Photocoagulators are one of the most popular laser devices in medicine. Due to different kind of interaction of particular
wavelength range of laser light with live tissues, sources of laser radiation which can cover as much as possible of visible
spectrum are still very wanted (see [1,2]). In last years it also can be observed the intensive developing works on new
photocoagulation technique called “micropulse coagulation” [3,4]. The most critical feature of lasers for micropulse
coagulation is the possibility of fast switching between two selected laser power values. It seems that the good proposal
for these applications can be ion laser filled with argon-krypton mixture. Authors previously have indicated the
possibility of improvement of generation conditions in this type of laser in presence of buffer gases [5,6] and with use
developed by authors pulse supply regime [7,8]. These improvements allow to obtain output power values of most
important argon and krypton laser lines in laser filled with mixture of both gases, similar to values available in laser
filled with pure gases. Presented in this paper the following researches are concerned on verification of possibilities of
use of the developed laser system in photocoagulation with possibility of use of the laser system in micropulse
coagulation technique.
In the previous our paper we have presented measurement results of the phenomenon of argon additions influence on
output parameters of krypton ion lasers. In that paper we have described that small argon admixtures to the krypton
discharge increase the laser output power of several krypton laser lines. In actual paper we present following
measurement results of this phenomenon. We have observed that neon admixtures cause much stronger effect on krypton
laser lines than we have previously observed with argon admixtures. We have also observed the positive influence of
neon additions on generation conditions of argon laser lines. The magnitude of this effect is weaker than influence
observed with krypton laser lines however the way of the effect is identical. This confirms our explanation of this
phenomenon described in. Results presented in actual paper were performed in wide range of mixture compositions,
gas pressures and discharge current values for several argon and krypton laser lines.
Argon ion lasers can generate several strong laser lines in short wavelength region of visible spectrum (green and blue
light). Krypton ones offer the generation of laser lines in long wavelength region (red and yellow light). Both gases have
complementary generation ranges thus ion lasers filled with mixture of argon and krypton are attractive laser sources for
many applications. In most of these applications the only one laser line selected with dispersion element within the
resonator are used at one time. After removing the dispersion element the simultaneous generation of many wavelengths
is possible. Unfortunately in this working mode of ion lasers the negative effect of competition between laser lines
appears. The effect has the most significant influence on the generation of yellow Kr II 568 nm line which is very needed
for some applications due to small number of other available strong laser sources for this light range. Generation
conditions of this line is strongly hampered when ion laser simultaneously generates other laser lines thus in this laser
working mode this laser line completely disappears. We have observed the exact reason of this effect and we have
described the way to improve laser generation conditions of Kr II 568 nm line which makes possible to obtain the laser
generation of this line simultaneously with other laser lines.
Ion gas lasers filled with pure argon or krypton are often used in medicine. The number of possible medical laser
applications are still increasing. Every type of application requires specific wavelength range. Due to number of
available laser wavelengths of argon and krypton lasers, laser filled with mixture of both gases could be interesting
universal medical laser source. However output power value of some interesting in medical point of view laser
wavelengths may be insufficient in laser filled with mixture. Developed by authors quasi-continuous ion laser supply
regime in connection with observed and described by authors the effect of laser power increase in presence of noble gas
admixtures allows to achieve laser power satisfactory for certain medical applications but unavailable in typical ion
lasers operated with standard continuous power supply regime.
In this paper authors will present the phenomenon of advantageous influence of noble gas additions on the output
parameters of krypton ion lasers. Authors have observed that small additions of argon to the krypton discharge causes
increase of laser output power of certain krypton laser lines. The power change depends on laser line wavelength,
mixture composition, gas pressure and discharge current values. Authors will present measurement results and
explanation of this phenomenon.
In many applications of ion gas lasers the laser beam is used for specified short periods of time. For these applications
laser systems are typically equipped with mechanical shutter. In consequence of this regime of laser beam modulation
the peak output power of laser pulses are equal to constant output power generated by laser. Results of our experiments
described in 1 shows that in pulse mode of supplying discharge current it is possible to obtain significant increase of peak
value of laser output power in comparison with laser output power generated in CW operation (without current
modulation).
In this paper we present results of our following experiments on pulse supply of ion laser filled with argon-krypton
mixture. For this laser operates in pulse regime we have observed the significant - up to 3.5 times - increase of peak
laser output power. This effect was especially strong in the UV range. This paper anwe measured in far field the sigxture
percentage on the output power of individual Ar and Kr spectral lines in pulse operation. The research suggests that the
most significant effect results from different gas pumping rate of the mixture components in the discharge path.a
In terms of maximal laser output power, the optimum gas pressure in the ion laser tubes depends on a wavelength of the
generated spectral line. In order to control the gas pressure we introduced a simple and effective method of gas pumping
from the laser tube to an additional reservoir. This method could be well employed in commercially available ion lasers.
Establishing of a correlation between the ion laser output power and controlled losses introduced to a resonator allowed
to determine basic parameters of the laser active medium i.e. unsaturated gain coefficient and gain saturation parameter.
The resonator losses as well as optimum mirror transmission and were also determined. The tests were performed for ten
Ar III and Kr III lines in UV spectrum.
