femtosecond lasers
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2022 ◽  
Author(s):  
Yao L. Wang ◽  
Noa W. F. Grooms ◽  
Samuel H Chung

Femtosecond lasers are capable of precise ablation that produce surgical dissections in vivo. The transverse and axial resolution of the laser damage inside the bulk are important parameters of ablation. The transverse resolution is routinely quantified, but the axial resolution is more difficult to measure and is less commonly performed. In some in vivo samples, fine dissections can also be difficult to visualize, but in vitro samples may allow clear imaging. Using a 1040-nm, 400-fs pulsed laser, we performed ablation inside agarose and glass, producing clear and persistent damage spots. Near the ablation threshold of both media, we found that the axial resolution is similar to the transverse resolution. We also ablated neuron cell bodies and fibers in C. elegans and demonstrate submicrometer resolution in both the transverse and axial directions, consistent with our results in agarose and glass. Using simple yet rigorous methods, we define the resolution of laser ablation in transparent media along all directions.


2022 ◽  
Vol 20 (2) ◽  
pp. 021408
Author(s):  
Shengjun Huang ◽  
Yiran Wang ◽  
Jingliang He ◽  
Xiancui Su ◽  
Jie Liu

2022 ◽  
Vol 20 (1) ◽  
pp. 010502
Author(s):  
Meng-Qiang Cai ◽  
Qiang Wang ◽  
Cheng-Hou Tu ◽  
Yong-Nan Li ◽  
Hui-Tian Wang
Keyword(s):  

Author(s):  
В.Н. Трухин ◽  
В.А. Соловьев ◽  
И.А. Мустафин ◽  
М.Ю. Чернов

We present the results of terahertz generation studies under excitation via femtosecond lasers pulses epitaxial films of InAs, which were synthesized on semi-insulating and highly doped GaAs substrates. It is shown that a terahertz emitter based on epitaxial InAs film grown on a heavily doped GaAs n-type substrate, has the same terahertz generation efficiency as the InAs-film emitter grown on a semi-isolating GaAs substrate, but it has a significantly better spectral resolution, which is mainly determined by the parameters of the optical delay line and the femtosecond laser’s stability.


Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1571
Author(s):  
Xintian Cai ◽  
Chaoyue Ji ◽  
Changkai Li ◽  
Zhiqiang Tian ◽  
Xuan Wang ◽  
...  

It is essential to develop pattern-related process windows on substrate surface for reducing the dislocation density of wide bandgap semiconductor film growth. For extremely high instantaneous intensity and excellent photon absorption rate, femtosecond lasers are currently being increasingly adopted. However, the mechanism of the femtosecond laser developing pattern-related process windows on the substrate remains to be further revealed. In this paper, a model is established based on the Fokker–Planck equation and the two-temperature model (TTM) equation to simulate the ablation of a sapphire substrate under the action of a femtosecond laser. The transient nonlinear evolutions such as free electron density, absorption coefficient, and electron–lattice temperature are obtained. This paper focuses on simulating the multiphoton absorption of sapphire under femtosecond lasers of different wavelengths. The results show that within the range of 400 to 1030 nm, when the wavelength is large, the number of multiphoton required for ionization is larger, and wider and shallower ablation pits can be obtained. When the wavelength is smaller, the number of multiphoton is smaller, narrower and deeper ablation pits can be obtained. Under the simulation conditions presented in this paper, the minimum ablation pit depth can reach 0.11 μm and the minimum radius can reach 0.6 μm. In the range of 400 to 1030 nm, selecting a laser with a shorter wavelength can achieve pattern-related process windows with a smaller diameter, which is beneficial to increase the density of pattern-related process windows on the substrate surface. The simulation is consistent with existing theories and experimental results, and further reveals the transient nonlinear mechanism of the femtosecond laser developing the pattern-related process windows on the sapphire substrate.


2021 ◽  
Author(s):  
Inna V. Ilina ◽  
Yulia V. Khramova ◽  
Anna D. Ivanova ◽  
Maxim A. Filatov ◽  
Dmitry S. Sitnikov

2021 ◽  
Vol 2086 (1) ◽  
pp. 012157
Author(s):  
A A Astafiev ◽  
A A Gulin ◽  
A A Vasin ◽  
A M Shakhov ◽  
A D Zalessky ◽  
...  

Abstract The production of carbon dots (C-dots) by femtosecond lasers within living cells and tissues is a novel approach, which has a great potency for intracellular bioimaging. An exact mechanism of fluorescent particles production as well as their composition still remains unknown. In this work we use L-lysine film as a model system to study the mechanism and the composition of C-dots produced by femtosecond laser irradiation investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS).


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Thomas Asshauer ◽  
Catharina Latz ◽  
Alireza Mirshahi ◽  
Christian Rathjen

Abstract This review provides an overview of the historical development and modern applications of femtosecond (fs) lasers in ophthalmology, with a focus on the optical concepts involved. fs-Laser technology is unique because it allows very precise cutting inside the eye through optically transparent tissue, without a need for any mechanical openings. fs-Lasers were historically first used for refractive cornea surgery, later also for therapeutic cornea procedures and lens surgery. Further new areas of ophthalmic application are under development. The latest laser system concept is low pulse energy and high pulse frequency: by using larger numerical aperture focusing optics, the pulse energy required for optical breakdown decreases, and athermal tissue cutting with minimal side effects is enabled.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2022
Author(s):  
Ming Li ◽  
Jiangpeng Gu ◽  
Dayuan Zhang ◽  
Qiang Gao ◽  
Bo Li

Femtosecond lasers have been used in combustion diagnostics. Based on the characteristics of femtosecond laser filamentation, many diagnostic techniques have been developed. Here, we propose a method, based on femtosecond laser filamentation, for equivalence ratio measurements in CH4/air gases. By measuring the spatially resolved spectra of the femtosecond laser-induced filament, we found that the variation of the equivalence ratio in the flow field would affect the spatial distribution of the emission intensity of femtosecond laser-induced filament. On this basis, the equivalence ratio was calibrated by using the relative spatial positions of N2 (337 nm) and C2 (516.5 nm) signals in the filament. This method overcomes the interference of local air disturbance, having lower measurement uncertainty.


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