Development of low energy and high repetition rate femtosecond laser with potential application to refractive surgery

• Ano de defesa: 2025
• Autor(a) principal: Pinto, Vinícius Pereira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Ablação laser; Alta taxa de repetição de pulsos; Femtosecond laser; High-repetition rate laser; Laser ablation; Laser femtossegundo; Nanocirurgia; Nanosurgery; Oftalmologia; Ophthalmology
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/76/76134/tde-07042025-105155/

This work aims to enhance the precision and safety of refractive surgery by developing a compact, cost-effective femtosecond laser system with a high repetition rate. The motivation behind this research stems from the need to improve surgical accuracy, which is hypothesized to be achievable through higher laser repetition rates, a feature characteristic of compact resonators. In line with this, a low-energy Kerr-lens mode-locked Ti:Sapphire laser oscillator was developed, operating at a 1 GHz repetition rate. This laser, utilizing a bow-tie cavity with dispersioncompensating mirrors and a Peltier temperature regulation system, achieved an average output power of 0.94 W at 7.4 W of pump power, with a broadband emission centered at 756 nm, generating low-energy pulses of 1 nJ with a temporal width of 61 fs and a peak power of 15 kW. To evaluate the application of the laser in refractive surgery, an in-depth analysis of laser-PMMA interactions was conducted using Polymethyl methacrylate (PMMA) as a corneal surrogate. This analysis aimed to elucidate the laser-induced ablation essential parameters for surgical applications. The characterization of the surgical process was performed using commercially available laser for refractive surgery to better understand the processing method. The study involved micromachining techniques characterized by surface and volume analysis, conducted with two different femtosecond lasers, examining varying combinations of pulse overlap and energy levels to determine the threshold pulse energy required for damage. The results revealed that higher repetition rates with low-energy pulses produced more precise damage compared to high-energy, low repetition rate pulses. These findings indicate that compact, high repetition rate femtosecond lasers with low-energy pulses offer substantial potential for improving the precision of refractive surgeries, while also facilitating equipment miniaturization and cost reduction.