High-efficiency resonantly pumped room temperature Ho:YVO4 laser

An efficient 2 μm room temperature Ho:YVO(4) laser resonantly pumped by a 1.94 μm Tm:YAP laser is demonstrated, for the first time to our knowledge, in this Letter. Up to 8.58 W of laser output at 2053 nm is obtained with the optical-to-optical conversion efficiency as much as 41.2%. The output beam had quality of M² factor with Mx(2) of 3.58 and My(2) of 1.76 at 8 W output level. In addition, we also obtained 4.18 W laser output at 2066 nm and 7.04 W at 2040 nm from the Ho:YVO(4) laser with conversion efficiency of 27.8% and 33.8%, respectively.     

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.     

Continuous-wave and Q-switched Operation of a Tm,Ho:YAP ring laser

We demonstrated continuous-wave (CW) and Q-switched operation of a Tm,Ho:YAP ring laser at 77 K. The maximum CW output power of 2 W at 2130.7 nm was obtained under the incident pump power of 12 W, corresponding to a slope efficiency of 23% and an optical-to-optical efficiency of 16.7%. For the Q-switched regime the maximum output energy of 5 mJ with the pulse width of 160 ns at the repetition rate of 100 Hz was achieved, corresponding to a peak power of 31.25 kW.     

Diode pumped operation of tm,Ho:YAP microchip laser

Single-wave length operation of a c-cut Tm (5%), Ho (0.3%):YAP microchip laser pumped by a fiber-coup led diode-laser was reported. Under cryogenic temperature, the output power of 188 mW was obtained under the incident power of 2230 mW, corresponding to the slope efficiency was 12.2%. As much as 168 mW output and slope efficiency of 5.7% was obtained under the pump power of 3400 mW at 291 K. In addition, a maximum single-wave length output power of 60 mW at wavelength of 2130.2 nm and 14 mW at wavelength of 2102.4 nm is demonstrated under 77 and 291 K, respectively.     

Q-switched Ho:YAP laser with a volume bragg grating pumped by a Tm-doped silicon fiber laser

We reported the Q-switched Ho:YAlO₃ laser with a volume Bragg grating pumped by the Tm doped fiber laser. The Ho:YAP laser maximum output energy was 1.04 mJ under the repetition frequency of 5 kHz when the incident power was 12.49 W with the threshold of 2.38 W. The Ho:YAP output wavelength was centered at 2117.9 nm with bandwidth of about 0.3 nm. The pulse width is 23.9 ns.     

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 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).     

Diode pumped operation of 1 mm Tm,Ho:YAP microchip laser

A single-longitudinal-mode (SLM) operation of a c-cut 1 mm Tm(5%), Ho(0.3%):YAP micro-chip laser pumped by a fiber-coupled diode-laser was reported. Under cryogenic temperature, the output power of 216 mW was obtained under the incident power of 2230 mW, corresponding to the slope efficiency was 13.6%. As much as 133 mW output and slope efficiency of 4.9% was obtained under the pump power of 3000 mW at 291 K. In addition, a maximum SLM output power of 30 mW at wavelength of 2130.56 nm is demonstrated under 77 K.     

Q-switched Er:YAG lasers resonantly pumped by Erbium fiber laser

The study describes efficient, acousto-optic Q-switching of Er:YAG laser at the 1645 nm eye-safe wavelength. For longitudinal pumping at wavelength 1532 nm, linear-polarized 10 W Erbium fiber laser radiation was used. The investigated Er:YAG crystals were 25 and 40 mm long and their Erbium concentration was 0.20 and 0.25%, respectively. For giant pulse generation, a fused silica acousto-optic modulator was inserted inside the Er:YAG laser oscillator. For a maximum incident pump power of 7.95 W, pulse energy up to 4.1 mJ was generated with pulse duration 34 ns at 500-Hz repetition rate; the corresponding peak power was 119 kW.     

Efficient single-axial-mode operation of a Ho:YAG ring laser pumped by a Tm-doped silica fiber laser

Efficient single-frequency operation of a Ho:YAG ring laser at room temperature with a traveling-wave TeO2 acousto-optic modulator to enforce unidirectional operation is reported. By use of a 2-at. % Ho3+-doped 10-mm-long Ho:YAG rod, end pumped by a cladding-pumped tunable Tm-doped silica fiber operating at 1.9 microm, the Ho:YAG ring laser yielded 3.7 W of single-frequency output at 2.1 microm in a diffraction-limited TEM00 beam with M2 < 1.1 for an incident pump power of 8.8 W. The rf power required for unidirectional operation was 0.3 W and corresponded to an increase in cavity loss for the lasing direction (due to diffraction) of only 0.5%. The prospects for further improvement in efficiency are discussed.     

