A 1064 nm seed-injection, single-frequency Nd:YAG pulsed laser based on a double-corner-cube-retroreflector (DCCR) structure has been demonstrated. The DCCR design provides inherent resistance to misalignment. By employing an intracavity optical-path compensation mechanism and an output coupler with a transmission of 14.28%, the laser has generated single-frequency pulses with an energy of 1.139 mJ. The corresponding beam quality factors are M-x(2) = 1.17, and M-y(2) = 1.02. Heterodyne measurements have revealed a spectral linewidth of 8.4 MHz. This work successfully extends the application of the DCCR to the 1 mu m spectral region, offering a promising, stable source for coherent detection and other precision applications.

In the paper, a heterodyne quartz-enhanced photoacoustic spectroscopy (H-QEPAS)-based integrated methane (CH4) sensor prototype is reported. The CH4 absorption line located at 1650.96 nm was selected as the target spectral line. The design features an integrated, 3D-printed gas chamber for reduced size and weight. To realize the coordinated operation of each hardware component, a control program was designed based on LabVIEW platform, enabling the adjustment of various hardware parameters. The piezoelectric signal generated by the quartz tuning fork (QTF) was amplified via a trans-impedance amplifier (TIA), acquired by a data acquisition card (DAQ), and then transmitted to a virtual lock-in amplifier (LIA) on the PC terminal for processing. The dimensions of the integrated CH4 sensor prototype are 33 cm in length, 27 cm in width, and 15 cm in height. The final test results demonstrate that the sensor prototype exhibits an excellent concentration linear response, with a detection limit of 26.72 ppm and a short detection time of approximately 4 s.

This paper reports an Nd:YVO4 laser employing a double-corner-cube-retroreflector (DCCR) ring cavity for bidirectional asymmetric single-longitudinal-mode emission. By inserting three Fabry-P & eacute;rot etalons into the cavity, stable bidirectional single-longitudinal-mode operation is achieved, with maximum output powers of 1.385 W and 0.322 W, respectively. As the pump power increases, the output power ratio between the two beams varies from 1.63 to 4.30. By shifting the intrinsic balance between gain and loss, this bidirectional asymmetric coherent laser enables asymmetric control of the laser power.

Strong-field-driven 2 mu m heterostructure passively mode-locked ultrafast lasers often exhibit unpredictable operational drift, yet its physical origin remains unclear. Existing theories usually treat nonlinear modulation as a static parameter independent of operational history, leaving out an intrinsic time variable required to describe continuous system evolution. By combining multiphysics thermo-mechanical calculations with cross-scale molecular dynamics simulations, it is shown that the interfacial atomic configuration of the MoS2/Ti3C2T x heterojunction accumulates operational history and undergoes progressive reconstruction under sustained optical-thermal driving. The evolution of local Mo-S, Ti-C, and terminal-group coordination environments further translates this atomic-scale history into a time-varying nonlinear response. Interfacial atomic evolution is therefore identified as an intrinsic time variable of heterostructure ultrafast lasers, while distinct interfacial memory states define a dynamic scale for the system's dynamical stage and modulation drift. On this basis, a ResNet-MLP predictive framework is established to directly map interfacial atomic states to macroscopic laser output, achieving an R 2 of 0.856 and a minimum relative error of 2.2%. Experimentally, 2 mu m passive mode-locking is obtained with a pulse width of 752 ps and a single-pulse energy of 10 nJ. These results establish heat-history-driven interfacial atomic evolution as the physical origin of operational drift in heterostructure ultrafast lasers.

We demonstrate an all-polarization-maintaining passively mode-locked thulium-doped fiber laser based on a nonlinear optical loop mirror. Based on the characteristic autocorrelation trace with a nanosecond-scale pedestal and a 285-fs coherent spike, it is determined that the mode-locked laser outputs noise-like pulses. Benefiting from the all-polarization-maintaining structure, the laser exhibits significantly improved stability, with an output fluctuation of merely 0.11% over 30 min and a high signal-to-noise ratio of 73 dB. This performance provides a high-quality laser source for precision and high-end applications.

