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.     

A comparison of resonantly pumped Ho:YLF and Ho:LLF lasers in CW and Q-switched operation under identical pump conditions

Singly 0.5 at.% Ho doped crystals of YLiF₄ (YLF) and LuLiF₄ (LLF) are studied under identical pump conditions in continuous-wave (CW) and Q-switched operation. Longitudinal end-pumped CW laser performance shows Ho:LLF to have a slightly lower threshold and a slightly higher slope efficiency with respect to absorbed pump power than Ho:YLF. Both lasers were operated on π-polarization. At a cavity output coupling of 20% and a crystal length of 30 mm, the Ho:LLF (Ho:YLF) laser yielded 18.8 W (18 W) of CW output at a wavelength of 2067.8 nm (2064.0 nm) for 41.4 W (42.2 W) of absorbed pump power with a slope efficiency of 67.1% (65.6%) and an optical-to-optical efficiency of 45.4% (42.6%) with respect to absorbed pump power. With the same output coupling and a crystal length of 40 mm, the Ho:LLF (Ho:YLF) laser yielded 20.5 W (18.1 W) of CW output at a wavelength of 2067.7 nm (2064.3 nm) for 51.5 W (50.0 W) of absorbed pump power with a slope efficiency of 58.4% (55.4%) and an optical-to-optical efficiency of 39.8 (36.1%) with respect to absorbed pump power. The influence of the temperature of the cooling mount on CW laser performance was studied and showed very similar results for both laser materials. At full pump power, a slope of −155 mW/°C (−149 mW/°C) was observed for the Ho:LLF (Ho:YLF) laser with a crystal length of 30 mm. In Q-switched operation, the Ho:LLF (Ho:YLF) laser produced 37 mJ (38.5 mJ) at a repetition rate of 100 Hz with a pulse duration of 38 ns (35 ns) at a wavelength of 2053.1 nm (2050.2 nm) with a slope efficiency of 30.3% (31%) and an optical-to-optical efficiency of 14.2% (13.9%) with respect to absorbed pump power. The beam quality was nearly diffraction limited (M ²<1.1).     

Laser spectrum of a high power Tm,Ho:GdVO<Subscript>4</Subscript> laser

In this paper, we report a 18.8 W continuous wave and 18.4 W Q-switched diode-pumped cryogenic Tm(5 at %), Ho(0.5 at %):GdVO₄ laser. The pumping source of Tm, Ho:GdVO₄ laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm, supplying 42 W power at 802.5 nm. For input pump power of 41.9 W at 802.4 nm, the output power of 18.8 W in CW operation, optical-to-optical conversion efficiency of 45% at 2.05 μm and the average output power of 18.4 W in Q-switched operation, optical-to-optical conversion efficiency of 44% at 2.04 and 2.05 μm have been attained. The emission wavelengths of the Tm(5 at %), Ho(0.5 at %):GdVO₄ laser were firstly compared when it worked in CW mode and Q-switched mode.     

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.     

Compact efficient diode-end-pumped intracavity frequency-tripled Nd:YVO<Subscript>4</Subscript> 355 nm laser

A compact efficient diode-end-pumped acousto-optically Q-switched intracavity-frequency-tripled Nd:YVO₄ 355 μm ultraviolet laser was realized. Intracavity sub-resonators with anti-reflection and high-reflection coated mirrors were used to get higher efficiency of third harmonic generation. With two LBO crystals used in frequency doubling and tripling processes, greater than 1.46 W 355 nm average output power was obtained under the absorbed pump power of 13.9 W and the repetition rate of 10 kHz. The corresponding pump-to-ultraviolet conversion efficiency was determined to be as high as 10.5%. At 10 kHz, the minimize pulse width was obtained to be 12 ns with the peak power of 10.4 kW and single pulse energy of 146 μJ.     

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.     

Study of LD pumped Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser with acousto-optic modulator

A laser-diode (LD) pumped Q-switched Nd:Y_0.5Lu_0.5VO₄ crystal laser with an acousto-optic (AO) modulator is presented in this paper. The maximum continuous wave (CW) output power of 5.53 W is achieved at the incident pump power of 14.09 W with the transmission of 10% for the output coupler, resulting in an optical-to-optical conversion efficiency of 39.2%. For Q-switching operation, the shortest pulse width of 8.3 ns and the highest peak power of 259 kW are generated under the incident pump power of 14.09 W at 1 kHz.     

