Niklaus Ursus Wetter

Optical properties of Nd doped Bi2O3-PbO-Ga2O3 glasses.

The optical properties of a new family of neodymium doped BPG (Bi2O3-PbO-Ga2O3 ) glasses are presented. We measured a high refractive index, of 2.5, and a transmission cutoff in the far infrared at 8microm. Three intense emission bands are observed centered at 877nm, 1066nm and 1341nm. The emission cross-section is 10 -20 cm 2 and the total spectral linewidth is 30nm at 1066nm. The Judd-Ofelt parameters are calculated and used to evaluate transition probability, radiative lifetime and branching ratios. The optical properties of these Nd:BPG glasses show promise for their use as a new active laser material.

Growth of LiYF4 crystals doped with holmium, erbium and thulium

Crystals of LiYF 4 (YLF) doped with holmium, erbium, and thulium were successfully grown by the Czochralski technique. The synthesis, growth conditions, and pulsed-laser performance using a LiY 0.555 Er 0.38 Tm 0.06 Ho 0.005 F 4 crystal, are presented.

Study of the most suitable new glass laser to incorporate ytterbium: alkali niobium tellurite, lead fluorborate or heavy metal oxide

Abstract Diode-pumped Yb-doped glass lasers have received considerable attention for applications such as high-power beam production or femtosecond pulses generation. In this paper, we evaluate the laser potential of three different glass families doped with Yb3+: alkali lead fluorborate (PbO–PbF2–B2O3), heavy metal oxide (Bi2O3–PbO–Ga2O3) and niobium tellurite (TeO2–Nb2O5–K2O–Li2O). Spectroscopic properties were studied for the samples and calculations of the minimum laser pump intensity (Imin), saturation fluence (Usat) and the theoretical limit of peak power (Pmax) are also presented. A comparison of laser properties of these three different glasses and their importance is shown and analyzed.

Low-Level Laser Therapy in Burning Mouth Syndrome Patients: A Pilot Study

OBJECTIVE The aim of this study was to investigate the effect of low-level laser therapy (LLLT) on the treatment of burning mouth syndrome (BMS). In addition, the laser effect was compared on the different affected oral sites. MATERIALS AND METHODS Eleven subjects with a total of 25 sites (tongue, lower lip, upper lip, and palate) affected by a burning sensation were selected. The affected areas were irradiated once a week for three consecutive weeks with an infrared laser (λ = 790 nm). The probe was kept in contact with the tissue, and the mucosal surface was scanned during the irradiation. The exposure time was calculated based on the fluence of 6 J/cm(2), the output power of 120 mW, and the area to be treated. Burning intensity was recorded through a visual analog scale before and after the treatment and at the 6-week follow-up. The percentage of the improvement in symptoms was also obtained. RESULTS Burning intensity at the end of the laser therapy was statistically lower than at the beginning (p < 0.01). Patients reported an 80.4% reduction in the intensity of symptoms after laser treatment. There was no statistical difference between the end of the treatment and the 6-week follow-up, except for the tongue site. CONCLUSION Under the investigated parameters, infrared LLLT proved to be a valuable alternative for BMS treatment, providing a significant and lasting reduction in symptoms.

Efficient and compact diode-side-pumped Nd:YLF laser operating at 1053?nm with high beam quality

A very efficient, diode-side-pumped Nd:YLF laser is demonstrated using a compact cavity design based on total internal reflection inside the gain medium. With one pass through the crystal using a single bounce at the pumped face, efficiency in excess of 40% in multimode operation was measured, giving 6.6 W of output power for 16.2 W of pump power. Using two bounces inside the crystal, the beam quality was improved to fundamental mode with 4.2 W of output power for 16.2 W of pump power.

Compact, diode-side-pumped Nd3+:YLiF4 laser at 1053 nm with 45% efficiency and diffraction- limited quality by mode controlling.

We demonstrate what we believe to be the highest efficiency obtained to date in a transversely diode-pumped Nd3+:YLiF4 slab laser operating at 1053 nm. The compact 11-cm-long laser cavity configuration is based on total internal reflection of the intracavity beam at the pump facet of the gain crystal to improve the overlap with the pump radiation. Multimode operation with 9.5 W of output power and an efficiency of 45% is obtained for 21 W of pump power in a single-pass configuration. Using a second pass through the crystal and a new mode-controlling technique, the beam quality is improved to the diffraction limit with 6.9 W of output power and 33% of optical-to-optical efficiency.

