A low-cost method for fabricating microlens arrays on commercial soda-lime glass is presented. The hybrid technique is composed by a laser direct writing technique and a laser assisted post-thermal ...treatment. In particular we use a nanosecond Q-Switch Nd:YVO4 laser for fabricating the initial structure of microposts on soda-lime glass substrates and a CO2 laser combined with a furnace for reshaping and improving its morphological and optical qualities. This new fabrication approach lets us obtain a high quality microlenses array with a diameter of 50μm, sag 1.5μm, focal length 1mm and a spot size of 7.8μm. Furthermore, the proposed technique preserves the advantages of the laser direct-write technique in terms of design flexibility, simplicity, fast prototyping, low cost and so on; while the alternative laser assisted thermal treatment lets us overcome the bounding problems presented in other conventional thermal treatments.
•We have developed a low cost process for fabricating microlens arrays on glass.•The hybrid technique is composed for a laser direct write and a post thermal treatment.•We avoid the bounding problems typical of conventional thermal treatments.
A passively Q-switched Nd:YAG/Cr:YAG microchip laser with the pulse duration of < 200 ps has been developed. To obtain such short pulses from Nd:YAG/Cr:YAG microchip lasers, a numerical model based ...on rate equations was introduced and a design strategy of microchips was discussed. Since the pump bleaching effect in Cr:YAG leads to an increase of output pulse duration, a method of small-spot pumping was employed to reduce the effect and shorten the pulse duration. In the experiments, 1064-nm laser pulses with the duration of 153 ps and the energy of 18 <inline-formula> <tex-math notation="LaTeX">\mu \text{J} </tex-math></inline-formula> at 4.5 kHz was achieved. A good beam quality of <inline-formula> <tex-math notation="LaTeX">M^{2} =1.15 </tex-math></inline-formula> was also measured.
•This research explores a 1.5 μm passively Q-switched pulse burst microchip laser, which is end-pumped by a 940 nm laser diode.•The laser utilizes Er:Yb:glass as the gain medium and Co:MALO as the ...passively Q-switched component. The performance of this pulse burst laser was exhaustively examined and optimized across a range of parameters.•A pulse train of up to 12 pulses, with a total pulse burst energy of 2 mJ was achieved.•A single pulse energy of 272 μJ was realized, featuring a pulse width of 6.2 ns, corresponding to a peak power of 43.9 kW.
Burst mode lasers, characterized by a sequence of high-intensity pulses, are integral to applications such as the examination of turbulent flows and optical metrology. This study investigates a 1.5 μm passively Q-switched pulse burst microchip laser, end-pumped by a 940 nm laser diode. Utilizing Er:Yb:glass as the gain medium and Co:MALO for passive Q-switching, delivering a pulse width of 5.5 ms and a repetition rate of 10 Hz. When the initial transmittance of the saturable absorber was 93 % and the maximum absorbed pump energy reached 85 mJ, we successfully generated up to 12, 8, and 4 pulses within a burst at 1.5 μm. These results corresponded to cavity lengths of 12 mm, 13 mm, and 14 mm, respectively. By using a saturable absorber with an initial transmittance of 90.5 %, a higher single pulse energy and a narrower pulse width were realized. The narrowest pulse width was reduced to 6.2 ns, with a corresponding single pulse energy of 272 μJ. The peak power in the Er:Yb:glass/Co:MALO pulse burst laser reached an estimated 43.9 kW.This research provides valuable experimental and theoretical insights for the development of human eye-safe lasers with adjustable pulse sequences.
•Molybdenum titanium aluminum carbide (Mo2Ti2AlC3) particles are utilized to form saturable absorber (SA)•Both physical and optical properties of Mo2Ti2AlC3-SA are experimentally ...demonstrated.•Mo2Ti2AlC3 film is one of an excellent promising material for a various photonic applications.•The proposed Q-switched EDFL can generate dual-wavelength laser pulses.•The proposed EDFL can be utilized in many photonics applications and terahertz wave generation.
In this paper, we experimentally generate dual-wavelength laser pulses from a Q-switched erbium-doped fiber laser (QS-EDFL) by utilizing molybdenum titanium aluminum carbide (Mo2Ti2AlC3) MAX Phase film. The Mo2Ti2AlC3-SA film, which belongs to the MAX phase compound, is prepared using the mechanical exfoliation. The optical and physical properties of Mo2Ti2AlC3-SA are investigated. The fabricated film has a linear absorption of 8 dB and modulation depth of 17 % at 1.55 mm region. A steady dual-wavelength Q-switched laser pulses are achieved with 1531.6 nm and 1557 nm peaks and a free spectral range (FSR) of 25.4 nm. By increasing the input pump power from 131.87 mW to 167 mW, the repetition rate of generated pulses is varied over 104 kHz to 126 kHz. At the highest input power (167 mW), the energy and output power of the obtained pulses are 87.30 nJ and 11 mW, respectively. The results reveal that the exfoliated Mo2Ti2AlC3-SA can be operated inside EDFL to produce stable pulses with dual wavelengths.
