New laser technologies reaching multi-kilowatt average powers, with the intrinsic capacity to deliver energetic pulses, are required for upcoming high-profile applications of intense lasers. We demonstrate that a diode-pumped, rotating multi-disk Yb:YAG technology, coupled with direct face-cooling by heavy water, reaches an average power of 2 kW in an 8-pass configuration, at a wavelength of 1030 nm in continuous wave mode, with a slope efficiency of 33%, an M2 of 2.4 at highest power, and a pointing stability of 2.5 µrad rms in spite of the disk rotation. The extractable energy is 4.3 J. This face-cooled rotating multi-disk amplifier (FCRMDA) technology paves the way to increase average powers for joule class picosecond lasers, with a horizon at the 10-kW level.

A 2.1 μm Ho:ZBLAN waveguide chip laser with improved slope efficiency

We demonstrate five dual-wavelength DFB lasers based on continuous-phase-shift gratings (CPSGs). The CPSG design preserves an effective coupling coefficient comparable to that of uniform Bragg gratings, while enabling deterministic control of the dual-mode spacing via a global phase ramp implemented in a single lithography step. Beat-note spacings ranging from 50 GHz to 1 THz are achieved, with dual‑mode operation exhibiting a side‑mode suppression ratio (SMSR) above 33 dB over a DFB drive current range exceeding 40 mA, albeit with increased threshold and reduced slope efficiency for the smallest 50 GHz spacing. These results establish CPSG-based dual-wavelength DFB lasers as compact optical beat sources for millimeter-wave/THz photomixing and heterodyne systems.

We report on continuous-wave and passively mode-locked operation of a diode-pumped Yb:Ca3TaGa3Si2O14 laser. In the continuous-wave regime, the laser delivered a maximum output power of 408 mW at 1045.5 nm, corresponding to a slope efficiency of 58.1% and a laser efficiency of 53.4%. By incorporating a quartz-based Lyot filter, a continuous wavelength tuning range of 82 nm, spanning from 1007 to 1089 nm, was achieved. In the mode-locked regime, a commercial semiconductor saturable absorber mirror was employed to initiate and sustain soliton-like pulse shaping, and pulses as short as 50 fs were generated at a central wavelength of 1052.4 nm, with an average output power of 40 mW at a pulse repetition rate of 73.9 MHz. To the best of our knowledge, this is the first demonstration of a mode-locked laser based on the Yb:Ca3TaGa3Si2O14 langasite-type non-centrosymmetric crystal, highlighting its significant potential as a gain medium for sub-100 fs solid-state lasers.

A continuous-wave (CW) multi-watt-level 1.76-μm all-fiber Tm-doped laser resonantly pumped at 1.56 μm is presented. To mitigate long-wavelength amplified spontaneous emission (ASE), an in-house-drawn depressed-cladding Tm-doped fiber (dc-TDF) was used as an active medium. In a linear cavity, an output power of 2.47 W, with an optical signal-to-noise ratio (SNR) exceeding 65 dB and a high slope efficiency of 75.8% relative to the launched power, was demonstrated. Furthermore, bidirectional pumping enabled output power scaling over 4 W with a slope efficiency of 66%. To our knowledge, this is the first demonstration of 1.7-μm laser operation using dc-TDFs.

We report inverted n‐p junction vertical‐cavity surface‐emitting lasers (VCSEL) arrays grown on an n‐type GaAs substrate to mitigate current‐crowding at the oxide aperture rim that degrades transverse mode stability and increases beam divergence in conventional p‐n oxide‐confined devices. This design incorporates a tunnel junction between the substrate and the bottom distributed Bragg reflector (DBR) to achieve junction polarity inversion. The n‐type top DBR provides higher lateral conductivity, promoting uniform carrier injection and enhanced current confinement. Arrays of 875 devices exhibit threshold currents of ∼0.4 A, slope efficiencies of ∼0.98 W/A, and peak power conversion efficiencies of ∼43%, comparable to those of conventional VCSELs. Near‐field imaging confirms that the inverted n‐p VCSEL sustains a compact, centrally peaked emission profile dominated by the LP 01 mode up to ∼1.0 A, whereas conventional p‐n devices with LP 02 dominance as early as 0.7 A. Corresponding far‐field measurements reveal divergence increasing gradually from 14.3° at 0.7 A to 24.1° at 5.0 A—on average ∼18% narrower (13.9%–23.1%)—compared with 16.6° to 27.8° for p‐n devices. This extended single‐mode operating range and consistent divergence reduction demonstrate the n‐p architecture's superior modal control, making it highly promising for scalable, high‐brightness VCSEL arrays in light detection and ranging, 3D sensing, and optical communication systems.

