3,675 research outputs found
High power diode-bar-pumped intracavity-frequency-doubled Nd:YLF ring laser
No full textWe report efficient cw operation of an intracavity-frequency-doubled Nd:YLF ring laser end-pumped by two beam-shaped 20W diode bars. A single-frequency, polarised output of 6.2W at 526.5nm (8.3W generated in the doubling crystal), was obtained in a TEMoo mode (M2 < 1.2
High power diode-bar-end-pumped Nd:YLF laser at 1.053µm
No full textWe describe efficient cw operation of a Nd:YLF laser on the 1.053µm transition, end-pumped by two beam-shaped 20W diode bars. Fundamental-transverse mode operation with output power of 11.1W for ~29.5W of incident pump power has been demonstrated. In Q-switched operation 8.4W of average power at a pulse repetition frequency of 40kHz and ~2.6mJ pulse energy at pulse repetition frequency of 1kHz were achieved
Efficient operation of an acousto-optically induced unidirectional and single-frequency Q-switched Nd:YLF laser
No full textA highly-efficient Q-switched Nd:YLF ring laser, end-pumped by two 20W diode-bars is reported, yielding 3.5 mJ of single frequency TEMoo output for ~25W of incident pump power
Multiline optical parametric oscillators based on periodically-poled lithium niobate
No full textSimultaneous multiple wavelength operation of optical parametric oscillators based on periodically-poled lithium niobate with different period gratings arranged in series or parallel is reported. The relative merits of these different OPO designs are discussed
Mode-hop-free tuning in high-power intracavity-frequency-doubled Nd:YAG and Nd:YLF ring lasers
No full textBy simple cavity length adjustment, continuous, mode-hop-free tuning over many axial-mode spacings has been observed in efficient, intracavity-frequency-doubled, single-frequency Nd:YAG and Nd:YLF ring lasers generating multiwatt output powers at 532nm and 526.5nm
High-power diode-bar-pumped intracavity-frequency-doubled Nd:YAG and Nd:YLF ring lasers
No full textThe use of diode-pumped solid-state lasers as sources of high power visible light is an area which has attracted growing interest in recent years. This interest stems from the increased efficiencies available and compact size compared to Ar+ lasers. A further attractive feature of intracavity-frequency-doubled, single-frequency lasers, on which initial results were recently reported, is that axial-mode-hopping is suppressed. The explanation for this behaviour is based on the fact that adjacent (non-lasing) axial modes are further suppressed by an additional loss due to sum-frequency generation. This is twice the loss experienced by the lasing mode due to second harmonic generation. In a low loss resonator with efficient intracavity-frequency-doubling this extra loss can more than offset any gain advantage of adjacent modes closer to the gain peak. The net result is that continuous (mode-hop-free) tuning is possible over many axial mode spacings. Here we describe an intracavity-frequency-doubled Nd:YAG ring laser end-pumped by a 20W diode bar, and a Nd:YLF ring laser end-pumped by two 20W diode bars. In each case, a simple bow-tie cavity design was employed, with a Brewster-angled LBO crystal. In the case of Nd:YAG for a non-optimised laser mode size in the LBO crystal the laser produced ~1.4W of single-frequency output in the green at 532nm. By varying the cavity length we obtained a single-frequency, continuous (mode-hop- free) tuning range of ~40GHz corresponding to ~80 axial mode spacings. This range is consistent with predictions of a simple model accounting for the effects of nonlinear loss due to sum frequency generation. Nd:YLF offers the potential of an extended tuning range through its broader linewidth. Furthermore Nd:YLF is attractive for operation at higher powers due to its superior thermo-optical properties on the sigma-polarisation compared to Nd:YAG, providing that appropriate steps are taken to avoid thermally-induced stress-fracture. Results for this laser, end-pumped by two 20W diode-bars, include the generation of ~10.3W of single frequency 1053nm output in a TEMoo beam (M2 < 1.1), and 6.2W of green output at 526.5nm (corresponding to ~8.5W generated internally in the LBO) and a conversion efficiency of ~5% with respect to intracavity power. We have obtained a single frequency, continuous (mode-hop-free) tuning range of 72GHz corresponding to ~150 axial mode spacings. So far, the mode-hop-free tuning range has been limited by etalon effects due to imperfect AR coatings on the TGG Faraday rotator. With the elimination of these etalon effects, mode-hop-free tuning over a considerable fraction of the gain bandwidth should be achievable
Upconversion lifetime quenching and ground-state bleaching in Nd<sup>3+</sup>:LiYF<sub>4</sub>
