Diode Laser

Introduction: Residual oxygen-free radicals of bleaching agents before composite restorations can increase microleakage in enamel and dentin margins, and also various bleaching techniques are being developed using light sources. The present study was conducted to compare the effect of diode laser bleaching and LED activated bleaching on the microleakage of composite restorations.
Materials & Methods: This in-vitro study was conducted on 84 extracted human premolars in three groups: In group one, class-V cavities were prepared and the teeth (n=12) were restored with composite ten days after bleaching with 35% hydrogen peroxide with no activator. In groups two and three (n=36 each), the teeth were bleached with a Diode laser activator and LED, respectively. Thereafter, each group was divided into three subgroups (n=12), cavities were prepared and restored with composite three, five, and ten days after bleaching. Digital photographs were used to assess microleakage in the enamel and dentin margins. Data were analyzed using Friedman and Wilcoxon Signed Ranks tests (p<0.05).
Results: The lowest amount of microleakage in the enamel margin pertained to the diode laser ten-day subgroup (0.17±0.38) and the diode laser ten-day subgroup in the dentin margin (0.50±1.03). Also, the highest amount of microleakage in the LED group was in the three-day subgroup of the dentin margin (2.78±0.42). Five-day subgroup of diode laser-activated bleaching had a lower amount of microleakage compared to the control group (P=0.042).
Conclusion: It may be concluded that diode laser-activated bleaching with 35% hydrogen peroxide has a better effect on reducing microleakage with an interval of five to ten days, compared to the control and LED activated bleaching group.

Twin wire arc-sprayed (TWAS) coating of commercially available SHS 7170-cored wire was obtained on Ti6AL4V alloy, and to improve its properties, it was further surface treated with high-power diode laser (HPDL). The cavitation erosion (CE) resistance of TWAS-coated samples was evaluated as per ASTM G-32-2003 and it was compared with laser-treated and untreated Ti6Al4V alloys. The CE resistance of TWAS-coated

Etiology of oral submucous fibrosis (OSMF) is not fully understood, henceforth treated unsatisfactorily. Generally surgical treatment aims to reopen mouth. Surgery includes relieving fibrous bands followed by grafting to prevent re-fibrosis. Different surgical techniques are used to improve the condition of the patient. Each technique has its own advantage and disadvantages. Lasers application in OSMF is not much studied. In our case, laser (Diode) fibrotomy had an excellent result with satisfactory mouth opening and no recurrence until the last follow up.

Medical breath tests are well established diagnostic tools, predominantly for gastroenterological inspections, but also for many other examinations. Since the composition and concentration of exhaled volatile gases reflect the physical condition of a patient, a breath analysis allows one to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that is based on photoacoustic spectroscopy and uses a DFB diode laser at 2.744 μm. The concentration ratio of the CO2 isotopologues is determined by measuring the absorption on a 13CO2 line in comparison to a 12CO2 line. In the specially selected spectral range the lines have similar strengths, although the concentrations differ by a factor of 90. Therefore, the signals are well comparable. Due to an excellent signal-noise-ratio isotope variations of less than 1% can be resolved as required for the breath test.

The optical output power of a laser diode can be enhanced by anti-reflection (AR) and high-reflection (HR) facet coatings, respectively, at the front and back facet. AR and HR coatings also serve the purpose of protection and passivation of laser diode facets. In this work, we have designed and optimized a single layer λ/4 thick Al2O3 film for the AR coating and a stack of λ/4 thick Al2O3/λ/4 thick Si bi-layers for the HR coating for highly strained InGaAs quantum-well edge emitting broad area (BA) laser diodes. Effect of the front and back facet reflectivities on output power of the laser diodes has been studied. The light output versus injected current (L–I characteristics) measurements were carried out on selected devices before and after the facet coatings. We have also carried out the numerical simulation and analysis of L–I characteristics for this particular diode structure. The experimental results have been compared and verified with the numerical simulation.

Recent advances in the development of sensors based on infrared diode and quantum cascade lasers for the detection of trace gas species is reported. Several examples of applications in environmental and industrial process monitoring as well as in medical diagnostics using quartz enhanced photoacoustic spectroscopy and laser absorption spectroscopy will be described. Keywords: Trace gas detection, near infrared diode lasers, mid infrared quantum and interband cascade lasers, quartz enhanced photoacoustic spectroscopy, laser absorption spectroscopy.

The design and measured performance characteristics of a range of index-patterned diode laser sources are presented. These devices incorporate slotted regions etched into the laser ridge waveguide, which are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex lithography and regrowth steps. We first demonstrate that the index profile of single and multimode devices can be obtained directly from an inverse problem solution based on a perturbative calculation of the threshold gain of the longitudinal modes of the cavity. Measurements of temperature stability, linewidth, and modulation bandwidth of single-mode devices obtained in this way are presented. It is then shown that the design of multimode devices including two-color and pulsed mode-locked devices designed to support a discrete comb of modes is also possible. We finally demonstrate a tunable source based on a multisection design defined using etched features. This device is shown to have wide tunability with narrow linewidth modes and fast wavelength switching speed.

A vertical cavity surface-emitting laser diode (VCSEL) was used as a spectrally tunable emission source for measurements of the radial-integrated gas temperature inside an inductively coupled plasma reactor. The data were obtained by profiling the Doppler-broadened absorption of metastable Ar atoms at 763.51 nm in argon and argon/nitrogen plasmas (3%, 45%, and 90% N2 in Ar) at pressures of 0.5–70 Pa and inductive powers of 100 and 300W. The results were compared to the rotational temperature derived from the N2 emission at the (0,0) vibrational transition of the C 3Π
u–B 3Π
g system. The differences in integrated rotational and Doppler temperatures were attributed to non-uniform spatial distributions of both temperature and thermometric species (Ar* and N2*) that varied depending on the conditions. A two-dimensional, three-temperature fluid plasma simulation was employed to explain these differences. This work should facilitate further development of a miniature sensor for non-intrusive acquisition of data (temperature and densities of multiple plasma species) during micro- and nano-fabrication plasma processing, thus enabling diagnostic-assisted continuous optimization and advanced control over the processes. Such sensors would also enable us to track the origins and pathways of damaging contaminants, thereby providing real-time feedback for adjustment of processes. Our work serves as an example of how two line-of-sight integrated temperatures derived from different thermometric species make it possible to characterize the radial non-uniformity of the plasma.