In order to study the spectroscopic characteristics of Nd3+:YVO4 crystal, the absorption spectrum of the Nd3+:YVO4 crystal was measured. The spontaneous emission rates, fluorescence branching ratios of the transitions from F-4(3/2) level as well as radiative lifetime of the F-4(3/2) level were calculated based on the Judd-Ofelt (J-O) theory. In addition, for the purpose of characterizing the emission properties of F-4(3/2) level in Nd3+:YVO4 crystal, the fluorescence emission spectra were measured under the pumping of similar to 808 nm laser. The emission cross section spectra of F-4(3/2) -> I-4(9/2), F-4(3/2) -> I-4(11/2) and F-4(3/2) -> I-4(13/2) transitions were calculated by the Fuchtbauer-Ladenburg (F-L) theory. The peak emission cross sections of 0.9 mu m (F-4(3/2) -> I-4(9/2)), 1.06 mu m (F-4(3/2) -> I-4(11/2)) and 1.3 mu m (F-4(3/2) -> I-4(13/2)) were determined to be 0.32 x 10(-19) cm(2), 13.1 x 10(-19) cm(2) and 1.93 x 10(-19) cm(2), respectively. The fluorescence lifetime of F-4(3/2) level was measured, and the quantum efficiency was calculated as well. In this work, the peak emission cross sections in similar to 0.9 and 1.3 mu m bands originated from F-4(3/2) level in Nd3+:YVO4 crystal were determined based on the spectroscopic method for the first time, to the best of our knowledge.

In recent years, deep-red lasers have received widespread attention due to the applications in medical treatment, chemistry and materials science. We demonstrated LD-pumped acousto-optic Q-switched Pr:YLF pulsed lasers at 719 nm and 696 nm. Measurements were performed at repetition rates of 5, 10, 20, and 50 kHz. The maximum peak power and minimum pulse duration of the pulsed lasers were obtained at 5 kHz. The maximum peak powers of the 719 nm and 696 nm pulsed lasers were 1.01 kW and 614.3 W, corresponding to the minimum pulse durations of 67.5 ns and 99 ns, respectively. This work provides a new method for generating stable 719 nm and 696 nm pulsed lasers, which will offer new insights for various applications.

We reported a diode-pumped Pr3+:LiYF4 (Pr:YLF) Q-switched pulsed laser and successfully extended the Q-switched pulsed wavelength into the near-infrared (NIR) region. The maximum average output powers of the 915 and 907 nm pulsed lasers are 568 and 486 mW, and the narrowest pulse duration and maximum peak power are 94 ns and 1462 W, 117 ns and 1035 W, corresponding to the single-pulse energies of 137.5 and 121.1 mu J, respectively. The peak powers of the two NIR pulsed lasers are in the kilowatt level. The successful realization of the NIR Q-switched pulsed laser compensates for the limitation that previously developed Pr:YLF Q-switched pulsed lasers focused on the visible region, and can provide practical applications in biomedicine, including dermatological and neurological disease treatment.

We demonstrate the first switchable deep-red dual-wavelength Pr:YLF laser and high-power deep-red dual-wavelength Pr:YLF lasers. The switchable deep-red dual-wavelength Pr:YLF laser can change the wavelengths between 679 nm & 719 nm and 679 nm & 729 nm, with maximum output powers of 1.14 W and 0.42 W, corresponding to slope efficiencies of 18.2 % and 6.6 %, respectively. We also obtained high-power deep-red dual-wavelength Pr:YLF lasers at 675 nm & 729 nm and 719 nm & 729 nm, with maximum output powers of 0.40 W and 1.13 W, corresponding to slope efficiencies of 8.5 % and 14.8 %, respectively. This work provides an effective solution for the dual-wavelength laser applications and demonstrates the vast potential of Pr:YLF in generating deep-red dual-wavelength lasers.