•The localization of gray losses during chemical etching has been determined.•A comparison is made of the effect of the type of Q-switch mode.•SA was created based on Bi2Te3 nanopowder - polymer.•The ...pulse duration in this case was 5 ns with a repetition rate of 4 MHz.•Taper-based Q-switch fiber laser has a pulse energy of more than 1000 nJ.
The presented work shows an influence of geometry passive Q-switch based on a nanopowder-polymer on the characteristics of an erbium ring fiber laser. The saturable absorber Bi2Te3 was applied to two types of specially prepared samples of thinned sections of optical fiber, and the resulting structures were built into the ring circuit of an erbium fiber laser. In the first case, the surface of the light guide segment was thinned by chemical etching, and in the second, by mechanical grinding. For the first time, the time-domain optical reflectometry technique was used to control the quality of the resulting sample surface and the resulting losses. For a more complete comparison, a set of different optical splitters was used, providing a change in the feedback coefficient in the resonator from 5 to 95 %. A study in the mode of passive Q-switching using polarized light showed that for both types of modulators there are optimal ratios of the amount of energy output from the resonator to obtain the highest values of the average generation power. The d-shape fiber modulator allows mode-locking to be observed without any additional changes to the laser circuit. The pulse duration in this case was 5 ns with a repetition rate of 4 MHz. A Q-switch based on a chemically thinned fiber segment made it possible to obtain narrower pulses in Q-switching mode (up to 700 ns at 38 kHz), a stable peak position in the transmission spectrum, and an average power of 34 mW.
This study demonstrated the use of a highly compact nanosecond laser system operating at 532 nm and producing a maximum output power of 70 W with a pulse width of 5 ns at 0.5 kHz, for space debris ...tracking. To improve the ranging accuracy while minimizing the influence of the pulse noise, a bidirectional Q-switch was adopted in the oscillator to generate a short pulse width with less tailing. The laser was applied for low-Earth-orbit space debris tracking, and space debris with the farthest distance of 1701.9 km at the minimum radar cross-section of 1 m2 could be detected with a ranging precision of up to 26.90 cm.
•A highly compact all-solid-state nanosecond laser with a maximum output power of 70 W at 532 nm was developed.•The bidirectional voltage supplied Q-switch was introduced in the oscillator, which delivered the adjustable pulse-width output in the range of 5–21 ns without tailing.•Space debris with the minimum radar cross-section of 1 m2 was tracked.
Two-dimensional (2D) graphitic carbon nitride (g-C3N4) was fabricated as saturable absorber (SA) and the nonlinear optical absorption properties were measured. A laser-diode (LD) pumped doubly ...Q-switched Tm-doped yttrium-aluminium perovskite YAlO3 (Tm:YAP) laser at 2 μm with g-C3N4 and acousto-optic modulator (AOM) is presented for the first time to the best of our knowledge. Under an absorbed pump power of 5.34 W, the minimum pulse width of 239 ns and the maximum peak power of 1146 W were obtained by the doubly Q-switched laser. In comparison with the singly Q-switched laser using g-C3N4 SA or AOM, the dual-loss-modulated Q-switched laser could generate shorter pulse width and higher peak power. The maximum pulse width compression ratio was 4.48 and the highest peak power enhancement factor was 241. The experimental results indicated that 2D g-C3N4 SA is potential in Q-switched laser at 2 μm and the doubly Q-switched technology is a useful way to compress the pulse width and improve the peak power.
•2D g-C3N4 SA was fabricated and the nonlinear optical absorption properties were measured.•A laser-diode (LD) pumped doubly Q-switched Tm:YAP laser at 2 μm with g-C3N4 SA and AOM is realized for the first time.•The pulse width of the Q-switched laser is compressed greatly.•The pulsed peak power is improved evidently.
Objective To observe the efficacy of Q switch ruby laser combined with tranexamic acid for melasma and its effects on melanin metabolism. Methods A total of 60 patients with melasma were divided into ...three groups: Drug group (oral tranexamic acid 500 mg/day for six months), the laser group (Q switched ruby laser, once every 2 weeks for 2 months), combination therapy (laser plus tranexamic acid, same method and course of treatment as in single modality). Results Combination therapy significantly lowered Melasma Area and Severity Index compared to single treatment modality (67.02±18.58)% vs. (53.13±20.66)% in laser and (53.97±18.48)% in drug group), both P<0.05. The effective rate in the groups of combination therapy, laser and drug treatments were 90.00%, 60.00% and 55.00%, respectively. Patients' satisfaction rate was higher in the combination group than in either laser or drug treatment alone (90.00% in combination therapy vs. 60.00% in both laser and drug groups, both P<0.05). Before the treatment, serum