We report a highly efficient, Nd-doped all-fiber laser operating based on the three-level transition at 915 nm. A key feature of the laser is a novel active fiber with cladding-embedded absorbing rods that suppress parasitic amplified spontaneous emission (ASE) at 1060 nm. The laser demonstrates 37% slope efficiency, which is, to the best of our knowledge, the highest reported value among all-fiber lasers with near-diffraction-limited beam quality (M² < 1.2). Strong ASE suppression with a signal-to-ASE ratio exceeding 50 dB was achieved. Further output power and efficiency scaling can be reached by optimization of fiber components used in the laser cavity.

We report broadly tunable diode-pumped laser operation of a disordered Tm:CALYO aluminate crystal on the 3H4 → 3H5 transition. By applying an intracavity birefringent filter, continuous tuning ranges of 258 nm (2254-2512 nm) and 225 nm (2235-2460 nm) were achieved for the π- and σ-polarized eigen polarization states of this uniaxial crystal, respectively. In the free-running regime, the Tm:CALYO laser delivered a maximum continuous-wave output power of 1.10 W at 2.3 µm with a slope efficiency of 6.4%. The polarized spectroscopic properties of Tm3+ ions in CALYO were systematically investigated to explain the observed laser behavior. The stimulated-emission cross section for π-polarized light reaches 0.23 × 10-20 cm2 at 2353 nm, corresponding to an emission bandwidth exceeding 250 nm, while the intrinsic luminescence lifetime of the 3H4 upper laser level is about 400 µs. Attention was devoted to crystal annealing conditions, which were found to play a critical role in optimizing laser performance and represent a pathway for further improvement. Owing to its exceptionally broad emission bandwidth and good thermal properties, Tm:CALYO emerges as a promising gain material for femtosecond pulse generation at 2.3-2.4 µm.

Quantum cascade lasers are highly desirable for chemical, physical, and biological research scenarios. Among the applications, mid-infrared frequency combs based on quantum cascade lasers have sparked increasing interest due to their unique advantages in small footprint, high power, and flexible designability. Despite significant performance improvement over a decade, the lasing spectrum bandwidths of the quantum cascade laser frequency combs are still limited to ~100 cm-1, limiting their applications in multi-gas spectroscopy and posing severe challenges in tracking their carrier-envelope offset frequency. To achieve a broad-gain spectrum, heterogeneous active regions consisting of multiple stacks of different wavelengths have been implemented. For example, stacking active regions of four different wavelengths results in a full width at half maximum of approximately 0.92 μm (110 cm-1) at 290 K, and of ~2.7 μm (360 cm-1) at 80 K. However, as more stages are stacked, ensuring a homogeneous and flat gain profile from both design and growth perspectives becomes very challenging. In this work, we present a demonstration of ultra-broadband quantum cascade lasers with a diagonal multi-state-to-continuum active region design. The proposed active region design exhibits a surprisingly wide electroluminescence with a full width at half maximum of ~600 cm-1 at 298 K. Devices, with a total peak output power of 2.72 W and a slope efficiency of 1.3 W/A, have shown a lasing spectrum of ~1 μm over 43% of the current dynamic range, with a maximum bandwidth of 1.2 μm around the rollover current. Moreover, a much broader lasing bandwidth of 1.93 μm is obtained from the same device at 80 K, accounting for 22% of the center wavelength. This work represents substantial progress on the single-stack ultra-broadband mid-infrared semiconductor lasers and may provide a novel platform for mid-infrared frequency combs, which are of paramount importance to broadband high-precision spectroscopy, imaging, and free-space communication systems.