A deep-red actively Q-switched fiber laser based on Ho3+-doped ZBLAN is experimentally demonstrated under 532 nm pumping using an acousto-optic modulator (AOM). The system achieves stable emission at 751 nm with pulse durations as short as 104 ns, pulse energies reaching 320 mu J, and peak powers up to 2.88 kW. Continuous wavelength tunability is implemented over an 8 nm spectral range (748.82-756.98 nm) via a Littman-Metcalf cavity configuration, demonstrating excellent spectral flexibility. At the central tuning wavelength of 752.4 nm, pulses as narrow as 111 ns are obtained while maintaining robust spectral and temporal stability. The effects of pump power, modulation frequency, and cavity parameters on pulse characteristics are systematically investigated. Rate-equation simulations with systematic sweeps of R and L agree well with the experiments and reproduce the measured pulse dynamics. This work illustrates the potential of high-peak-power, tunable deep-red fiber lasers using rare-earth-doped fluoride fibers, which enable wavelength-selective excitation schemes for spectroscopy and imaging.

Abstract In this work, we propose a method to achieve dual-wavelength deep red laser based on Pr:YLF crystal. Laser with the central wavelength of 691.7 nm and 697.7 nm is simultaneously generated with an insertable cavity Lyot filter. The maximum output power is 1.001 W with the pump power of 11.88 W. The corresponding slope effciency is 11.8%. And the beam quality factor is also measured to be approximately 2.32 and 2.87 in the x and y directions, respectively. To the best of our knowledge, it is the first time we have achieved dual-wavelength laser with such a wavelength combination.

Pr3+-doped fibers have garnered significant interest due to their diverse visible emission lines. Here, we demonstrate the first visible-wavelength cavity-dumped operation in a single-clad Pr3+-doped fluoride fiber. Pumped by a commercial blue laser diode and utilizing an acousto-optic modulator with custom high-damage-threshold mirrors, stable cavity-dumped pulses were generated in the orange (603 nm), red (635 nm), and deep-red (716 nm) spectral regions. Operating across a broad repetition rate range, the system achieved its maximum average output powers of 150 mW, 288 mW, and 102 mW at 1 kHz. At this specific frequency, maximum single-pulse energies of 150 mu J, 288 mu J, and 102 mu J were successfully extracted, yielding impressive peak powers of 3.53 kW, 7.27 kW, and 2.64 kW, respectively. Furthermore, frequency-dependent analysis revealed that while increasing the pump power effectively narrows the pulse width, elevating the repetition rate reduces the average output power within the pure cavity-dumped regime up to 3 MHz. These findings provide critical guidance for optimizing high-energy visible fiber lasers, significantly expanding their potential for practical applications.

Direct generation of deep-red lasers while preserving high output performance has become increasingly important for the applications in scientific research and industry. In this study, the efficient deep-red laser operation of a Pr3+-doped fluoride fiber directly pumped by a commercial blue laser diode (LD) is experimentally investigated at two different active fiber lengths. In the free-running cavity structure, we achieved a maximum continuous-wave (CW) output power of 185 mW at 716 nm with a slope efficiency of 54.57 %, which represents the highest direct output power recorded in a single clad Pr:ZBLAN fiber. Moreover, by utilizing an AOM, stable actively Q-switched lasers are successfully generated. Under the 1 kHz repetition rate, the pulse has a duration of 40 ns, a single-pulse energy of 40 mu J, and a peak power of 1 kW. To the best of our knowledge, this is the first demonstration of an actively Q-switched laser at a deep-red wavelength of 716 nm. We believe that this work could provide an appreciable alternative for the next generation of pulsed deep-red laser sources.

In recent years, the Pr ion has gained great interest due to its vast spectral resources in the visible range. High slope and output power have been the focus of laser development in Pr-doped fibers. In this study, we investigated three different lengths of single-mode Pr:ZBLAN fiber with transitions of( 3)P(0)-> H-3(6) and F-3(2). The maximum output power of 204 mW and 555 mW were obtained with an optimum length of 23.5 cm and slope efficiencies as high as 65.4 % and 66.28 % at 603 nm and 635 nm, respectively. To the best of our knowledge, these are the maximum output power and slope efficiency at 603 nm and 635 nm in single-mode Pr:ZBLAN fiber pumped by blue laser. These results indicate the potential of single-clad Pr:ZBLAN fiber for visible laser operation with high output performances.

