Blue Laser (450 nm) Treatment of Solar Lentigines.

This study tested a blue light source for the treatment of solar lentigines. A total of 14 patients with solar lentigines were treated with radiation from a novel, high-power 450 nm blue laser that was created for this project. The group contained eight patients with solar lentigines on the face, two patients with the lesions on the dorsal of the hands, and four patients with the lesions on the trunk and forearms. The best results (complete recovery) have been achieved for the lesions on the face and dorsal of the hands. The treatment of lesions on the trunk and forearms was not fully satisfying due to the occurrence of slight scarring. This study shows that, in some cases, the use of a blue laser may be an alternative to the use of longer wavelength sources.

Fractal Dimension and Texture Analysis of Lesion Autofluorescence in the Evaluation of Oral Lichen Planus Treatment Effectiveness.

BACKGROUND: Oral Lichen planus (OLP) is a chronic inflammatory disease. Topical steroids are used as the treatment of choice. The alternative is photodynamic therapy (PDT). The study aimed to fabricate optimal biodegradable matrices for methylene blue or triamcinolone acetonide because of a lack of currently commercially available carriers that could adhere to the mucous. METHODS: The study was designed as a 12-week single-blind prospective randomized clinical trial with 30 patients, full contralateral split-mouth design. Matrices for steroid and photosensitizer and laser device were fabricated. Fractal and texture analysis of photographs, taken in 405, 450, 405 + 450 nm wavelength, of lesions was performed to increase the objectivity of the assessment of treatment. RESULTS: We achieved two total responses for treatment in case of steroid therapy and one in the case of PDT. Partial response was noted in 17 lesions treated using local steroid therapy and 21 in the case of PDT. No statistically significant differences were found between the effectiveness of both used methods. Statistically significant differences in fractal dimension before and after treatment were observed only in the analysis of photographs taken in 405 + 450 nm wavelength. CONCLUSIONS: Photodynamic therapy and topical steroid therapy are effective methods for treating OLP. Using a carrier offers the possibility of a more predictable and effective method of drug delivery into the mucous membrane. Autofluorescence enables the detection of lesions especially at the early stage of their development.

Blue Laser (450 nm) in the Treatment of Port Wine Stains and Telangiectasia.

This study aimed to test a blue light source for the treatment of port wine stains (PWS) and telangiectasia and to compare this with the application of green and yellow lasers based on data in the literature. A total of 22 patients with PWS were treated with radiation from a novel, high-power 450 nm blue laser that was created for this project. The group contained 15 patients with red PWS and 7 with pink PWS. The best results were achieved for red PWS, using 15-20 ms light pulses and 47 W power. For patients with pink malformations, the results were unsatisfactory. The group with telangiectasia consisted of six patients with facial lesions and three with leg lesions. The recovery was completed for all patients with facial telangiectasia, while the blue laser therapy was ineffective for patients with leg telangiectasia. This study shows that, in some cases, the use of a blue laser may be an alternative to the use of green and yellow lasers.

Assessment of Human Gingival Fibroblast Proliferation after Laser Stimulation In Vitro Using Different Laser Types and Wavelengths (1064, 980, 635, 450, and 405 nm)-Preliminary Report.

PURPOSE: to assess the effect of photobiomodulation (PBM) on human gingival fibroblast proliferation. METHODS: The study was conducted using the primary cell cultures of human fibroblasts collected from systemically healthy donors. Three different laser types, Nd:YAG (1064 nm), infrared diode laser (980 nm), and prototype led laser emitting 405, 450, and 635 nm were used to irradiate the fibroblasts. Due to the patented structure of that laser, it was possible to irradiate fibroblasts with a beam combining two or three wavelengths. The energy density was 3 J/cm2, 25 J/cm2, 64 J/cm2. The viability and proliferation of cells were determined using the (Thiazolyl Blue Tetrazolium Blue) (MTT) test conducted 24, 48, and 72 h after laser irradiation. RESULTS: The highest percentage of mitochondrial activity (MA = 122.1%) was observed in the group irradiated with the 635 nm laser, with an energy density of 64 J/cm2 after 48 h. The lowest percentage of MA (94.0%) was observed in the group simultaneously irradiated with three wavelengths (405 + 450 + 635 nm). The use of the 405 nm laser at 25 J/cm2 gave similar results to the 635 nm laser. CONCLUSIONS: The application of the 635 nm and 405 nm irradiation caused a statistically significant increase in the proliferation of gingival fibroblasts.

Assessment of Effects of Laser Light Combining Three Wavelengths (450, 520 and 640 nm) on Temperature Increase and Depth of Tissue Lesions in an Ex Vivo Study.

BACKGROUND: Lasers are widely used in medicine in soft and hard tissue surgeries and biostimulation. Studies found in literature typically compare the effects of single-wavelength lasers on tissues or cell cultures. In our study, we used a diode laser capable of emitting three components of visible light (640 nm, red; 520 nm, green; 450 nm, blue) and combining them in a single beam. The aim of the study was to assess the effects of laser radiation in the visible spectrum on tissue in vitro, depending on the wavelength and pulse width. METHODS: All irradiations were performed using the same output power (1.5 W). We used various duty cycles: 10, 50, 80 and 100% with 100 Hz frequency. Maximum superficial temperature, rate of temperature increase and lesion depth were investigated. RESULTS: Maximum superficial temperature was observed for 450 + 520 nm irradiation (100% duty cycle). The highest rate of increase of temperature was noted for 450 + 520 nm (100% duty cycle). Maximum lesion depth was observed in case of three-wavelength irradiation (450 + 520 + 640 nm) for 100, 80 and 50% duty cycles. CONCLUSIONS: The synergistic effect of two-wavelength (450 + 520 nm) irradiation was observed in case of maximum temperature measurement. The deepest depth of lesion was noted after three-wavelength irradiation (450 + 520 + 640 nm).

