We demonstrate a high power, Er:LuAG single-longitudinal-mode laser in an anti-misaligned resonator. Based on the Faraday effect, a 1.61 W single-longitudinal-mode (SLM) laser is obtained with the double corner-cube-retroreflector (CCR) structure, and the tunable wavelength is 1649.2–1650.3 nm. Additionally, we investigate the anti-misalignment characteristics when the CCR moves and rotates along the optical axis. Furthermore, by utilizing the Er:LuAG amplifier, the maximum 2.32 W single-longitudinal-mode laser at 1649.6 nm is achieved. The beam quality factors M2 of the 2.32 W Er:LuAG single-longitudinal-mode laser are 1.23 and 1.25 along the horizontal (x) and vertical (y) directions, respectively.

A 1650 nm seed-injection, single-frequency Er:LuAG pulsed laser with the double corner-cube-retroreflector (DCCR) structure has been demonstrated in this paper. In the total CCR structure (seed and slave laser), the maximum pulse energy of 2.15 mJ, with a pulse width of 225 ns under the pulse repetition frequency (PRF) of 200 Hz has been obtained, through the "ramp-hold-fire" injection-seeding technique. By utilizing the heterodyne technique, we have determined that the half-width pulse spectrum, which is 2.27 MHz. It is noteworthy that this marks the first successful realization of the 1650 nm single-frequency, Er:LuAG pulsed laser.

We demonstrated a narrow-linewidth Ho:yttrium aluminum garnet (YAG) injection-locked laser by using a 1908 nm thulium-doped fiber laser as a pumping source to generate 2.09 mu m single-frequency pulses. A compact single-longitudinal-mode nonplanar ring oscillator (NPRO) based on Ho:YAG material with a beam quality factor of 1.01 at the central wavelength of 2090.91 nm was considered as the seed source. In the experiment, the pulse energy of 3.6 mJ with a pulse width of 161.6 ns from single-frequency Ho laser was achieved at a pulse repetition frequency (PRF) of 100 Hz. The linewidth of the single-frequency pulse spectrum monitored through the heterodyne method was approximately 1.9 MHz at the lowest Ho laser energy.

The thermal focal lengths, absorption efficiencies, and laser performances of Er:YAG and Er:LuAG crystals are systematically demonstrated within an anti-misalignment double corner-cube-prisms resonator. The maximum continuous-wave output power of 5.12 W at 1645.39 nm and 6.43 W at 1650.33 nm are obtained, with slope efficiencies of 16.29 % and 36.78 %. In pulsed operation, Er:YAG yielded a maximum pulse energy of 5.1 mJ, and Er:LuAG delivered 4.7 mJ, both at the pulse repetition rate of 200 Hz. The beam qualities, represented by M2 factors, are measured at 1.52 for Er:YAG and 1.44 for Er:LuAG.

We demonstrate a tri-corner cube Q-switched Ho:YAG spatial ring cavity laser, which was resonantly pumped by a 1908 nm fiber laser. The polarization state of the intracavity oscillating laser was adjusted by a half-wave plate, and a continuous s-polarized laser of 2.57 W at 2090.9 nm was obtained at a pump power of 18.5 W, corresponding to an optical-to-optical conversion efficiency of 13.9 % and a slope efficiency of 33.3 %. When the corner cube prism, which has the weakest anti-misalignment capability, was tilted vertically by 1 degrees or horizontally by 0.92 degrees, the laser could still output the laser. For Q-switched operation, the tri-corner cube Ho:YAG laser has a pulse energy of 9.86mJ and a pulse width of 178.8 ns at a repetition rate of 100 Hz. At the maximum output energy, the beam quality was M-x(2) = 1.3, M-y(2) = 1.2.

