Search Results (102)

To address the poor thermal performance and low output efficiency of conventional solid-state microchip lasers, this study proposes and implements a bonded Nd:YAG/Cr⁴⁺:YAG laser based on fiber splitter pumping. Experimental results demonstrate that at a 4.02 mJ pump pulse energy and a 100 Hz repetition rate, the system achieves four linearly polarized output beams with an average pulse energy of 0.964 mJ, a repetition rate of 100 Hz, and an optical-to-optical conversion efficiency of 23.98%. The energy distribution ratios for the upper-left, lower-left, upper-right, and lower-right beams are 22.61%, 24.46%, 25.50%, and 27.43%, with pulse widths of 2.184 ns, 2.193 ns, 2.205 ns, and 2.211 ns, respectively. As the optical axis distance increases, the far-field spot pattern transitions from a single circular profile to four fully separated spots, where the lower-right beam exhibits beam quality factors of M_x² = 1.181 and M_y² = 1.289. Simulations at a 293.15 K coolant temperature and a 4.02 mJ pump energy reveal that split pumping reduces the volume-averaged temperature rise in Nd:YAG by 28.81% compared to single-beam pumping (2.57 K vs. 3.61 K), decreases the peak temperature rise by 66.15% (6.97 K vs. 20.59 K), and suppresses peak-to-peak temperature variation by 78.6% (1.34 K vs. 6.26 K). Compared with existing multi-beam generation methods, the fiber splitter approach offers integrated advantages—including compact size, low cost, high energy utilization, superior beam quality, and elevated damage thresholds—and thus shows promising potential for automotive multi-point ignition, multi-beam single-photon counting LiDAR, and laser-induced breakdown spectroscopy (LIBS) online analysis. Full article

We describe the output characteristics of a compact, passively Q-switched, diode-end-pumped (Er/Yb):Glass laser operating in a multi-pulse burst mode. Such operation enables much higher optical efficiency and larger output of total energy than possible with conventional solitary pulse emissions. The laser generated a 15-pulse burst of pulses at 1.5 μm with a combined energy of 5.8 mJ. Measurements of pulse energies, spatial mode characteristics, output beam divergence, and impact of thermal effects in the (Er/Yb):Glass are described. These results are compared to predictions of a numerical simulation using a finite-difference beam propagation method (FD-BPM) that incorporates thermal effects caused by distributed local heating in the glass. We show good agreement between the measured and simulated laser output characteristics. Full article

We report a passively Q-switched self-Raman laser using a dual-end composite c-cut Nd:YVO₄ crystal, which generates switchable visible emissions at 533 nm, 560 nm, and 589 nm. A Cr⁴⁺:YAG/YAG composite crystal served the role of a saturable absorber to achieve passive Q-switching. An angle-tuned BBO crystal was used to achieve the frequency mixing between the first-tokes wave and the fundamental wave. At an incident pump power of 9.5 W, the maximum average output powers were 425 mW for the 589 nm yellow laser, 193 mW for the 560 nm lime laser, and 605 mW for the 533 nm green laser, with corresponding pulse widths of approximately 3.8, 3.6, and 35.1 ns, respectively. This result shows that a passive Q-switching operation with self-Raman crystals presents a promising approach for compact multi-wavelength pulse laser sources. Full article

We present a model of a Cr²⁺-doped saturable absorber (SA), which is employed in passively Q-switched (PQS) Tm:CaF₂ lasers. The overall round-trip loss, the time evolution of the intracavity photon density, and the effective population inversion density can all be obtained through numerical solutions. Under the mode-matching condition, this model can be used to easily determine the PQS laser’s main output parameters, including the average output power, repetition frequency, peak power, pulse energy, and pulse width. This concept is also applicable to a range of thulium-doped solid-state lasers (SSLs) operating on the transition from the ³F₄ level to the ³H₆ level, which are Q-switched by a Cr²⁺-doped SA. This model is helpful for the design and optimization of this kind of laser. Full article

