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Vladimir G Lemberg, Saidur Rahaman, Nima Khatibzadeh, Alireza Malek Tabrizi, Hong Fu; Fiber Beam Delivery for Novel Ultrashort Femtosecond Laser Technologies . Invest. Ophthalmol. Vis. Sci. 2017;58(8):5291.
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© ARVO (1962-2015); The Authors (2016-present)
Femtosecond lasers are widely used for various ophthalmic applications ranging from creating flaps in LASIK procedures, corneal lenticule incisions, creating pockets for the corneal inlays to cataract surgery. The use of conventional optical fiber laser beam delivery is a common and convenient way to deliver the laser energy to the target tissue. However, the uses of conventional fiber based beam delivery for ultrashort laser pulses are limited due to the optical fibers dispersion. The recent advances in development of the hollow-core photonic crystal fibers opened up new opportunities to build a flexible beam delivery configuration for novel femtosecond laser technologies.
The femtosecond laser (pulsewidth 100-200fs) was coupled into Kagome hollow-core photonic crystal fiber PMC-C-Yb-7C. We matched the laser beam waist to fiber mode field diameter and the numerical aperture of the fiber, using variable NA optical system to achieve the high coupling efficiency. The low NA fiber output beam was re-collimated and delivered to the scanning and high numerical aperture (NA 0.6) focusing system. We attempted to create variety of the corneal cuts, using the flexible delivery configuration.
By using the variable NA optical system we have achieved the high (more than 94%) coupling efficiency and low (less than 2.5%) transmission losses (attenuation of -0.05 dB per meter at 1030 nm). Due to close to zero dispersion (~1 fs/nm/meter) at 1030 nm wavelength the femtosecond laser pulses were transmitted with virtually no pulse width broadening. Particular attention was given to the study the mechanical stability in the axial and radial directions as well as the beam quality and transmission losses as a function of the fiber bending radius. The high quality of the re-collimated beam, the high coupling efficiency and low transmission losses allowed us to demonstrate variety of corneal cuts ranging from flap, intrastromal lenticule and keratoplasty incisions and inlay pockets.
Our study demonstrated that the recent advances in development of the hollow-core photonic crystal fibers (zero dispersion at the design wavelength, absence of Fresnel reflections from the fiber-end faces high damage threshold and low transmission and bend losses) opened up new opportunities to build flexible beam delivery configuration for novel femtosecond laser technologies.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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