High-performance blue-violet lasers are essential for compact quantum sensing and metrology. However, light sources in this spectral range currently rely on bulky external cavities or complex nonlinear frequency conversion, limiting their robustness and field deployment. While monolithic InGaN-based distributed feedback laser diodes (DFB LDs) offer a path toward miniaturization, precisely targeting narrow atomic transitions remains challenging due to fixed grating periods and fabrication-induced wavelength deviations. In this work, we demonstrate a 420-nm DFB laser array with an ultrafine 0.2-nm channel spacing, enabled by a continuously phase-shifted grating design. This approach allows for precise wavelength control without compromising coupling efficiency, while significantly enhancing the array's robustness against fabrication variations. By integrating ten devices, the array spans a 2-nm spectral range around 420 nm, enabling coarse wavelength selection through individual device addressing. This strategy minimizes the required thermal or electrical tuning range, thereby keeping the LD within its optimal operating regime while reaching the target atomic transitions. The fabricated LDs exhibit a 40 mA threshold current, 1 W/A slope efficiency, and up to 40 mW single-mode output power, with tuning coefficients of 1.6 pm/mA and 20 pm/∘C for current and temperature, respectively. Optical heterodyne measurements reveal a Lorentzian linewidth of 9.8 MHz, highlighting a practical and manufacturable path toward robust blue-violet light sources for next-generation chip-scale atomic and quantum photonic systems.

Abstract Photonic-crystal surface-emitting lasers (PCSELs) can deliver watt-level, diffraction-limited emission from millimeter-scale, lens-free systems. However, scaling this performance to high-power red PCSELs remains challenging, as strong intrinsic absorption in III-V materials obstructs the integration in a common platform for embedded air holes and substrate-side emission. Here we introduce a novel red-emission PCSEL based on the air-column architecture that breaks the mirror symmetry of the double-lattice photonic-crystal along y=x diagonal to enhance its output efficiency. Three-dimensional coupled-wave theory (3D-CWT) combined with multi-parameter scanning is employed to quantify the radiative ability, inter-modal crosstalk, and coupling strength in infinite structures, as well as to extract the slope efficiency and threshold margin of finite devices. The optimized double-ellipse lattice with a 14° rotation yields a high slope efficiency of 0.82 W/A while maintaining robust transverse-mode discrimination and exhibiting tolerance to ±0.01 variations in the filling factor. Our work demonstrates that the symmetry deliberately broken by rotation in plane geometry provides an additional degree of freedom for maximizing the radiation efficiency of double-lattice PCSELs and enables a compact high-brightness red laser design for laser display and medical lighting.

Abstract This paper demonstrates a diode-pumped continuous-wave σ-polarized Nd:YLF laser operating on the 4 F 3/2 → 4 I 9/2 transition, achieving tunable output at 863, 873, 880, and 885 nm within a single resonator. A quasi-three-level gain model was established to analyze the polarization-dependent gain characteristics and predict threshold power rankings. Experimentally, stable multi-wavelength operation was realized through optimized crystal parameters, pump conditions, and an intracavity Lyot filter for polarization control and wavelength selection. The laser delivered maximum output powers ranging from 327 mW to 1.46 W with slope efficiencies between 3.8% and 10.2% across the four wavelengths, all exhibiting narrow linewidths and good power stability. This work validates Nd:YLF’s potential for tunable operation in the 800 nm band and provides design guidelines for quasi-three-level laser systems.

All-ceramic channel waveguides (CWGs) in Yb:YAG transparent ceramics have been fabricated for the first time, to the best of our knowledge, via direct ink write (DIW) and their laser performance has been demonstrated. Single filaments of Yb:YAG nanoparticle-loaded ink were extruded into undoped YAG; the Yb:YAG filaments formed the CWGs, surrounded by undoped cladding. Elemental mapping confirmed the Yb doping profile and waveguide integrity. Optical characterization showed low cladding scatter losses (<1.3%/cm at 1.3 µm), and laser testing with a 940 nm Ti:sapphire pump demonstrated efficient lasing at 1030 nm. The best-performing waveguide, with an elliptical cross-section (100 µm × 60 µm and a length of 1.4 cm), achieved a slope efficiency of 61% and a roundtrip loss of 12.4%. These results identify DIW as a promising approach for fabricating high-performance channel waveguides in transparent ceramics.

