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.     

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.     

A comparative study on diode-pumped continuous wave Tm:Ho:YVO<Subscript>4</Subscript> and Tm:Ho:GdVO<Subscript>4</Subscript> lasers

In this paper, we presented experimental results concerning on the laser characteristics of two microchip lasers emitting in the 2 μm range, Tm:Ho:YVO₄ microchip laser and Tm:Ho:GdVO₄ microchip laser. At a heat sink temperature of 283 K, the maximum output power of Tm:Ho:YVO₄ laser and Tm:Ho:GdVO₄ laser is 47 and 34 mW under absorbed pump power of 912 mW, respectively. High efficiency can be achieved for both lasers at room temperature. Nevertheless, compared with Tm:Ho:GdVO₄ laser, Tm:Ho:YVO₄ laser can operate on single frequency with high power easily. At the heat sink temperature of 288 K, as much as 16.5 mW of 2052.3 nm single-longitudinal-mode (SLM) laser was achieved for Tm:Ho:YVO₄ laser. Under the same condition, only 8 mW of 2048.5 nm SLM laser was achieved for Tm:Ho:GdVO₄ laser.     

A single-longitudinal-mode CW 0.25 mm Tm,Ho:GdVO<Subscript>4</Subscript> Microchip Laser

A single-longitudinal-mode of 0.25 mm Tm,Ho:GdVO₄ Microchip Laser was reported. The maximal continuous wave (CW) output power was 26.4 mW and the threshold of 118 mW. The Tm,Ho:GdVO₄ Microchip Laser output wavelength was centered at 2039.7598 nm with bandwidth of about 57.1 pm. The beam quality factor was M ² ∼ 1.52 ± 0.03 measured by knife-edge method. The Longitudinal-Mode was scanned by a FPI and the transverse mode was monitored by an infrared vidicon camera.     

High-power,high-quality ZGP OPO pumped by a Tm,Ho:GdVO<Subscript>4</Subscript> laser

We report a ZGP OPO system capable of producing >6 W at a signal wavelength of 3.80 μm and an idler wavelength of 4.45 μm. The pumping source is the Tm,Ho:GdVO₄ laser operated at 2.049 μm with an M ² of 1.07. The ZGP OPO generated a total combined output power of 6.1 W at signal wavelength and idler wavelength under pumping power of 18.3 W, and an M ² of 1.7 for OPO output was obtained.     

Tunable narrowband filter based on a combination of Fabry-Perot etalon and volume Bragg grating

A new type of tunable narrowband filter is proposed. This filter is a combination of a Fabry-Perot etalon, which permits the selection of a comb of discrete narrow bands, and a high-efficiency rotating volume Bragg grating recorded in photo-thermo-refractive glass, which permits tuning between the Fabry-Perot resonances. A tunable filter for fixed wavelengths in the region of 1.5 mum with a spectral width of 220 pm (FWHM), separation between channels of 800 pm, and throughput of 95% (losses <0.2 dB) is demonstrated.     

Comparison of RTP electro-optic Q-switch and acousto-optic Q-switch in Tm,Ho:GdVO<Subscript>4</Subscript> laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

Single-longitudinal-mode erbium-doped fiber laser based on a fiber Bragg grating Fabry-Perot filter

A novel single-longitudinal-mode (SLM) erbium-doped fiber laser with a simple linear cavity based on a fiber Bragg grating Fabry-Perot filter (FBG-FPF) and a narrowband (～0.06 nm) FBG is proposed and demonstrated experimentally. Two uniform FBGs form the FBG-FPF, which has two ultranarrow transmission bands with a bandwidth of 0.12 pm and a wavelength spacing of 0.095 nm. By slightly tuning the central wavelength of the narrowband FBG, SLM lasing at 1549.658 or 1549.563 nm (corresponding to the two transmission peaks of the FBG-FPF) is achieved with a laser output power of ～4 mW, when the pump power is ～75 mW.     

Diode-pumped Tm:GdVO<Subscript>4</Subscript> lasers with double etalons

Diode end-pumped single-frequency Tm:GdVO₄ laser at room temperature was reported. The maximal output power of single-frequency is as high as 51 mW by using two uncoated fused YAG etalons, which are respectively 0.05 mm thick and 1 mm thick. We obtained the single frequency Tm:GdVO₄ laser at 1919.7 nm. The slope efficiency is 1.4%. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

Room temperature diode-pumped 1875.1 nm Tm:GdVO<Subscript>4</Subscript> laser

A diode end-pumped single-frequency Tm:GdVO₄ laser at room temperature was reported. The maximal output power of single-frequency is as high as 66 mW by using two uncoated fused etalons, which are respectively 0.05 mm thick YAG and 1 mm thick quartz. We obtained the single frequency Tm:GdVO₄ laser at 1875.1 nm. The slope efficiency is 1.5%. The change of the lasing wavelength on temperature was also measured. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

Effect of resonator length on ZnGeP<Subscript>2</Subscript> doubly resonant optical parametric oscillator pumped by a Tm,Ho:GdVO<Subscript>4</Subscript> laser

The effect of resonator length on ZnGeP₂ doubly resonant optical parametric oscillator was reported in this letter. With the employment of a Tm,Ho:GdVO₄ laser as the pump source at 2.05 μm, we have found that there are obvious peaks of the output power when the resonator lengths are matched to the length of the pump source. The ZGP OPO can generate a maximum output power of 4.27 W at 3.80 μm signal and 4.45 μm idler when the resonator length matches that of the pump source.     