This study presents the synthesis of manganese molybdenum tetraoxide (MnMoO₄)-based nanoparticles and then their experimental demonstration as saturable absorbers (SAs) in erbium-doped fiber lasers (EDFLs). The MnMoO₄ nanoparticles were prepared and then embedded between the fiber ferrule to act as an SA to generate Q-switched pulsed operation in EDFLs. For the characterization, scanning electron microscopy (SEM) was employed to confirm the particle size of the prepared MnMoO₄ nanoparticles, and the SA optical properties were further investigated by measuring their modulation depth and saturation intensity. By implementing the prepared SA within the cavity, the measured results revealed that under pump power ranging from 28 to 312.5 mW, the laser exhibited Q-switched pulse durations varying from 15.22 to 2.35 µs and repetition rates spanning from 24.98 to 88.11 kHz. The proposed EDFL system delivered an average output power between 0.128 and 2.95 mW, pulse energies ranging from 5.12 to 33.49 nJ, and peak power from 0.281 to 6.26 mW. The laser stability was also confirmed by continuously noticing the pulse duration, emission wavelengths, and pulse repetition rates for 4 h. Finally, a numerical model based on a nonlinear Schrödinger equation (NLSE) was employed to validate both experimental and theoretical results of the passive Q-switched EDFL. These findings highlight the potential of EDFLs utilizing MnMoO₄-based SAs for potential applications in pulsed laser sources. Full article

A passively Q-switched Thulium-doped fiber laser based on glycerin as the saturable absorber is experimentally demonstrated for the first time. The saturable absorber consists of two FC/PC connectors aligned within a mechanical fiber-fiber coupler, with the intervening gap filled with glycerin. Such a saturable absorber is integrated into a compact ring cavity, enabling passive Q-switched laser operation. Starting at a minimum pump power of 1.7 W, Q-switched pulses with a central wavelength of 1946 nm are obtained. At the maximum pump power of 2.4 W, the laser generates pulses with a duration of approximately 2 µs, a repetition rate of 26.7 kHz, and a pulse energy of 1.08 µJ. To the best of our knowledge, this is the first demonstration of passively Q-switched laser operation utilizing a glycerin-based saturable absorber for generating pulsed emission at the 2-µm wavelength region. This breakthrough represents a significant advancement in fiber laser technology, introducing a novel and efficient approach to pulse generation. Full article

Pulsed lasers have a wide range of applications in scientific and industrial fields, and the saturable absorber (SA) is the core device of pulsed lasers. Tungsten carbide (WC) has garnered significant attention due to its exceptional physicochemical properties, making it a promising candidate for optoelectronic applications, particularly as an SA in pulse lasers. This study is the first to report the nonlinear optical properties of WC thin film at a 1064 nm wavelength and its use as an SA device to generate pulsed lasers. A high damage threshold of 472.4 mJ/cm² was achieved, which is a critical parameter for high-power laser applications. The constructed laser demonstrated pulsed output with a central wavelength of 1064.12 nm, an average output power of 185 mW, and a narrow pulse width of 684 ns. Our research has provided a strong candidate for the development of future economically stable high-power laser systems. Full article

Quasi-one-dimensional (quasi-1D) transition metal chalcogenides (TMCs), a subclass of low-dimensional materials, have attracted significant attention due to their unique optical and electronic properties, making them promising candidates for nonlinear photonics. In this work, NbTe₄, a quasi-1D transition metal tetrachalcogenide, was synthesized and employed for the first time as a broadband saturable absorber (SA) for pulsed laser applications. The nonlinear optical (NLO) properties of NbTe₄ were systematically characterized at 1.0 μm, 2.0 μm, and 3.0 μm, revealing saturation intensities of 59.53 GW/cm², 14 GW/cm², and 6.8 MW/cm², with corresponding modulation depths of 17.4%, 5.3%, and 21.5%. Utilizing NbTe₄-SA, passively Q-switched (PQS) pulses were successfully generated in the 1.0 μm and 2.0 μm bands, achieving pulse durations of 86 ns and 2 μs, respectively. Furthermore, stable mode-locked operation was demonstrated in an Er-doped fluoride fiber laser at 3.0 μm, yielding a pulse duration of 19 ps. These results establish NbTe₄ as a highly promising broadband SA material for next-generation ultrafast photonic devices and pave the way for the development of other quasi-1D materials in nonlinear optics. Full article

