High efficiency,high repetition-rate Nd:YVO<Subscript>4</Subscript> laser with TEM<Subscript>00</Subscript> end-pumped by 887 nm

Thermal effect of laser crystal is a very important factor for solid lasers. The most of heat is generated from the quantum loss between pump light and lasing light. If a longer wavelength of pump light is adopted, quantum loss and quantum loss efficiency can be reduced and improved, respectively. In this paper, a Nd:YVO₄ laser end-pumped by 887 nm LD is reported. Output power of 25 W is obtained from a single Nd:YVO₄, when the crystal absorbs pump light power of 38 W. The corresponding opto-optic conversion efficiency is up to 65.7%. When 30.7 W pump light is absorbed in the crystal, 19.4 W TEM₀₀ is obtained with M _x ² = 1.30, M _y ² = 1.26 and opto-optic conversion efficiency of 63.2%. The laser can work at the Q-switched mode. The uniform pulses are generated at high repetition of 100 kHz. And the conditions of pulse stability are analyzed in this paper.     

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%.     

A novel prism beam-shaping laser diode bar end-pumped TEM<Subscript>00</Subscript> mode Nd:YVO<Subscript>4</Subscript> laser

A beam-shaping diode end-pumped TEM₀₀ mode CW Nd:YVO₄ laser is presented. A special beam-shaping element made up of isosceles right-angled prism pieces is adopted to realize beam symmetric. Two cylinder lenses are used to couple the shaped beam into a 3 × 3 × 9 mm Nd:YVO₄ crystal with 0.3 at % neodymium doping. By using this laser system, we have achieved 6.1 W CW laser operated in single transverse mode at 1064 nm with 95.2% reshaping efficiency and 25.6% optical-optical conversion efficiency.     

Ultrahigh-efficiency TEM<Subscript>00</Subscript> diode-side-pumped Nd:YVO<Subscript>4</Subscript> laser

Ultrahigh-efficiency TEM₀₀ operation is demonstrated in a diode-pumped Nd:YVO₄ laser in a bounce amplifier geometry using a specially designed astigmatically optimised cavity configuration. Optical efficiency >68% is demonstrated and up to 27.1 W of output power for multimode operation. For single-mode TEM₀₀ operation, an output power of 23.1 W for 39.5 W of diode pumping was produced with beam propagation parameters of M_x ²=1.3 and M_y ²=1.1. Received: 10 October 2002 / Revised version: 9 December 2002 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: a.minassian@ic.ac.uk     

High-efficiency 17 W, 80 MHz repetition rate,passively mode-locked TEM<Subscript>00</Subscript> Nd:YAG oscillator pumped at 885 nm

We report on a passively mode-locked TEM₀₀ Nd:YAG oscillator with the beam quality at M ² = 1.1 by a semiconductor saturable absorber mirror under 885 nm laser diode direct pumping for the first time. A maximum average output power of 17 W at a repetition rate of 80 MHz with 39 ps pulse width was obtained under the absorbed pump power of 38 W, corresponding to an optical-optical efficiency of 44% and the slope efficiency of 69%, respectively.     

High efficiency 1341 nm Nd:GdVO<Subscript>4</Subscript> laser in-band pumped at 912 nm

A high-efficiency 1341 nm Nd:GdVO₄ laser in-band pumped at 912 nm is demonstrated for the first time. Using an all-solid-state Nd:GdVO₄ laser operating at 912 nm as pump source, 542 mW output was obtained with 1.14 W absorbed pump power. The slope efficiency with respect to the absorbed pump power was 56.6%, and the fluctuation of the output power was better than 2.6% in the given 30 min. The beam quality factor M ₂ is 1.15.     

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     

High efficiency 1341 nm Nd:GdVO<Subscript>4</Subscript> bounce laser in-band pumped at 879 nm

A high-efficiency Nd:GdVO₄ bounce laser in-band pumped at 879 nm is demonstrated for the first time. From a side-pumped Nd:GdVO₄ crystal, 8.2 W output was obtained with 18.5 W absorbed pump power. Corresponding slope efficiency with respect to the absorbed pump power was 51.4%, and the beam quality factor M2 is 1.13 and 1.15 for tangential direction and sagittal direction, respectively. Effects of crystal’s doping concentration and temperature on laser power and conversion efficiency were also investigated.     

Compact diode-directly-pumped passively mode-locked TEM<Subscript>00</Subscript> Nd:GdVO<Subscript>4</Subscript> laser at 1341 nm using a semiconductor saturable absorber mirror

We report on a compact 880-nm diode-directly-pumped passively mode-locked TEM₀₀ Nd:GdVO₄ laser at 1341 nm with a semiconductor saturable absorber mirror (SESAM) for the first time. Under the absorbed pump power of 14.6 W, the maximum output power of 1.27 W was obtained at the repetition rate of 85.3 MHz with the pulse width of 45.3 ps, corresponding to an optical-optical efficiency of 8.8% and the slope efficiency of 33.3%, respectively. The beam quality factor was measured to be M ² = 1.18, indicating a TEM₀₀ mode.     

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.     

High power Q-switched TEM<Subscript>00</Subscript> Nd:YVO<Subscript>4</Subscript> laser with self-adaptive compensation of thermal lensing effect

a high power dual-end-pumped Nd:YVO₄ laser with adaptive compensation of thermal lensing effect by adjusting HR mirror along the optical axis was proposed. In Q-switching operation at 70 kHz, the laser worked at different pump power (from 90 W to 70 W) with stable beam quality (M ² ∼ 1.15) and high output power (from 39 to 28.4 W), corresponding to the absorbed-output conversion efficiency of 55%. In the meantime, the pulse duration was increased from 24 to 31.7 ns. At various repetition rate from 60 to 100 kHz, the beam quality factors were all measured less than 1.2.     