This work experimentally investigates a solar and laser-diode hybrid-pumped Nd-doped fiber laser enabled by a port-matched aspheric lens array. A seven-element aspheric lens array is designed and constructed for solar end coupling, in which each lens concentrates sunlight into an individual pump fiber, and a standard 7 × 1 multimode pump combiner aggregates the seven channels into a single pump delivery path. An 808 nm LD is used as a reference pump to quantify the net gain of the solar end-pumping stage by comparing the 1064 nm output with and without the solar channel under otherwise identical cavity conditions. A single-pass bandpass-filter method isolates the 1064 nm laser component, indicating a net slope efficiency increase of 48.77% under hybrid pumping and an average output power enhancement of approximately 1.67 mW. Although solar-only pumping does not yet reach the oscillation threshold, the array-based solar channel provides a measurable positive gain at 1064 nm. The prototype relies exclusively on standard commercial fiber components. It requires neither sensitizers nor complex water-cooling infrastructure, which is attractive for mass- and complexity-constrained deployments such as spaceborne platforms. The array architecture further supports cascaded pump-power scaling by expanding the collection area and increasing the number of pump channels, providing a practical engineering pathway toward solar-only fiber-laser operation.

The rapid expansion of large-scale artificial intelligence data centers and the growing demand for high-performance radio-over-fiber (RoF) systems necessitate high-efficiency, ultra-low noise, highly linear, and thermally stable lasers. Here we demonstrate a high-performance O-band InAs/GaAs quantum-dot (QD) distributed-feedback (DFB) laser architecture incorporating a laterally coupled, shallow-etched sidewall grating within a trapezoidal ridge waveguide. At room temperature, the fabricated devices achieve a single-facet output power of 70 mW with an impressive slope efficiency of 0.372 W·A −1 , while maintaining excellent single-mode emission with a side-mode suppression ratio (SMSR) up to 61 dB. For optical interconnect applications, these lasers exhibit exceptional thermal stability, sustaining stable single-mode operation at 125°C with an output power exceeding 6 mW. Furthermore, they show robust tolerance to optical feedback, with the SMSR remaining over 50 dB even at a returned power level of −15 dB , enabling isolator-free integration. For RoF applications, the devices achieve an ultra-low relative intensity noise (RIN) of &lt;−170 dB / Hz over the 4–22 GHz frequency range and demonstrate high linearity, with an input 1 dB compression point ( IP 1 dB ) of approximately 25 dBm and a third-order intercept point ( IIP 3 ) of approximately 34.4 dBm. The demonstrated architecture represents a significant advance, as it simultaneously optimizes multiple critical performance metrics—efficiency, thermal stability, feedback resilience, low-noise performance, and large-signal linearity—within a single device. The simple, regrowth-free fabrication process is compatible with heterogeneous integration platforms, making it a highly promising solution for future wafer-scale manufacturing of QD lasers on silicon or thin-film lithium niobate (TFLN) wafers.

We report a core-pumped, all-fiber, monolithic holmium-doped silica fiber laser (HDFL) pumped at 1940 nm by a high-power Tm-doped fiber laser. The system delivers up to 95W of continuous-wave output power at 2109 nm, representing one of the highest reported powers for a core-pumped holmium fiber laser. A slope efficiency of 84% with respect to launched pump power is achieved, making a 10% improvement over previously published papers. These results confirm the effectiveness of core pumping using advanced Tm-doped fiber architectures and highlight the potential of compact, efficient Ho-doped fiber sources for high-power applications in the 2.1 µm spectral region. All experiments were further supported by numerical modelling together with a simulation of possible further power-scaling up to 250 W.

