor tips andRPE consistent with nonconforming FCE. Central serous chorioretinopathy(CSC, n =1) and choroidal neovascularization(CNV, n =1) developed during follow-up.CONCLUSION: FCE could be interpreted as congenital focal choroidal dysplasia involving the RPE,choriocapillaris, and photoreceptor associated with the faulty anatomy. The abnormal anatomy of FCE was similar to anatomy at risk of CSC and CNV.

Long-range surface plasmon polaritons with subwavelength mode expansion in an asymmetrical system

Long-range surface plasmon polariton （LRSPP） modes in an asymmetrical system, in which the thin metal film is sandwiched between a semi-infinite substrate and a high permittivity polymer film with a finite thickness, are theoret~ ically calculated and analyzed. Due to the high permittivity of the polymer film, at proper polymer film thicknesses, the index-matching condition of the dielectrics at both sides of the metal can be satisfied for supporting LRSPP modes, and the electromagnetic field above the metal can be localized well. It is found that these LRSPP modes have both long propagation lengths and subwavelength mode expansion above the metal at the optimal polymer film thickncsses. Furthermore, the requirements on the refractive index and the thickness of the polymer film to support LRSPP modes at the optimal thicknesses are found to be not critical.

Relationship between Myopia and Optical Components - A Study among Chinese Hong Kong Student Population

Purpose: To establish the prevalence and severity of myopia among the Chinese Hong Kong students and to study the relationship between myopia and optical components.Methods;One thousand and seventy-five freshmen of the 1993-1994 academic year in the Chinese University of Hong Kong underwent the eye examination including evaluation of refractive error, keratometry, and A-scan ultrasonic biometry. The data were analyzed with the SPSS/PC+4. 01 statistical package. Results: The prevalence of myopia was 91. 7% with the mean refraction being -4. 00 ± 2. 64D in this young adult population. The statistical analyses demonstrated a significant correlation between refractive value and axial length of the globe (r=-0. 78), vitreous length (r=-0. 76), anterior chamber depth (r=-0. 33), lens thickness (r = 0. 13) and corneal curvature (r = 0. 19). Conclusion: The refractive status is mainly dependent on the axial length. In general, the higher the myopia was, the longer the eyeball, the deeper the anterior chamber,

Optimum Optical Length of the Gas Cell Used for Monitoring Gas-In-Oil with FTIR

Dedicated experiments are designed to collect the infrared spectra of dissolved gas-in-oil of power transformers. Spectra of diagnostic gases are collected by 3 different laboratorial FTIR spectrometers using 3 different gas cells with various sets of equipment parameters. A formula is deduced to calculate the shortest optical length to detect a specific concentration according to measurements on gases with known concentrations near to the minimum detection limit. Collected spectra and calculated results suggested that the optimum optical length of the gas cell should be 150 mm to realize on-line monitoring of diagnostic gases within the required concentration range. At the end, an economic novel design of the gas cell is proposed based on the optimum length.

Theoretical analysis and experimental research on thermal focal length of a YVO_4/Nd:YVO_4 composite crystal

This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd：YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd：YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd：YVO4 rectangular crystal for the YVO4/Nd：YVO4 composite crystal and the Nd：YVO4 single crystal are researched respectively. Calculating the thermal focal length within the Nd：YVO4 rectangular crystal was done by an analysis of the additional optical path differences （OPD） caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd：YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd：YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd：YVO4 crystal and the Nd：YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd：YVO4 laser is more advantageous than the laser with Nd：YVO4 single crystal.

Dual-Wavelength Bad Cavity Laser as Potential Active Optical Frequency Standard

We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.