High-efficiency continuous-wave diode-pumped Tm:Ho:LuAG laser at 2.1 μm

Continuous Wave (CW) laser action has been observed from a Ho:Tm:LuAG rod at 2.1 m pumped by a diode laser at 785 nm in the temperature range of 77–200 K. The maximum power observed was 1.38 W at an incident power of 4 W at a crystal temperature of 77 K. The optical-to-optical conversion efficiency was observed to be 35.6% at a threshold power of 0.2 W with a 95% output coupling mirror.     

2.1 μm waveguide laser fabricated by femtosecond laser direct-writing in Ho3+, Tm3+:ZBLAN glass

We report the first Ho3+ doped waveguide laser, which was realized by femtosecond direct-writing of a depressed cladding structure into ZBLAN glass. Tm3+ sensitizing allows the 9 mm long Ho3+ gain medium to be conveniently pumped at 790 nm, achieving an optical-to-optical slope efficiency of 20% and a threshold of 20 mW. The potentially widely tunable laser produces up to 76 mW at 2052 nm and also operates at shorter wavelengths near 1880 nm and 1978 nm for certain cavity configurations.     

Graphene mode-locked femtosecond laser at 2 μm wavelength

We experimentally demonstrated a passively mode-locked femtosecond laser by using a graphene-based saturable absorber mirror (graphene SAM) in the spectral region of 2 μm. The graphene SAM was fabricated by transferring chemical-vapor-deposited, high-quality, and large-area graphene on a highly reflective plane mirror. Stable mode-locked laser pulses as short as 729 fs were obtained with a repetition rate of 98.7 MHz and an average output power of 60.2 mW at 2018 nm.     

Efficient Tm:LuVO₄ laser at 1.9 μm

We report an efficient laser-diode-pumped Tm-doped LuVO? crystal laser at about 1.9 μm. For the first time to our knowledge, the π-polarized Tm:LuVO? laser was achieved. The maximum output power and slope efficiency were 1.32 W and 28.7%, respectively. By comparison, it has been found that the a-cut Tm:LuVO? crystal should be more suitable for applications in high-power lasers. The central laser wavelength was observed to be located at about 1.9 μm and shifted to shorter with the increase of intracavity light intensity, which could be explained based on the reabsorption of light in the Tm:LuVO? crystal.     

Diode-pumped CW Tm:GdVO_4 laser at 1.9 μm

A high power cryogenic cooling Tm-doped (2%) GdVO4 laser double-end-pumped by fiber-coupled-diode with the center wavelength of 804.5 nm at 21 ℃ is reported. The highest continuous-wave (CW) power of 2.35 W at 1903 nm is attained at pump power of 24 W. The slope efficiency is 12.5% and the threshold is 3.2 W. Single- and double-end-pumped types are investigated.     

Highly efficient 2 μm Tm:YAG ceramic laser

We have experimentally demonstrated a highly efficient diode-pumped Tm:YAG ceramic laser operating at 2 μm wavelength. The maximum output power of 6.05 W was realized with a slope efficiency as high as 65%. As far as we know, it is the highest slope efficiency reported for Tm:YAG ceramic laser. The wavelength tuning experiment of Tm:YAG ceramic laser was carried out and the results suggest that Tm:YAG ceramic laser could operate simultaneously at multiple wavelengths in a wide range of 1884-2017 nm.     

Graphene oxide for diode-pumped Tm:YLF passively Q-switched laser at 2 μm

A diode-pumped Tm:YLF passively Q-switched laser at 2 μm was first demonstrated by using graphene oxide(GO) as a saturable absorber(SA).In this letter,continuous-wave(CW) laser and pulse laser performances were studied meticulously and systematically.It reasonably showed the dependence of the pulse duration,pulse energy,and pulse repetition rate on the absorbed power.A maximum repetition rate of 38.33 kHz and a single pulse energy of 9.89 μJ were obtained.     

2 μm single-frequency Tm:YAG laser generated from a diode-pumped L-shaped twisted mode cavity

A 2 μm single-frequency Tm:YAG laser was developed by using a diode pumped L-shaped twisted-mode-cavity. By suppressing the spatial hole-burning, the 2 μm single-frequency laser was obtained, with the output power of 1.46 W and the slope efficiency of 19.2%.     

Efficient high-power continuous wave Er:Lu2O3 laser at 2.85 μm

We report on crystal growth, spectroscopy, thermal conductivity and (4)I(11/2)→(4)I(13/2)-laser performance of Er:Lu(2)O(3). Pumping with an optically pumped semiconductor laser at 971 nm, 1.4 W of cw output power with a slope efficiency of ～36% at 2.85 μm was obtained at room temperature. This exceeds the Stokes efficiency due to an upconversion process recycling population of the lower laser level back into the upper laser level, yielding the highest efficiency of any Er-sesquioxide laser around 3 μm. Under diode pumping, 5.9 W of output power with 27% of slope efficiency was achieved with an M(2) of 1.2 to 1.4.     

High-power diode-pumped fiber laser operating at 3 μm

A high-power diode-cladding-pumped Ho3?-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The ?I?→?I? and ?I?→?I? laser transitions produced 0.77 W at a measured slope efficiency of 12.4% and 0.24 W at a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the ?I?→?I? transition, a wavelength of 3.002 μm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.     