In order to study the spectral properties of Ho3+:YLiF4 (Ho3+:YLF), we measured the absorption spectra f Ho3+: YLF crystal. The experimental and calculated electric dipole line strength are calculated based on Judd-Ofelt theory, so do other spectral parameters. In order to characterize the emission characteristics of energy level, we measured the emission spectra of Ho3+:YLF crystal under the pumping of lasers at 450 nm and 640 nm, and the partial emission cross-sections spectra was calculated according to the Fuchtbauer-Ladenburg theory. Moreover, the fluorescence lifetimes of 537 nm, 656 nm, 750 nm, 1195 nm and 1964 nm are measured. As far as we know, the fluorescence lifetime of 1964 nm (similar to 2 mu m) and the emission cross-sections of similar to 750 nm and similar to 961 nm are confirmed for the first time. This work lays the foundation for the generation of lasing at novel wavelength on Ho3+:YLF crystal.

We demonstrate continuous-wave (CW) and pulsed laser based on Pr:YLF crystal at 522 nm in this work. In actively Q-switched operation, an acousto-optic modulator (AOM) is used as a modulation switch, a pulsed laser with a tunable repetition rate from 2 kHz to 50 kHz is obtained. The performance of the lasers at different repetition rates is compared at a maximum absorbed pump power of 12.47 W. The maximum average output power, maximum peak power and single pulse energy at the repetition rate of 2 kHz are 258 mW, 3146.3 W, and 129 mu J, respectively, which, to the best of our knowledge, are the maximum values of Q-switched laser at 522 nm reported so far. The power fluctuations at the repetition rates of 2 kHz, 20 kHz and 50 kHz are 4.7%, 4%, 5.8%, respectively. The beam quality factors M2 at repetition rate of 2 kHz are 1.83 (x) and 1.97 (y), respectively.

We report a watt-level visible-near-infrared (NIR) dual-wavelength Pr3+:LiYF4 (Pr:YLF) laser. This is the first report about the realization of visible-NIR dual-wavelength lasing in Pr:YLF crystal. The dual-wavelength lasers of 698 & 868 nm and 721 & 915 nm are directly realized without inserting any elements in the resonant cavity. The maximum output powers of the 698 & 868 nm and 721 & 915 nm dual-wavelength lasers are 1.31 W and 1.74 W, corresponding to slope efficiencies of 25.7% and 23.8%, and laser output power stabilities of 1.18% and 1.21%, respectively. The successful realization of the watt-level high-performance visible-NIR dual-wavelength laser can provide practical applications in medical diagnostics, treatment, and laser precision detection.

As the broad applications in biomedical imaging, radar detection, and scientific research, pulse lasers in the deep-red region have gained extreme interest. Herein, we successfully generated the actively Q-switched and cavity-dumped lasers at 717 nm. By utilizing AOM, the pulse laser has a maximum average output power of 836 mW at 200 kHz and a narrow pulse width of 40 ns at 5 kHz, which was the first demonstration in double-cladding Pr:ZBLAN fiber. The pulse energy reaches 128 mu J and the corresponding peak power is 3.6 kW at 5 kHz. In the cavity-dumping operation, the pulse laser has a maximum output power of 1.05 W, and the narrowest pulse width of 126 ns was measured at 5 kHz. The maximum pulse energy of 8.9 mJ and the peak power of 48 kW was achieved at 100 Hz, which is the highest than those of the deep-red lasers previously reported. We believe this work paves the way for narrow-pulse width and high single-pulse energy lasers in other rare-earth-doped fibers.

Lasers from 1I6 to 3F4 transitions were first demonstrated in a Pr3+∶YLF crystal by inserting a birefringent filter.Output powers up to 2.44 W,2.10 W,2.01 W,and 2.42 W were obtained at 691.7 nm,701.4 nm,705.0 nm,and 708.7 nm,respectively.Their slope efficiencies were 19.8％,16.5％,15.8％,and 19.4％,respectively.The M2 and My2 factors were measured to be 2.29 and 2.03 at 691.7 nm,2.23 and 1.86 at 701.4 nm,2.31 and 2.08 at 705.0 nm,and 2.41 and 2.04 at 708.7 nm,with corresponding power fluctuations of less than 5.3％,5.6％,5.8％,and 2.9％.

