Krypton Laser Research Articles

Laser photocoagulation treatment of choroidal melanoma

Ten cases of choroidal melanoma were treated with Argon and/or Krypton laser photocoagulation in this retrospective study. Each patient received an average of 9.6 laser treatment sessions. Three female and seven male patients were treated and followed for an average of 69.9 months. Clinical regression was observed in seven cases (70%). Tumour size in these successfully treated cases ranged from 4.5 x 5.0 x 1.5 mm to 7.0 x 7.0 x 3.5 mm. Continued growth occurred in one case (10%), tumour recurrence which failed to respond to additional laser treatment in another (10%), and although a recurrence appeared to respond to additional laser in a third case (the largest tumour in the series 11.0 x 9.0 x 2.5 mm) extraocular extension was found at enucleation (10%). Complications of laser treatment included cystoid macular oedema (Case 5), branch retinal vein occlusion (Cases 3 and 6), vitreous haemorrhage from neovascularisation at the edge of the scar, optic atrophy and thrombotic glaucoma (Case 8), and macular involvement by laser (Cases 4, 7 and 10). All patients remain alive without any clinical evidence of metastatic disease at the end of the follow-up period. These results suggest that laser photocoagulation treatment is a useful option in the management of small choroidal melanomas. It avoids the psychological trauma of enucleation, and maintains some vision, without compromising life expectancy.

A Miniaturized, No-Moving-Parts Raman Spectrometer

A solid-state acousto-optic tunable filter (AOTF) is combined with krypton laser excitation (647 nm), holographic Raman filters, and photon-counting silicon avalanche photodiode (APD) detection to construct a miniaturized Raman spectrometer with no moving parts. The physically compact AOTF and the highly integrated APD provide a rugged, digitally controlled spectrometer of moderate spectral resolution and with a footprint comparable in size to a laboratory notebook. Instrument design details are considered and representative spectra are reported. Potential areas of application for this prototype Raman spectrometer are also discussed.

Temperature dependence of the splay and bend viscosities of PAA

Quasielastic laser light scattering is used to study the splay and bend modes of p-azoxyanisole (PAA) as a function of temperature. At values of the scattering wave vector, where more than one mode is present, extraction of single mode parameters is complicated by the need to fit the data to sums of exponentials. At the relatively large scattering angles at which the modes are isolated, the scattered signals are usually weak. By using the 647.1 nm line of a Krypton Ion laser, significant improvement in signal-to-noise ratios are achieved and by experimentally isolating a single mode, more reliable fits are obtained. The two viscosities, ηsplay and ηbend, are obtained from the decay rates of the director fluctuations using the K1 and K3 data from Freedricksz transition experiments performed at Cambridge [J. Phys. 40, 1513 (1985)]. An empirical approach is used to describe the temperature dependence of the viscosities. The nature of the coupling of the order parameter to the viscosities is believed to be responsible for the behavior of the two viscosities.

Photocoagulation of choroidal neovascular membranes with a diode laser.

Nine eyes with parafoveal choroidal neovascular membranes due to age-related macular degeneration or angioid streaks were treated with a diode laser and were followed up to 40 weeks (mean 26 weeks). Angiographically proved closure of the membrane was achieved in seven eyes. Four lesions needed a second treatment for growth of subretinal neovascular tissue. Post-treatment visual acuity ranged from 6/9 to 6/60. Two eyes developed subfoveal membranes resulting in poor visual acuity. The morphology of the diode laser lesions differed from that of the argon green laser and was more similar to that of the krypton laser, producing a 'black hole' on the fluorescein positive print. In one particular eye fluorescein angiography revealed subfoveal choroidal non-perfusion next to the site of the diode lesion suggesting choroidal vascular closure.

Blue and green upconversion in Er3+-doped fluoroindate glasses

Abstract The upconversion properties of Er3+ in fluoroindate bulk glasses (composition: 40InF3−20ZnF2−16BaF2−(20−x)SrF2−2GaF3−2NaF−xErF3 with x=1,2,3 and 4 mole %) are investigated, following 4 F 9 2 excitation with a red krypton laser. A strong green and a weaker blue luminescence is observed at room temperature corresponding to emissions from the thermally coupled 4 S 3 2 and 2 H 11 2 bands and the 2 H 9 2 level respectively. Resonant energy transfer processes involving two excited erbium ions and a two-step absorption process are proposed to explain the upconversion phenomena. The emission intensities depend on the excitation power as Pexcn with 1.5≤n≤1.7 for the green and 1.6≤n≤1.9 for the blue emission. The decay times and the relative intensities of the luminescence are also studied as a function of Er3+ concentration.

