Search Results (131)

We report the simultaneous generation of conventional solitons (CSs) and dissipative solitons (DSs) in an erbium-doped mode-locked fiber laser with a dual-branch cavity configuration based on the nonlinear polarization rotation (NPR) technique. By incorporating fibers with different dispersion properties in two propagation branches, the laser can establish simultaneous operation in the normal and anomalous dispersion regimes within the respective loops, enabling the generation of two distinct soliton types. The CSs exhibit a 3 dB spectral bandwidth of 9.7750 nm and a pulse duration of 273 fs, while the DSs have a quasi-rectangular spectrum spanning 18.7074 nm and a pulse duration of 2.2 ps, which can be externally compressed to 384 fs. The fundamental repetition rate is approximately 21 MHz, with a repetition rate difference of 216 Hz for the two pulse trains. Stable second-order, third-order, and fourth-order harmonic mode-locking (HML) can be achieved through optimization of pump power and intracavity polarization states. The laser we build in this work has significant potential for applications in high-precision spectroscopy and asynchronous optical sampling. Full article

In laser wireless power transmission systems, the powersphere serves as a spherical enclosed receiver that performs photoelectric conversion, achieving uniform light distribution within the cavity through infinite internal light reflection. However, in practical applications, the high level of light absorption displayed by photovoltaic cells leads to significant disparities in light intensity between directly irradiated regions and reflected regions on the inner surface of the powersphere, resulting in poor light uniformity. One approach aimed at addressing this issue uses a spectroscope to split the incident beam into multiple paths, allowing the direct illumination of all inner surfaces of the powersphere and reducing the light intensity difference between direct and reflected regions. However, experimental results indicate that light transmission through lenses introduces power losses, leading to improved uniformity but reduced output power. To address this limitation, this study proposes a method that utilizes multiple incident laser beams combined with a centrally positioned spherical reflector within the powersphere. A wireless power transmission system model was developed using optical simulation software, and the uniformity of the intracavity light field in the system was analyzed through simulation. To validate the design and simulation accuracy, an experimental system incorporating semiconductor lasers, spherical mirrors, and a powersphere was constructed. The data from the experiments aligned with the simulation results, jointly confirming that integrating a spherical reflector and distributed incident lasers enhances the uniformity of the internal light field within the powersphere and improves the system’s efficiency. Full article

Stimulated Brillouin scattering (SBS) in microresonators offers a unique way to develop narrow-linewidth chip-scale lasers. Yet their coherence performance is hindered by the cascaded SBS process, which clamps the output power and broadens the fundamental linewidth of the first-order Stokes wave. Resonance splitting proves to be an effective approach to suppress intracavity SBS cascading. However, precisely aligning and controlling the resonance splitting behavior remains challenging. We address these issues by proposing a piezoelectrically actuated grating-embedded tantalum pentoxide (Ta₂O₅) microring resonator. This microresonator comprises a Bragg grating segment that induces a counter-propagating wave and a ring segment that is integrated with a lead zirconate titanate (PZT) actuator. The half-circumference Bragg grating has a peak reflectivity of 31% at 1549.8 nm and a bandwidth of 88.89 pm, which is narrow enough to ignite resonance splitting in only one azimuthal mode. The PZT actuator empowers the resonator with a frequency tuning rate of 0.1726 GHz/V, particularly useful for post-fabrication compensation and splitting control. The proposed architecture offers a promising solution to breaking the intracavity cascaded SBS chain with frequency tuning capability, paving the way towards highly coherent chip-scale laser sources. Full article

Quartic solitons in ultrafast fibre lasers (intra-cavity optical fibre modulation systems) have been theoretically and experimentally analysed in recent years. However, there are few reports about extra-cavity modulating quartic solitons. In this situation, the purpose of this work is to investigate a quartic soliton’s extra-cavity modulation. In this paper, we theoretically simulate an extra-cavity-modulating quartic soliton with negative fourth-order dispersion at 1550 nm. The simulation relies on a physical model of a single-mode optical fibre system. Through controlling soliton parameters in an extra-cavity modulation system, a quartic soliton’s orthogonal polarisation modes will show unique characteristics depending on which kind of parameter is changed (seven parameters are considered for variation). For example, through the variation in the projection angle, only a horizontally polarised quartic soliton pulse is generated. These results explore the dynamics of quartic solitons in single-mode optical fibre modulation systems and are applicable to optical soliton transmission techniques in the field of optical fibre communication. Full article