Argon and krypton ion lasers work typically in CW (continuous wave) mode. In many of applications, the continuous operation of ion lasers is not required. Presented in this article laser power supply makes possible to operate in two regimes: continuous and quasi-continuous (multi-pulse). In multi-pulse operation the most of output power limits for continuous regime was overcame. This allowed increasing the laser output power considerably. Particularly excellent results were obtained for laser tube filled with Ar-Kr mixture and operating in UV range. The main phenomenon deciding on output laser power increasing in pulse and multi-pulse operation is minimization of harmful effects of gas pumping. Possibility of multi-pulse operation creates new advantages of ion lasers and extends range of its applications.
Significant progress observed in last years in structure and technology of ion laser discharge tubes created new possibilities of the continuous generation of the ultraviolet radiation. Segmented metal-ceramic laser discharge tube was used in our experiments. CW generation of 3 new UV lines in double ionized argon and krypton was observed. Generation of two of these lines (Ar III, λ=350.4 nm and Kr III, λ=330.4 nm) was unknown up today even in high current pulse operation. The shortest (λ=324.8 nm) Kr III line, well known in pulse mode but unknown in CW operation is particularly important. Relatively low threshold current and comparable with known Kr III (337 nm) output power level makes easy its application. Laser UV operation on the mixture of two most important, active gases Ar and Kr were studied. Simultaneous generation of the all laser lines of Ar III and Kr III was achieved. For the optimal mixture composition relatively high power generation of 10 laser lines in a wide spectral range 324 - 363 nm were obtained. Preliminary experiments on determining the influence of high ionization potential inert gases (Ne, He) on the UV generation in the argon were carried out. Advantageous influence of Ne results on the distinct increasing of the laser power and similar distinct lowering the threshold current of the generation was observed.
In this paper a new construction and technology of argon laser discharge tube is presented. The discharge capillary consists of silicon carbide discs brazed to copper segments. Basic parameters of the new tube (laser output power and magnitude of a gas pumping effect) were measured. These parameters are better in comparison to classical metal-ceramic laser tube.
A positive effect of application of permanent magnets field in argon ion laser has been observed. Some ring magnets producing quasi-homogeneous field increases several times the output power. This influence is stronger with respect to magnet coil application. The reason of this phenomenon is caused by electron temperature increasing in radial magnetic field areas. Application of permanent magnets field should substantially enhance the output power of air cooled argon lasers.
Wieslaw Wolinski, Tadeusz Adamowicz, H. Ciesielski, S. Jonak, Antoni Kazmirowski, Jerzy Kesik, Joern Kowalewski, Antoni Siejca, Piotr Warda, Jan Kasprzak, Tadeusz Kecik, Iwona Switka-Wieclawska
In this paper a unit with two krypton lasers is described. This apparatus is designed to be used in photodynamic diagnosis and therapy of tumors in ophthalmology. Some technical data are given.
Wieslaw Wolinski, Tadeusz Adamowicz, H. Ciesielski, S. Jonak, Antoni Kazmirowski, Jerzy Kesik, Antoni Siejca, Piotr Warda, Jan Kasprzak, Dariusz Kecik, Tadeusz Kecik
An endocoagulator with an ion argon laser designed and manufactured at Warsaw Technical University is described in this paper. Technical data and a short description of this unit are given.
Application of an axial magnetic field in ion argon lasers causes rotation of the polarization plane of output radiation. This fact increases the optical losses of the resonator. This effect can be reduced remarkably by using the crystal quartz Brewster windows instead of the fused silica ones. A Faraday effect can be calculated with the help of Jones matrix formalism. It has been shown that by using crystal quartz windows we can decrease the optical losses 10 times in comparison with the fused silica windows. This effect has been confirmed experimentally.
Introducing the quasi-homogenous axial magnetic field from permanent magnets to metal- ceramic argon discharge tube it is possible to increase considerably the output power of laser. This power is approximately close to the output power of laser with a classical magnet coil. The use of permanent magnets allows it to apply an air cooling system. The cw power of air cooled argon laser with active medium length 320 mm is about 2 W and increases to 3.5 W in pulsing excitation.
Argon and krypton lasers are widely used in medicine. The paper contains information on ion lasers parameters and a description of diagnostic and therapeutic systems containing ion lasers used in different branches of medicine: ophthalmology, dermatology, micro-surgery, and photodynamic therapy of tumors.
Argon-dye laser photocoagulator for the microsurgery of the interior structure of the eye is described. Some technical specifications like power stability shape of the spots and the dependence of the power on the tissue vs. wavelenght for dye laser are given. Argon-dye photocoagulator was designed and constructed including argon laser tube and dye laser in Institute of Microelectronics and Optoelectronics Technical University of Warsaw.
In this paper a description of the construction and technology of manufacturing of ion argon laser with 1 m long metal-ceramic discharge tube is presented (The previous paper on the subject [2] has concerned discharge tube of the same kind but consisting of ten 10 cm long parts). There is also an analitical approach to the gas pumping effect in the paper.
Argon - dye photocoagulator for the microsurgery of the interior structure of the eye is deseribed. The technical specifications are given. Some technical parameters of the argon laser tube are described.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.