High slope efficiency and low threshold in a laser-diode-pumped passively Q-switched ion-implanted Nd:YVO<Subscript>4</Subscript> planar waveguide laser with GaAs saturable absorber

A passively Q-switched waveguide laser, to our knowledge, has been firstly demonstrated in Nd: YVO₄ crystal formed by 3 MeV Si⁺ ion implantation at a dose of 1 × 10¹⁵ ions/cm² at room temperature, in which GaAs was used as saturable absorber. The dependences of the average output power, pulse width, pulse repetition rate on absorbed pump power have been measured at different output plane mirror transmissions. At an absorbed pump power of 78.8 mW and output transmission of 20%, the shortest pulse width of 3.88 ns was obtained, corresponding to the peak power and single pulse energy of 212 W and 0.82 μJ, respectively. The threshold pump power was as low as 40 mW, and the slope efficiency was about 64.5% when the absorbed pump power was lower than 70 mW.     

High repetition rate passive Q-switching of diode-pumped Nd:GdVO<Subscript>4</Subscript> laser at 912 nm with V<Superscript>3+</Superscript>:YAG as the saturable absorber

The character of a diode-pumped passively Q-switched Nd:GdVO₄/V³⁺:YAG 912 nm laser was demonstrated for the first time to our knowledge. With an absorbed pump power of 7.4 W, an average output power of 360 mW with a Q-switched pulse width of 328 ns at a pulse repetition rate of 163 kHz was obtained. The Q-switching efficiency was found to be 32.7%. Our work further indicated V³⁺:YAG could be an effective fast passive Q-switch for 0.9 μm radiation.     

Diode-pumped passively Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with a GaAs saturable absorber

By using a-cut Nd:Lu_0.15Y_0.85VO₄ mixed crystal as laser gain medium, a diode-pumped passively Q-switched and mode-locked (QML) laser with a GaAs saturable absorber in a Z-type folded cavity is demonstrated for the first time. The Q-switched mode-locked laser pulses with about 90% modulation depth are obtained as long as the pump power reached the oscillation threshold. The repetition rate of the passively Q-switched pulse envelope ranges from 50 to 186 kHz as the pump power increases from 0.915 to 6.520 W. Under an incident pump power of 6.52 W, the QML pulses with the largest average output power of 694 mW, the shortest pulse width of 200 ns and the highest pulse energy of 3.73 μJ are obtained. The mode-locked pulse width inside the Q-switched envelope is estimated to be about 275 ps. The experimental results show that Nd:Lu_0.15Y_0.85VO₄ is a promising mixed crystal for QML laser.     

Actively Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/LBO green laser with an acousto-optic modulator

This work presents experimental results concerning an actively Q-switched intracavity frequency-doubled Nd:LuVO₄/LBO green laser with an acousto-optic modulator operated at the wavelength of 0.53 μm. The green average output power of 2.8 W was obtained at a pump power of 16.3 W and a pulse repetition rate of 20 kHz, resulting in an optical conversion efficiency of 17%. When the pulse repetition rate is operated at 5 kHz, the shortest pulse width and the highest peak power at 0.53 μm were measured to be 26.5 ns and 8.43 kW, respectively.     

Power scaling of a continuous-wave and passively Q-switched Yb:KLu(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> laser end-pumped by a high-power diode

The power scaling capacity of a diode end-pumped Yb:KLu(WO₄)₂ laser, operating in the continuous-wave (cw) and passively Q-switched regimes, has been investigated. A cw output power of 11.5 W was achieved with an optical-to-optical efficiency of 41% with respect to the incident pump power, while the slope efficiency amounts to 60%. The passively Q-switchedoperation yielded an average output power of 4.3 W at the fundamental wavelength of 1031.7 nm, and 1.15 W of Raman radiation at 1139.3 nm. The total slope efficiency for Q-switched operation was 40%. The highest pulse energy, duration, and peak power were 170 μJ, 2.2 ns, and 77.3 kW for the fundamental radiation, and 51 μJ, 2.3 ns, and 22.2 kW for the Raman radiation. PACS 42.55.Rz; 42.55.Xi; 42.55.Ye     

A high efficient end-pumped TEM<Subscript>00</Subscript> laser with pulse repetition rate of 5 kHz

An end-pumped Nd:YVO₄ laser fiber-coupled diode was designed. A maximum output power of 4.74 W TEM₀₀ mode CW laser was obtained for a pump power of 10.5 W. The optical efficiency and slope efficiency were measured as 45.1 and 57.8% at 1064 nm, respectively. In Q-switching operation, 4.45 W average power at a pulse repletion rate of 5 kHz was produced, with a stability of pulse peak value <2%.     