Raman spectroscopy is capable of precisely identifying and analyzing the composition and properties of samples collected from the lunar surface, providing crucial data support for lunar scientific research. However, in situ Raman spectroscopy on the lunar surface faces challenges such as weak Raman scattering from targets, alongside requirements for lightweight and long-distance detection. To address these challenges, time-gated Raman spectroscopy (TG-LRS) based on a passively Q-switched pulsed laser and a linear intensified charge-coupled device (ICCD), which enable simultaneous signal amplification and background suppression, has been developed to evaluate the impact of key operational parameters on Raman signal detection and to explore miniaturization optimization. The TG-LRS system includes a 40 mm zoom telescope, a passively Q-switched 532 nm pulsed laser, a fiber optic delay line, a miniature spectrometer, and a linear ICCD detector. It achieves an electronic gating width under 20 ns. Within a detection range of 1.1–3.0 m, the optimal delay time varies linearly from 20 to 33 ns. Raman signal intensity increases with image intensifier gain, while the signal-to-noise ratio peaks at a gain range of 800–900 V before declining. Furthermore, the effects of focal depth, telescope aperture, laser energy, and integration time were studied. The Raman spectra of lunar minerals were successfully obtained in the lab, confirming the system’s ability to suppress solar background light. This demonstrates the feasibility of in situ Raman spectroscopy on the lunar surface and offers strong technical support for future missions. Full article

This paper presents a time-shared pumping technology for semiconductor lasers based on polarization-combined technology, which enables a compact passively Q-switched Nd³⁺:YAG/Cr⁴⁺:YAG laser to generate tunable pulse sequence output. Two 808 nm laser diodes (LDs) with high polarization were integrated into a casing system measuring 61.5 mm × 32 mm × 12.5 mm through the implementation of fast and slow axis collimation, polarization-combined, and beam-shaping techniques. The study introduces a temporal modulation function to the electrical driving signals, allowing for synchronous and delayed control of the two laser pump sources. By adjusting the pumping delays (200 μs, 240 μs, 280 μs, and 320 μs), two types of pulse sequences combined by “1 + 1” and “2 + 2” at 1064 nm were successfully generated. Experimental results demonstrated that the energy and intensity of each sub-pulse within the burst-mode remain stable throughout the entire sequence, with adjustable sub-pulse interval. Furthermore, the laser system exhibited good beam quality with near-diffraction-limited output characteristics (M² < 1.5). In general, the tunable pulse sequence laser source offers significant potential for applications in high-precision laser processing, laser ranging and precision measurement, demonstrating its broad application potential. Full article

In the presented work, erbium fiber lasers operating in the pulsed mode with a nonlinear element containing a vanadium oxide saturable absorber are demonstrated. The structure of the saturable absorber is based on a segment of thinned silica fiber coated with a thin-film vanadium oxide by the method of metalorganic chemical vapor deposition. A fiber laser scheme is demonstrated that allows controlling the transmission of the internal cavity of the resonator during laser generation and deposition of a thin film. We have demonstrated a method for obtaining and annealing nanocoatings with laser generation control. We controlled the laser output parameters directly during the synthesis of the saturable absorber material. Vanadium oxides obtained in the work demonstrated the Mott–Paierls phase transition practically at room temperature. In this work, the optical characteristics of the output radiation of a fiber laser with a saturable absorber were measured. At temperatures above 70 °C, the coatings demonstrate a passive Q-switch with a repetition rate of 38 kHz and a pulse duration of 3.8 μs. At temperatures below the phase transition, a short-term mode-locking mode occurs. The transmission jump at a wavelength of about 1350 nm during structural rearrangement was 24%. For comparison, VO₂ nanopowder in a polydimethylsiloxane elastomer matrix was used as a saturable absorber material. The nanopowder modulator made it possible to obtain pulses with a frequency of 27 kHz and a duration of about 7.2 μs. Full article