A comparative study on diode-pumped single-frequency Tm:YAG and Tm:GdVO<Subscript>4</Subscript> lasers

In this paper, we present experimental results concerning on the laser characteristics of Tm:YAG laser and Tm: GdVO₄ laser. At room temperature, the maximum output power of Tm:YAG laser and Tm:GdVO₄ laser is 210 and 145 mW, respectively. High efficiency can be achieved for both lasers at room temperature. Nevertheless, compared with Tm:GdVO₄ laser, Tm:YAG laser can operate on single frequency with high power easily. As much as 60 mW of 2013.9 nm single-longitudinal-mode (SLM) laser was achieved for Tm:YAG laser. For Tm:GdVO₄ laser 51 mW of 1919.7 nm SLM laser was achieved. The SLM Tm:YAG laser is better for using as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

diode-pumped single-frequency Tm:GdVO<Subscript>4</Subscript> laser at 1897.6 nm

A diode end-pumped Tm:GdVO₄ laser at room temperature is reported. The maximal output power of single-frequency is as high as 34 mW by using two uncoated fused etalons, which are respectively 0.05 mm thick YAG and 1mm thick quartz. We obtained the single frequency Tm:GdVO₄ laser at 1897.6 nm with the slope efficiency of 1.3%. The single-longitudinal-mode (SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems.     

A High-Power,Long-Wavelength Infrared ZnGeP<Subscript>2</Subscript> Opo Pumped by a <Emphasis Type="Italic">Q</Emphasis>-Switched Tm,Ho:GdVO<Subscript>4</Subscript> Laser

We report a high-power, long-wavelength infrared ZnGeP₂ (ZGP) optical parametric oscillator (OPO) pumped by a Q-switched Tm,Ho:GdVO₄ laser. The wavelength tuning range of 7.8–9.9 μm is realized by rotating the external angle of the ZGP crystal. We obtain an output power over 30 mW across the whole wavelength range and achieve a 1.71 W output power at 8.08 μm by transmitting the OPO parameters, corresponding to an idler laser slope efficiency of 12.1%.     

Diode-end-pumped Tm,Ho:YVO<Subscript>4</Subscript> microchip laser at room temperature

Room temperature Tm, Ho:YVO₄ microchip laser operated around 2 μm was demonstrated for the first time to our knowledge. At a heat sink temperature of 283 K, a maximum output power of 47 mW was obtained by using a 0.25 mm length crystal at an absorbed pump power of 912 mW, corresponding to a slope efficiency of 9.1%. Increasing the temperature to 288 K, as much as 16.5 mW 2052.3 nm single-longitudinal-mode laser was achieved. The M ² factor was measured to be 1.4.     

Compact TEM<Subscript>00</Subscript> grazing-incidence Nd:GdVO<Subscript>4</Subscript> laser using a folded cavity

A compact diode-side-pumped Nd:GdVO₄ laser system using a folded cavity and grazing-incidence configuration is presented. The highest multimode output power obtained was 21.8 W at 36 W of effective diode pump power. Highest optical-to-optical conversion efficiency of 61.5% was achieved at 33 W of effective diode pump power with 20.3 W of multimode output power. For single-mode TEM₀₀ operation, an intracavity telescope was adopted for mode matching in the horizontal direction. Because of the folded cavity and the intracavity telescope, this laser head was the most compact to our knowledge of the TEM₀₀ grazing-incidence laser geometry. At last, an output power of 15 W was produced at 36 W of effective diode pump power. The stable Q-switching operation was also obtained. PACS 42.55.-f; 42.55.Xi; 42.60.Gd     

Diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> laser

By using both an acoustooptical (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, a diode-pumped doubly Q-switched Nd:GdVO₄ laser, which can generate short pulses with high peak powers and symmetric temporal profiles, has been demonstrated. A peak power of 3.05 kW with a corresponding pulse width of 16 ns has been achieved at an incident pump power of 7.7 W. A reasonable analysis about the experimental results has been given by considering the ground-state absorption and excited-state absorption of a Cr⁴⁺:YAG crystal.     

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.     

2041.3 nm/2054.6 nm simultaneous dual-wavelength single-longitudinal-mode Tm,Ho:YVO<Subscript>4</Subscript> microchip laser

We report a single-longitudinal-mode CW diode-pumped Tm, Ho: YVO₄ microchip laser emitting at both 2041.3 and 2054.6 nm. At each wavelength, the laser has a single longitudinal mode. The total single-longitudinal-mode output power reaches 185 mW with 20.4% optical conversion efficiency at 905 mW incident pump power.     

Raman spectroscopic study of structural disordering in YVO<Subscript>4</Subscript>, GdVO<Subscript>4</Subscript>, and CaWO<Subscript>4</Subscript> crystals

The Raman spectra of single-crystal YVO₄, GdVO₄, and ZrSiO₄ with a zircon structure, as well as CaWO₄ and BaWO₄ with a scheelite structure, are studied in detail over a wide temperature range 14–800 K. An inhomogeneous splitting of the A _1g (ν₂) vibrational lines in the Raman spectra of YVO₄ and GdVO₄ and the A _g (ν₁) vibrational lines in the spectrum of CaWO₄ is detected. It is shown that the profiles of these lines can be decomposed into two components, whose integrated intensities are redistributed with temperature and also depend on the matrix kind in which they are detected. The phenomenon observed is associated with the thermally activated processes of disorientation of the tetrahedral anions in the zircon and scheelite structures.