thermal lens
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2022 ◽  
Vol 128 (2) ◽  
Author(s):  
Krzysztof Dobek

AbstractThe thermal lens formed in a thermo-optical material as a result of its inhomogeneous heating, is a well-known phenomenon that has found widespread interest in the last decades, especially in the field of laser engineering and photo-thermal spectroscopy. In recent years, growing interest in the application of thermal lensing in different fields of optics and material studies has been observed. This review summarizes the latest efforts made by the scientific community to develop ways of using the phenomenon of thermal lensing. Its applications in spectroscopy, in laser beam formation and in imaging are described. The advantages and disadvantages of the thermal lensing in regard to these areas along with the potential future applications of the phenomenon are discussed.


Author(s):  
Hamid Rashidnejad ◽  
Hamideh Motiei ◽  
Mohammad Ramezanitaghartapeh ◽  
Nader Noroozi Pesyan ◽  
Ahmad Poursattar Marjani ◽  
...  

2021 ◽  
Author(s):  
John alexis jaramillo osorio ◽  
Alejandro Velez-Zea ◽  
Humberto Cabrera ◽  
J J Niemela ◽  
John Fredy Barrera-Ramírez ◽  
...  

Abstract We present the implementation of an experimental optical encryption configuration in the Fresnel domain using the thermal lens effect to modulate the phase of the illumination beam. We corroborate the basic performance of our cryptosystem by performing the encryption-decryption procedure of a single object. Then, we test the tolerance of the proposed scheme to decrypt decryption with keys registered for different modulations of the illumination beam induced by the phase generated due to thermal lens effect. These different phase modulations are obtained by introducing axial displacements of a sample, where the thermal lens effect is induced by an excitation beam. Considering the phase modulation changes in the illumination due to sample displacements, we propose an undercover procedure to further protect the target information using decoy data. The key associated with the target information is obtained when the probe and excitation beams are focused on the same point of the sample, while the decoy object key is registered when the beams are not focused on the same region of the sample. Finally, we analyzed the resistance of the undercover ciphertext to some of the attacks reported in the literature. All experimental results presented in this work demonstrate the basic capabilities, viability, and versatility of our proposals.


Optik ◽  
2021 ◽  
pp. 168499
Author(s):  
A. Ghanem ◽  
M.D. Zidan ◽  
M.S. EL-Daher ◽  
A. Allahham
Keyword(s):  

2021 ◽  
pp. 127676
Author(s):  
Peijin Shang ◽  
Mengyao Wu ◽  
Shiyu Wang ◽  
Defang Cai ◽  
Bing bin Li
Keyword(s):  

Author(s):  
Yuantao Zhao ◽  
Shengzhi Zhao ◽  
Tao Li ◽  
Yizhou Liu ◽  
Chun Wang ◽  
...  

Abstract Directly measuring thermal focal length is important for designing and optimizing the mode locking oscillator, especially for a 2-μm mode-locking laser. In this paper, we propose a novel interferometric method for measuring the thermal focal length in a 2-μm mode-locking laser. This method could give a precise measurement of the thermal focal length inside a long-folded oscillator in both lasing and non-lasing operation. We also theoretically calculate the thermal focal length based on the temperature distribution inside the laser crystal, which matches well with the experimental result


Author(s):  
Niyati K

Abstract: The spectroscopic characterization of materials involves the use of various optical tools. Spectrometers, interferometers etc, are some of the examples of optical tools. Thermal lens technique is one of the potential optical tools for the thermal characterization of different materials. The thermal lens effect is a photothermal effect which results when energy from a laser beam is absorbed by a sample, causing heating of the sample along the beam path. In this paper an overview of thermal lensing, its significance as potential optical tool and its applications are discussed. Index Terms: Optical tool, Photothermal spectroscopy, TLS application, Thermal diffusivity


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stefan Reich ◽  
Sebastian Schäffer ◽  
Martin Lueck ◽  
Matthias Wickert ◽  
Jens Osterholz

AbstractWhen laser beams propagate through media with non-vanishing absorption, the media is heated resulting in a change of the refractive index, which can lead to thermal lensing and thermal blooming. However, experimental details about both phenomena for propagations in water are lacking, especially for high-power lasers in the kilowatt range. We show that significant thermal lensing occurs only for high input powers before the onset of convective flow, while for low input powers, no strong thermal lens arises. After the onset of water flow, thermal blooming occurs at low input powers comparable to that known for propagations over kilometres in the air. However, for high input powers a thermal blooming on a qualitatively higher level is shown. By wavefront sensing, the change of refractive index distribution in water is investigated. This clearly shows the fast development of a strong thermal lens for high input powers and the onset of convection. Furthermore, a qualitatively good agreement of the accompanying simulations is observed. It is found that the absorption coefficient is linear with a value of $$\mu ={13.7}\,{\mathrm{m}^{-1}}$$ μ = 13.7 m - 1 at least up to 7.5 kW, i.e. 8 $$\mathrm{kW/cm}^2$$ kW / cm 2 . However, the directed transmission into an aperture is only constant before any thermal lensing of blooming occurs.


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