In this manuscript, we demonstrated a switchable single-/dual-wavelength Yb:YAG laser based on intracavity loss modulation in a dual-confocal resonator configuration. The laser employed a dual-confocal resonator with a length of 175 mm that enabled the controlled adjustment of geometric losses through precise angular modulation of the output coupler, achieving stable switching between single- and dual-wavelength operations. Under a maximum pump power of 20.98 W, the laser delivered 1.868 W of single-wavelength output at 1050 nm with an optical-to-optical (O–O) conversion efficiency of 8.9%, exhibiting excellent power stability (RMS < 0.6%). When it was switched to a dual-wavelength operation at 1030 nm and 1050 nm, the total output power reached 0.376 W with respective powers of 0.180 W (1030 nm) and 0.196 W (1050 nm), corresponding to a 1.792% O–O conversion efficiency and a power stability of RMS < 3.0%. When it was switched to single-wavelength operation at 1030 nm, the maximum output power reached 0.193 W with a 0.920% O–O conversion efficiency and a power stability of RMS < 1.5%. These experimental results confirm that the controlled modulation of geometric losses in a dual-confocal resonator provides an effective approach for achieving flexible wavelength switching while maintaining stable output performance. This methodology offers promising potential for expanding the application scope of dual-wavelength lasers in precision optical systems. 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

A laser diode (LD) end-pumped continuous-wave (CW) tunable Nd³⁺:LiYF₄ (Nd:YLF) laser operating on the ⁴F_3/2→⁴I_13/2 transition was performed. Four single-wavelength (SW) lasing at 1321, 1314, 1371, and 1364 nm in the π-polarized direction and three SW lasing at 1314, 1326, and 1371 nm in the σ-polarized direction were achieved using a tuning prism. At 20 W pump power, the σ-polarized 1314 nm emission generated 7.3 W power output with 39.4% slope efficiency. Further, the three-pair of switchable π-polarized dual-wavelengths (DWs) at 1321/1314 nm, 1371/1364 nm, and 1321/1364 nm and the two-pair of switchable σ-polarized DWs at 1314/1326 nm and 1314/1371 nm were also realized by rotating an intracavity birefringence filter (BF). In addition, by employing dual intracavity BFs, the balanced DW output power was attained, achieving 6.4 W total maximum output at 1314/1321 nm in the π-polarized direction. Full article

An orthogonally polarized green dual-wavelength (OPGDW) laser output in a Pr³⁺:LiLuF₄ (Pr:LLF) crystal with the power ratio of 1:1 was realized for the first time. We calculated the condition for obtaining the identical power of the two output wavelengths and achieved the OPGDW laser by adjusting the tilt angle of the intracavity etalon and optimizing the output coupling transmittance. Using a frequency-doubled (2ω) optically pumped semiconductor (OPS) laser of 10 W at 479 nm, a continuous wave (CW) OPGDW laser output at 523 nm (π-polarized) and 538 nm (σ-polarized) was achieved with a combined power of 1.83 W. In addition, by type-II critical phase-matched (CPM) β-BaB₂O₄ (BBO) nonlinear crystal, a 57 mW, 265 nm CW UV laser was also realized by sum-frequency generation (SFG) of 523 nm and 538 nm wavelengths. CW OPGDW lasers with identical power output were ideal for both medical detection and generating UV lasers. Full article

A dual-wavelength (DW) Pr³⁺:LiLuF₄ (Pr:LLF) laser with the same threshold and slope efficiency was achieved for the first time. We theoretically deduced the conditions for obtaining the same threshold and slope efficiency of the DW operation, and experimentally demonstrated the orange-red DW Pr:LLF laser by optimizing the output coupling transmittance and adjusting the rotation angle of the intracavity Lyot filter. A CW orange-red DW laser, pumped by a 10 W 479 nm frequency-doubled optically pumped semiconductor laser (2ω-OPSL), delivers combined outputs of 607 nm and 640 nm with a total power of 2.69 W. The orange and red wavelengths maintained balanced power output under each pump level. Furthermore, by a type-I critical phase-matched (CPM) β-BaB₂O₄ (BBO) crystal, a CW ultraviolet (UV) second harmonic generation (SHG) at 312 nm was also obtained through intracavity sum-frequency mixing (SFM) of the 607 nm and 640 nm fundamental beams, achieving a maximum power output of 812 mW. Full article

