Conventional semiconductor saturable absorber mirror (SESAM)-based mode-locked fiber lasers at GHz repetition rates often rely on Q-switching instability to initiate mode-locking, which generates intense Q-switched pulses that can permanently damage the SESAM and degrade long-term reliability. In this work, we demonstrate a 1.73 GHz Er-doped fiber Fabry-Pérot laser that directly self-starts into a stable mode-locked state. The ultrashort resonator consists of a 60.2-mm-long Er-doped silica fiber, a dielectric mirror deposited on the common-port end face of a wavelength-division multiplexer, and a semiconductor saturable absorber mirror directly contacted with the gain fiber. When the pump power is increased from zero, the oscillator directly enters continuous-wave mode locking at an LD output power of approximately 150 mW, without a discernible Q-switched mode-locking stage. The same direct mode-locking initiation is consistently observed in dozens of power-cycling tests. The laser delivers 2.1 ps pulses centered at 1565.8 nm with a 3-dB spectral bandwidth of 2.76 nm and an average output power of about 15 mW. The RF spectrum exhibits a signal-to-noise ratio of 88.3 dB. The elimination of the Q-switching transient not only prevents SESAM damage and extends the operational lifetime of the saturable absorber, but also simplifies the laser startup procedure, offering a robust and damage-resistant solution for high-repetition-rate 1560 nm fiber laser sources in optical communications and precision measurement applications.

Microbial fuel cells (MFCs) offer a sustainable route for simultaneous wastewater remediation and bioelectricity generation, yet their performance remains strongly limited by inefficient anode interfaces. Here, we report a low-cost nitrogen-doped graphene oxide/lignocellulose aerogel (NGO/LA) prepared via room-temperature inductively coupled N-2 plasma treatment. The plasma process introduces pyrrolic and graphitic nitrogen species, which enhance electroactive sites and improve interfacial conductivity. By chemically integrating two-dimensional NGO nanosheets with a three-dimensional lignocellulosic scaffold, a robust crosslinked network is formed, providing enlarged electrochemical surface area (ECSA), optimized porosity, and reduced charge-transfer resistance (R-ct). When applied as the anode in a single-chamber air-cathode MFC, NGO/LA achieves a peak power density of 0.3365 mW cm(-2) and enables similar to 96% degradation of methyl orange (25 mg mL(-1)) within 15 h. Furthermore, a MATLAB-based multi-factor coupling model quantitatively correlates specific surface area, ECSA, bacterial load, and R-ct with power output, showing < 5% deviation from experimental results. This work highlights the importance of interfacial chemical coupling and provides a predictive strategy for rational bioanode design in sustainable energy and wastewater treatment.

Translating advanced luminescent materials into field-deployable screening tools remains a core challenge, demanding synergy between advanced optical materials and device engineering. Here, we demonstrate a portable dual-mode near-infrared semi-quantitative screening device. the luminescence performance of the core emitting materials, specifically lead-free Nd³⁺/Yb³⁺ co-doped Cs₂NaYCl₆ double perovskite phosphors, was first optimized through a machine-learning (ML) guided approach. Subsequently, these optimized phosphors were integrated to enable the device. Specifically, the Nd³⁺-doped emitter targets the 885 nm characteristic absorption band of alcohol while exhibiting anomalous thermal quenching, whereas the Nd³⁺/Yb³⁺ variant leverages 78.66% energy transfer efficiency to yield stable 985 nm emission (70% retention at 500 K) matching the characteristic absorption band of water. These optimized phosphor-converted LEDs were integrated into a compact detector featuring a coaxial dual-disc stepper mechanism and a customized three-stage circuit that amplifies faint optical signals into a five-level visual indicator. This configuration enables rapid screening of alcohol (30–60%) and water content (45–100%). Validated on commercial samples, this work establishes a holistic platform bridging high-precision instrumentation and real-world portability. Translating advanced luminescent materials into field-deployable screening tools requires integrating optical materials with device engineering. Here, the authors demonstrate a portable dual-mode near-infrared screening device using optimized lead-free phosphors for rapid detection of alcohol and water.

High brightness pump sources are crucial for Kerr-lens mode-locked (KLM) femtosecond laser operation. In the current work, we use an optically pumped semiconductor disk laser (OPSL) to play a role as pump source of a KLM Yb:GdScO3 laser and we achieve a stable ultrashort pulse laser output of 47 fs at about 1068 nm. The KLM laser has an average laser output power of 56 mW and a repetition rate of 93.7 MHz. To our knowledge, this is currently the shortest pulse duration of Yb-doped mode-locked laser pumped by OPSL. Moreover, OPSL has the potential for high power output, which is expected to bring new development for the research of KLM femtosecond lasers.