Restoration of the Outer Blood-Retinal Barrier after Krypton Laser Photocoagulation

The restoration of the outer blood-retinal barrier following krypton laser injury to the rat retina was studied at small and large laser lesions using intravenously injected sodium fluorescein, horseradish peroxidase, and catalase. The regenerated choriocapillaris and new blood vessels were permeable to fluorescein and peroxidase, but not to catalase. The regenerating retinal pigment epithelium gradually reformed a continuous sheet of cells covering all small laser sites and the periphery of large lesions. Zonulae occludens between the regenerated cells restored the outer retinal barrier and prevented diffusion of peroxidase into the retina. This occurred along Bruch's membrane and the new blood vessels that were covered by the regenerated pigment epithelial cells, but not in the center of the large lesion that was not relined by regenerated cells.

Photocoagulation in Eales' disease

Between 1970 and 1991 the authors examined 466 cases with Eales' disease. 359 eyes of 295 of these 466 cases received photocoagulation treatment. The mean age was 30.4, ranging between 14 and 55 years. Ten eyes with persistent vitreous hemorrhage underwent pars plana vitrectomy before photocoagulation. 210 eyes were treated with xenon arc, 135 with argon laser, 12 with krypton laser and two with yellow dye laser. Hypoxic areas and retinal neovascularizations were closed completely in 298 eyes. In 21 eyes with elevated neovascularizations intruding into the vitreous cavity feeder vessel photocoagulation was used. 24 eyes with disc neovascularization were treated with panretinal photocoagulation. 12 eyes with branch vein occlusion and four eyes with central vein occlusion received photocoagulation treatment to areas of non-perfusion and retinal neovascularization. At a mean follow-up of 43 months, seven new retinal neovascularizations and three new disc neovascularizations developed in eyes which previously had received photocoagulation for retinal neovascularization and hypoxia. Nine out of 21 eyes with elevated neovascularizations developed vitreous hemorrhage. Disc neovascularization resolved completely in 13 out of 24 eyes, it partially regressed in eight eyes and did not respond to treatment in three eyes. The visual acuities were improved in 12.3%, maintained in 77.4% and deteriorated in 10.3% of the eyes after treatment. Periodic follow-up and early photocoagulation treatment is useful in stabilizing the retinal lesions and in maintaining functional levels of vision in Eales' disease.

Krypton fluoride excimer laser for advanced microlithography

The excimer-laser-based stepper is now expected to play a significant role in the manufacturing of ULSI devices requiring sub-0.4-μm design rule features. They will be used in a mix-and-match strategy along with high NA <i>i</i>-line steppers for critical layers in the production of 64-Mbit dynamic random access memory (DRAM) generation of IC devices. This is supported by the present availability of a number of production worthy high-NA, wide-field excimer stepper models, along with the recent introduction of several process worthy and moderate cost, positive tone deep-UV photoresists. The excimer laser for the stepper, since its introduction in 1987, has evolved from a laboratory instrument to fully production worthy fab-line equipment. The status of such a laser is discussed. We will discuss the operating theory and the design features of an excimer laser; in particular, the discharge chamber, spectral narrowing module, and the wavemeter. Some of the latest technical innovations incorporated into the laser that reduce maintenance intervals and increase reliability are also presented. Finally we will present and discuss the performance specifications of a current production lithography excimer laser.

Demonstration of Z-d(5BrCGAT5BrCG) and B-d(CGCGATCGCG) form crystal structures in DNA-cobalt hexammine complexes by Kr 647.1 nm excitation of Raman spectra.

