BACKGROUND: Complaints of vitreous floaters are not new to veteran ophthalmologists, and many can attest to the reported burden symptomatic floaters have on visual clarity and quality of life. Classic treatment paradigms recommend indefinite observation or, in the case of severely bothersome floaters, pars plana vitrectomy (PPV). Despite the proven efficacy, PPV requires intraocular access and has a side effect profile that warrants severe visual impairment to justify the risks of surgery. Floater laser treatment has the potential to fill the treatment gap as a less invasive alternative using photodisruption to vaporize floaters. Studies have attempted to quantify the efficacy of Nd:YAG laser treatment with moderate success, but the safety profile of the laser floater treatment (LFT) is still limited in duration of follow-up. OBJECTIVE: To analyze the efficacy and safety of Nd:YAG laser vitreolysis performed in-clinic as measured by number of sessions, patients who went on to pursue secondary vitrectomy, and a self-reported survey comparing visual satisfaction before and after LFT. METHODS: In a retrospective study, 32 eyes with a history of symptomatic floaters of varied etiology were treated with the Ellex Nd:YAG laser set to single-shot mode with a maximal pulse energy of 7mJ. The number of treatments each patient underwent until receiving full visual benefit served as an objective measure of the efficacy of the laser. Secondary vitrectomy patients who failed laser vitreolysis were sampled as evidence of inadequate response to treatment. A self-administered survey explored patient satisfaction in terms of overall quality of vision, frequency/severity of floaters, and impact floaters have on activities of daily life (ADLs) before and after the laser, graded on a 4-point scale. RESULTS: Laser Floater Treatment performed in-clinic at Boston Vision/Boston Laser (BVBL) yielded moderate success in resolving symptomatic floaters, as indicated by improved mean patient scores following treatment for quality of vision (+1.13), frequency/severity of floaters (+1.00), and impact floaters have on ADLs (+1.33) when compared to pretreatment scales. The mean number of discrete treatment sessions to gleam full benefit of laser vitreolysis was 2.5 sessions per patient. Approximately 6% (2/32) patients failed vitreolysis and went on to pursue PPV. CONCLUSIONS: Our results showed an improvement of mean patient scores in overall quality of vision, severity of floaters, and floaters’ impact by at least 1 scale point, supporting the efficacy of laser vitreolysis. Patients underwent a mean of 2.5 treatment sessions, and offering multiple sessions likely bolstered the overall efficacy of the procedure. The sample population of 32 yielded only two patients (6%) who went on to pursue secondary vitrectomy, suggesting LFT could potentially serve as another treatment option filling the gap between observation and PPV.

Abstract The breakthrough technology in dry fiber fabrication has opened the possibility for using fiber bandwidths all the way from 1.3 to 1.6 £gm. The fiber amplifier that is in common use can not fully cover the whole, which its range is from 1.3 to 1.6 £gm. Recently, the Cr4+-doped fiber has shown a broadband emission from 1.3 to 1.6 £gm. Therefore, it is eminently suitable for super-wideband optical source. In this study, we first propose and fabricate a Cr4+-doped fiber by employing a commercial drawing-tower method, which has good core diameter uniformity, the growth speed is up to 200 m/min, and the core diameter is less than 10 £gm. The central wavelength of the ASE spectrum is at 1310 nm, and a 3-dB bandwidth is 300 nm. The divergent angle of the Cr-doped fiber is 17 o ¡Ñ 15 o and it¡¦s also similar to a single mode fiber of 16 o ¡Ñ 16 o. Low-loss fusion splice can readily be done with the standard single mode fiber, and is beneficial when integrated with the broadband WDM couplers. Therefore, it is good for commercial production and application to light wave systems.

Chromium doped crystals exhibit different emitting properties for their different valance species and the host crystals. Ruby shows narrow twin peaks around 694 nm for its Cr3+ ions. Cr4+:YAG has a broadband luminescence range on 1.1~1.6£gm, which is suitable for optical communication. The thesis aims to study the luminescent spectra of Cr ions in different crystal structure (Al2O3 and YAG). Cr concentration dependent spectra indicate Cr3+ moving toward the octahedron sites. It results the change of luminescent spectra and luminescent decay lifetime. Both FTIR and confocal microscopy are used for the investigations. Step-scan FTIR provides the relation of luminescence intensity relating to both wavenumber and delay time, of the external light source.The high numerical aperture optics in the confocal microscope provides higher collection efficiency, and results a better S/N ratio. In addition, Raman spectra are measured. Ruby and sapphire crystals exhibit different Raman spectra, which results from the electronic resonance of the Cr3+ ions in the ruby crystal.