We have demonstrated a single-longitudinal-mode (SLM) Er:YAG laser operating at a central wavelength of 1645.10 nm, which is constructed with an acousto-optic Q-switch (AOQS) integrated into a double corner-cube-retroreflector (CCR) ring cavity. By tilting the AOQS (with radio frequency (RF) power applied) to deviate slightly from the Bragg angle, a maximum continuous-wave (CW) SLM output power of 0.953 W is achieved, corresponding to a slope efficiency of 6.32%. Furthermore, a single-frequency pulsed Er:YAG laser with a repetition rate of 1 kHz is realized by periodically driving the AOQS with a RF signal generated from the signal generator. At this repetition rate, the laser delivers a single-frequency pulse with an energy of 0.258mJ and a pulse width of 824 ns. Additionally, the beam quality factors M-2 of the pulsed laser are measured to be 1.08 and 1.19 along the horizontal (x) and vertical (y) directions, respectively.

In this paper, we demonstrate a temperature-tunable long-wave infrared optical parametric oscillator (OPO) based on a 76 mm BaGa4Se7 (BGSe) crystal pumped by a 2117.4 nm Ho:YAP laser. To the best of our knowledge, this is the first demonstration of BGSe-OPO pumped at this wavelength. The 76 mm BGSe crystal is the longest single crystal ever used in OPO. At 33 degrees C, the OPO delivers a maximum output power of 300 mW at 9976 nm, with a slope efficiency of 2.71 % and beam quality factors of 2.0 and 2.3. By tuning the crystal temperature from 14 degrees C to 33 degrees C, the wavelength is continuously tuned from 9976 nm to 10937 nm with a high tuning efficiency of 50.6 nm/degrees C. Compared with the 2090 nm pumping scheme, the output wavelength is extended by up to similar to 1 mu m at 14 degrees C, verifying that a longer pump wavelength can effectively broaden the long-wave infrared output range.

We demonstrate a high-power picosecond long-wave infrared (LWIR) source based on type-II difference frequency generation (DFG) in ZnGeP2 (ZGP) and BaGa4Se7 (BGSe), pumped by a 2089.1 nm laser at 10 kHz repetition rate. When seeded by a double-pass optical parametric generator (OPG), the system delivers a record tabletop 1.91 W idler output beyond 10 μm from BGSe DFG under 56 W total pump power. The type-II ZGP DFG stage alone generates 2.84 W beyond 10 μm, while cascading with BGSe boosts the average power to 3.31 W, corresponding to 5.9% optical-to-optical conversion efficiency. The idler spectrum centers at 10.02 μm with 278 nm full-width at half-maximum (FWHM) bandwidth. With measured a 252.5 ps pulse duration, the system achieves 1.31 MW peak power and beam quality M2 = 3.64/2.67 in x/y directions. To our knowledge, this represents the highest average power reported from LWIR parametric sources beyond 10 μm.

A 10 kHz non-critical phase matching (NCPM) optical parametric oscillator based on BaGa4Se7 crystal is demonstrated. By utilizing a dual-crystal cascade configuration, an average output power of 0.96 W at a wavelength of 9387 nm is achieved, with a slope efficiency of 5.73 %. In addition, the temperature-dependent wavelength-tuning characteristics of the BGSe crystal are systematically investigated. By decreasing the crystal temperature from 38 degrees C to 6 degrees C, an idler wavelength tuning range of 9387-10107 nm is achieved, corresponding to a central wavelength shift of 720 nm (22.5 nm/degrees C) and a linewidth variation of 40-60 nm. This study has unveiled the great potential of BGSe crystal in high power, high repetition rate long-wave infrared pulse generation.

