Optimizing photoablation parameters in the Mid IR - A predictive model for the description of experimental data

Proceedings of SPIE - The International Society for Optical Engineering

Volumn 2391, Issue , 1995, Pages 138-149

  Ostertag, Manfred ^a   Walker, Rudolf ^a   Bende, Thomas ^a   Jean, Benedikt ^a  

^a UNIVERSITY OF TÜBINGEN   (Germany)

Author keywords

Ablation model; Ablation rate; Calculations for heat conduction; Er:YAG laser ablation; Free Electron Laser ablation; H2O D2O exchange; Thermal damage; Variation of absorption coefficient; Wavelength variation

Indexed keywords

ABLATION; ELECTRONS; FREE ELECTRON LASERS; HEAT CONDUCTION; HEAVY WATER; LASER ABLATION; LASER TISSUE INTERACTION; TISSUE; WATER ABSORPTION; YTTRIUM ALUMINUM GARNET;

ABLATION MODEL; ABLATION RATES; ABSORPTION CO-EFFICIENT; ER:YAG LASERS; THERMAL DAMAGE;

PULSED LASERS;

EID: 84925001298     PISSN: 0277786X     EISSN: 1996756X     Source Type: Conference Proceeding    
DOI: 10.1117/12.209876     Document Type: Conference Paper

References (16)

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4. Ostertag M, Walker R, Hartmann WD, Jean B. Photoablation with the FEL in gelatine by infrared wavelengths: Comparison of measured ablation rates with a model. submitted to Lasers Surg Med.
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7. Jean B, Bende T, Seiler T, Brau ChA. Photoablation of Gelatine with the Free-Electron Laser between 2. 7 and 6. 7 /nn. Refr Corn Surg 1994; 10(4):433-438.
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10. Zweig AD, Weber HP. Mechanical and Thermal Parameters in Pulsed Laser Cutting of Tissue. IEEE J Quantum Electron 1987; QE-23:1787-1793.
11. ed = ΔT pc with ΔT the temperature at which thermal damage occurs, the density p = 10 kg/ni3 and the specific heat c = 3. 5 J/(kgC) (values of water). The temperature at which thermal (lamage occurs is 57 C 14 and the preablation temperature of the rehydrated corneas was 20 061thus ΔT = °C.
12. Bende T, Walker It, Jean B. Photoablation in Porcine Corneas with the Free-Electron Laser between 2. 7 and 6. 7 itin-Thermal Collateral Damage. Refr Corn Surg 1994; accepted.
13. Ostertag M, Walker R, Jean B. Laser Ablation of Tissue (Cornea): effect of Absorption Coefficient on Ablation Efficiency and Thermal Damage. Submitted to Appi Phys B.
14. Zweig AD, Meierhofer B, Muller OM, Mischler C, Romano V Frenz M, Weber HP. Lateral Thermal Damage Along Pulsed Laser Incisions. Lasers Surg Med 1990; 10:262-274.
15. In our perforation experiments we defined cornea is perforated when 1/5 of the total energy per pulse is measured with the energy monitor behind the cornea. With a Gaussian beam profile the fluence is not constant over the ablation area and-y should be determined by ' = F/e, with F the fluence at the area where perforation occured exactly at the time when our definition cornea is perforated is fulfilled.
16. For example Ren et al. 2 performed ablation of the cornea with an Er:YAG (2. 94 tin) and with an Er:YSGG (2. 79 inn) for two different pulse durations (200 ps normal spiking mode; 100 us Q-switched mode). They obtained for the wavelength 2. 94 pm and a pulse length of 200 jts (100 us) an extension of the damage zone of 16±2 pm (4±2 pm) and for the wavelength 2. 79 pm and a pulse length of 200 ps (100 us) an extension of the damage zone of 39±7 pm (4 2±pm).