Frequency doubling of high-performance Pr3+-doped visible lasers to obtain continuous-wave (deep) ultraviolet lasers bring new opportunities to the miniaturization of (deep) ultraviolet lasers, and also provides opportunities for the application and development of more high-end miniaturized (deep) ultraviolet single frequency lasers. In this work, we report on a 640-nm single frequency laser with a maximum output power of 4.19 W by optimizing an all-solid-state Pr:LiYF4 ring laser, and the beam quality of the laser is close to the diffraction limit. By incorporating a LBO crystal into the ring cavity for frequency conversion, more than 1.41 W single-frequency laser at 320 nm is also successfully achieved. The half-hour power stability of this ultraviolet single-frequency laser is measured to be about 0.54 %. This study indicates that the combination of Pr3+-doped visible laser intracavity frequency doubling and single frequency laser technology is a highly efficient and feasible method for realizing ultraviolet continuous wave single frequency lasers.

We developed a high brightness optically pumped vertical external-cavity surface emitting laser (OP-VECSEL) at 985 nm for pumping a Yb:GdScO(3 )crystal at its absorption peak. A stable Kerr-lens mode-locked (KLM) laser at 1056 nm with a pulse width of 55 fs and an average output power of 52 mW was achieved. To the best of our knowledge, this is the first time that VECSEL has been used as a pump source for Yb-doped KLM laser generation. The high brightness and potential high power characteristics of VECSEL are expected to bring new developments to high-performance femtosecond laser research.

We report on an alexandrite laser pumped by an all-solid-state Pr:LiYF4 (YLF) continuous-wave laser for the first time, to the best of our knowledge. The self-developed Pr:YLF laser at 639 nm has a power of 3.8 W. For continuous-wave alexandrite laser operation, we have achieved continuous tuning of the wavelength range from 718 nm to 785 nm. For Kerr-lens mode-locked alexandrite laser operation, we have realized a pulse width of 32 fs, which, to our knowledge, is currently the shortest pulse width for alexandrite laser. In the current research on alexandrite femtosecond lasers, 532 nm and 589 nm pump sources based on solid-state laser nonlinear frequency conversion technology are commonly used. The 639-nm laser we use in this work is the fundamental wave, which exhibits advantages in efficiency and system compactness.

We have successfully used a mixed sesquioxide ceramic (Yb 0.058 Sc 0.508 Y 0.434 ) 2 O 3 (Yb:YScO 3 ) as a gain medium for femtosecond laser generation via Kerr-lens mode-locked laser technology. A high-brightness diode laser has been used for pumping the ceramic sample, and a stable pulsed laser with a time duration of 64 fs and an average output power exceeding 100 mW at a peak wavelength of 1046 nm has been achieved. This is the first, to the best of our knowledge, report of femtosecond laser operation using mixed sesquioxide ceramic as a gain medium, and the time-domain width of the obtained pulsed laser is also one of the shortest in Yb-doped ceramic material mode-locked lasers.

In this work, we report on the recent research progress on watt-level all-solid-state single-frequency Pr:LiYF4 (YLF) lasers in the orange spectral region. Combining dual-end pumping and ring-cavity technologies, we have achieved a maximum singlefrequency output of 1.19 W at 607 nm with a linewidth of about 20.3 MHz. Based on this study, by inserting a 0.15 mm etalon inside the ring cavity, we find that the 607 nm lasing can be completely suppressed and a single-frequency laser at 604 nm with a 0.69 W output power and a linewidth of about 16.7 MHz can also be obtained. Moreover, the wavelengths of the two single-frequency lasers can be tuned from 607.16 to 607.61 nm and from 603.99 to 605.02 nm, respectively. Furthermore, the single-frequency Pr:YLF laser can also operate in a state of the two orange wavelengths, simultaneously, with a maximum output power of 0.97 W. We believe that this is the highest output power of a direct generation of single-frequency orange lasers and the first demonstration of the wavelength-tuned operation of the achieved single-frequency orange lasers, which could bring opportunities for the application of single-frequency orange lasers.