In this Letter, we report a high-power picosecond Ho:YAG amplifier system delivering an average output power exceeding 111 W at a repetition rate of 10 kHz, achieving an overall gain of 93 dB, with beam quality characterized by M2 values of 1.53 and 1.65 in two orthogonal directions and highly stable operation (1.7% RMS fluctuation). To the best of our knowledge, this represents the highest average power demonstrated thus far for a 2-μm picosecond laser amplifier. Utilizing this robust amplifier as a pump source, we further developed a ZnGeP2 (ZGP) optical parametric generator (OPG) for mid-infrared radiation, successfully achieving direct emission at 10.1 μm with an output power of 123 mW under a pump power of 16 W. Notably, this work demonstrates the first direct 10 μm generation from a ZGP-based OPG.

We developed a high-energy picosecond mid-infrared laser based on ZnGeP2 (ZGP) optical parametric generator (OPG)/optical parametric amplifier (OPA), operating at a pulse repetition frequency (PRF) of 1 kHz. The laser system was equipped with a 2.09 mu m high-energy picosecond laser amplification system as the pump source. The pump source itself incorporated a gain-switched laser diode (GSLD) as the seed. By employing a holmium:yttrium-aluminum-garnet (Ho:YAG) regenerative amplifier (RA) and multi-stage power amplifiers, we successfully achieved a maximum pulse energy of 26.2 mJ at a wavelength of 2.09 mu m. Initially, using a ZGP OPG and a one-stage OPA, we achieved mid-infrared laser output of over 6.4 mJ. However, the corresponding beam quality deteriorated, with beam quality factors (M-2) exceeding 50 in both the x and y directions. To mitigate this issue, we transitioned to a ZGP OPG coupled with a two-stage OPA configuration, resulting in a mid-infrared laser output of over 6 mJ, accompanied by improved beam quality factors of 17.2 and 14.7 in the respective directions. Notably, the overall optical-to-optical conversion efficiency (OOCE) of the system surpassed 40%, with the second-stage OPA demonstrating an impressive OOCE exceeding 45%.

In this paper, we demonstrated a high-efficiency mid-infrared ZnGeP2 (ZGP) OPG/OPA system, operating at the mJ-level with hundred-picosecond pulses. The ZGP-based OPG configuration achieved a maximum pulse energy of 1.06 mJ at a repetition rate of 1 kHz, utilizing a pump pulse energy of 2.59 mJ and operating at a central wavelength of 3.9 mu m. The system achieved a maximum slope efficiency of 51.1 %, leading to a corresponding total optical-to-optical conversion efficiency (OOCE) of 40.9% and an output threshold as low as 0.046 GW/cm2. However, the beam quality factor M2 deteriorated, reaching values above 45. To optimize the beam quality of the mid-infrared laser, we employed an OPG/OPA tandem configuration and a double-pass OPG configuration, resulting in maximum pulse energies of 0.85 mJ and 0.36 mJ, respectively. At the highest output energy, for the OPG/OPA tandem configuration, the beam quality factors M2 were measured to be 3.2 in the x direction and 2.7 in they direction. For the double-pass OPG configuration, the beam quality factors M2 in the two directions were measured to be 3.5 and 3.2, respectively.

We report a high-power, all-fiber Tm-doped laser system operating at 1908 nm, based on a master-oscillator power amplifier（MOPA） configuration. The oscillator utilizes two polarization-maintaining（PM） fiber Bragg gratings（FBGs） with orthogonal principal axes to achieve single-polarization output. The system generates a linearly polarized output power of 12.6 W, with a slope efficiency of 40.6%. The power is subsequently scaled to 207.6 W through a primary amplifier, which uses a large mode area（LMA） fiber while maintaining single-mode operation. The amplifier achieves a beam quality factor（M 2 ） of 1.36 and a polarization extinction ratio（PER） exceeding 18.3 d B.