We proposed a Ho:GdVO4 laser operating at 2.05 mu m in-band directly pumped by the 1.94 mu m fiber-coupled laser diode, which electro-optically Q-switched by an LGS(La3Ga5SiO14) crystal. Adopting 1.0 at.%-doped Ho:GdVO4 crystal as the gain medium, a maximum output power of 6.5 W at 2047.9 nm with the absorbed pump power of 28 W was obtained in the continuous-wave mode, corresponding to a slope efficiency of 37.6 %. At a pulse repetition frequency of 1 kHz, the highest pulse energy of 3.25 mJ with a pulse width of 4.2 ns was achieved, corresponding to a peak power of 773.8 kW. In addition, the beam quality factor M2 was measured to be 1.9 at the maximum output level by the 90/10 knife-edge method. TEM00 propagation has been verified by a camera. To the best of our knowledge, this is the first demonstration of high peak power electro-optically Q-switched Ho: GdVO4 laser directly pumped by the 1.94 mu m laser diode.

A single-longitudinal-mode Ho:YLF unidirectional ring laser with single anti-misalignment corner cube retro-flector (CCR) for providing the stable local oscillator to 2.05 mu m laser lidar was demonstrated in this paper. The single-longitudinal-mode output power of 569 mW at 2051.76 nm was obtained by inserting a half-wave plate and a Faraday rotator to the ring oscillator. The output wavelength was tuned from 2050.94 nm to 2054.18 nm through a 0.3-mm-thick F-P etalon, which close to the free spectrum range of the etalon. In addition, the anti-misalignment characteristic of the unidirectional ring laser was investigated when the single CCR moved along the optical axis and perpendicular to the optical axis. The beam quality factors M2 of the Ho:YLF single-longitudinal-mode laser were 1.05 in the x direction and 1.02 in the y direction, respectively.

A high-energy, alignment-insensitive, injection-seeded Q -switched Ho:yttrium aluminum garnet (YAG) single-frequency laser is developed. Both the slave Q -switched laser and the seed laser are Ho:YAG ring lasers based on a pair of corner cubic reflectors. The seed laser has an available power of 830 mW at 2096.667 nm. At 100 Hz, the Q -switched Ho:YAG laser provides a single-frequency pulsed output using injection-seeded technology. The 7.3 mJ single-frequency pulse energy from the slave laser has a pulse width of 161.2 ns and is scaled to 33.3 mJ after passing through the Ho:YAG single-pass amplifier. According to the measurement results of the heterodyne beating technique, the single-frequency pulse has a half-width of 4.12 MHz.

This paper demonstrates a single-frequency injection-seeded laser with a Q-switched Ho:YAG laser consisting of two corner cube reflectors. As a seed laser, the Ho:YAG NPRO has an available output power of 1.8 W and operates at 2090.6964 nm. The single-frequency pulse energy obtained in the case of injection-seeded is 6.8 mJ, the pulse width is 166 ns, and the Q-switched Ho:YAG laser operates at a repetition rate of 100 Hz. The Ho:YAG single-pass amplifier scales single-frequency energy from 6.8 mJ to 32.3 mJ. The pulsed spectrum has a half-width of 2.84 MHz. The Ho:YAG amplifier has a beam quality of 1.1 and 1.17 in the x and y axes.

We demonstrate a continuously operating Er:YAG single-longitudinal-mode laser and its amplifier with a corner cube retroreflector based on the Faraday effect. A maximum power of 1.02 W, the central wavelength of 1645.46 nm, Er:YAG single-longitudinal-mode laser with a line-width of 204 kHz has been realized. The slope efficiency is 9.38% and the beam quality factors M2 are 1.16, 1.05 in the x and y directions. Additionally, the singlelongitudinal-mode laser is amplified to 1.86 W by the double-pass amplifier. The results indicate that the unidirectional operation ring laser in combination with the corner cube prism provides a 1.6 & mu;m continuous-wave single-longitudinal-mode laser with high-power and stability.

