High efficient continuous wave operation of diode-double-passing-pumped Tm:YAP laser

A high efficient continuous wave diode-pumped Tm:YAP laser at room temperature was presented in this paper. Tm:YAP crystal with doped concentration of 4 at % was c-cut and had a cross section of 3 × 3 mm² and length of 5 mm. Using double-passing-pumped cavity structure, under the pump power was 25.5 W, the highest output power reached 8.5 W by use of 10% output coupling, corresponding to optical conversion efficiency was 33.3% and the slope efficiency was 44.5%. The laser wavelength was 1936 nm with FWHM of 4 nm.     

Efficient continuous wave and Q-switched operation of a dual-end-pumped <Emphasis Type="Italic">c</Emphasis>-cut Tm:YAP laser

An efficient continuous wave (CW) and Q-switched c-cut Tm:YAP laser is reported in this letter. With the dual-end-pumped convex-concave resonator, CW output power up to 13.6 W at 1.99 μm was obtained under a total incident pump power of 50 W. The corresponding slope efficiency was 34.3% and conversion efficiency was 27.2%. The active Q-switched operation of the laser had an average output power of 12.5 W at 10 kHz pulse repetition frequency, with a minimum pulse width of 126 ns. With 6 kHz pulse repetition frequency, the maximum pulse energy of 1.6 mJ was obtained. In addition, using the Tm:YAP laser as a pumping source for gain-switched Cr:ZnSe laser, as much as 4 W output power in the wavelength range of 2.5–2.6 μm was obtained.     

High power and efficiency of a 2044-nm c-cut Tm, Ho:YAlO3 laser

A high power and efficiency of c-cut Tm, Ho:YAlO₃ (YAP) laser is reported in the paper. The laser operated in continuous wave (CW) mode or Acousto-optical (AO) Q-switched mode at 2044 nm. The Tm, Ho:YAP crystal was cooled at the temperature of 77 K and pumped by a fiber-coupled laser diode (LD) with the centre output wavelength of 794.8 nm. In CW operation, a 9.30-W output power was obtained at a 150-mm physical cavity length, corresponding to a slope efficiency of 42.5%. In Q-switch mode, the output average power of 9 W was achieved at the pulse repetition frequency (PRF) of 10 kHz with a 130-ns pulse width. Moreover, the energy per pulse of 3.54 mJ in 47 ns was acquired at 2.5 kHz with a 75.3-kW peak power.     

Room temperature efficient continuous wave and Q-switched operation of a Ho:YAP laser

We report the continuous wave and acousto-optically Q-switched operation of a Tm:YLF-pumped Ho:YAP laser at room temperature. Continuous wave output power of 6.8 W at 2118 nm was obtained under the incident pump power of 13.4 W, corresponding to a slope efficiency of 65.6% and a conversion efficiency of 50.7%. For the Q-switched mode, a maximum pulse energy of 1.28 mJ and a minimum pulse width of 31 ns at the repetition rate of 5 kHz were achieved, resulting in a peak power of 41.3 kW. In addition, the Ho:YAP laser was employed as a pumping source of ZGP optical parametric oscillator, the total average output power of which was 3.2 W at 4.08 and 4.41 μm with a slope efficiency of 69.5%, corresponding to the diode-to-mid-IR conversion efficiency of 9.0%.     

A high efficiency Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser with a Volume Bragg Grating

We report a CW Ho:YAlO₃ (Ho:YAP) laser at room temperature pumped by a Tm:YLF laser with a Volume Bragg Grating (VBG) instead of the conventional mirror. The Ho:YAP laser operated at 2117.9 nm with output power 9.12 W. The optical-to-optical conversion efficiency is 60.4% and slope efficiency is 71.2%. The Ho:YAP output wavelength is centered at 2117.9 nm with bandwidth of about 1 nm. The beam quality factor is M ² ∼ 1.29 measured by the traveling knife-edge method.     

Continuous-wave operation of a room-temperature Ho:YAP laser pumped by a Tm:YAP laser

We reported the Ho:YAP laser pumped by the Tm:YAP laser. The Ho:YAP laser maximum output power was 4.91 W when the incident power was 10.1 W with the threshold of 2.63 W. The slope efficiency was 63.7%, corresponding to an optical-to-optical efficiency of 48.6%. The Ho:YAP output wavelength was centered at 2118.2 nm with bandwidth of about 1 nm. We estimate the beam quality to be M² = 1.29.     

