Until recently, Laser Diodes (LD) have been limited in their ability to deliver high peak power levels, which, in turn, limited their clinical capabilities. New technological developments made possible advent of “super pulse” LD (SPLD). Moreover, advanced means of smart thermal feedback enable precise control of laser power, thus ensuring safe and optimally efficacious application. In this work, we have evaluated a prototype SPLD system ex vivo. The device provided up to 25 W average and up to 150 W pulse power at 940 nm wavelength. The laser was operated in the thermal feedback-controlled mode, where power of the laser was varied automatically as a function of real-time thermal feedback to maintain constant tip temperature. The system was also equipped with a fiber tip initiated with advanced TiO2 /tungsten technique. Evaluation methods were designed to assess: 1) Speed and depth of cutting; 2) Dimensions of coagulative margin. The SPLD system was compared with industry-leading conventional diode and CO2 devices. The results indicate that the SPLD system provides increase in speed of controlled cutting by a factor of >2 in comparison with the conventional diode laser and approaching that of CO2 device. The produced ratio of the depth of cut to the thermal damage margin was significantly higher than conventional diodes and close to that of the CO2 system, suggesting optimal hemostasis conditions. SPLD technology with real-time temperature control has a potential for creating a new standard of care in the field of precision soft tissue surgery.
With new fiber systems available for 3 μm, Erbium lasers become more interesting for precise tissue ablation in a water
environment enabling new application in e.g. dentistry. The dynamics of explosive bubble formation was investigated at
2.78 μm (Er,Cr;YSGG) and 2.94 μm (Er:YAG), in relation to energy (10-50 mJ), pulse length (20–150 μs) and fiber tip
shape (flat or taper). The dynamics of exploding and imploding vapor bubbles were captured with high speed imaging
(10 - 300 μs range). Increasing the pulse length and energy, the vapor bubble became more elongated with an opaque
surface for flat tip fibers. Tapered fibers produced spherical vapor bubbles with an optically transparent surface expected
to be more forceful for creating mechanical effects in both hard and soft tissues. There was no significant difference
between bubbles formed at 2.78 μm (Er,Cr;YSGG) and 2.94 μm (Er:YAG).
The use of Fe:ZnSe polycrystals as passive Q-switches for the Er:Cr:YSGG laser operating at 2.8&mgr;m is introduced.
Fe:ZnSe samples with 1-7cm-1 coefficients of absorption were prepared using thermal diffusion of iron in CVD grown
polycrystalline ZnSe. A flashlamp pumped Er:Cr:YSGG laser with a variable (40 - 80% reflectivity) output coupler (OC)
was used as a test bed for passive Q-switching. Using a 90% initial transmission Fe:ZnSe placed at the Brewster angle
we obtained a single giant pulse lasing with a pulse duration of ~65 ns and a maximum output of 13 mJ under 30 J of
flashlamp pump. Multi-pulse (19 pulses) output was obtained with 85 mJ total output energy at a pump energy of 30 J.
The saturation curve of Fe:ZnSe was measured. Fitting this data with a theoretical model results in absorption crosssection
of 0.56 × 10-18 cm2, which is close to the value of the absorption cross-section obtained from spectroscopic
measurements (0.85 × 10-18 cm2 at 2.8 &mgr;m).
The structural changes in a human tooth enamel have been investigated by SEM method with action of submillisecond pulses of YAG:Nd and YAG:Cr;Tm;Ho lasers at the energy densities below the threshold of surface tissue ablation. The conditions of laser treatment leading to the essential increase of the acid resistance and microhardness of the intact enamel are defined. Influence of the laser radiation parameters on the acid resistance of the tooth crown in the pits and fissure area are investigated.
For the first time the investigation results of acid resistance and microhardness of the dentin in root canals of the human tooth irradiated by Nd:YAG and Ho:YAG lasers are presented. The morphological changes in root dentin at the operated area were observed by SEM.
The new type of seif-electrooptic--effect--device is presented.
Optical nonlinearity and bistability due to the internal electric
field redistribution in nonuniform i-layer of double GaAs/A1GaAs
PIN heterostructure are achieved.