No full textSince the Nd3+:LiYF4 system has some advantage over Nd3+:YAG and Nd3+:YVO4 for high-power scaling of diode-end-pumping, this system has been investigated under strong excitation. in this case using a Ti:sapphire pump. The interionic processes responsible for fluorescence saturation have been determined, due allowance being taken for the significant ground-state bleaching under these conditions. Their temperature dependence, which is relevant to scaling consideration, has been investigated theoretically, and found to be rather small over a wide temperature range. By comparing the experimental data with finite-element rate-equation calculations, the influence of interionic upconversion is determined quantitatively, and a published value of the upconversion parameter is confirmed. The spatial dependence of ground-state bleaching and quenching of the fluorescence lifetime is calculated. Analytical expressions are derived, including the influence of interionic upconversion, for the dependence of ground-state bleaching, excitation density, and storage time on pump parameters and dopant concentration
High-power Nd:YLF master oscillator power amplifier with 15W single-frequency output at 1053nm
No full textA diode-pumped Nd:YLF ring laser incorporating a frequency doubling crystal to suppress axial-mode-hopping and producing 5W of single-frequency output with M2<1.1 at 1.053µm is amplified in a Nd:YLF amplifier to 15W without degradation of beam quality
Simultaneous multiple line optical parametric oscillators based on periodically-poled lithium niobate
No full textCoherent sources emitting in the mid-infrared (2-5µm) spectral region have received increasing interest over the last few years owing to numerous applications. Optical Parametric Oscillators, pumped by reliable diode-pumped solid-state lasers, offer an attractive route to these wavelength regions, providing enormous flexibility in the choice of operating wavelength. Although widely tunable, the emission linewidth of OPOs is often rather narrow (typically a few nm) limited by factors such as the phase-matching bandwidth of the crystal. For some applications, a broadband or multiple wavelength output spanning a much wider spectral region is desirable
Thermal lensing in high-power end-pumped Nd:YLF lasers
No full textOne of the major limitations of scaling diode-end-pumped solid-state lasers to high powers is introduced by thermal effects. An attractive feature of Nd:YLF has been its superior thermo-optical properties compared to other laser crystals. This is due to a decrease of refractive index with increasing temperature, creating a negative thermal lens, which partially compensates for the positive lens due to bulging of the rod end faces. Other advantages of Nd:YLF include its natural birefringence and its long fluorescence lifetime. The latter feature is of interest for high-power Q-switched operation. Problems in realising the true potential of the laser, however, have often been encountered, for underlying spectroscopic reasons as indicated, e.g., in [1]. We investigated the thermal lensing under lasing and non-lasing conditions within a diode-bar-pumped system. Under non-lasing conditions the thermal lens was measured using a Nd:YAG probe laser which double-passed the Nd:YLF rod. The resulting change in beam divergence was measured. Under lasing conditions the laser-beam waist size on the output coupler was measured. Hence, using the ABCD-matrix formalism, focal-length values for the thermal lenses were determined. The results showed a significant difference in the thermal lens under lasing and non-lasing conditions. In the former case a weak thermal lens was observed which varied linearly with pump power. Under non-lasing conditions a much stronger thermal lens was measured, whose power increased non-linearly with pump power. With 11 W of pump power incident on the crystal, a factor of 6 difference between lasing and non-lasing values of focal length was determined (Pi-polarisation, plane perpendicular to c-axis). These measurements demonstrate that significant additional heat is generated in the non-lasing case. A finite-element calculation, which considered the relevant processes including interionic upconversion, their contribution to thermal loading, as well as the temperature distribution in the Nd:YLF crystal, was performed. An experimentally observed fluorescence saturation at 1.05µm of more than 50 % under Ti:sapphire pumping was numerically reproduced, and the value of the published upconversion parameter [2] was thereby confirmed. With this information, the heat generation, spatial temperature distribution, and thermal lens under diode pumping were determined. The calculated thermal lens powers were in reasonable agreement with experimental results. Upconversion processes as well as the temperature dependencies of heat conductivity and thermo-optical parameters were found responsible for strong thermal lensing under non-lasing conditions and its non-linear behaviour with respect to absorbed pump power. Design improvement by a significant decrease of thermal lens power and spherical aberrations under Q-switched conditions can be achieved by increasing the pump-spot size, decreasing the dopant concentration and using a longer crystal, or detuning the pump wavelength from the absorption peak
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