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AIM: To evaluate the role of internal limiting membrane (ILM) peeling in preventing secondary epiretinal membrane (ERM) formation in pars plana vitrectomy (PPV) for proliferative diabetic retinopathy (PDR). METHODS: This retrospective study analyzed the medical records of patients who underwent PPV for PDR and were followed up for minimum 3mo. ILM peeling was performed based on the intraoperative surgeons' judgments. ERM was assessed by optical coherence tomography photography. The relationship between ILM peeling and postoperative ERM was analyzed. RESULTS: In total, 212 eyes from 197 patients were included in this study. The incidence of secondary ERM in the ILM non-peeling group was significantly higher than that in the ILM peeling group (37.0% vs 14.0%; P

AIM: To investigate the safety and efficacy of sticky silicone oil (SSO) removal using a 22-gauge vein detained needle and inner limiting membrane (ILM) wrap-and-peel technique. METHODS: This retrospective consecutive case series reviewed the records of patients with a history of retinal detachment who had received silicone oil and perfluorocarbon liquid (PFCL) as intraocular tamponades. Patients were included in the analysis if they exhibited SSO remnants during silicone oil removal. The aspiration of most of the SSO remnants was performed by a 22-gauge vein detained needle. The small amounts of droplets adhered to the macula and epi-macular membrane were subsequently removed by the ILM warp-and-peel technique. The anatomical and functional outcomes, and postoperative complications were recorded. In vitro experiments were performed to simulate the formation of SSO remnants in four groups. RESULTS: Of 711 patients who underwent silicone oil removal during the study period, 9 patients exhibited SSO remnants and underwent follow-up for at least 3mo. Seven eyes (78%) underwent the ILM wrap-and-peel technique to completely remove small droplets of SSO that were glued to the macula and epi-macular membrane. No obvious complications occurred. Postoperative optical coherence tomography revealed normal retinal structure in all patients. In vitro analyses showed that balanced salt solution and prolonged vibration (for 1wk) had the strongest effects on silicone oil and PFCL compound opacities. CONCLUSION: SSO remnants could be removed in an intact manner and without complications, using a vein detained needle-assisted and ILM wrap-and-peel technique. The findings suggest that PFCL and infusion fluid should be completely removed before silicone oil injection to prevent SSO formation.

We investigate the effect of rapid thermal annealing on InGaNAs/GaAs quantum wells. At optimized annealing temperatures and times, the greatest enhancement of the photoluminescence intensity is obtained by a special two-step annealing process. To identify the mechanism affecting the material quality during the rapid thermal annealing, differential temperature analysis is applied, and temperature- and power-dependent photoluminescence is carried out on the samples annealed under different conditions. Our experiment reveals that some composition redistribution or other related ordering process may occur in the quantum-well layer during annealing. Annealing at a lower temperature for a long time primarily can remove defects and dislocations while annealing at a higher temperature for a short time primarily homogenizes the composition in the quantum wells.

High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3 μm to 1.5 μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N2 flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54 μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31 μm.

We report a systematical study on the molecular beam epitaxy growth and optical property of (GaAs1-xSbx/In-y Ga1-yAs)/GaAs bilayer quantum well (BQW) structures. It is shown that the growth temperature of the wells and the sequence of layer growth have significant influence on the interface quality and the subsequent photoluminescence (PL) spectra. Under optimized growth conditions, three high-quality (GaAsSb0.29/In0.4GaAs)/GaAs BQWs are successfully fabricated and a room temperature PL at 1314 nm is observed. The transition mechanism in the BQW is also discussed by photoluminescence and photoreflectance measurements. The results confirm experimentally a type-II band alignment of the interface between the GaAsSb and InGaAs layers.

Effects of SiO2, encapsulation and rapid thermal annealing (RTA) on the optical properties of GaNAs/GaAs single quantum well (SQW) were studied by low temperature photoluminescence (PL). A blueshift of the PL peak energy for both the SiO2-capped region and the bare region was observed. The results were attributed to the nitrogen reorganization in the GaNAs/GaAs SQW. It was also shown that the nitrogen reorganization was obviously enhanced by SiO2 cap-layer. A simple model [1] was used to describe the SiO2-enhanced blueshift of the low temperature PL peak energy.