Ultrashort pulsed lasers operating in the deep ultraviolet (UV) spectrum, with high energy and peak power, are crucial for a wide range of advanced applications. In this study, we successfully developed a high-power, mode-locked Nd & ratio; YVO4 laser operating at 1064 nm, achieving an average output power of 9. 32 W, a pulse repetition rate of 78. 12 MHz, and a pulse width of 13. 9 ps. The 1064 nm picosecond laser was subsequently used as a seed in a regenerative amplifier, where a stable pulsed laser was obtained at 200 kHz with a maximum average output power of 26. 7 W and a pulse width of 16. 3 ps. Furthermore, we generated a green laser at 532 nm and a deep UV laser at 266 nm through two stages of nonlinear frequency doubling. The green laser exhibited an average output power of 14. 24 W and a pulse width of 12. 6 ps, whereas the deep UV laser achieved an output power of 3. 94 W and a pulse width of approximately 14. 3 ps. The 266 nm laser delivered a single pulse energy of 19. 7 mu J and a peak power of 1. 37 MW.

In the current work, the growth of Yb:CLNGG disordered crystal by the Czochralski method and its optical features, including laser performance were explored. The absorption and emission cross-sections of such crystal have been studied, followed by a measurement of the fluorescence decay curve. Using a cost-effective diode laser as a pump source, for the first time to our knowledge, we have demonstrated a Kerr-lens mode-locked Yb:CLNGG laser at about 1058 nm wavelength with the shortest pulse width of about 67 fs at a 77.85 MHz pulse repetition rate, and the maximum average output power reached up to 35 mW. By optimizing the crystal quality, we believe that this Yb:CLNGG crystal has the potential to develop a high-performance all-solid-state femtosecond laser.

Crystal fiber is highly valued in high-power laser research due to its excellent thermo-optic property. In this paper, we report on the result of studying high-energy nanosecond pulse laser at 1064 nm using Nd:YAG single crystal fiber as gain medium based on electro-optic Q-switching. With a 808-nm continuous wave diode laser as pump source, we obtained an average output power of 6.06 W at a repetition rate of 500 Hz with a pulse width of 29 ns, corresponding to a pulse energy of 12.12 mJ, and a peak pulse power of 0.42 MW. To our knowledge, this is actually the first research combining electro-optic Q-switching technology and end-pumped crystal fiber laser technology, and the results have indicated that crystal fiber has advantages in improving laser performance for directly obtaining high pulse energy and peak power with less system complexity and cost.

We have successfully used a mixed sesquioxide ceramic (Yb0.058Sc0.508Y0.434)2O3 (Yb:YScO3) as a gain medium for femtosecond laser generation via Kerr-lens mode-locked laser technology. A high-brightness diode laser has been used for pumping the ceramic sample, and a stable pulsed laser with a time duration of 64 fs and an average output power exceeding 100 mW at a peak wavelength of 1046 nm has been achieved. This is the first, to the best of our knowledge, report of femtosecond laser operation using mixed sesquioxide ceramic as a gain medium, and the time-domain width of the obtained pulsed laser is also one of the shortest in Yb-doped ceramic material mode-locked lasers.

In this work, a novel multi-component middle entropy Yb:CaSrBaF6 (Ca0.33Sr0.33Ba0.33F2) single crystal has been used as laser gain medium, for the first time to our knowledge, for Kerr-lens mode-locked laser operation. We used a high brightness 976-nm semiconductor laser as pump source and built a typical X-type laser resonant cavity. We generated intensity modulation and optimized beam quality through a built-in slit as hard aperture inside the cavity. Combined with dispersion compensation, we obtained a stable Kerr-lens mode-locked laser. In the mode-locked state, the maximum average output power reaches 159 mW at a repetition rate of 77.7 MHz, the peak wavelength of the laser is 1057.3 nm with spectral bandwidth of 10.2 nm, and the mode-locked laser pulse width is 123 fs, corresponding to a peak power of 16.6 kW. This study preliminarily proves that this novel multicomponent highly disordered laser crystal is effective in studying femtosecond pulse lasers via Kerr lens modelocked technology. By optimizing crystal quality, we believe that breakthroughs will soon be made in the study of femtosecond lasers with shorter pulses.

We report on the first demonstration of diode-pumped wavelength-tunable Yb3+-doped low silica calcium aluminosilicate (LSCAS) glass lasers. Using a 976 nm diode laser as pump source, a Yb:LSCAS laser has been successfully achieved with a maximum output power of about 0.28 W. Using an MgF2 thin plate as birefringence filter, we have found that the lasing wavelength can be tuned with a range of about 60 nm. We have also analyzed the intracavity round-trip loss of the current laser cavity, and related it to the optical quality of the used Yb glass. This sheds light on the path of the development of upcoming Yb3+ glass lasers in the future since it has many advantages, and after improving the optical quality, the wide and smooth emission spectrum of Yb:LSCAS will be very conducive to obtaining femtosecond pulse lasers.

