نتایج جستجو برای: laser beam
تعداد نتایج: 283190 فیلتر نتایج به سال:
any change in the refractive index of a laser active medium can lead to serious degradation of beam quality, laser beam modes, laser performance and variation in the intensity distribution. alteration in the refractive index of laser active medium is especially notable in high power lasers. it is clear that in the laser beam production, the pumping agent induces a great amount of heat which...
In this paper propagation of combined laser beam through atmosphere is investigated. Laser beam is combined via lens array arrangement. Turbulence is considered as an affecting factor of atmosphere and its effects on transverse coherence length (Fried parameter), peak intensity, propagation efficiency, and spot size of the laser beam is investigated. Coherent and incoherent combined beam are co...
In this article, M2 factor of a thin disk laser with unstable resonator in two regimes is calculated numerically. In the first case, thermal effects are ignored and the parameters of beam width, divergence angle, radius of wave front curvature and finally, M2 factor of laser beam are calculated by using generalized beam parameters. These calculations show that the beam quality of the laser is d...
the modulation response, relative intensity noise and frequency noise characteristics of qd lasers are investigated theoretically, in presence of an additional optical pumping. it is revealed that the modulation response of qd laser enhances under additional optical beam. by small signal analysis of the carriers' and photons' rates, it is proposed that by injecting excess carriers to ...
Damage of the normal tissue is a serious concenrn in cancer treatment. Hyperthermia by laserhas been considered as a safe cancer treatments methods with lower harmful effects on normaltissues. Using nanoparticles in cancer treatment has improved laser therapy, which is based ona selective cell targeting method to localize cell damages. Metallic nanoparticles such as gold,silver, and copper have...
Transient thermal field in laser surface hardening treatment of medium carbon steel was analyzed by employing both three-dimensional analytical model and finite element model. In finite element model the laser beam was considered as a moving plane heat flux to establish the temperature rise distribution in the work-piece, while in analytical model laser beam was considered as an internal heat s...
Control the laser beam hazards for class IIIB and IV laser is concluded: engineering and executive controls. In executive control, when laser beam enters to the free space, the controlled area must be identified to protect people and control the radiation exposure limits. Given the fact that the laser light of the laser is entering the environment, the identification of the area under control i...
in this work, laser bending of perforated sheets has been investigated numerically. laser bending of perforated sheets is more complicated than non-perforated sheets due to their complex geometries. in this paper, laser bending of perforated sheets is studied numerically in the form of thermo-mechanical analysis with abaqus/implicit code. for this purpose, the effects of process and sheet param...
Thermal diffusivity of Au nanofluid was measured by using a dual beam mode-mismatched thermal lens method. The samples were prepared in various sizes by utilizing the gamma radiation method. In the dual beam mode-mismatched thermal lens, a diode laser (532 nm) was used as an excitation beam and a He-Ne laser with the beam output at 632.8 nm was used as a probe beam. Thermal diffusivity of gold...
The modulation response, relative intensity noise (RIN) and frequency noise (FN) characteristics of quantum dot (QD) lasers are investigated theoretically in the presence of an external optical beam. Using small signal analysis of the rate equations for carriers and photons, it is demonstrated that by injecting excess carriers into the QDs excited state through optical pumping, the modulation r...
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