Cr4+:YAG is an attractive gain medium due to its broad 3-dB emission spectrum ranging from 1253 to 1530 nm, which cover the low-loss window of the silica fiber. Such a broadband haracteristic offers a potential to develop a broadband amplified spontaneous emission (ASE) light source, optical amplifier, and tunable laser. Growing the Cr4+:YAG bulk crystal into fiber form is necessary for generating larger gain by the better optical confinement of the waveguide structure. For the application of laser, it is superior to bulk crystals for reducing lasing threshold and obtain the high slope efficiency due to the beter optical confinement and heat dissipation. A record-low threshold of 0.75 mW was achieved at room temperature. It is more than 500 times lower than any previously reported Cr4+:YAG lasers, and a slope efficiency of 6.9% was obtained. The ultralow-threshold lasing is made possible by the low propagation loss of 0.08 dB/cm and the high pump intensity of the core. Such a low-threshold operation makes the double-clad crystal fiber laser be compatible to present optical communication systems. Furthermore, we demonstrate that the proposed optimization algorithm can provide an efficient and direct approach to analyzing both fiber structure and bulk medium in terms of practical application requirements. The simulation results reveal that Cr4+:YAG DCF lasers offer advantages over bulk lasers in terms of low-threshold lasing and high efficiency, which are essential for their use in optical communication systems.

Aachen, Techn. Hochsch., Diss., 2006.

Techn. Universiẗat, Diss., 2003--Berlin.

Submitted by Etelvina Domingos (etelvina.domingos@ufpe.br) on 2015-04-08T18:57:45Z No. of bitstreams: 2 DISSERTAÇÃO Marina Lins Maymone de Melo.pdf: 897152 bytes, checksum: bced8c7adc190105e134586fa6da3fec (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-04-08T18:57:45Z (GMT). No. of bitstreams: 2 DISSERTAÇÃO Marina Lins Maymone de Melo.pdf: 897152 bytes, checksum: bced8c7adc190105e134586fa6da3fec (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014 / REUNI-UFPE / O objetivo deste estudo foi comparar, em modelo animal, o tratamento da osteonecrose dos maxilares induzida por bisfosfonatos (OMIB) realizado por cirurgia com laser Er:YAG com a cirurgia convencional. Foi realizado um estudo controlado experimental in vivo, utilizando 12 ratos Wistar machos, divididos em três grupos: controle (C), cirurgia convencional (CONV) e cirurgia a laser (LAS). Os animais foram tratados por 12 semanas com uma injeção intra-peritoneal semanal utilizando soro fisiológico na dosagem de 0,1ml/100g (grupo C) ou ácido zoledrônico (ZA) com doses de 0,15mg/Kg (grupos CONV e LAS). Os animais foram submetidos a exodontia de primeiro e segundo molares mandibulares para indução da OMIB, e então tratados com curetagem (grupo CONV) ou ablação a laser de Er:YAG (grupo LAS). Após a eutanásia, as mandíbulas foram removidas, fixadas em formol a 10% e analisadas através microtomografia computadorizada (microCT) para avaliação do padrão de trabeculado e densidade óssea. Os espécimes foram então processados e corados em HE para avaliação microscópica.A análise das imagens do microCT mostrou presença de sequestros ósseos, com aumento dos espaços medulares do osso esponjoso no grupo CONV. O trabeculado do grupo LAS apresentou padrão semelhante ao grupo C. A densidade óssea não apresentou diferença estatisticamente significante entre os grupos. A análise microscópica evidenciou reparo ósseo alveolar avançado (acima de 60%) em todos os animais do grupo C e 75% do grupo LAS, sendo ausente em 50% do grupo CONV. O laser de Er:YAG apresenta-se como uma importante estratégia terapêutica para o tratamento cirúrgico da OMIB, sendo superior à curetagem.

It was shown analytically and experimentally that when the cavity losses are perturbed, the output intensity experiences an amplitude modulation or becomes a regular train of spikes, with the frequency depending on both the frequency of perturbation as well as pump power. Coupled nonlinear rate equations including the cavity perturbation term, are solved numerically by a Runga-Kutta method using experimentally-measured parameter values for Nd: Y AG laser. A continuously pumped Nd: Y AG laser was used to verify this theory.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3 mm to 1.6 mm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1.3 mm to 1.6 mm. Besides, its absorption spectrum is between 0.9 mm to 1.2 mm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. We have successfully fused the double cladding Cr4+:YAG crystal fiber with single mode fiber by fusion splicer. The crystal fibers are grown by the laser-heated pedestal growth technique. The splicing parameters are optimized to achieve an insertion loss of below 1 dB. Since, the core diameter tapering will increase the propagation loss and reduce the gross gain. Adiabatically tapered fiber is discussed. Simulations are performed to predict the loss, and compare with the experimental results, then find out the way to improve the gross gain. Numerical simulation indicates that the gross gain could reach 37.2 dB at 0.5 W pump, if the core diameter of the double cladding Cr4+:YAG crystal fiber is reduced to 5 mm. In the future, in order to increase gross gain we will improve the mode matching between the cores of single mode fiber and the double cladding Cr4+:YAG crystal fiber. Gradual change of the refractive index at the splicing region as well as high Cr4+ doping concentration can also improve the gross gain.

In this study, we have successfully demonstrated the use of laser scanning confocal microscopy in studying the fluorescence spectroscopy of Cr3+ and Cr4+ ions in Cr:YAG crystal fibers, double-clad crystal fibers, and glass fibers.