Q-switched Research Articles

Q-switched Erbium Doped Fiber Laser Generation Using the Kerr Effect of Multimode Interference

This work demonstrates a single mode fibre-step index multimode fibre-single mode fibre (SMS) structure as saturable absorber (SA) to generate Q-switched laser based on the Kerr-effect of multimode interference (MMI) in an Erbium-doped fibre laser (EDFL) cavity. A 156 mm length of step index multimode fibre (SIMF) was spliced directly into a ring cavity to modulate the cavity loss. By bending and applying proper pressure on the SIMF, steady Q-switched pulse was generated without strict length restriction of the SIMF. The Q-switched laser had a high repetition rate from 87 to 158 kHz, while the corresponding pulse width was low, ranging from 4.2 μs to 2.5 μs as the pump power increased from 115 to 342 mW. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was about 67 dB at a central wavelength of 1530 nm. The experiment demonstrated that SMS structure can be used as stable SA to generate Q-switched laser for high power applications. It also indicated that even with large core diameter step index multimode fiber, SMS structure can be utilized to generate stable Q-switched pulsed laser with very simple cavity settings.

A prospective comparative study of efficacy and safety of 15% trichloroacetic acid peel, 35% glycolic acid peel and Q-switched Nd-YAG laser in patients of macular amyloidosis.

The unappealing appearance of skin in macular amyloidosis (MA) interferes with the patient's quality of life, and treating the condition has been challenging. To compare the efficacy and safety of 15% trichloroacetic acid (TCA) peel, 35% glycolic acid (GA) peel, and Q-switched Nd-YAG Laser in MA. Open, prospective study was conducted over 2 years, where after fulfilling the criteria, randomization was done into three groups. Group A: 15% TCA peel; Group B: 35% GA peel; Group C: Q-switched Nd-YAG Laser. Procedures were repeated at monthly intervals for six sittings. On each visit, patients were scored on the following parameters: color score, visual analog score (VAS), physician global assessment (PGA) scale, subjective improvement, and adverse effects. A total of 75 patients (25 patients in each group) completed the treatment. The mean age of study-population was 35.68 ± 9.8 years, with female to male ratio of 11.5:1. The mean change in color score (1.68) was more by Group A, followed by Group C (1.4), followed by Group B (1.16). Similar results were noted by subjective improvement, VAS, and PGA. Adverse events were more in Group A, followed by Group C, followed by Group B. No patient showed permanent adverse events. TCA-peel showed superior results over Nd-YAG laser and glycolic-acid peel. TCA-peel being cost-effective with excellent acceptability should be considered a treatment modality.

All-fiberized amorphous carbon nitride (a-CNx) based passive Q-switcher

This research presents the first-ever demonstration of a passively Q-switched fiber laser in the 1.5 μm wavelength region using amorphous carbon nitride (a-CNx) as a saturable absorber (SA) in an all-fiber configuration. The a-CNx thin film was prepared using plasma-enhanced chemical vapor deposition. The laser operation showed remarkable stability, achieving a repetition rate of 57.99 kHz and a pulse duration of 1.36 μs at maximum input pump power. The peak power and pulse energy reached 100.56 mW and 136.77 nJ, respectively. The utilization of a-CNx as an SA offers potential benefits such as a simpler and more flexible cavity design, making it an attractive candidate for various applications, including material processing and medical laser equipment. This work contributes to the advancement of fiber lasers and expands the possibilities for utilizing carbon nitride-based SAs in practical laser systems.

Diode-pumped, Q-switched Alexandrite laser as emitter for general purpose atmospheric Lidar systems

We present design and performance of four prototypes of narrow-bandwidth emitters based on diode-pumped Alexandrite lasers for atmospheric Doppler-Mie, -Rayleigh and -resonance lidar systems. Furthermore, lab results for efficient frequency-doubling into the UV are presented.

500-W Average Power, 100-mJ level Pulse Energy by Q-switched 7x7 Multicore Fiber Lasers

This work focuses on achieving high peak and average power through incoherent beam combination of Q-switched 49-core fiber laser. Results show 1.5-MW peak power, and 502-W average power between 1-10 kHz.

Tm:CYA Q-switched mode-locked laser realized by tandem-pumping

Tm:CYA Q-switched mode-locked laser realized by tandem-pumping

Comparing Oral Tranexamic Acid and Q-Switched Nd-YAG Laser for Melasma: A Randomized Study

Comparing Oral Tranexamic Acid and Q-Switched Nd-YAG Laser for Melasma: A Randomized Study

Смена режимов генерации в эрбиевых волоконных лазерах

Operation features of the erbium fiber lasers with short cavities near two phase transitions have been established experimentally for the first time. The power-law behavior of the system parameters in the vicinity of the critical point in a wide range of pump power values was revealed. The parameters and operation regimes dependence on the cavity length and pump power, namely the switching from pulsed to CW operation, was investigated. The pulse duration and frequency dependencies with varying cavity length have been investigated, which made it possible to experimentally establish the universal dependence of these parameters on the lasing power for passively Q-switched erbium fiber lasers. The critical indices for pulsed operation of the erbium fiber lasers are determined weakly depending on the cavity parameters. The results of the study can be used for designing high-coherent fiber laser sources.

