title: Kagome fiber based ultrafast laser microsurgery probe delivering micro-Joule pulse energies.
abstract: We present the development of a 5 mm, piezo-actuated, ultrafast laser scalpel for fast tissue microsurgery. Delivery of micro-Joules level energies to the tissue was made possible by a large, 31 μm, air-cored inhibited-coupling Kagome fiber. We overcome the fiber's low NA by using lenses made of high refractive index ZnS, which produced an optimal focusing condition with 0.23 NA objective. The optical design achieved a focused laser spot size of 4.5 μm diameter covering a 75 × 75 μm2scan area in a miniaturized setting. The probe could deliver the maximum available laser power, achieving an average fluence of 7.8 J/cm2on the tissue surface at 62% transmission efficiency. Such fluences could produce uninterrupted, 40 μm deep cuts at translational speeds of up to 5 mm/s along the tissue. We predicted that the best combination of speed and coverage exists at 8 mm/s for our conditions. The onset of nonlinear absorption in ZnS, however, limited the probe's energy delivery capabilities to 1.4 μJ for linear operation at 1.5 picosecond pulse-widths of our fiber laser. Alternatives like broadband CaF2crystals should mitigate such nonlinear limiting behavior. Improved opto-mechanical design and appropriate material selection should allow substantially higher fluence delivery and propel such Kagome fiber-based scalpels towards clinical translation.
authors.affiliation: Department of Mechanical Engineering, The University of Texas at Austin, Texas 78712, USA; These authors contributed equally to this work.
authors.forename: Kaushik
authors.initials: K
authors.lastname: Subramanian
authors.affiliation: Department of Mechanical Engineering, The University of Texas at Austin, Texas 78712, USA; These authors contributed equally to this work.
authors.forename: Ilan
authors.initials: I
authors.lastname: Gabay
authors.affiliation: Department of Mechanical Engineering, The University of Texas at Austin, Texas 78712, USA.
authors.forename: Onur
authors.initials: O
authors.lastname: Ferhanoğlu
authors.affiliation: Department of Bioengineering, Rice University, Houston 77005, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Shadfan
authors.affiliation: Department of Bioengineering, Rice University, Houston 77005, USA.
authors.forename: Michal
authors.initials: M
authors.lastname: Pawlowski
authors.affiliation: Department of Bioengineering, Rice University, Houston 77005, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Bioengineering, Rice University, Houston 77005, USA.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Tkaczyk
authors.affiliation: Department of Mechanical Engineering, The University of Texas at Austin, Texas 78712, USA; Department of Biomedical Engineering, The University of Texas at Austin, Texas 78712, USA.
authors.forename: Adela
authors.initials: A
authors.lastname: Ben-Yakar
keywords: (140.7090) Ultrafast lasers; (170.1020) Ablation of tissue; (170.3890) Medical optics instrumentation; (190.4370) Nonlinear optics, fibers; (190.4400) Nonlinear optics, materials