The radiation of Er-YAG laser ((lambda) equals 2.94 micrometer) gives selective interaction with tissues. The extinction in soft tissues is only a few micrometers and in hard tissues is of the order of hundreds of micrometers. This makes this type of laser very suitable for treatments in dentistry, orthopedy, or ophthalmology. Because the usual silica fibers are not transmitting the radiation at lambda equals 2.94 micrometer of this laser, many applications cannot be presently performed. Fused silica hollow fibers for Er-YAG radiation were developed in our laboratory and several possible applications in dentistry, orthopedy and ophthalmology were indicated. Hole opening and implantation preparation of teeth were experimented, using Er-YAG laser and hollow plastic waveguide delivery systems. Hole drilling in cow bones was demonstrated for applications in orthopedy. A new procedure of delivering Er-YAG radiation on fibrotic membranes of inner eggshell as a model of the membranes in eyes was developed employing silica hollow waveguides of 0.5 and 0.7 mm ID or a plastic waveguide of 1.0 mm ID. For this purpose waveguides with sealed distal tip were employed to enable us to approach the delivery system through liquid media near to the membrane. This experiment demonstrates the possibility of surgical applications in vitectomy in ophthalmology using Er-YAG laser and silica hollow waveguides.

Scattering of visible and mid-IR radiation transmitted through hollow flexible waveguides was measured employing two methods: total integrated scattered (TIS) and back scattered (BS) radiation. The root mean square ((sigma) ) of roughness was evaluated employing these two methods. This has also enabled evaluation not only of the (sigma) but also the location of important centers of scattering of the metal and dielectric deposited layers on the internal wall of waveguide tubes. Measurements of beam profile were performed using perspex cubes, in which the formed crater image has given information of the mode propagation into the waveguides as a function of distance from: (a) the coupling to the laser, (b) radius of bending, (c) ID of hollow tubes, and (d) coupled energy of laser in waveguide. It was shown that for given radii of bending whisper gallery mode of propagation appears.

The direct or waveguide transmitted beam shape of carbon dioxide laser was recorded by irradiating perspex blocks. The influence of waveguides materials, geometry, defects and roughness on the crater produced in the blocks was observed. Fused silica transmitted beams are narrower and sharper than the plastic transmitted beams, and the energy distribution can be clearly observed. The main effect on the beam shape comes from the wall roughness. The moving tip method was applied for non-destructive attenuation measurements.

Fused silica flexible hollow wave guides developed at TAU were used to deliver Er-YAG laser radiation to a biological membrane model. The model was composed of fibrotic (inner egg shell) membranes that were either brushed with or immersed in physiological saline solution. Waveguides used included fibers with an inner diameter of 0.7 mm and 0.5 mm. Membrane aperture size and fiber output power density were obtained. Results for the 0.5 mm waveguides yielded average apertures of 100 micrometer length at a power density of 5.35 W/cm2 and threshold fluence of 10 mJ/cm2 for exposed membranes and 35 mJ/cm2 for wet membranes. The results indicate that this waveguide can be used to cut dense membranes, finally, we have succeeded in delaminating immersed membranes using a sealed waveguide. These results show the applicability of using fused silica flexible hollow waveguides for Er-YAG surgical applications of dense membranes in aqueous surroundings such as vitrectomy and posterio-copsulectomy in ophthalmology, and possibly for procedures involving pleural membranes.

Two types (plastic and fused silica) of waveguides suitable for transmitting and Er-YAG laser radiation were prepared and characterized. The temperature of several points on the external surface of the waveguides was measured. Optical parameters (transmission, focusing, misalignment) of the two types of waveguides were measured and compared. The importance of heating (due to losses) on the long time delivery performance is also shown.

The effect of external energy source on waveguide's transmitted blackbody radiation is examined. It is shown that the radiometric signal is increased because of external heat sources. This effect can be avoided by a proper external protecting layer. The transmitted laser energy is another cause of heating the waveguide's walls. To analyze these effects, the wall temperature was recorded by thermocouples and thermal camera. It is shown that the most-affected regions in the waveguide are the curved regions and the distal end. Gas cooling and external metal layers reduce this undesired heating of the walls.

Surface roughness of sections of hollow waveguides is examined by measuring the backscattering reflection and using the total integral scattering (TIS) method. The iodination of silver was found as the main factor affecting the surface roughness. The AgI layer thickness also affects an interference phenomena as a function of wavelength.

Plastic and fused silica waveguides suitable for transmitting CO2 and Er-YAG laser radiation were prepared and characterized. The temperature of several points on the waveguide was measured. Optical parameters (transmission, focussing, misalignment) of the two types of waveguides were determined and compared.

A new method for characterizing hollow waveguides has been developed in which the laser radiation is coupled into the waveguide hollow bore through an optical fiber. By moving the distal end of the fiber along the waveguide we achieved scanning of the incident radiation in the waveguide at various points on the internal walls. This method can be employed for measuring attenuation without cutback or for detecting point defects on the waveguide's guiding layers.

Flexible plastic waveguides (FPW) were devised for the delivery of Er-YAG laser radiation. The FPW characteristics were studied under various conditions. In vitro studies were carried out to explore the drilling procedure on extracted teeth and the FPW-tissue mutual effects. The results which were obtained proved that the FPW as a delivery device might be a substitute hand applicator for the pneumatic turbine for drilling in teeth.

Flexible plastic waveguides were used in several fields of dentistry for treatments in the oral cavity. Soft tissue lesions were treated applying CO2 laser energy. A new technique for dental implants was suggested using a combination of Er-YAG and CO2 laser energy. Cavity preparation in the teeth was performed using the Er-YAG laser radiation and CO2 energy transmitted by the waveguides was used for root canal treatments.

The scattering phenomenon of infrared and visible radiation from hollow waveguides, made of teflon or fused silica, having Ag and AgI guiding layers, was measured by two methods; Total Integrated Scattered and Backscattering. The root means square roughness was evaluated by both methods. It was found that the roughness of the silver layer is influenced by the substrate. The AgI is the main contributor to roughness and this is a function of its preparation method.

Flexible plastic waveguides (WG) were devised for the delivery of Er-YAG laser energy in curved trajectories. The WG were optically characterized. The WG transmitted energy could drill a hole in teeth enamel hence it can be used as a substitute for a pneumatic drill.

Flexible plastic waveguides (FPW) were first developed for CO2 laser radiation. Further investigation of the factors which influence the quality of the reflecting and refracting layers, have led to the development of a method of smoothing of the substrate and the layers. A mechanism of controlling the dielectric layer thickness was also devised. Based on this knowledge we produced waveguides which can transmit several wavelengths of laser radiation. Measurements of the transmission characteristics of FPW coupled to Er-YAG (2.94 micrometers ), and Ho-YAG (2.1 micrometers ), CO (5.5 micrometers ), CO2 (10.6 and 9.6 micrometers ), and TEA laser (9.6 micrometers ), under various conditions (power, bending) were made and show good results. The use of the FPW in transmitting these types of laser radiation may broaden the spectrum of uses of the waveguides in medical application, i.e., hard tissues (bone, teeth) and in the eyes.

Transmission properties of a plastical hollow waveguide at wavelength of 2.94 micrometers have been studied. The measured transmitted beam profiles for different waveguide bending curvatures are compared with theoretical transmissions, and profiles of ablation holes in hard dental tissue.