A continuous-wave (CW) orthogonally polarized dual-wavelength (OPDW) Pr³⁺:LiLuF₄ (Pr:LLF) green laser with a balanced output power on the ³P₀→³H₅ transition was demonstrated for the first time. We theoretically analyzed the conditions for achieving equal output power in the OPDW laser operation using two intracavity etalons and experimentally realized the OPDW green laser in a Pr:LLF crystal. Under pumping with a frequency-doubled optically pumped semiconductor laser (2ω-OPSL) generating 10 W at 479 nm, an OPDW green laser at 546 nm in π-polarization and 550 nm in σ-polarization was obtained with a total output power of 1.68 W. The output powers of the two wavelengths were equal for all the pump power levels. Further, a CW ultraviolet (UV) laser at 274 nm by intracavity sum-frequency mixing was also achieved with a maximum output power of 386 mW. The OPDW Pr:LLF green lasers with the balanced output power were desirable for medical detection and the generation of UV lasers. Full article

Over the last decade, the number of demonstrations of Tm-doped fiber lasers has increased rapidly thanks to the applications of 2 $\mathsf{\mu }$m fiber laser in sensing, surgery, and polymer processing. In the literature, there is plenty of evidence that increasing the output power and the efficiency of this class of fiber lasers is of interest to the scientific and industrial communities. This article presents a theoretical and experimental study on three possible pumping methods for a Tm-doped fiber laser: out-of-band pumping, using a semiconductor-based module emitting at 793 nm; in-band pumping, using an ad hoc homemade fiber laser emitting at 1600 nm; an intracavity configuration, in which in the pump light is generated within the laser cavity itself. This work demonstrates how applying alternative pumping methods does not lead to significant improvements in laser performance without first taking into account the losses introduced in the system when switching from a cladding-pumped to a core-pumped configuration. Full article

The research on high-order transverse modes in lasers is a subject as old as the laser itself and has been largely abandoned. However, recently several studies have demonstrated an interest in using, instead of the usual Gaussian beam, a radial Laguerre–Gauss LG_p0 beam, as, for instance, one can observe a strong improvement, for a given power, in the longitudinal and radial forces in optical tweezers illuminated by a LG_p0 beam instead of the usual Gaussian beam. Since in most commercial lasers, the delivered laser beam is Gaussian, we therefore think it opportune to consider the problems of forcing a laser to oscillate individually on a higher-order transverse LG_p0 mode. We propose a comprehensive analysis of the effects of an intra-cavity phase or amplitude mask on the fundamental mode of a plano-concave cavity. In particular, we discuss the best choice of parameters favouring the fundamental mode of a pure radial Laguerre–Gauss LG_p0 model. Full article

This paper presents an integrated tunable hybrid multi-laser module designed to simultaneously generate multiple radiofrequency (RF) local oscillator (LO) signals through optical heterodyning. The device consists of five hybrid InP/Si₃N₄ integrated lasers, each incorporating an intracavity wavelength-selective optical filter formed by two micro-ring resonators. Through beating the wavelengths generated from three of these lasers, we demonstrate the simultaneous generation of two LO signals within bands crucial for satellite communications (SatCom): one in the Ka-band and the other in the V-band. The device provides an extensive wavelength tuning range across the entire C-band and exhibits exceptionally narrow optical linewidths, below 40 kHz in free-running mode. This results in ultra-wideband tunable RF signals with narrow electrical linewidths below 100 kHz. The system is compact and highly scalable, with the potential to generate up to 10 simultaneous LO signals, being a promising solution for advanced RF signal generation in high throughput satellite payloads. Full article

This study presents a compact intracavity difference-frequency generation (DFG) source designed for mid-infrared (mid-IR) applications. By optimizing overlap between the pump and signal beams, we obtained a black-box efficiency (${\eta }_{BB}$) of 3.4% W⁻¹ and a maximum DFG output power of 63 mW at a wavelength of 3437 nm for a 50 mm long periodically poled lithium niobate (PPLN) crystal. The mid-IR laser was systematically studied for various PPLN lengths (29 mm, 40 mm, and 50 mm), demonstrating extensive tunability across a range of mid-IR wavelengths. Stability assessments over short-term (2 min) and long-term (2 h) periods were also investigated, showing stability values of 0.91% and 1.08%, respectively. These advancements position our DFG laser as a promising candidate for potential applications in greenhouse gas detection and satellite communication, addressing the growing demand for reliable and efficient mid-IR sources. Full article

In response to the demand for high-power, long-pulse-width 532 nm lasers in the medical and industrial processing fields, this paper explains how the laser cavity of a high-power Nd:YAG 532 nm laser can be extended while maintaining the laser’s q-parameter by using a 4f optical system. The results show that at a repetition rate of 10 kHz, the extended cavity achieved a maximum average power of 112 W. Compared with the short cavity, the power was not significantly reduced. The pulse width was extended from 56 ns to 85 ns, and its broadening ratio reached 46.5%. The laser maintained good beam quality during high-power operation. Full article