This study demonstrates, for the first time, an innovative gain-switched Ho:YAP laser designed for laser distance measurement and remote sensing applications. The laser operates at a wavelength of 2117 nm, well positioned within the short-wavelength infrared (SWIR) atmospheric transmission window of between 2.1 and 2.5 µm. The laser delivers short pulse durations of 6.7 ns, and pulse energies of 0.645 mJ, allowing for an enhanced range and improved resolution. The Ho:YAP laser is pumped by a passively Q-switched Tm:YLF laser, resulting in a compact and energy-efficient system suitable for various sensing applications in precise distance measurement and environmental gas detection. Full article

A highly sensitive sulfur dioxide (SO₂) photoacoustic gas sensor was developed for the sulfur hexafluoride (SF₆) decomposition detection in electric power systems by using a novel 266 nm low-cost high-power solid-state pulse laser and a high Q-factor differential photoacoustic cell. The ultraviolet (UV) pulse laser is based on a passive Q-switching technology with a high output power of 28 mW. The photoacoustic signal was normalized to the laser power to solve the fluctuation of the photoacoustic signal due to the power instability of the UV laser. A differential photoacoustic cell can obtain a high Q-factor and reduce the gas flow noise in SF₆ buffer gas. The parameters of the SO₂ sensor system were optimized in terms of laser power and operating pressure. A 1σ detection limit (SNR = 1) of 2.34 ppb was achieved with a 1 s integration time, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 7.62 × 10⁻¹⁰ cm⁻¹WHz^−1/2. Full article

The 228 nm deep ultraviolet laser, leveraging its advantages of short wavelength, high photon energy, and low thermal effect, can significantly enhance the Raman signal in resonance Raman spectroscopy and demonstrates broad application potential in areas such as precision processing of photonic devices. This paper investigates a solid-state linear-cavity passively Q-switched 228 nm deep ultraviolet laser. Firstly, the laser employs an Nd:GdVO₄ crystal as the gain medium, combined with Cr⁴⁺:YAG crystal passive Q-switching technology to generate 912 nm pulsed fundamental frequency light. Subsequently, a lithium metaborate (LBO) crystal is used to generate 456 nm second-harmonic light, and finally, a barium metaborate (BBO) crystal is utilized to achieve 228 nm fourth-harmonic laser output. In this paper, we investigate the variation in 456 nm and 228 nm laser output power under the cavity length of 63 mm. Ultimately, at a pump power of 41.75 W, the highest average power of 670 mW was achieved for a 456 nm blue laser output with a repetition rate of 12 kHz and a pulse width of 32 ns. Additionally, a maximum average power of 18 mW was obtained for a 228 nm deep ultraviolet laser output, featuring a repetition rate of 12 kHz and a pulse width of 33 ns. Full article

A low-timing jitter passively Q-switched monolithic non-planar ring oscillator (NPRO) with diffusion-bonded Cr⁴⁺: YAG in a single-frequency operation was realized. The pulse parameters were controlled by a Cr⁴⁺: YAG saturable absorber, while the single-frequency operation was ensured by the unidirectional ring cavity structure. The pulse trigger was actively provided by a gain switcher utilizing a composite pumping scheme. The dependence of the timing jitter between the output pulse and the trigger signal on the parameters of the composite pumping scheme was investigated both theoretically and experimentally. Using this approach, we achieved a single-frequency pulsed laser output with a timing jitter of 14.568 ns (RMS) at a repetition rate of 100 Hz corresponding to a pulse width of 5.99 ns. This novel Q-switched monolithic NPRO, which integrates the benefits of both active and passive Q-switching, results in a simple and reliable structure that achieves a low-timing jitter single-frequency pulse output. Full article