Saeid Radmard, Ahmad Moshaii, Mohammad Abazari,
Volume 16, Issue 1 (1-2022)
Abstract
This paper presents the design procedure of folded-resonators for high-average power thin-disk lasers (TDLs). Because of the oblique angle of incidence in the laser path inside the resonator, folded resonators introduce astigmatism. Additionally, the dependency of the dioptric power of the active medium on the pump power made the resonator design more complicated. In the first section of this work, the disk thermal lensing was measured using a wavefront sensor, and the measurement procedure was presented and thoroughly discussed. The disk radius of curvature varied between 4.3 m to 6.4 m depending on the pump power. The disk was considered a variable lens inside the resonator based on the measurement results. V-shaped and L-shaped configurations' stability and M2 factor were predicted, optimized, and compared. Astigmatism in the resonator parameters was considered and discussed. While the V-shaped cavity has better beam quality, the L-shaped cavity has less sensitivity to cavity misalignment. The primary approach of this paper was the resonator design of a cavity-dumped disk laser. However, the designed resonator configurations could be utilized in many laser resonators, such as industrial TDLs (to reduce the overall length of the system) and second harmonic-generation in TDLs.
Tahereh Dirikvand, Mehdi Zadsar, Mina Neghabi, Jamshid Amighian,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >ta charset="UTF-8" >A green microcavity organic light-emitting diode combining an Al electrode (top mirror) with a distributed Bragg reflector (bottom mirror) was designed and fabricated to improve the quality factor (more than 51) and enable high reflectance and optimal electrical properties. Experimental results indicated a remarkable increase in electroluminescence and reduction of spectral width at half maximum. Distributed Bragg reflector (DBR) films were prepared at 550°C with a surface roughness of 0.25nm (root mean square: RMS). In addition, according to SiO2/TiO2 refractive indices, they obtained the highest reflection compared to all organic or inorganic DBR devices. The reflectance peak at 591 nm is 94.4% for five pairs of SiO2/TiO2 layers indicating good agreement with theoretical simulation samples. Microcavity Organic Light-Emitting Diode (OLED) with structure: 5 pairs of SiO2/TiO2/ITO(120nm) /MoO3(5nm) /MoO3:NPB(190nm) /NPB(10nm) /Alq3(35nm) /BCP(5nm) /LiF(0.7nm) /AL(200nm) has a quality factor of more than 51, high luminous (30%), remarkable increase in electro-luminescence (EL) and reduction of the spectral full width at half maximum of 10.93nm. This is an applied research that was obtained after detailed investigations on OLED microcavities and has a practical aspect to solving the problems of designing and manufacturing electrical and optical systems such as organic display screens. The innovative aspect of research in the technical knowledge of designing and manufacturing OLED microcavities and achieving an optimal structure using metal mirrors and Bragg reflectors to achieve coherent light output is a new and up-to-date issue that has not been done in Iran so far. As an essential step toward realizing organic lasers, the proposed approach can be used to produce new light sources.
Farshad Khoshnood, Mohammad Sabaeian,
Volume 17, Issue 1 (1-2023)
Abstract
The authors report on the impact of electrode doping on the optical and electrical properties of argon flash lamps. In this work, the lamps are made using borosilicate glass tubes with an outer diameter of 6 mm and a discharge distance of 35 mm. In the construction of the lamps, five types of tungsten electrodes doped with thorium at two different percentages, cerium, lanthanum as well as pure tungsten are used. Properties such as threshold voltage, light intensity, tube temperature, and flash time profile at various argon pressures are measured. The results indicated that, first, the threshold voltage is a linear function of gas pressure inside the tube. Second, the lamp with 1.7%-2.2% thorium doped tungsten cathode showed a lower threshold voltage, higher light intensity, and lower temperature rise at continuous wave operation. These characteristics of electrodes doped with thorium make them an appropriate option for use in the fabrication of argon flash lamps.