Photodynamic diagnosis and photodynamic therapy in basal cell carcinoma using a novel laser light source.

The aim of the present study was evaluating the effects and safety of new laser light source in PDD and PDT of basal cell carcinoma, BCC. The patients presented challenging localizations of the tumor or tumor combined with Gorlin syndrome. The PDD and PDT was performed in 50 patients with 54 histologically confirmed BCCs. The photosensitizer precursor, 5-ALA in cream, was used and the tumors were then illuminated, for PDD at 405 nm, and for PDT at 638 nm by means of newly designed laser. The novel feature of the laser was the combination of violet and red light in a single fiber output which enabled us to perform PDD and PDT alternatingly. The patients received one or more PDT sessions and they were observed during the next 36 months. The complete responses (CR, remissions) of the lesions were considered as no visible tumor after that time period. CR were observed in 87 % of the lesions in the entire group of patients. The results of present study show that the new laser allowing for both PDD and PDT was effective in producing satisfactory responses in the treatment of basal cell carcinoma.

Anomalous photocurrent in wide InGaN quantum wells.

We show that in a wide In0.17Ga0.83N quantum well, placed within an undoped region of the pin diode, a photocurrent in the forward direction is observed. The photocurrent switches to reverse direction when the light intensity is increased and/or photon energy is above the bandgap of the quantum barrier. We propose a model showing that the anomalous photocurrent is due to the fact that when the carriers are pumped into the wide quantum well they cannot recombine until the built-in field is screened. For low-intensity light it takes a long time (milliseconds) for the screening to occur and during that time we observe current flowing in the forward direction. This current originates from the reorganization of carriers forming the depletion regions, rather than directly from the photogenerated carriers. The observed effects lead to the dependence of PC spectra on chopper frequency and on light power. They may also affect the operation of laser diodes and solar cells with wide InGaN quantum wells.

Assessment of in vivo experiments: The newly synthesized porphyrin with proper light source enhanced effectiveness of PDT comparing to 5-ALA-mediated PDT.

BACKGROUND: The search for new photosensitizers for application in photodynamic therapy has quite a long history. In the past, a large number of potent photosensitizers were used in both basic and clinical studies; however, only a few turned out to be effective and safe. METHODS: In the present study, two compounds were used: 5-aminolevulinic acid in two formulations (free and liposomal), and the newly synthesized porphyrin, 5,10,15,20-tetra-p-tolyl-22,24-dithiadibenzocarbaporphyrin, termed DTDB. Two different light sources, a halogen lamp (wavelength 450+/-20nm) and a diode laser (wavelength 450nm), were used to sensitize the compounds. The entire experiment was performed on mice bearing mouse mammary carcinoma, 4T1. RESULTS: The results showed that the DTDB-PDT applied by means of a laser proved to be most effective and caused the 83.3% necrosis of treated tumors. The overall effect of laser PDT was more potent than that of the halogen lamp-mediated PDT. CONCLUSIONS: In the present study, we would like to show that modifications of porphyrins lead to an increase in the effectiveness of PDT and that this effect could also be potentiated by using a proper light source.

Note: Photoluminescence excitation measurements in the 1.1-1.6 µm spectral range.

Pressure-tuned laser diodes are used for photoluminescence excitation in quantum-well samples grown on InP. With two bent-waveguide, external cavity lasers, the spectral range from 1.1 to 1.6 µm can be covered. This range is important for telecommunication devices, for quantum-dot emitters etc. while it is inaccessible to solid-state tunable lasers or dye lasers.

Photoluminescence excitation measurements using pressure-tuned laser diodes.

Pressure-tuned laser diodes in external cavity were used as tunable sources for photoluminescence excitation (PLE) spectroscopy. The method was demonstrated in the 720 nm-1070 nm spectral range using a few commercial laser diodes. The samples for PLE measurements were quantum-well structures grown on GaAs and on InP. The method is superior to standard PLE measurements using titanium sapphire laser because it can be extended to any spectral range where anti-reflection coated laser diodes are available.

Gradient index collimator lens for high pressure applications.

A modified gradient index (GRIN) lens is optimised for use in a liquid-type high pressure cell. It was found that high pressure changes the optical power of the gradient-index lenses by changing the index profile of the glass. In this paper, we present a modified GRIN lens in which these changes are compensated by the pressure-induced changes of the refraction index of the liquid used as a pressure medium. New lens was used for the collimation of the pressure tuned tapered laser working in external resonator. The lens proved to have the optical power almost independent of the pressure up to 1.6 GPa, as it allowed to obtain tuning range almost independent on pressure without the need of any modification of the optical setup.

Pressure tuning of laser diodes in the near-infrared up to 1850 nm: operational characteristics and reliability studies.

Wavelength tuning of infrared laser diodes in the high-hydrostatic pressure setup is demonstrated and its reliability is discussed in detail. Major reliability issues concern the photochemical reactions on the laser facet and the presence of strong absorption bands above 1650 nm in typical pressure liquids that do not undergo phase transitions up to 20 kbar. Despite these difficulties spectrally wide-range pressure tuning can be achieved with sufficient reliability for spectroscopic applications.