Cobalt hexammine [Co(NH3)6(3+)] is an efficient DNA complexing agent which significantly perturbs nucleic acid secondary structure. We have employed red excitation (647.1 nm) from a krypton laser to obtain Raman spectra of the highly colored complexes formed between cobalt hexammine and crystals of the DNA oligomers, d(5BrCGAT5BrCG) and d(CGCGATCGCG), both of which incorporate out-of-alternation pyrimidine/purine sequences. The Co(NH3)6(3+) complex of d(5BrCGAT5BrCG) exhibits a typical Z-form Raman signature, similar to that reported previously for the alternating d(CGCGCG) sequence. Comparison of the Raman bands of d(5BrCGAT5BrCG) with those of other oligonucleotide and polynucleotide structures suggests that C3'-endo/syn and C3'-endo/anti thymidines may exhibit distinctive nucleoside conformation markers, and tentative assignments are proposed. The Raman markers for C2'-endo/anti adenosine in this Z-DNA are consistent with those reported previously for B-DNA crystals containing C2'-endo/anti dA. Raman bands of the cobalt hexammine complex of d(CGCGATCGCG) are those of B-DNA, but with significant differences from the previously characterized B-DNA dodecamer, d(CGCAAATTTGCG). The observed differences suggest an unusual deoxyguanosine conformer, possibly related to a previously characterized structural intermediate in the B-->Z transition. The present results show that crystallization of d(CGCGATCGCG) in the presence of cobalt hexammine is not alone sufficient to induce the left-handed Z-DNA conformation. This investigation represents the first application of off-resonance Raman spectroscopy for characterization of highly chromophoric DNA and illustrates the feasibility of the Raman method for investigating other structurally perturbed states of DNA-cobalt hexammine complexes.

Cr(VI)- and Fe(III)-doped polymer systems as real-time holographic recording materials

Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), dichromated poly(acrylic acid) (DCPAA), and ferric chloride poly(vinyl alcohol) (FePVA) films using a 488-nm light (from an argon-ion laser), and the hologram development has been monitored in real time using a 647-nm line of the krypton laser. The influence of different chemical parameters (e.g., pH and electron donor) on the holographic efficiency has been determined, and an efficiency value as high as 70% was achieved in all three recording media. Further, the possible primary photoprocesses responsible for the hologram formation are tentatively identified and discussed

Self-mode-locked Cr^3+:LiCaAlF_6 laser

A cw-pumped Cr3+:LiCaAlF6 laser has been configured to produce chirp-free, self-mode-locked pulses of 170-fs duration. The prism-dispersion-compensated cavity contained no active or passive mode-locking device. Mode locking was accomplished through self-focusing in the LiCaAlF6 crystal with 2.5 W of red light from a cw krypton laser. Rocking of the output coupler initiated the ultrashort-pulse formation.

Comparison of Photocoagulation with the Argon, Krypton, and Diode Laser Indirect Ophthalmoscopes in Rabbit Eyes

The purpose of this study is to compare photocoagulation with the argon green, krypton red, and diode infrared laser indirect ophthalmoscopes in an experimental setting. Photocoagulation was performed with each of the laser indirect ophthalmoscopes in a grid pattern within one sector of the same eye of 14 Dutch-belted rabbits. Treatment was performed either with or without scleral depression. Measurements of the retinal burn diameters were performed after hemisecting the globes, and the burns were examined with light microscopy. Variation in burn intensity and diameter (10% to 28%) was common with all 3 laser indirect ophthalmoscopes. Five times more output energy was required to make equivalent burns with the diode laser indirect ophthalmoscope than with the argon or krypton laser indirect ophthalmoscopes. Choriovitreal hemorrhages only occurred during scleral depression. Histopathologically, the argon green laser indirect ophthalmoscope burns spared the choroid and inner sclera, while the intense krypton and diode burns had full-thickness choroidal involvement and even thermal injury to the inner sclera. Scleral depression reduced the mean energy required to create equivalent burns with all three laser indirect ophthalmoscopes. There was a 10% to 40% reduction in the mean retinal burn diameter with scleral depression (argon green, P < 0.0005; krypton red, P < 0.0005; and diode, P < 0.025). Photocoagulation with the argon green, krypton red, or diode infrared laser indirect ophthalmoscopes is a safe and effective method of retinal ablation. Decreasing the posterior nodal distance of the eye with scleral depression will produce a smaller spot on the retina with the laser indirect ophthalmoscope.

