In situ monitoring of second-harmonic generation in human corneas to compensate for femtosecond laser pulse attenuation in keratoplasty

2007 ◽  
Vol 12 (6) ◽  
pp. 064032 ◽  
Author(s):  
Valeria Nuzzo ◽  
Karsten Plamann ◽  
Michèle Savoldelli ◽  
Michele Merano ◽  
David Donate ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Femtosecond Laser Pulse ◽  
Second Harmonic ◽  
In Situ Monitoring

scholarly journals High-Speed Imaging of Second-Harmonic Generation in MoS2 Bilayer under Femtosecond Laser Ablation

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1786
Author(s):  
Young Chul Kim ◽  
Hoseong Yoo ◽  
Van Tu Nguyen ◽  
Soonil Lee ◽  
Ji-Yong Park ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
High Speed ◽  
Second Harmonic ◽  
Twist Angle ◽  
Layer By Layer ◽  
Threshold Behavior ◽  
Time Duration

We report an in situ characterization of transition-metal dichalcogenide (TMD) monolayers and twisted bilayers using a high-speed second-harmonic generation (SHG) imaging technique. High-frequency laser modulation and galvano scanning in the SHG imaging enabled a rapid identification of the crystallinity in the TMD, including the orientation and homogeneity with a speed of 1 frame/s. For a twisted bilayer MoS2, we studied the SHG peak intensity and angles as a function of the twist angle under a strong interlayer coupling. In addition, rapid SHG imaging can be used to visualize laser-induced ablation of monolayer and bilayer MoS2 in situ under illumination by a strong femtosecond laser. Importantly, we observed a characteristic threshold behavior; the ablation process occurred for a very short time duration once the preheating condition was reached. We investigated the laser thinning of the bilayer MoS2 with different twist angles. When the twist angle was 0°, the SHG decreased by approximately one-fourth of the initial intensity when one layer was removed. Conversely, when the twist angle was approximately 60° (the SHG intensity was suppressed), the SHG increased abruptly close to that of the nearby monolayer when one layer was removed. Precise layer-by-layer control was possible because of the unique threshold behavior of the laser-induced ablation.

scholarly journals Генерация второй оптической гармоники и ее фотоиндуцированная динамика в сегнетоэлектрике-полупроводнике Sn-=SUB=-2-=/SUB=-P-=SUB=-2-=/SUB=-S-=SUB=-6-=/SUB=-

2018 ◽  
Vol 60 (1) ◽  
pp. 33
Author(s):  
К.А. Брехов ◽  
К.А. Гришунин ◽  
Д.В. Афанасьев ◽  
С.В. Семин ◽  
Н.Э. Шерстюк ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Nonlinear Optical ◽  
Second Harmonic ◽  
Electric Polarization ◽  
Ultrafast Dynamics ◽  
Optical Pump ◽  
Pump Probe

AbstractBy means of optical pump–probe technique, the ultrafast dynamics of nonlinear optical response of the ferroelectric semiconductor Sn_2P_2S_6 crystal excited with a femtosecond laser pulse has been investigated. It has been shown that, under the action of femtosecond pulses, change in optical second harmonic generation occurs in the sample, which can be due to screening of existing electric polarization.

scholarly journals An Optical Frequency Domain Angle Measurement Method Based on Second Harmonic Generation

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 670
Author(s):  
Wijayanti Dwi Astuti ◽  
Hiraku Matsukuma ◽  
Masaru Nakao ◽  
Kuangyi Li ◽  
Yuki Shimizu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Frequency Domain ◽  
Harmonic Generation ◽  
Measurement Method ◽  
Second Harmonic ◽  
Angle Measurement ◽  
Laser Source ◽  
Optical Frequency ◽  
Measurable Range

This paper proposes a new optical angle measurement method in the optical frequency domain based on second harmonic generation with a mode-locked femtosecond laser source by making use of the unique characteristic of the high peak power and wide spectral range of the femtosecond laser pulses. To get a wide measurable range of angle measurement, a theoretical calculation for several nonlinear optical crystals is performed. As a result, LiNbO3 crystal is employed in the proposed method. In the experiment, the validity of the use of a parabolic mirror is also demonstrated, where the chromatic aberration of the focusing beam caused the localization of second harmonic generation in our previous research. Moreover, an experimental demonstration is also carried out for the proposed angle measurement method. The measurable range of 10,000 arc-seconds is achieved.

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