We report the development of a low-loss, thulium-doped yttrium aluminum perovskite (Tm:YAP) single-crystal fiber (SCF), fabricated using the Czochralski method. This SCF features undoped YAP end caps that are directly grown on both ends, aimed at improving thermal management and enhancing the guidance of pump light. This innovative design also removes differences in crystallographic orientation, exhibiting a propagation loss of 0.0112 cm(-1) at 1.94 mu m. When pumped by diode lasers at 788 nm, the SCF laser delivers continuous-wave output powers of 11.9 W and 20.6 W under single-end and double-end pumping configurations, respectively. The slope efficiencies achieved are 53.2 % and 40.7 %, relative to the incident pump power. To the best of our knowledge, this is the inaugural report of a Tm:YAP SCF laser.

ABSTRACT We present a single longitudinal mode Ho:YLF MOPA laser operating at 2050.7 nm by utilizing the Fabry–Perot etalon method to construct a compact SLM seed laser and employing Tm‐doped fiber as the amplifier. With an output power of 336 mW generated by the seed laser, the maximum output power of 13.1 W for the single longitudinal mode MOPA laser was recorded at a pump power of 88.7 W. A peak slope efficiency of 26.9% was achieved when the pump power exceeded 58.7 W. To our knowledge, this is the first report of utilizing Tm‐doped fiber to amplify the SLM operation of Ho:YLF laser.

Using an acousto-optic modulator (AOM) to enforce the unidirectional operation of a Nd:YAG ring laser based on double corner cube retroreflectors (CCRs) was demonstrated for the first time, to the best of our knowledge. By tilting the AOM with RF applied to deviate from the Bragg angle, a different diffraction loss was introduced between the counterpropagating beams in the ring cavity. A continuous wave single-frequency laser with a maximum output power of 2.99 W was successfully obtained at 1064.5 nm, with a tunable wavelength range from 1064.3 nm to 1064.7 nm. The experimental results indicated the unidirectional operated ring cavity comprising the double CCRs performed significant tolerance to the misalignment of the cavity. By changing the RF to pulsed mode and adjusting the angle of the AOM closer to the Bragg angle, the unidirectional Q-switched operation was achieved with the increase of the diffraction loss of the oscillating light. At the repetition frequency of 110 Hz, a 0.882 mJ single-frequency pulse energy with a pulse width of 70.2 ns was obtained, corresponding to a peak power of 12.6 kW. Sngle-frequency pulses with energy of 0.761 mJ and pulse width of 72.4 ns were also obtained at the repetition frequency of 1 kHz, corresponding to a peak power of 10.5 kW.

A single longitudinal mode thulium doped fiber master-oscillator-power-amplifier (MOPA) laser operating at wavelength of 2081 nm has been developed. The MOPA system employs a free-space structure with a single longitudinal mode operating Ho:YAG laser serving as the master oscillator, and a Tm-doped fiber is used for power amplifier. A single longitudinal mode laser with an output power of 7.81 W was extracted from the amplifier by injecting 173 mW of seed laser into the Tm-doped fiber. The beam quality factor was measured as M-2 similar to 1.87. To our knowledge, this is the first study on the amplification of a 2 mu m solid state single longitudinal mode laser in Tm-doped fibers.

Our study reveals results from an all-polarization-maintaining Ho-doped fiber laser that is passively modelocked, consisting of both an oscillator and an amplifier. A stable, self-starting, noise-like mode-locked pulse is achieved in the Ho-doped fiber laser oscillator based on a nonlinear optical loop mirror at a wavelength of 2.05 mu m. The mode-locked oscillator achieves a peak output power of 20.2 mW, generating pulses with a duration of 284 ps and exhibiting a coherence peak at 690 fs. Moreover, with the use of Ho-doped fiber amplifier, the mode-locked pulse can reach a peak output of 1.05 W while maintaining a power stability of 1.43 % over the course of an hour. The highest pulse energy reaches approximately 333.6 nJ, which equates to a peak power of 1.18 kW. The polarization extinction ratio is approximately 24.9 dB.