Compact resonantly intra-cavity pumped tunable Ho:Sc2SiO5 laser

A compact intra-cavity pumped low threshold continuous-wave Ho:Sc₂SiO₅ laser is reported. The characteristics of output wavelength tuning are investigated by use a intra-cavity briefringent (BF) filter. A wavelength tunable range of 140 nm from 2020 to 2160 nm is achieved. For the free-running mode, the laser slope efficiency is 24.8%, when the output central wavelength is 2110 nm. The laser threshold is about 820 mW of incident pump power. With the BF filter, a maximum output power of 870 mW is obtained at the incident pump power of 5 W, corresponding to a slope efficiency of 20.3%. The characteristics of output wavelength verse the crystal temperature are also investigated.     

Q-switch operation of a c-cut 2132-nm Tm, Ho:YAP laser pumped by a laser diode of 794.3 nm

Q-switch 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. A 5.29-W Q-switch output power was acquired at pulse repetition frequency (PRF) of 10 kHz, corresponding to an optical-optical conversion efficiency of 24.7% and a slope efficiency of 28.1%. The energy per pulse of 3.57 mJ in 38 ns was achieved at 1.25 kHz with the peak power of 93.9 kW.     

5-W repetitively Q-switched Er:LuAG laser resonantly pumped by an erbium fiber laser

We report a high-average-power, near-diffraction-limited Er:LuAG laser generating 5 W of power at 1.648 microm in either cw or repetitively Q-switched operation. When the laser is Q switched at 9 kHz, we measure 0.52 mJ/pulse. The laser is end pumped by a 20-W erbium fiber laser and achieves >30% optical conversion efficiency and >40% incident slope efficiency. This is, to our knowledge, the highest performance (average power and conversion efficiency) obtained from a bulk solid-state erbium laser.     

Experimental study of continuous-wave and Q-switched laser performances of Ho:YVO4 crystal

In this letter, we report a Ho:YVO4 laser pumped by a 1.94-μm laser in both continuous-wave(CW)and Q-switched modes. The output performance of the Ho:YVO4 laser is compared with different output coupler transmissions. By use of the output coupler transmissions of T =30%, we obtain the maximum CW output power of 3.9 W at 2052 nm, with beam quality factor of M2=1.09 for the absorbed pump power of 12.5 W. For the Q-switched mode, we achieve maximum output energy per pulse of 0.38 mJ and the minimum pulse width of 25 ns, corresponding to the peak power of 15.2 kW.     

Watt-level continuous-wave and passively Q-switched red lasers pumped by a single blue laser diode

Praseodymium-ion-doped gain materials have the superiority of lasing at various visible wavelengths directly.Simple and compact visible lasers are booming with the development of blue laser diodes in recent years. In this Letter, we demonstrate the watt-level red laser with a single blue laser diode and Pr:YLiF_4 crystal. On this basis,the passively Q-switched pulse lasers are obtained with monolayer graphene and Co:ZnO thin film as the Q-switchers in the visible range.     

High-efficiency continuous-wave and Q-switched diode-end-pumped multi-wavelength Nd:YAG lasers

We demonstrate high-efficiency diode-end-pumped multi-wavelength Nd:YAG lasers for continuous-wave and Q-switched operation. For the continuous-wave case, the Nd:YAG laser oscillates at 1.06 and 1.3 μm simultaneously; the maximum output power of 2.0 W (M² = 1.3) and 3.6 W (M² = 1.8) have been achieved at the incident pump power of 20.3 W, with the respective average slope efficiencies of 12.0% and 21.4%, for the lines of 1.06 and 1.3 μm, respectively. For the Q-switched operation, we achieve the average output power of 1.3 W (M² = 2.7) at 1.06 μm and 2.0 W (M² = 3.0) at 1.3 μm with the corresponding peak power of 10.2 and 4.2 kW under an incident pump power of 20.3 W.     

Diode-end-pumped CW and actively Q-switched Tm,Ho:YLF ring laser

This paper presents CW and acoustic-optical Q-switched Tm,Ho:YLF laser performance in a laser-diode end-pumping figure-eight ring resonator structure at 77 K. Under CW operation, different transmission of output couplers and different cavity length were used to achieve best characteristics of the laser. The maximum power of 1.85 W is achieved with the threshold of 2.09 W, slope efficiency of 28.14% and optical-to-optical efficiency of 20.3% on the condition of 1 m cavity length and 18% transmission. Under pump power of 4 W, laser characteristics under Q-switched operation with different pulse repeat frequency was investigated. Maximum energy of 5.86 mJ is achieved with pulse width of 171.2 ns, peak power of 34.2 kW and dynamic-static ratio about Q-switch laser of 0.62 at pulse repeat frequency 70 Hz.