We reported an 868 nm Pr3+:LiYF4 (Pr:YLF) laser pumped by an InGaN blue laser diode (LD) for the first time. The maximum power of the laser was 641 mW and the beam quality M-x(2) and M-y(2) factors were -2.66 in the xdirection and -2.32 in the y-direction, respectively. The output power fluctuation was stable within +/- 2 %. The 868 nm laser was successfully realized in Pr:YLF crystal by designing and optimizing the laser resonant cavity and optical thin films. In addition, we theoretically simulated the nonlinear relationship between the laser output power and the absorbed pump power, and the theoretical simulation results were in agreement with the experimental data. The first realization of the 868 nm Pr:YLF laser further expands the near-infrared lasers.

We demonstrated an actively acousto-optic Q-switched pulsed laser based on Pr:YLF at 604 nm. A 604 nm continuous-wave (CW) laser with a maximum output power of 3.84 W was achieved for the first time, to the best of our knowledge. The Q-switched laser with a maximum average output power of 0.384 W, a narrowest pulse duration of 44.5 ns, a maximum single pulse energy of 64.1 mu J, and a maximum peak power of similar to 1.44 kW was obtained at a repetition rate of 6 kHz. As far as we know, this was the first report of such a narrow pulse duration, high-power, and high-energy Q-switched pulsed laser at 604 nm. The beam quality factors M-x(2) and M-y(2) were measured to be 2.87 and 2.40, respectively. The results show that acousto-optic Q-switching is a promising method for obtaining pulsed lasers.

We reported a continuous-wave (CW) deep red laser at 718.5 nm in a Pr3+:YLF crystal pumped by an InGaN laser diode. A maximum output power of 3.95 W with an average slope efficiency of 41.3% was achieved at 718.5 nm. The full width at half maximum (FWHM) of the laser spectrum was 0.82 nm. To the best of our knowledge, the laser output power and slope efficiency were both the highest values that have been reported so far. In addition, the theoretical model was built to interpret the input-output power characteristics, and the simulated results were essentially consistent with the experimental results.

We report the first demonstration on four new wave-lengths of 609 nm, 613 nm, 618 nm in both sigma- and pi-polarized direction based on continuous-wave Pr3+:LiYF4(Pr3+:YLF)lasers. The transitions mechanism combined dual upper energy levels of (3)P(1)and I-1(6) with Stark sub-levels of (3)H(6)and F-3(2) was designated. The CW lasers achieve output power greater than watt levels at room temperature, with 2.36 W at 609 nm, 1.85 Wat 618 nm, in the sigma-polarized direction and 1.93 W at 613 nm,1.40 W at 618 nm, in the pi-polarized direction.

Lasers from 1 I 6 to 3 F 4 transitions were first demonstrated in a Pr3+:YLF 3+ :YLF crystal by inserting a birefringent filter. Output powers up to 2.44 W, 2.10 W, 2.01 W, and 2.42 W were obtained at 691.7 nm, 701.4 nm, 705.0 nm, and 708.7 nm, respectively. Their slope efficiencies were 19.8%, 16.5%, 15.8%, and 19.4%, respectively. The M x 2 and M y 2 factors were measured to be 2.29 and 2.03 at 691.7 nm, 2.23 and 1.86 at 701.4 nm, 2.31 and 2.08 at 705.0 nm, and 2.41 and 2.04 at 708.7 nm, with corresponding power fluctuations of less than 5.3%, 5.6%, 5.8%, and 2.9%.

We present the development and characterization of high-power single-longitudinal-mode (SLM) Pr:YLF lasers across the visible spectrum using a ring cavity design integrated with an optical diode (OD) and Fabry-Perot etalons. Our study achieved notable single-frequency outputs at 639 nm (red), 604 nm, and 607 nm (orange), and 522 nm (green). Specifically, we obtained a maximum output of 1.4 W at 639 nm, while the orange lasers produced outputs of 435 mW at 604 nm and 1.03 W at 607 nm. The green laser achieved a maximum output of 313 mW at 522 nm. The narrowest linewidths recorded were 7.8 MHz for red, 9.4 MHz and 7.6 MHz for orange, and 9.7 MHz for green. These results demonstrate the feasibility of using a ring cavity combined with an F-P etalon to achieve high-power, narrow-linewidth SLM operation across a significant portion of the visible spectra, offering potential applications in precision spectroscopy, optical communications, and metrology.