Passive Q-Switched Laser Based on Zinc Indium Sulfide Nanoflowers

Passive Q-Switched Laser Based on Zinc Indium Sulfide Nanoflowers

A narrow pulse width and high peak power passively Q-switched laser based on the saturable-absorption characteristic of 2-layer TeSe2

We prepared TeSe2 saturable-absorption nanosheets. The match of band-gap energy with laser wavelength was analysed, and the TeSe2 SA was applied in solid-state lasers to obtain narrow temporal-width and high peak pulse output.

Type-I intermittency route to chaos in passively Q-switched Tm:YLF laser emitting at 2.3 μm

We report on an original chaotic dynamic behaviour of a passively Q-switched 2.3-μm Thulium laser operating on the 3H4 → 3H5 transition. The experiment employs a Tm:LiYF4 laser crystal within various laser cavity configurations, involving optional additional cascade laser operation on the 3F4 → 3H6 transition at 1.9 μm. The saturable absorber employed is Cr2+:ZnSe, which is exclusively saturated by the 2.3 μm laser emission. A precise analysis of the Q-switching dynamics shows a pronounced inclination of the cascade laser scheme towards chaotic operation. To investigate the origins of chaos, we originally monitor the metastable 3F4 level population using cascade laser operation at 1.9 μm, which proves to be a crucial underlying parameter for explaining the observed instabilities. This analysis allows for explaining the specific dynamics of the Q-switched 2.3 μm Tm-laser intrinsically linked to Tm3+-doped materials. A very atypical route to chaos for a Q-switched laser is demonstrated involving type I intermittencies. The obtained results are of great interest for studying the premises of chaos in pulsed solid-state lasers.

Large mode area waveguide based high-energy passively Q-switched laser in silicon photonics

We demonstrate high energy Q-switched pulse generation with the help of a large mode area gain waveguide in a silicon photonics device. Output pulse energy >150 nJ and laser slope efficiency of 40% is shown.

High-power and high-energy coherent sources at 1.1-μm based on compact diode-end-pumped Nd:YAG crystal fiber lasers

In this work, we have reported the first Nd:YAG single crystal fiber lasers at 1.1 μm spectral region operating in continuous-wave and passively Q-switched modes. A maximum continuous-wave output power of 34.52 W is achieved and the corresponding slope efficiency with respect to pump power is 39.9 %. Using Cr4+:YAG as saturable absorber, a maximum average output power of 10.37 W is obtained during passively Q-switched laser operation. The maximum pulse peak power and single pulse energy reach approximately 103.7 kW and 1.1 mJ, respectively. In terms of diode end pumping geometry, these reported results represent the best achievements of 1.1-μm lasers, which indicate that crystal fiber has great potential in improving laser power and energy.

Q-switched fiber laser generation utilizing metal oxide-based saturable absorber in the region of 1.0 µm and 1.5 µm

In this study, we explored a saturable absorber (SA) using a metal oxide-biopolymer film, resulting in the generation of Q-switched fiber lasers at 1.0 µm and 1.5 µm wavelengths. A straightforward sonochemical technique was employed to synthesize a nickel oxide (NiO) film in cooperation with Chitosan as a host polymer. The fabricated NiO-Chitosan film exhibits nonlinear absorption properties with modulation depth of 32.20%, saturation intensity of 0.43 kW/cm2, and non-saturable loss of 7.80%. Upon integrating the NiO-Chitosan film into the cavities of Erbium-Doped Fiber Laser (EDFL) and Ytterbium-Doped Fiber Laser (YDFL), the emergence of stable self-starting Q-switched pulsed lasers were observed at 1040.86 nm and 1557.60 nm central wavelength, respectively. Notably, the shortest pulse widths of 0.73 µs and 2.44 µs were achieved, along with maximum repetition rates of 111.61 kHz and 61.73 kHz, respectively, at these wavelengths. Our investigation identifies an effective SA material with good nonlinear absorption properties for inducing Q-switching in the 1.0 µm and 1.5 µm regions. Significantly, the Chitosan properties, encompassing biocompatibility, non-toxicity, and high thermal resistance, combined with the uncomplicated NiO fabrication process and cost-effectiveness, hold promise for diverse applications.

Fine Structure of High-Energy Pulses from a Stimulated Brillouin Scattering-Assisted Q-Switch Tm-Doped Fiber Laser

We have demonstrated a simple all-fiber thulium (Tm) laser Q-switched by stimulated Brillouin scattering (SBS). The maximum output pulse energy was 80 μJ. This allowed us to generate a broadband spectrum directly at the laser outputs. For the first time, we measured the fine structure of the output pulses with a resolution of less than 100 ps. It was found that the SBS Q-switched laser is capable of generating bunches of picosecond pulses. The effect of modulation instability on the pulse decay is discussed. The potential application of the investigated laser radiation for producing destructive effects on soft biological tissues has been demonstrated.