Simultaneous self-mode-locking of TEM<Subscript>0,0</Subscript> and TEM<Subscript>1,0</Subscript> modes in a Nd:YVO<Subscript>4</Subscript> laser: Application for measuring the thermal focal length

We demonstrate that the simultaneous self-mode-locking of TEM_0,0 and TEM_1,0 modes can be achieved in a standard end-pumped Nd:YVO₄ laser. With this simultaneous self-mode-locking, the transverse beat frequency can be accurately measured as a function of the absorbed power. We employ the measured beat frequency and the cavity theory to precisely determine the effective focal length of the thermal lens in the gain medium.     

Influence of LD temperature fluctuation on the performance of corner-pumped TEM<Subscript>00</Subscript> CW composite Nd:YAG laser

The influence of LD temperature fluctuation on the performance of corner pumped TEM₀₀ CW composite Nd:YAG laser was investigated by numerical ray tracing method and experiment. Both the theoretical analysis and experimental results show that the corner-pumped TEM₀₀ laser has a good tolerance to temperature fluctuation. At a drive current of 40 A, when the LD temperature varies from 15 to 25°C the fluctuation of output power as less than 5% and the beam quality remains almost invariable.     

Diode pumped Nd:Lu<Subscript>0.5</Subscript>Y<Subscript>0.5</Subscript>VO<Subscript>4</Subscript>-LBO red laser at 671 nm

We report a efficient compact red laser at 671 nm generation by intracavity frequency doubling of a continuous wave laser operation of a diode pumped Nd:Lu_0.5Y_0.5VO₄ laser on the ⁴ F _3/2-⁴ I _13/2 transition at 1342 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an absorbed pump power of 17.8 W, as high as 2.25 W of continuous wave output power at 671 nm is achieved with 10-mm-long LBO. The optical-to-optical conversion efficiency is up to 12.6%, and the fluctuation of the red output power was better than 3.6% in the given 30 min.     

All solid-state CW Nd:GdVO<Subscript>4</Subscript>-GdCOB laser at 670 nm

We report the efficient compact red laser at 670 nm generation by intracavity frequency doubling of a continuous wave laser operation of a diode pumped Nd:GdVO₄ laser on the ⁴ F _3/2 → ⁴ I _13/2 transition at 1340 nm. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 18.2 W, as high as 1.32 W of continuous wave (CW) output power at 670 nm is achieved with 15-mm-long GdCOB. The optical-to-optical conversion efficiency is up to 7.3%, and the fluctuation of the red output power was better than 3.5% in the given 30 min.     

All-solid-state 543 nm green laser generated by frequency doubling of a diode pumped Nd:YVO<Subscript>4</Subscript> laser at 1086 nm

An efficient and compact green laser at 543 nm is generated by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode pumped Nd:YVO₄ laser at 1086 nm under the condition of suppression the higher gain transition near 1064 nm. With 10 W diode pump power and a frequency doubling crystal LBO, as high as 2.13 W of CW output power at 543 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 21.3% and the output power stability in 3 h is better than 2.27%.     

CH<Subscript>3</Subscript>OH optically pumped by a <Superscript>13</Superscript>CO<Subscript>2</Subscript> laser: new laser lines and assignments

We report 12 new THz (far-infrared) laser lines from methanol (CH₃OH), ranging from 58.1 μm (5.2 THz) to 624.6 μm (0.5 THz). A ¹³CO₂ laser of wide tunability (110 MHz) has been used for optical pumping, allowing access to previously unexplored spectral regions. Optoacoustic absorption spectra were used as a guide to search for new THz laser lines, which have been characterized in wavelength, polarization, offset, relative intensity, and optimum operation pressure. For 20 laser lines previously observed, we have measured the absorption offset with respect to the ¹³CO₂ laser line center. PACS 33.20.Ea; 33.20.Vq; 33.80.-b     

Diode pumped Pr<Superscript>3+</Superscript>:LiYF<Subscript>4</Subscript>-BBO ultraviolet laser at 320 nm

A diode pumped Pr³⁺:LiYF₄ laser at 639.5 nm has been demonstrated. With an incident pump power of 920 mW, the maximum red output power was 272 mW. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a maximum ultraviolet power of 23 mW by using a β-BaB₂O₄ (BBO) nonlinear crystal. To the best of our knowledge, this is the first report on continuous-wave ultraviolet generation by intracavity frequency doubling Pr³⁺:LiYF₄ laser.     

All solid-state CW Nd:LuVO<Subscript>4</Subscript>-LBO yellow-green laser under direct 888 nm pumping

We report a yellow-green laser at 544.5 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1089 nm Nd:LuVO₄ laser under in-band diode pumping at 888 nm. An LBO crystal, cut for critical type I phase matching is used for second harmonic generation of the laser. At an incident pump power of 17.9 W, as high as 3.81 W of CW output power at 544.5 nm is achieved. The optical-to-optical conversion efficiency is up to 21.3%, and the fluctuation of the yellow-green output power was better than 3.7% in the given 4 h.     

All solid-state continuous-wave intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>-LBO red laser at 671.5 nm

We report for the first time a efficient compact red laser at 671.5 nm generation by intracavity frequency doubling of a continuous wave laser operation of a diode direct pumped Nd:LuVO₄ laser on the ⁴ F _3/2 → ⁴ I _13/2 transition at 1343 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an absorbed pump power of 16.2 W, as high as 4.3 W of continuous wave output power at 671.5 nm is achieved with 10-mm-long LBO. Comparative results obtained for the pump with diode laser at 808 nm, into the highly-absorbing ⁴ F _5/2 level, are given in order to prove the advantages of the 880 nm wavelength pumping.