Orange laser source at 605.98 nm corresponding to 3H4→ 1D2 optical transition of the Pr3+ ions in Pr:Y2SiO5 crystal is very crucial for quantum information experiments, which was only provided by dye laser in previos experiments. Although optical parametric oscillators (OPOs) or frequency doubling may be utilized in these years, high-power laser diodes are not yet accessible at this wavelength, and neither have appropriate output powers nor frequency stability. In this work, Pr :SrF2 and Pr,Gd:SrF2 single crystals were grown by TGT method and the spectroscopic investigation was carried out systematically. By co-doping Gd3+ ions into Pr:SrF2 single crystal, the intensity of orange emission at about 606 nm is strengthened while the red emission is suppressed. The first demonstration of all-solid-state continuous-wave orange laser at this specific wavelength was first reported in Pr3+ doped SrF2 crystal, to the best of our knowledge. Moreover, by using an un-doped YAG etalon for wavelength tuning, the orange emission of Pr,Gd:SrF2 laser showed certain wavelength tunability, which indicates Pr,Gd:SrF2 crystal could be promising for generation of ultrashort pulse laser in visible region.

Single-frequency (SF) lasers in the visible spectral region are usually obtained through an indirect method, i.e., frequency doubling of near-infrared SF lasers. In this work, we report on the direct generation of a high-power continuous-wave (CW) SF laser in red based on a diode-pumped Pr:LiYF4 (YLF) ring cavity technology. A maximum output power is scaled to 3.98 W at 640 nm with a linewidth of about 17.2 MHz and a power stability of 0.6%. Moreover, by inserting a LBO crystal into the ring cavity for intracavity frequency doubling of the 640 nm SF laser, we have also successfully demonstrated an ultraviolet (UV) SF laser at 320 nm, for the first time to the best of our knowledge, with a maximum power of 670 mW. This work provides a promising route for the development of simple, compact, and high-power SF lasers operating in visible and UV spectral regions.

Short wavelength single frequency lasers are mostly indirectly achieved through a combination of single frequency laser technology and nonlinear frequency doubling. This work applies the ring laser cavity technology to the study of Pr3+ single frequency laser generation, for the first time to the best of our knowledge. Using a blue diode laser as pump source and Pr:YLF crystal as laser gain medium, we have directly achieved an all-solid-state short wavelength single frequency laser at green with a maximum output power of 0.52 W and a beam quality close to the diffraction limit. Pr3+ ions have a rich emission range in visible spectral region, and ring cavity technology is a mature commercial high-power single frequency laser technology. Therefore, it is expected that through this method demonstrated in this work, a series of simple, compact and stable single frequency laser sources operating in visible can be achieved for potential applications.

We report on the first watt-level single frequency all-solid-state Pr3+-doped laser operating in continuous-wave mode based on ring cavity method. The achieved red (639.52 nm) single frequency laser has a maximum output power of 1.19 W at an absorbed power of 5.91 W with a slope efficiency of about 24.9%. Linewidth of the single frequency was measured to be about 20 MHz. By inserting an F-P etalon into the ring cavity, we also obtained a dual-wavelength laser (639.22+639.63 nm) still operating in single longitudinal mode. This dual-wavelength single-longitudinal-mode laser has the potential to generate a microwave source. In comparison to a conventional method for obtaining single frequency laser in visible through frequency doubling, using Pr3+-doped materials combined with single frequency laser technology to directly obtain visible single-longitudinal-mode laser has certain advantages in simplicity, miniaturization, high efficiency and cost efficiency of the total system.

Using a CZ-grown a-cut Pr:YLF crystal as laser gain medium after processing it into crystal fiber, we have demonstrated real Pr3+-doped single-crystal fiber lasers for the first time to the best of our knowledge. This Pr3+ crystal fiber has absorbed up to 20.4 W of pump power, which is the highest absorbed power among Pr3+ lasers. For two representative laser emissions at about 639 nm and 607 nm, we have achieved maximum output powers of 5.45 W and 3.04 W, respectively. Output powers of the two lasers show very good linearities, which indicate that the present output powers are only limited by the available pump power. Both laser emissions have exhibited near diffraction-limited beam qualities. This proposal has provided a good and feasible route for the development of compact, high-power, and high-brightness all-solid-state Pr3+ visible lasers via crystal fiber.