Simultaneous spatial and temporal focusing for tissue ablation

Block, Erica; Greco, Michael; Vitek, Dawn; Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Mandava, Naresh; Durfee, Charles G.; Squier, Jeff

doi:10.1364/boe.4.000831

Cited by 52 publications

(28 citation statements)

References 15 publications

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“…28,29 Furthermore, the suitability of SSTF for tissue ablation by laser-induced optical breakdown has recently been shown. 30,31 In this paper, we present detailed experimental and numerical investigations of the nonlinear pulse propagation and breakdown formation induced by SSTF and conventional focusing at low repetition rate. Special emphasis is put on possible applications of SSTF in ophthalmic fs-laser surgery.…”

Section: Introductionmentioning

confidence: 99%

“…7 We therefore analyze plasma formation and subsequent disruptions as well as nonlinear side effects such as filamentation in a water cell through pump-probe shadowgraphy. While previous studies of SSTF were frequently based on strongly elliptical beams caused by spectral separation, 30,[32][33][34] this study emphasizes equivalent focusing parameters such as a comparable NA to compare the nonlinear pulse-material interaction induced by conventional focusing and SSTF. This factor is of special importance because several applications, including ophthalmic laser surgery, require certain focusing conditions, where, for example, the NA is limited by the pupil size of the eye.…”

Section: Introductionmentioning

confidence: 99%

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Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

et al. 2014

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In recent years, femtosecond (fs)-lasers have evolved into a versatile tool for high precision micromachining of transparent materials because nonlinear absorption in the focus can result in refractive index modifications or material disruptions. However, when high pulse energies or low numerical apertures are required, nonlinear side effects such as self-focusing, filamentation or white light generation can decrease the modification quality. In this paper, we apply simultaneous spatial and temporal focusing (SSTF) to overcome these limitations. The main advantage of SSTF is that the ultrashort pulse is only formed at the focal plane, thereby confining the intensity distribution strongly to the focal volume and suppressing detrimental nonlinear side effects. Thus, we investigate the optical breakdown within a water cell by pump-probe shadowgraphy, comparing conventional focusing and SSTF under equivalent focusing conditions. The plasma formation is well confined for low pulse energies ,2 mJ, but higher pulse energies lead to the filamentation and break-up of the disruptions for conventional focusing, thereby decreasing the modification quality. In contrast, plasma induced by SSTF stays well confined to the focal plane, even for high pulse energies up to 8 mJ, preventing extended filaments, side branches or break-up of the disruptions. Furthermore, while conventional focusing leads to broadband supercontinuum generation, only marginal spectral broadening is observed using SSTF. These experimental findings are in excellent agreement with numerical simulations of the nonlinear pulse propagation and interaction processes. Therefore, SSTF appears to be a powerful tool to control the processing of transparent materials, e.g., for precise ophthalmic fs-surgery.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

et al. 2014

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“…[19][20][21][22][23] This control has led to various advances in laser writing and ablation applications. [24][25][26] In this proceedings paper, we numerically explore material modification and damage due to radially chirped annular pulses via simulated propagation of time-chirped femtosecond pulses through the system shown in Fig. 1.…”

Section: -16mentioning

confidence: 99%

Calculation of nonlinear optical damage from space-time-tailored pulses in dielectrics

Lanier

Gulley

2015

SPIE Proceedings

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Control of the time duration of a laser pulse as it focuses spatially in a material provides a means for delaying the onset of nonlinear e↵ects during propagation. We investigate simultaneous space-time focusing (SSTF) of femtosecond radially-chirped annular pulses in Kerr dielectrics. The energy and temporal chirp of pulses incident upon a grating-grating-lens system are varied in simulations that solve the unidirectional pulse propagation equation. This system is modeled by inserting transformations that act on the electric field obtained from propagation from one component to the next. The propagation is coupled to the time evolution of the free charge density as a function of space. The resulting "ionization tracks" are taken as a metric for predicting material modification and/or damage in bulk fused silica. As expected from linear-optical considerations, the temporal pre-chirp determines the overall pulse duration as the focusing annulus closes. We find in addition that, for a given pulse energy, the temporal pre-chirp also determines the on-axis intensity distribution as energy collapses onto the propagation axis. This e↵ect determines how the local ionization-induced decrease in refractive index shifts energy in time relative to energy arriving on-axis from the spatially collapsing beam. The magnitude of the pre-chirp can thus control the spatial structure of ionization that may lead to material modification and/or damage.

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“…While experimental setups are easily controlled, they suffer from lack in fabrication throughput and end-quality of the machined samples. In addition, spatio-temporal enhanced front-side ablation [11][12][13] is used when high quality cuts or precise patterns are required. For transparent materials, all of the above-mentioned techniques are applicable, and, in addition, several modification-based techniques exist: chemical etching of laser-induced bulk modifications [14][15][16][17][18][19], dicing techniques [20,21] etc.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Micromachining Process of Dielectric and Metallic Substrates Immersed in Water with Femtosecond Pulses

et al. 2015

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Abstract:Micromachining of 1 mm thick dielectric and metallic substrates was conducted using femtosecond pulse generated filaments in water. Several hundred microjoule energy pulses were focused within a water layer covering the samples. Within this water layer, non-linear self-action mechanisms transform the beam, which enables higher quality and throughput micromachining results compared to focusing in air. Evidence of beam transformation into multiple light filaments is presented along with theoretical modeling results. In addition, multiparametric optimization of the fabrication process was performed using statistical methods and certain acquired dependencies are further explained and tested using laser shadowgraphy. We demonstrate that this micromachining process exhibits complicated dynamics within the water layer, which are influenced by the chosen parameters.

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Simultaneous spatial and temporal focusing for tissue ablation

Cited by 52 publications

References 15 publications

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

Enhancing precision in fs-laser material processing by simultaneous spatial and temporal focusing

Calculation of nonlinear optical damage from space-time-tailored pulses in dielectrics

Analysis of the Micromachining Process of Dielectric and Metallic Substrates Immersed in Water with Femtosecond Pulses

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