A high power CW Ho,Tm:GdVO<Subscript>4</Subscript> laser

In this paper, we report a 22.7 W continuous wave (CW) diode-pumped cryogenic Ho( at %), Tm(3 at %):GdVO₄ laser. The pumping sources of Ho,Tm:GdVO₄ laser are two fiber-coupled laser diodes with fiber core diameter of 0.4 mm, both of them can supply 42 W power laser operating near 802 nm. For input pump power of 64.7 W at 802.5 nm, the output power of 22.7 W in CW operation, optical-to-optical conversion efficiency of 35.1% at 2.05 μm has been attained. The M ² factor was found to be 2.0 under an output power of 16.5 W.     

High efficient double end-pumped <Emphasis Type="Italic">b</Emphasis>-cut Tm,Ho:YAlO<Subscript>3</Subscript> laser

High efficient continuous wave (CW) and acousto-optical (AO) Q-switched operation of a b-cut Tm,Ho:YAlO₃ (Tm,Ho:YAP) laser are reported in the paper. The Tm,Ho:YAP crystal was cooled by liquid nitrogen and pumped by a fiber-coupled laser diode (LD). Different pump wavelengths were tried in the experiment. An 8.36-W output power was acquired at 2.12 μm in the CW operation with an optical-optical conversion efficiency of 33.3%, and an 8.14-W average power was obtained at the pulse repetition frequency (PRF) of 10 kHz with an optical-optical conversion efficiency of 32.4%.     

High-power and efficiency continuous-wave operation of <Emphasis Type="Italic">a</Emphasis>-cut Ho:YAP laser at room temperature

We report the continuous-wave (CW) operation of a room-temperature a-cut Ho:YAP laser resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. A maximum CW output power of 14.6 W at 2118.7 nm for a-oriented Ho:YAP was obtained, corresponding to the slope efficiency of 69.35% and optical-to-optical conversion efficiency of 63.04% with respect to absorbed pump power. The laser operated at a single mode (TEM₀₀) with the beam quality factor of M ² ∼ 1.51.     

Experimental study on the 1.94-μm laser performance of c-Cut Tm:YAP crystal with various doping concentration

The influence of the thulium ion concentration on the 1.94-??m laser performance of c-cut Tm:YAP crystal was investigated in this paper. Three crystals with 3, 4, and 5% Tm³⁺ (atom concentration) were examined at 18°C. Our experimental results showed that, the best power performance was obtained with the 4% Tm:YAP crystal. By using 24.8 W of incident pump power at 795 nm, a maximum of 7.5 W of output power was obtained. The slope efficiency was 48.8%, corresponding to diode-to-Tm conversion efficiency of 30.2%.     

Q-switched operation of <Emphasis Type="Italic">a</Emphasis>-cut Ho:YAlO<Subscript>3</Subscript> laser pumped by a diode-pumped 1.91 μm thulium laser

Q-switched operation of a room temperature Ho:YAP laser was resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. The CW Ho:YAP laser generated 9.9 W of linearly output at 2119.03 nm with beam quality factor of M ² ∼1.46 with respect to absorbed pump power of 19.16 W, corresponding to an optical-to-optical conversion efficiency of 51.7% and slope efficiency of 60.6%. Under Q-switched operation, the maximum output power of 9.8 W in relation to 10 kHz pulse repetition frequency (PRF) was obtained, however, the maximum peak power of 60 kW at the PRF of 5 kHz was demonstrated. At 5 kHz pulse energies of 1.92 mJ with pulse width of 32 ns was achieved.     

High-efficiency continuous-wave and Q-switched operation of a resonantly pumped Ho:YAP ring laser

We demonstrated continuous-wave (CW) and Q-switched operation of a room-temperature Ho:YAP ring laser that is resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 ??m. Continuous wave output power of 3 W at 2119 nm is obtained under the absorbed pump power of 10.17 W, corresponding to a slope efficiency of 60%. For the Q-switched regime the maximum pulse energy of 1.58 mJ and the minimum pulse width of 590 ns at the repetition rate of 1 kHz are achieved.     

Q-switched Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser at room temperature

A Q-switched high efficient Ho:YAlO₃ (Ho:YAP) laser pumped by a diode-pumped Tm:YLF laser at room-temperature is realized. The maximum output energy reaches 1.58 mJ under the repetition frequency of 5 kHz, when the incident pump power is 15.6 W. The pulse width is 22 ns. The wavelength is 2118 nm when the transmission of output coupler is 30%. The beam quality factor is M ² ∼ 1.39 measured by the traveling knife-edge method.     