Efficient diode-pumped laser operation of Tm:Lu2O3 around 2 μm

We report on the first diode-pumped laser operation of thulium-doped Lu2O3. With a very compact setup an output power of 75?W and slope efficiencies of around 40% with respect to the incident pump power were achieved at room temperature. Free running laser operation was observed at wavelengths of 2065?nm and 1965?nm. With a birefringent filter the wavelength could continuously be tuned from 1922?nm to 2134?nm. The thermal conductivity of Tm:Lu2O3 was measured for different dopant concentrations and is compared to the one of thulium-doped YAG.     

Passive mode locking of an in-band-pumped Ho:YLiF4 laser at 2.06 μm

We demonstrate the passive mode-locking operation of an in-band-pumped Ho:YLiF(4) laser at 2.06 μm using a semiconductor saturable absorber mirror based on InGaAsSb quantum wells. A transform-limited pulse train with minimum duration of 1.1 ps and average power of 0.58 W has been obtained at a repetition frequency of 122 MHz. A maximum output power of 1.7 W has been generated with a corresponding pulse duration of 1.9 ps.     

Tunable CW Tm,Ho:YLF laser at 2μm

A tunable continuous wave (CW) low temperature operating Tm (6 at.-%),Ho (0.6 at.-%):YLF laser pumped by fiber-coupled diode laser is reported. The maximum output power is 4.16 W at 2073 nm by use of 30% output coupling, the slope efficiency is 33%. A tuning range from 2049 to 2081 nm is achieved with a birefringent filter (BF). The factors that contribute to the output power and tuning range are discussed.     

Efficient Tm：YAG Ceramic Laser at 2 μm

We demonstrate a high-efficiency continuous-wave Tm： YAG ceramic laser pumped with a Ti：sapphire laser. An output power up to 860mW is obtained under an absorbed pump power of 2.21 W at 785nm, corresponding to a slope efficiency of 42.1% and optical to optical efficiency of 22%. The measured central wavelength is 2012nm.     

Short-term and long-term frequency characteristics of 2 μm single frequency Tm:YAG laser at room temperature

Placing one 0.1 mm YAG F-P etalon at nearly Brewster angle and combined use 1 mm fused silica in the cavity, a diode-pumped linear-polarized single-longitudinal-mode (SLM) Tm:YAG laser operating at 2 μm is achieved. This paper is focused on the stability of the linear-polarized SLM laser, including power stability, long-term frequency stability and short-term frequency stability. And the factors affecting the frequency characteristics of laser were also analyzed. The instability of the linear-polarization SLM laser is less than 1%. The long-term frequency stability is in the range from 1.16 × 10⁻⁷ to 1.75 × 10⁻⁷ monitored by the wave meter. And the short-term frequency stability is 97 Hz/μs measured with the self-beating heterodyne detection method.     

Waveguide CW 118.6 μm H2O laser

This paper reports results of an experimental study of a cw 118.6 m H₂O waveguide laser. The laser cavity is a 3 cm inner diameter, 3.2 m long Pyrex tube, with plane reflectors against its ends, one of them being a copper mesh coupler. The active medium is a H₂O:H₂ gas mixture. Successive optimizations lead to a reliable output power of 50 mW, for the EH₁₁ mode. The power density is the highest ever reported, and the stability is such that the power drifts by less than 2% per hour. This laser is competitive with the optically pumped 118.8 m CH₃OH laser.     

Ultra-broadband highly efficient mode converter at 1 μm fabricated by a line-focused CO_2 laser

We report here an ultra-broadband linearly polarized(LP) LP_(01)-LP_(11) mode converter operating at 1 μm based on a long period fiber grating(LPFG) fabricated in a conventional two-mode fiber(TMF) by a line-focused CO_2 laser. The measured 3d B bandwidth is about 240 nm, which is the broadest bandwidth for such fiber mode converters. The maximum conversion efficiency between the LP_(01) and LP_(11) modes is 99% over the range of 1000 nm to 1085 nm, almost covering the whole emission band of Yb~(3+), which is useful for further power scaling of high-power fiber lasers operating at the 1 μm band.     

Single-frequency distributed Bragg reflector Tm:YAG ceramic derived all-glass fiber laser at 1.95 μm

A 135 mW single-frequency distributed Bragg reflector fiber laser at 1.95 μm was obtained based on a Tm:YAG ceramic-derived all-glass fiber. The fiber laser achieved an optical signal-to-noise ratio of ～ 77 dB. Moreover, the threshold and linewidth of the single-frequency laser were measured to be 15.4 mW and 4.5 kHz, respectively. In addition, the measured relative intensity noise was less than -140 dB· Hz^-1 at frequencies of over 10 MHz. The results show that the as-drawn Tm:YAG ceramic-derived all-glass fiber is highly promising for ～ 2 μm single-frequency fiber laser applications.     

Passively Q-Switched Tm,Ho：YVO4 Laser with Cr：ZnS Saturable Absorber at 2 μm

A stable diode-pumped passively Q-switched Tm,Ho：YVO4 laser with Cr：ZnS saturable absorber is reported. The shortest pulse duration of -500 ns with the central wavelength of 2041 nm is obtained at the pump power of 7.4 W, corresponding to the pulse energy of 3.5 μd at repetition rate of 65 kHz.     

Diode-pumped Nd:YGG continuous-wave laser at 1.33 μm

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet (Nd:YGG) crystal continuous wave (CW) laser at 1.33 μm for the first time to our knowledge. At an incident pump power of 18.5 W, as high as 3.09 W of CW output power at 1.33 μm is achieved. The slope efficiency with respect to the incident pump power was 21.3%, and the fluctuation of the output power was better than 2.8% in the given 4 h. The beam quality factor M² is 1.14 and 1.16 for tangential direction and sagittal direction, respectively.