Passively mode locked femtosecond Tm:Sc2O3 laser at 2.1 µm.

We report on the passive mode locking of a Tm3+:Sc2O3 laser at 2.1 µm using a semiconductor saturable absorber mirror based on InGaAsSb quantum wells. Transform-limited 218 fs pulses are generated with an average power of 210 mW. A maximum output power of 325 mW is produced during mode locking with the corresponding pulse duration of 246 fs at a pulse repetition frequency of 124.3 MHz. A Ti:sapphire laser is used as the pump source operating at 796 nm.

Optimized evaluation of a pulsed 2.09 microns holmium:YAG laser impact on the rat brain and 3 D-histomorphometry of the collateral damage.

Since more than 20 years CO2 and Nd:YAG lasers are established in the microsurgery of the nervous system. CO2 lasers can be used handheld, but may be focused on the target area by mirror optics and sideports of the operating microscope's micromanipulator. Nd:YAG lasers have the disadvantage of deep penetration into the brain and provocation of a large collateral damage. The need is for a fibre conducted solid system for surgery in delicate areas as for brain stem surgery. Fibre conduction of near infrared lasers allows better exposure of the target area compared to hollow wave guides or mirror equipment. Fibres can be tapered and modified according to the purpose. The holmium:YAG (Ho:YAG) laser has acquired interest by introducing the system into microsurgery of parenchymal tissue. They have not been proven yet sufficiently for neurosurgical tasks. The effort to minimalize the collateral tissue damage has to be maximalized in the surgery of nervous tissue and functional low redundant brain stem or spinal cord tissue. Volumetric data may be more precise in comparison to depth and width data of the laser lesion even when the different levels of the tissue interaction have to be analyzed for estimation of the real side effects in nervous tissue. We have used 50-800 ml delivered Ho:YAG single pulses in cortical areas of Sprague-Dawley rats and investigated the different lesion zones by volumetric data. The functional lesion zone was detected and measured by immunohistological staining of the heat shock protein HSP 72. For further reduction of the focus area, we have used tapered 400 to 200 microns fibres.

Seventeen live births after the use of an erbium-yytrium aluminum garnet laser in the treatment of male factor infertility.

Mechanical partial zonal dissection (PZD) is one of the microinsemination techniques developed to improve the chances of fertilization by in-vitro insemination in subfertile males. We developed a new and safe laser method (erbium laser ablation) for PZD, with the aim of producing a precise opening as well as ablation of some layers of the zona pellucida. From February 1992 to March 1993, 104 couples suffering from male factor infertility were treated in our centre. All patients were affected by severe oligoasthenozoospermia and had previously undergone one failed in-vitro fertilization attempt each. Photoablation of the zona pellucida was induced in 512 oocytes by exposure to an erbium--yytrium aluminium garnet (Yag) laser. The openings obtained were approximately 14 microns in diameter. Of the laser-treated oocytes, 158 (30%) fertilized and 139 (88%) cleaved. Nineteen (18.3%) clinical pregnancies resulted and produced 17 newborns, all in good health. In our series there were four miscarriages, 23 damaged oocytes (4.4%) and 13 with three or more pronuclei (2.5%). Considering that the incidence of damaged oocytes and polyspermy is low, it seems that in some cases of male factor infertility erbium-Yag laser photoablation of the oocyte zona pellucida can be considered a procedure which is effective in enhancing fertilization and which is safe, allowing normal embryo development.

Immunohistochemical and electronmicroscopic effects of a new 2.1 microns Ho:YAG laser on the rat brain.

Using an experimental animal model, the thermal single-pulse lesion derived from a mid-infrared 1.0 Joule 300 microns fibre-conducted Holmium: Yttrium-Aluminum-Garnet (Ho:YAG) laser was examined, with special emphasis on the orientation and depth of the tissue reaction. Performing biparietal craniotomy in Sprague-Dawley rats weighing 250-300 g, both hemispheres were targeted by different radiant exposures from 20 to 140 J/cm2 derived from a 600-800 microsecond single pulse. After survival periods of one to 30 days, the animals were sacrificed and both hemispheres were processed for light- and electronmicroscopic investigations. To resolve the depth and orientation of the tissue reaction regarding the localization of reactive astrocytes, we looked for the expression of glial proteins like glial fibrillary acidic protein (GFAP), Vimentin and S 100 with a three-step biotin-avidin immunoperoxidase method. Neuronal and secondary axonal damage was investigated by labelling Neurofilament and Synaptophysin. The tissue reaction beneath the ablated material, consisting of a vacuolation and coagulation zone resulting from heat diffusion, was further elucidated by localization of the heat shock protein (HSP 72 kilo Dalton). Revealing the extension of reactive astrocytes and the degree of the electronmicroscopically depicted glial oedema, the depth of the tissue damage was estimated to reach about 700 microns beneath laser excision. Since McKenzie predicted the depth of tissue damage beneath CO2 and YAG laser excisions in a theoretical mathematical model, the authors were able to develop a sensitive model for testing new laser systems and as a promising instrument for neurosurgery.