High-power diode-pumped Tm:YLF laser

A high-power, continuous-wave 3.5% Tm³⁺ doped LiYF₄ (Tm:YLF) laser has been developed. Using two Tm:YLF rods in a single cavity, 55 W of laser output at 1910 nm was obtained with a slope efficiency of 49%. The M² factor was found to be <3. With a single Tm:YLF rod, a maximum laser power of 30 W was obtained with a slope efficiency of 50%. The laser was tuned to the peak absorption wavelength of Ho:YAG of 1907.5 nm by an intracavity quartz etalon with an output power loss < 1 W. PACS 42.55.-f; 42.55.Xi; 42.60.Pk     

Diode-pumped CW Nd<Superscript>3+</Superscript>:YAlO<Subscript>3</Subscript> laser at 1339 nm

A diode-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser emitting at 1339 nm is described. At the incident pump power of 17.8 W, as high as 3.4 W of continuous-wave (CW) output power at 1339 nm is achieved. The slope efficiency with respect to the incident pump power was 23.6%. The output power stability over 60 min is better than 3.5%. The laser beam quality M ² factor is 1.33.     

Linearly-polarized Tm-doped double-clad fiber laser

We report a linearly polarized Tm doped fiber laser. The fiber laser was set up by using a piece of polarization maintaining Tm doped double clad fiber of 5 m length as gain medium and a polarization beam splitter as a polarization selector. The fiber laser was pumped by a fiber pigtailed laser diode working at 790 nm with a maximum output power of 90 W. The linearly polarized Tm laser operated at wavelength around 2030 nm. A maximum output power up to 21.9 W was achieved when the pump power was 63.27 W with a threshold of 11.92 W, a slope efficiency of about 43.7%, and a polarization extinction ratio of 92.7% (11.37 dB). In addition to the blue fluorescence, we also observed the violet fluorescence under high pump power level. The up-conversion fluorescence was considered to be attributed to the ¹ G ₄ → ³ H ₆, and ¹ D ₂ → ³ F ₄ transitions of Tm ions, respectively.     

6.17-W continuous wave operation of a 2132-nm c-cut Tm,Ho:YAP pumped by a laser diode of 794.3 nm

Continuous wave (CW) operation of a c-cut Tm (5 at %), Ho (0.3 at %):YAP laser at 2132 nm wavelength were reported in this paper. In the temperature of 77 K, the Tm,Ho:YAP crystal was double end-pumped by a 21.4 W fiber-coupled laser diode (LD) at the center wavelength of 794.3 nm. Different resonator lengths and output couplers for the total pump power were tried. The resonator length was 205 mm, and the maximum CW output power of 6.17 W was acquired, corresponding to an optical-optical conversion efficiency of 28.8% and a slope efficiency of 35.6%.     

High-power diode-pumped Tm:YLF slab laser

A 2% Tm³⁺-doped LiYF₄(Tm:YLF) slab is double-end-pumped by two laser diode stacks. The pumped volume has a rectangular cross section. The Tm:YLF laser produced 148 W of continuos-wave output at 1912 nm in a beam with M _x ²≈199 and M _y ²≈1.7 for 554 W of incident pump power. The slope efficiency with respect to the incident pump power was 32.6%, and the optical-to-optical efficiency was 26.7%.     

Highly-Efficient Ho:S<Subscript>i</Subscript>Sc<Subscript>2</Subscript>O<Subscript>5</Subscript> Laser Pumped by a Narrow Line-Width Tm:YAP Laser at 1.94 <Emphasis Type="Italic">μ</Emphasis>m

We present a highly-efficient continuous-wave Ho:SSO laser pumped by a diode-pumped Tm:YAP laser with a narrow linewidth (NL) of 0.3 nm. With the free-running (FR) Tm:YAP laser, we obtain a maximum output power of 2.23 W at an absorption pump power of 7.2 W, corresponding to an optical conversion efficiency of 31% and a slope efficiency of 42.6%. With the NL Tm:YAP laser, we obtain a maximum output power of 2.88 W at the same absorption pump power. The optical conversion efficiency increases to 40% when the slope efficiency increases to 55.5%. The output linewidth of the Ho:SSO laser is 0.8 nm when we use the Tm:YAP laser with a narrow linewidth of 1.8 nm pumped by a FR Tm:YAP laser. The beam quality also changes from 1.31 to 1.22.     

The output characteristics of double-end-pumped Ho:LuAG laser at room temperature

Continuous-wave (CW) and Q-switched operation of a room-temperature Ho:LuAG laser was resonantly double-end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. The CW Ho: LuAG laser generated 24.5 W of linearly output at 2094.4 nm with beam quality factor of M ² = 1.11 ± 0.02 for an absorbed pump power of 44.0 W, corresponding to optical-to-optical conversion efficiency of 55.7% and slope efficiency of 60.5%. Under Q-switched operation, a maximum output power of 24.1 W with a slope efficiency of 58.1% at 12 kHz was obtained. Also, the minimum pulse width of 32 ns was achieved, corresponding to the peak power was 37.7 kW.