Controlled Nonlinear Energy Deposition In Transparent Materials: Experiments And Theory

Vogel, Alfred; Linz, Norbert; Freidank, Sebastian; Liang, Xiaoxuan

doi:10.1063/1.3507142

Cited by 3 publications

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“…11,[14][15][16] Briefly, atoms are ionized through multiphoton or tunneling ionization within the focal zone of a high-intensity laser pulse. Free electrons can then absorb more photons through inverse-Bremsstrahlung absorption, gaining sufficient kinetic energy to ionize even more atoms during subsequent collisions.…”

Section: Finesse Of Transparent Tissue Cutting By Ultrafast Lasers Atmentioning

confidence: 99%

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

2015

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Abstract. Transparent ocular tissues, such as the cornea and crystalline lens, can be ablated or dissected using short-pulse lasers. In refractive and cataract surgeries, the cornea, lens, and lens capsule can be cut by producing dielectric breakdown in the focus of a near-infrared (IR) femtosecond laser, which results in explosive vaporization of the interstitial water, causing mechanical rupture of the surrounding tissue. Here, we compare the texture of edges of lens capsule cut by femtosecond lasers with IR and ultraviolet (UV) wavelengths and explore differences in interactions of these lasers with biological molecules. Scanning electron microscopy indicates that a 400-nm laser is capable of producing very smooth cut edges compared to 800 or 1030 nm at a similar focusing angle. Using gel electrophoresis and liquid chromatography/mass spectrometry, we observe laser-induced nonlinear breakdown of proteins and polypeptides by 400-nm femtosecond pulses above and below the dielectric breakdown threshold. On the other hand, 800-nm femtosecond lasers do not produce significant dissociation even above the threshold of dielectric breakdown. However, despite this additional interaction of UV femtosecond laser with proteins, we determine that efficient cutting requires plasma-mediated bubble formation and that remarkably smooth edges are the result of reduced thresholds and smaller focal volume. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Finesse Of Transparent Tissue Cutting By Ultrafast Lasers Atmentioning

confidence: 99%

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

2015

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“…Current applications include corneal ablation by excimer lasers in refractive surgery 1 , corneal dissection by femtosecond lasers in LASIK 2 or keratoplasty 3 , as well as dissection of the lens and lens capsule in cataract surgery 4,5 . Basic research into laser-tissue interaction mechanisms 6,7 has helped to introduce new lasers such as 355 nm sub-nanosecond laser 8 or 1650 nm femtosecond laser 9 to corneal flap-cutting or new applications for currently used femtosecond lasers such as refractive index shaping 10 . In this study, we look at the interactions of femtosecond pulses from Ti:Sapphire laser with lens capsule, and compare the quality of cuts produced by two wavelengths: 400 and 800 nm.…”

Section: Introductionmentioning

confidence: 99%

Role of molecular photodissociation in ultrafast laser surgery

et al. 2015

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Transparent ocular tissues such as cornea and crystalline lens can be precisely ablated or dissected using ultrafast ultraviolet, visible, and infrared lasers. In refractive or cataract surgery, cutting of the cornea, lens, and lens capsule is typically produced by dielectric breakdown in the focus of a short-pulse laser which results in explosive vaporization of the interstitial water and mechanically ruptures the surrounding tissue. Here, we report that tissue can also be disrupted below the threshold of bubble appearance using 400 nm femtosecond pulses with minimal mechanical damage.Using gel electrophoresis and liquid chromatography/mass spectrometry, we assessed photodissociation of proteins and polypeptides by 400 nm femtosecond pulses both below and above the cavitation bubble threshold. Negligible protein dissociation was observed with 800 nm femtosecond lasers even above the threshold of dielectric breakdown. Scanning electron microscopy of the cut edges in porcine lens capsule demonstrated that plasma-mediated cutting results in the formation of grooves. Below the cavitation bubble threshold, precise cutting could still be produced with 400 nm femtosecond pulses, possibly due to molecular photodissociation of the tissue structural proteins.

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“…These low bubble energy conversion efficiencies, as well as the absence of visible plasma luminescence, are hallmarks of LDP generation in which the rate of free electron generation via multi-photon and avalanche ionization processes is counteracted by electron-hole recombination which limits the free electron density in the focal volume. 8,24 Our use of sub-nanosecond pulses to form LDPs is likely due to the short cavity length of the Q-sw microchip laser that promotes single-frequency operation free of mode beating resulting in a smooth and reproducible temporal pulse shape. 25 For all the media formulations tested, we find a high-energy regime characterized by both bright plasma luminescence and larger bubble formation with conversion efficiencies g տ 2%.…”

mentioning

confidence: 99%

“…5 The production of microscopic bubbles via LDP formation using 500 ps laser microbeam irradiation at 0.25 NA is unprecedented and approaches the precision achieved using femtosecond pulses. 8,24 For example, Vogel and co-workers have shown that irradiation of DI water using femtosecond pulsed microbeams at 0.9 NA resulted in maximum bubble radii of R max ¼ 1-5 lm for k ¼ 1040 nm and R max < 1-3.5 lm for k ¼ 520 nm. 8 Moreover, the LDP formation with subnanosecond pulses at low NA enables rapid and precise cellular modification over large areas which is simply not possible using femtosecond laser irradiation without implementation of strategies to mitigate self-focusing and laser beam filamentation.…”

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confidence: 99%

Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

Genc

Venugopalan

2014

Applied Physics Letters

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We demonstrate the formation of low-and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA ¼ 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of E p % 4-5 lJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (R max ¼ 2-20 lm) due to a tiny conversion (g < 0.01%) of laser energy to bubble energy E B . The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (E p ¼ 11-20 lJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1-2 orders of magnitude larger in size ðR max տ 100 lmÞ due to a roughly two-order-of-magnitude increase in bubble energy conversion (g տ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA. V C 2014 AIP Publishing LLC.

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Controlled Nonlinear Energy Deposition In Transparent Materials: Experiments And Theory

Cited by 3 publications

References 0 publications

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

Role of molecular photodissociation in ultrafast laser surgery

Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

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