Effective Transmission of Light for Media Culture, Plates and Tubes

The results of many investigations on low‐level laser therapy are contradictory and this is due to the large number of illumination parameters as well as the inability to measure the possible effects after irradiation with the necessary objectivity and the fact that the light needs to pass thorough barriers (usually the plastic of the culture dish/plate and culture medium) to reach the cells. In this manner, the objective of this study was to determine the absorption coefficient, penetration depth and effective transmission in materials commonly used in cell cultures. Among the most commonly used wavelengths in low‐level laser therapy, the lowest absorption coefficients were reached by DMEM and RPMI (α = 0.03 cm−1), from 633 to 690 nm, which reach an effective transmission of 93% of incident radiation and penetration depth of 33 cm. Among the solid materials in the same range of the electromagnetic spectrum, the lowest absorption coefficient was obtained for the polystyrene (Petri dish and well plate), with α = 1.31 cm−1, 78% of effective transmission and 0.76 cm of penetration depth. This article also presents a simple equation for estimating the amount of energy that will actually reach the sample.

Spectroscopic properties of lead fluoroborate and heavy metal oxide glasses doped with Yb3

Abstract A new glass of heavy metal oxide (25.0Bi2O3–57.0PbO–18.0Ga2O3 (mol%)) doped with Yb3+ is presented and compared with lead fluoroborate glass (43.5H3BO3–22.5PbCO3–34.0PbF2 (mol%)), also doped with ytterbium. The interest in Yb3+ for laser action and short pulse generation under diode pumping has been reported in the literature. Spectroscopic properties were studied for both glasses doped with 0.5 mol% of Yb2O3. The absorption cross-section of the heavy metal oxide glass is (2.20±0.15)×10−20 cm2 at the absorption peak wavelength of 968 nm and its emission cross-section is (0.75±0.05)×10−20 cm2 at the extraction wavelength of 1012 nm. A fluorescence effective linewidth of 86 nm and a fluorescence lifetime of 0.40 ms were measured. In the case of the lead fluoroborate glass used for comparison, these values change to (2.56±0.18)×10−20 cm2 (absorption cross-section), (1.07±0.08)×10−20 cm2 (emission cross-section at 1022 nm), 60 nm (fluorescence effective linewidth) and 0.81 ms (fluorescence lifetime). Calculations of the minimum pump intensity are also presented. Both have spectroscopic properties for laser applications that are similar to those of other known glasses (phosphate and tellurite laser glasses) used as active laser media. The large emission bandwidth measured for the heavy metal oxide is of interest for tunable lasers.

Mode-controlling in a 7.5 cm long, transversally pumped, high power Nd:YVO4 laser

A side pumped Nd:YVO4 laser with a very compact, 7.5 cm long resonator is presented. In single pass configuration this cavity provides 74% slope efficiency and 22 W output power in multimode operation. With a second pass through the gain media, using a double bounce configuration, this short and simple cavity results in 17 W and a large improvement in beam quality with an M 2 of 1.7 × 1.4 in the horizontal and vertical direction, respectively. A theoretical, experimental and numerical analysis of this double bounce configuration is made.

Spectroscopic properties of lead fluoroborate glasses doped with ytterbium

A new lead fluoroborate glass (PbO-PbF2-B2O3) doped with ytterbium (Yb:PbFB) is presented. Samples with different concentrations of Yb3+ were produced and had their emission cross-sections, fluorescence lifetimes and minimum pump intensities determined. They have high refractive index of 2.2 and a density of 4.4 g/cm3. For a doping level of 1.153x1020 ions/cm3, the fluorescence lifetime, after excitation at 968 nm, is 0.81 ms, which is comparable to Yb:tellurite laser glass. Also, an emission band at 1022 nm is measured with emission cross-section of approximately 1.07x10-20 cm2 and fluorescence effective linewidth of 60 nm, which is comparable to Yb:phosphate laser glass.