Antimicrobial processes

Antimicrobial processes

Generation of 150-fs tunable pulses in Cr:LiSrAlF_6

We report ultrashort-pulse generation in a Cr:LiSrAlF6 solid-state laser. The 15-mm crystal was pumped by 1 W of red light from a cw krypton laser and actively mode locked at an 82-MHz repetition frequency using an acousto-optic modulator. Wavelength tuning was demonstrated over the range 800–880 nm, limited by the bandwidth of the optical components. By including intracavity dispersion compensation, pulse widths of 150 fs were obtained with evidence that self-phase modulation contributes to spectral broadening and pulse shortening.

糖尿病網膜症に対するクリプトンレーザーおよび半導体レーザー局所光凝固術の有効性の検討

糖尿病網膜症に対するクリプトンレーザーおよび半導体レーザー局所光凝固術の有効性の検討

Vascular remodeling after laser photocoagulation: concurrent regeneration and atrophy.

Laser photocoagulation is associated with paradoxical results: it causes obliteration of vessels, but leads also to the formation of new ones. In an attempt to better understand this dual vascular response we conducted an ultrastructure study of the choroidal vascular repair following krypton laser injury in rats. Three processes were observed: recanalization, neovascularization, and atrophy of both recanalized and newly formed capillaries. Post-lasering repair of the choroidal vasculature can therefore be described as a remodeling process, characterized by both regeneration and involution. The latter appears to be a secondary process of atrophy, contributing to permanent vascular obliteration. These mechanisms might explain why, in spite of initial vascular regeneration, laser photocoagulation treatment has a beneficial effect on choroidal subretinal neovascularization.

Modelocked Cr 3+ :LiSr 0.8 Ca 0.2 AIF 6 laser producing 150 fs pulses

Mode-locked operation has been achieved in a CW pumped Cr3+:LiSr0.8Ca0.2AIF6 laser. Pulses of 150 fs duration were directly generated from the actively mode-locked laser. A CW krypton laser operating with 1 W in the red, was used to pump the 15 mm long crystal.

Photodynamic therapy with chlorin e 6. A morphologic study of tumor damage efficiency in experiment

Morphological changes in rat sarcoma M-1 after photodynamic treatment with chlorin e 6 were studied. The frequency of necrosis appearance and the depth of its spreading in tumor tissue were evaluated after intraperitoneal injection of chlorin e 6 in doses of 1–10 mg kg −1 and subsequent irradiation by a krypton laser with light energy density 22.5–135 J cm −2, using the method of vital staining with Evans blue. It was found that the antitumoral effect of photodynamic treatment was strengthened by increasing the dose of the agent and light and reduced by increasing the time interval between chlorin e 6 injection and light irradiation. The treatment being given in the parameters mentioned produced a depth of tumor necrosis which varied from 4.0 mm to 16.6 mm. The mechanisms of tumor tissue damage after photodynamic treatment in vivo are discussed.

Transcleral contact krypton‐laser photocoagulation of the retina in rabbits

Transcleral contact retinal krypton laser photocoagulation of the retina was studied in rabbit eyes. The laser application was performed under indirect ophthalmoscope visual control with indentation of the sclera by the laser probe. Retinal lesions were produced with powers ranging from 0.2 to 0.3 W and application times between 1 and 2 sec. The lesions were studied histologically 2, 5, 10, 12, 20, 30 and 70 days after treatment. Histopathological examination of the lesions showed damage of mainly the outer retinal layers in light lesions, and to all layers of the retina in the more intense lesions. No scleral damage was observed in the light lesions, whereas transient oedema of the inner sclera was seen in the intense lesions. Studies with enucleated rabbit eyes showed that indentation of the sclera by the laser probe substantially decreased the power needed to produce a retinal lesion. It is concluded, that when used with scleral indentation, transscleral krypton laser photocoagulation of the retina can be performed with minimal damage to the sclera.

Measurement of the reflection coefficient at the core-cladding interface in plastic scintillating fibers

We have measured the reflection coefficient, that is the loss of light, at the boundary between the cladding and the core of a plastic scintillating fiber. The coefficient was measured as a function of the wavelength of light, produced by a krypton laser, between 400 and 620 nm, and as a function of the angle of incidence of the light. The optical scintillating fibers, with a polystyrene core and a PMMA cladding, are those widely used for the detection of high-energy particles. We observed losses of the order of 10 −4 per reflection, which increase when going to shorter wavelengths and which have roughly a linear dependence on the angle of incidence.