The Nd:GYSAG crystal enables multi-wavelength near-infrared laser output, with adjustable wavelengths tailored for specific application requirements, making it highly valuable for space-borne water vapor detection. This study reports, for the first time, the side-pumping characteristics and electro-optical Q-switching performance of this crystal. Using Ø3 × 73 mm and Ø4 × 73 mm crystal rods doped with 1.21 at.% Nd:GYSAG (chemical formula Nd0.033Gd0.93Y1.79Sc0.70Al4.54O11.99), 1060.4 nm laser output was achieved under 808 nm laser diode (LD) side-pumping at a repetition rate of 100 Hz and a pump pulse width of 250 μs. The experimental results show that the Ø4 × 73 mm rod had a higher laser threshold but exhibited significantly superior slope efficiency and maximum output power compared to the Ø3 × 73 mm rod. Using a flat–flat resonator, optimal laser performance was obtained with an output coupler transmission of 35%, yielding a slope efficiency of 37.2%. A maximum output energy of 179.4 mJ was achieved at a pump energy of 646 mJ. Thermal lensing effects were compensated using a flat–convex cavity, leading to improved laser performance and beam quality. Electro-optical Q-switching experiments were conducted using a KD*P crystal. A comparison between voltage-applied and voltage-removed Q-switching techniques revealed superior performance for the voltage-applied method. High-performance laser output was realized, achieving a maximum pulse energy of 59.6 mJ, a pulse width of 14.93 ns, and a peak power of 3.99 MW. This study provides an important foundation for the development of near-infrared laser devices based on Nd:GYSAG.

Multi-core fibers have emerged as a promising solution for high-power fiber laser systems, which allow for the simultaneous mitigation of thermal and nonlinear effects through core-count scaling. This makes them highly attractive for high-average-power applications. However, there has been no demonstration of a multi-kilowatt, multi-core fiber laser system to date. In this work, we present a Yb-doped, multi-core fiber laser system, delivering up to 3.2 kW of average power (over all cores) with excellent short- and long-term stability. The system exhibited a slope efficiency with respect to launched power of 86.3%, and the output power was limited only by the available pump power.

High-brightness yellow lasers are in high demand for applications such as atomic cooling and trapping, optogenetics, and sodium laser guide stars. Herein, we demonstrate the potential of Metal-Organic Chemical Vapor Deposition (MOCVD) for the rapid mass production of high-strain 1.2 μm InGaAs quantum well vertical external cavity surface emitting lasers (VECSELs). Two distinct growth strategies were explored, with a primary focus on enhancing crystal thermal stability and mitigating indium segregation. The as-grown gain chips achieved over 45 W of output power and a slope efficiency exceeding 50%. Furthermore, we verified the feasibility of generating yellow second harmonic generation (SHG), attaining a 590 nm CW power of ~6.2 W with a slope efficiency of 17%. The beam quality factor (M²) was <1.1, approaching diffraction-limited performance, corresponding to a brightness of ~1.65 GW cm-2 sr-1. Overall, these investigations not only expand the performance envelope of MOCVD-grown semiconductor lasers but also deepen the understanding of indium segregation behaviors.

Motivated by strong demand for high-power mid-infrared sources in spectroscopic detection, minimally invasive surgery, and precision polymer processing, we report a record-breaking 20.2 W all-fiber laser operating at 3550 nm, representing, to our knowledge, the first demonstration exceeding 20 W beyond 3 μm in monolithic fiber architecture. The system incorporates a 2.5-m-long, lightly Er 3+ -doped ZrF 4 fiber (1% molar fraction) paired with a pair of femtosecond-laser-direct-written fiber Bragg gratings (FBGs), and achieves a slope efficiency of 37.2% through dual-wavelength pumping at 981 nm and 1980 nm. Precision independent thermal control effectively compensated for relative wavelength shifts between the high-reflectivity (HR) and low-reflectivity (LR) FBG pair, significantly improving spectral overlap. Comprehensive testing confirmed robust operation, demonstrating 2 h power stability with 1.36% root mean square fluctuation and 30 min wavelength stability with less than ±0.12 nm variation at 12.5 W output power.