Investigation of mortality rate of Drosophila melanogaster irradiated with nanosecond passively Q-switched microchip laser

Lasers have been widely used for pest control because they are efficient and effective to kill pests. Efficient pest control has been achieved with pulsed lasers, however, there is less investigation of effects of pulse characteristics on the pest mortality. Here, the effects of laser beam diameter, pulse width, peak power, and repetition rate of a compact passively Q-switched microchip laser on the mortality rate of Drosophila melanogaster have been studied. The lethality dosing for 90% mortality rate (LD90) Drosophila melanogaster has been utilized for evaluating the effects of passively Q-switched laser on mortality of insects. The beam diameter comparable to the size of Drosophila melanogaster is effective and economic for killing insects. The energy fluence required for LD90 decreases about 6.5% as pulse width is shortened from 1.5 ns to 850 ps. The energy fluence required for LD90 decreases about one-third as the peak power of passively Q-switched microchip laser increases four times from 6.94 kW to 27.48 kW. The energy fluence required for LD90 decreases dramatically from 16.02 J/cm2 to 12.77 J/cm2 as repetition rate increases from 5.05 kHz to 9.9 kHz and then tends to keep as a constant around 12.7 kHz with further increase of repetition rate. Nanosecond passively Q-switched microchip laser with high peak power and high repetition rate is a promising light source for effective and efficient pest control.

All-fiber Q-switched erbium-doped fiber laser generation with SMF-SIMF-SMF structure as artificial saturable absorber

A passively Q-switched Erbium-doped fiber laser (EDFL) was successfully demonstrated using SMF (single-mode fiber)-SIMF (step-index multimode fiber)-SMF or SMS structure as a saturable absorber (SA). The SMS structure operates on the Kerr-effect of multimode interference (MMI). To modulate the cavity loss, a 158 mm length of SIMF was fusion spliced into a ring cavity. By properly adjusting the in-line polarization controller (PC) that holds the SIMF, we were able to generate steady Q-switched pulses. As the input pump power increased from 115 to 343 mW, the repetition rate of the Q-switched laser increased from 87 to 158 kHz, while the corresponding pulse width decreased from 4.2 µs to 2.5 µs. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was around 72 dB at a central wavelength of 1530 nm. Our results indicate that the SMS structure can be used as an SA to generate stable Q-switched EDFL with very simple cavity settings.

Doubly Q-switched Tm:YAP laser based on the Cr2+:ZnS crystal and electro-optical modulator

A doubly Q-switched Tm3+:YAlO3 (Tm:YAP) laser based on the Cr2+:ZnS saturable absorber (SA) and electro-optical modulator (EOM) is presented. The pulse duration of the doubly Q-switched lasers is shorter as compared to single actively and passively Q-switched operations. The shortest pulse duration of 17.3 ns with a repetition rate of 100 Hz was measured at the pump power of 12 W in the doubly Q-switched laser. The corresponding pulse peak power of 184.8 kW and the pulse energy of 3.2 mJ was obtained. The center wavelength of the doubly Q-switched operation was 1.94 μm. The results demonstrate that Cr2+:ZnS is an excellent saturable absorber for 2 μm Tm:YAP laser, and the doubly Q-switched operation can greatly narrow the Q-switched pulse width.

Picosecond lasers in cosmetic dermatology: where are we now? An overview of types and indications.

Q-switched lasers have undeniably revolutionized the field of laser dermatology since four decades ago. Just as the first-generation laser emits its photonic signal in a few nanoseconds, the picosecond laser delivers pulse widths of at least ten times shorter. These devices offer a powerful tool for treating a wide range of skin conditions with a minimal downtime for visible improvement. For the current study, a literature research was performed on the dermatological applications of picosecond laser. The literature searched on this topic between 1999 and 2023 accessible through various platforms produce a result of 62 articles. The included studies have discussed the application of picosecond laser technology in tattoo removal, treatment of epidermal and dermal pigmentation, and collagen remodeling. After sifting the data from the articles into tables, the results were discussed in detail. The study shows a lot of evidence towards the efficacy of picosecond laser, yet it draws attention to its downsides.

Simulation of spatial rogue waves in actively Q-switched solid-state laser with transverse mode locking

We report the generation of spatial rogue waves in the actively Q-switched Nd:YAG laser with several transverse modes and negligible nonlinear effects in the cavity. We discuss a basic theoretical model that is able to reproduce the experimental observations of spatial rogue waves in the output Q-switched pulses as a result of the coherent superposition of transverse modes. The simulated rogue wave statistics depends on the configuration of the lasing modes and take a more pronounced L-shaped form in the case of highly anisotropic mode distribution and reduced frequency spacing between the modes. For larger frequency spacing between the modes, the mode-locking effects result in the periodic dynamics of the transverse beam profile and formation of spatio-temporal rogue waves. These results indicate that transverse mode-locking and spatial symmetry breaking through anisotropy in the mode configuration represent factors responsible for spatial rogue wave emergence in multimode lasers with low nonlinearity.