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.     

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%.     

Passive Q-switching performance with Co:LMA crystal in a diode-pumped Nd:LuVO<Subscript>4</Subscript> laser

A diode-pumped passively Q-switched Nd:LuVO₄ 1.34 μm laser using Co:LMA saturable absorber was successfully demonstrated. The average output power, pulse width, repetition rate of a-cut and c-cut Nd:LuVO₄ lasers were studied with different output couplers. The maximum average output power of 164 mW was obtained at the pump power of 10.3 W and the narrowest pulse width of 168 ns was achieved at repetition rate of 457 kHz under pump power of 8.59 W in a-cut Nd:LuVO₄ laser with T = 8%.     

Diode-pumped high-efficiency passively Q-switched Yb:CaYAlO<Subscript>4</Subscript> laser

We experimentally demonstrated a high-efficiency passively Q-switched Yb:CaYAlO₄ (Yb:CYA) laser based on a semiconductor-saturable absorber mirror (SESAM), and the output characteristics of the laser including the average output power, repetition frequency, pulse duration, pulse energy and pulse peak power were investigated by adopting output mirrors with different transmittances. When the transmittance of the output mirror was 5% and the pump power was set at about 7.76 W, a maximum average output power of as high as 2.480 W was achieved with a slope efficiency and light-to-light efficiency of the Q-switched Yb:CYA laser of up to 37.1% and 31.2%, respectively.     

Continuous wave and passively Q-switched laser performance of a composite crystal bonded with three Nd:YVO<Subscript>4</Subscript> single crystals

The laser performance of a composite crystal bonded with three Nd:YVO₄ single crystals has been investigated for the first time as far as we know. The largest continuous wave output power of 2.68 W is obtained at the incident pump power of 6.2 W, giving an optical conversion efficiency of 43.1% and a slope efficiency of 45.9%. For passively Q-switched operation with Cr⁴⁺:YAG of 71% initial transmission, the shortest pulse width of 18.2 ns, the largest single-pulse energy of 19.9 μJ, and the highest peak power of 1.12 kW are achieved, with the pulse repetition rate being 44.9 kHz, at the incident pump power of 6.2 W. The composite crystal can generate more excellent laser performance, when compared with the single crystals.     

Tri-wavelength laser with Nd:CLTGG crystal

Continuous-wave (CW) and passively Q-switched operations of laser diode-end-pumped Nd:CLTGG laser at 1.06 μm was demonstrated for the first time. The laser spectrum was found to be tri-wavelength, with respective wavelengths of 1058.4, 1060.5, and 1065.5 nm for both CW and passive Q-switching regime. The highest CW output power of 2.6 W was obtained with an optical-optical conversion efficiency of 13.9% and a slope efficiency of 17.1%. In the passive Q-switching regime, the highest output power, shortest pulse width, largest pulse energy and highest peak power were achieved as 242 mW, 45.8 ns, 1.65 μJ and 0.4 kW, respectively. The passively Q-switched tri-wavelength laser should have the potential to be used for terahertz radiation generation.     

Passively Q-switched <Emphasis Type="Italic">a</Emphasis>-cut Nd:YVO<Subscript>4</Subscript> self-Raman laser

A passively Q-switched a-cut Nd:YVO₄ self-stimulating Raman laser using a Cr:YAG saturable absorber has been demonstrated for the first time. The maximum average output power of the self-Raman laser at 1176 nm is 347 mW at the incident pump power of 10 W with a pulse repetition frequency (PRF) of 66 kHz. The pulse width, pulse energy of the 1176 nm are found to be 10 ns and 5.6 μJ. The conversion efficiency from diode laser input power to Raman output power is 3.47%.