Zahra Heydarinasab, Mohammad Karami, Farrokh Sarreshtedari,
Volume 17, Issue 1 (1-2023)
Abstract
Sub-Doppler dichroic atomic vapor laser lock (DAVLL) is a modulation-free laser stabilization method that combines DAVLL and saturated absorption spectroscopy (SAS). The performance of this highly sensitive stabilization technique strongly depends on the characteristics of the generated error signal. The slope of the error signal determines the lock sensitivity or how fast the frequency compensation could be made in the feedback loop, and the amplitude of the error signal determines the lock stability or how much noise the feedback loop can tolerate before laser unlocking. We have analytically modeled the error signal of the sub-Doppler DAVLL considering all possible transitions between Zeeman sublevels and compared it with the experimental results. Using the analytical and experimental results, it is shown that the values of the required magnetic fields for maximizing the slope and amplitude of the error signal are close to each other. Selecting the mentioned values of the magnetic field for optimization of the sub-Doppler DAVLL error signal is highly useful for sensitive and stable laser locking.
Hasan Ebadian, Mohammad Mahdi Moslem, Nabiollah Azarpoor,
Volume 17, Issue 1 (1-2023)
Abstract
The simulation results of a 10-kW heat capacity slab laser are presented. Two different schemes for optical pumping with high-power laser diodes are investigated. The simulation of optical pumping using ZEMAX software demonstrates a uniform pump distribution within the laser slabs. Additionally, the temperature distribution in the laser slab is examined using COMSOL. The findings for two distinct laser designs reveal that increasing the slab dimensions reduces the temperature distribution and thermal issues. Furthermore, cooling schemes indicate that the cooling phase of a 10-kW HCL falls within the range of 20-40 seconds. A comparison of water and air cooling of the optically pumped slabs during the cooling phase demonstrates that water cooling is more efficient than air cooling. The simulation results confirm that the proposed laser will be an efficient device for laser material processing. A focused 10-kW HCL laser will melt the steel sheet after less than 1 s at 1490 K.
Reza Pourahmad, Sheila Shahidi, Amirhossein Sari, Mohammadreza Hantezadeh,
Volume 17, Issue 1 (1-2023)
Abstract
In this research, an attempt is made to approach a specific type of carbon, such as graphene or carbon nanotubes by using pulsed laser ablation technique in deionized water environment with changing the laser factors such as wavelength and fluence. Nd:YAG laser with two wavelengths of 1064 and 532 nm and three fluence of 0.8, 1 and 1.2 J/cm2 were selected that number of pulses was 5000 with a frequency of 10 Hz to be irradiated on the graphite target at about 10 minutes. The medium was distilled water. Graphite was located in the 40 ml of distilled water.
The effects of wavelength and fluence of the laser have been experimentally investigated on types of carbon characteristics with different analysis such as Raman scattering spectrum, FE-SEM images, UV–Vis-NIR spectrum and X-ray diffraction (XRD). By using the mentioned analysis, the type of synthesized nano carbon is studied.
This study evaluates the effects of the pulse energy and laser wavelength on properties of synthesized carbon nanoparticle in laser ablation method in medium of distilled water.
Zahra Ahmadimanesh, Babak Jaleh, Mahtab Eslamipanah, Milad Daneshnazar, Hassan Hassan Sepehrmansourie, Mohammad Ali Zolfigol,
Volume 17, Issue 2 (6-2023)
Abstract
In this research, palladium nanoparticles (Pd NPs) were first synthesized using laser ablation in the deionized (DI) water environment. Also, metal-organic framework (MOF) was produced using the solvothermal method at a temperature of 150°C. To accumulate Pd NPs on the synthesized MOF, ultrasonic and magnetic stirring methods were used. Different analytical methods were used to investigate the structure and morphology of the synthesized nanocomposite. Also, the sensitivity of the synthesized nanocomposite to ethanol and methanol organic vapors was investigated. The results showed an increase in the response of the MOF in the presence of nanoparticles.
Arezou Joudaki, Babak Jaleh, Ensiye Shabanlou, Saeid Azizian,
Volume 17, Issue 2 (6-2023)
Abstract
In recent years, global climate change and population growth have exacerbated freshwater shortages. To address this issue, harvesting water from atmospheric fog has emerged as a promising technique. Inspired by natural processes, the fabrication of hybrid hydrophilic (HI) and superhydrophobic (SHB) surfaces has gained significant attention for enhancing water harvesting efficiency. This study presents a simple, cost-effective laser ablation method for creating wettability contrast surfaces with triangular and parallel patterns on brass metal. Through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), we investigated the structural and morphological effects on the wettability behavior of irradiated and non-irradiated brass. Additionally, we examined the influence of pattern shapes on water harvesting efficiency. Our findings indicate that triangular patterns significantly enhance water harvesting performance compared to parallel patterns.