Effective cavity length method is introduced to vertical cavity surface emitting laser for characterizing some properties, including reflectivity, FWHM, mode wavelength and threshold gain. Some experiment results are demonstrated, showing the agreement of theoretical analysis with experiment.

Based on the band anticrossing model, the effects of the strain-compensated layer and the strain-mediated layer on the band structure, gain and differential gain of GaInNAs/GaAs quantum well lasers have been investigated. The results show that the GaNAs barrier has a disadvantage in increasing the density of states in the conduction band. Meanwhile, the multilayer quantum wells need higher transparency carrier density than the GaInNAs/GaAs single quantum well with the same wavelength. However, they help to suppress the degradation of the differential gain. The calculation also shows that from the viewpoint of band structure, the strain-compensated structure and the strain-mediated structure have similar features.

GaInNAs/GaAs single-quantum-well (SQW) lasers have been grown by solid-source molecular beam epitaxy. N is introduced by a home-made de-active plasma source. Incorporation of N into InGaAs decreases the bandgap significantly. The highest N concentration of 2.6% in a GaInNAs/GaAs QW is obtained, corresponding to the photoluminescence (PL) peak wavelength of 1.57 mum at 10 K. The PL peak intensity decreases rapidly and the PL full width at half maximum increases with the increasing N concentrations. Rapid thermal annealing at 850 degrees C could significantly improve the crystal quality of the QWs. An optimum annealing time of 5s at 850 degrees C was obtained. The GalnNAs/GaAs SQW laser emitting at 1.2 mum exhibits a high characteristic temperature of 115 K in the temperature range of 20 degrees C- 75 degrees C.

To evaluate the anterior segment complications of phacovitrectomy and foldable intraocular lens (IOL) implantation in eyes with significant cataract and co-existing vitreoretinal diseases.This retrospective study was consisted of 285 eyes of 238 patients with various vitreoretinal abnormalities and visually significant cataracts. Vitreoretinal surgery was combined with phacoemulsification and foldable IOL implantation. Main outcome measures were visual acuity, the preoperative data, and the anterior segment complications at postoperative 6 to 72 months.The most common indications for surgery were non-diabetic vitreous hemorrhage, proliferative diabetic retinopathy. Preoperative vision ranged from 20/30 to light perception and postoperative vision ranged from 20/20 to no light perception. Postoperatively, in 245 eyes (85.9%), visual acuity improved by 3 lines or more on the Snellen chart. In 24 eyes (8.4%), vision remained within 3 lines of preoperative levels and in 16 eyes (5.6%), vision had decreased at the last follow-up. The most common anterior segment pathological change was PCO in 50 eyes (17.5%), the second was corneal edema in 32 eyes (11.2%) and the third was elevated IOP in 31 eyes (10.8%).The combined vitreoretinal surgery and phacoemulsification with foldable IOL implantation is safe and effective.

A novel idea of InAlAs native oxide utilized to replace the p-n-p-n thyristor blocking layer and improve the high-temperature performance of the buried heterostructure first proposed and demonstrated. A temperature (To) of 50 K is achieved from an InAlAs native oxide buried heterostructure (NOBH) InGaAsP-InP multiquantum-well laser with 1.5-/spl mu/m-wide diode leakage passage path. The threshold current and slope efficiency of NOBH laser changes from 5.6 mA, 0.23 mW/mA to 28 mA, 0.11 mW/mA with the operating temperature changing from 20/spl deg/C to 100/spl deg/C. It is comparable to conventional p-n reverse biased junction BH laser with minimized diode leakage current, and is much better than the buried ridge strip with proton implanted laterally confinement laser.

A small signal equivalent circuit model of vertical cavity surface emitting lasers (VCSELs) is given in this paper. The modulation properties of the VCSEL are simulated using this model in the Pspice program. The simulation results are in good agreement with experimental data. An experiment is performed to testify the circuit model.

We first proposed and realized a 1.5 /spl mu/m buried hetero-structure InGaAsP-InP MQW laser with a native-oxidized InAlAs current block layer (NO-InAlAs-BH). The primary results are Ith=5.6 mA, slope efficiency /spl eta/=0.23 mW/mA and an linear output power surpassing 22.5 mW.

We proposed to eliminate the current leakage from p-n reverse-biased-junction BH InGaAsP-InP laser under high temperature operation by utilizing native-oxidized InAlAs current blocking layer. The characteristic temperature of 50 K has been preliminarily achieved.