An acousto-optic Q-switching Ho:YLF ring oscillator at 2066.33 nm with two anti-misalignment corner cube reflectors (CCRs) pumped by a 1940 nm thulium-doped fiber laser is demonstrated. The depolarization effect of the CCR is expressed in the form of equivalent transmission, and the transmission from two output directions of the oscillator is changing synchronously and periodically as the waveplate angle changes. In the experiment, under the pump power of 21.76 W, the optimum bidirectional energy of 3.13 mJ for a pulse duration of 122 ns at a repetition rate of 50 Hz is realized. The pulse energy reduction percentage at 50 Hz is 8% by changing the horizontal drift angle of one of the CCRs to 4.5°. The beam quality factor M2 is calculated to be about 1.10, revealing that the Ho laser is working in a fundamental transverse mode.

We have demonstrated an injection-seeded, single-frequency Q-switched Er:YAG laser at the pulse repetition frequency (PRF) of 500 Hz with the 'double piezoelectric transducers (PZTs) structure', in a double corner cube retroreflector (DCCR) resonator. With the 'ramp-hold-fire' method, the maximum 1.34 mJ pulse energy with a pulse width of 482 ns has been achieved. With the heterodyne beating technique, the full width at the half maximum (FWHM) of the laser spectrum is 1.12 MHz. And the M2 factors of the 500 Hz, single-frequency pulsed laser are 1.2, 1.24 along the horizontal and vertical directions.

We demonstrate a 2.5 m ring laser with the Ho:YAG and Ho:YLF crystals end-pumped by the Tmdoped fiber laser. In the Ho:YAG laser, the continuous-wave (CW) output power was 4.72 W at a wavelength of 2090.8 nm when the incident pump power was 21.5 W, which corresponded to a slope efficiency of 26.3%. For theQ-switched operation with the 100 Hz pulse repetition frequency (PRF), an output energy of 5.16 mJ and a pulse width of 125.6 ns were achieved at a pump power of 9.53 W. In the Ho:YLF laser, up to a 4.14 CW output power was realized under an incident pump power of 22.3 W, which corresponded to a slope efficiency of 27.3%. At the 100 HzQ-switched operation, the output energy was 4 mJ and the corresponding pulse width was 165.4 ns, when the pump power was 9.86 W.

A continuously tuned single-longitudinal-mode (SLM) Ho:YLF laser around the P12 C O 2 absorption line was demonstrated. The continuous tuning range of 5.75 pm within one longitudinal mode spacing of the Ho:YLF resonator was realized by using a novel intra-cavity wedge prism device fixed on the piezoelectric transducer (PZT) as the cavity length controller. High SLM power of 11.3 W was obtained from a Ho:YLF amplifier with three crystals at the pump power of 31.8 W and master oscillator power of 323 mW, corresponding to a gain of 15.44 dB and an optical-to-optical conversion efficiency of 34.5%. The beam quality factors M 2 of the SLM Ho:YLF amplifier in the x and y directions were estimated to be 1.04 and 1.05, respectively.

A single-frequency pulsed holmium-doped yttrium lithium fluoride (Ho:YLF) amplifier pumped by a Tm-doped fiber laser was demonstrated. The seed was an injection-seeded Q-switched Ho:YLF laser. The output energy from the single-frequency pulsed amplifier was 24.2 mJ, with a pulse width of 250 ns at a pulse repetition frequency (PRF) of 100 Hz. The energy stability during 30 min was improved to 1% after the single-frequency pulsed Ho:YLF laser was amplified. The line width of the single-frequency pulsed spectrum of the Ho:YLF amplifier was 2.81 MHz. The single-frequency pulsed Ho:YLF amplifier can be applied to differential absorption lidar (DIAL), since its output spectrum is around the P12 CO2 absorption line.

Two-photon absorption properties of rhodamine 6G in ethanol and PMMA were researched applying femtosecond pulses. The two-photon absorption cross section of rhodamine 6G in PMMA was found much larger than that in ethanol. Fluorescence properties of this kind of dye in ethanol and PMMA were also researched. The detuning of two-photon absorption for rhodamine 6G dissolved in PMMA is diminished compared with that in ethanol when excited at 800 nm. And the increase of two-photon absorption cross section of rhodamine 6G in PMMA was attributed mainly to the diminishing of detuning.