[Show abstract][Hide abstract] ABSTRACT: An optically pumped tunable HBr laser has been demonstrated for the first time. The pump source was a single-frequency Ho:YLF laser and amplifier system which was locked to the 2064 nm absorption line of HBr. Laser oscillation was demonstrated on nineteen molecular transition lines, including both the R-branch (3870 nm to 4015 nm) and the P-branch (4070 nm to 4453 nm), by the use of an intra-cavity diffraction grating. The highest output energy was 2.4 mJ at 4133 nm.
[Show abstract][Hide abstract] ABSTRACT: We report on a double-pass Ho:YLF slab amplifier which delivered 350 ns long single-frequency pulses of up to 330 mJ at 2064 nm, with a maximum M<sup>2</sup> of 1.5 at 50 Hz. It was end pumped with a diode-pumped Tm:YLF slab laser and seeded with up to 50 mJ of single-frequency pulses.
[Show abstract][Hide abstract] ABSTRACT: A 1314 nm Nd:YLF laser was designed and operated both CW and passively Q-switched. Maximum CW output of 10.4 W resulted from 45.2 W of incident pump power. Passive Q-switching was obtained by inserting a V:YAG saturable absorber in the cavity. The oscillator delivered a maximum of 825 μJ energy per pulse, with a pulse duration of 135 ns at a pulse repetition frequency of 6.3 kHz, effectively delivering 5.2 W of average power.
[Show abstract][Hide abstract] ABSTRACT: A tunable optically pumped HBr laser has been demonstrated for the first time. As pump source for the HBr oscillator, we developed a single-frequency Ho:YLF laser- amplifier system which was locked to the 2064 nm absorption line of HBr. Through the implementation of an intra-cavity diffraction grating, laser oscillation was demonstrated on nineteen molecular transition lines including both the R-branch (3870 nm to 4015 nm) and the P-branch (4070 nm to 4453 nm). The highest output energy for the given input energy was 2.4 mJ at 4133 nm.
Proc. SPIE 8543, Technologies for Optical Countermeasures IX, 85430E, Edinburgh, , United Kingdom; 11/2012
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present the preliminary methods for detection of the boundary layer based on backscattered signals from a mobile LIDAR (Light Detection And Ranging) developed at Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25.5° S; 28.2° E), South Africa. We have concentrated on two different methods, such as (a) statistical and (b) slope. The preliminary study concludes that the statistical method provides a reasonable temporal evolution of the boundary layer height in comparison with the slope method.
Geoscience and Remote Sensing Symposium (IGARSS), 2011 IEEE International; 08/2011
[Show abstract][Hide abstract] ABSTRACT: A single-frequency single-pass amplifier based on Ho:YLF and Ho:LuLF in a scalable slab architecture delivering up to 210 mJ at 2064 nm is demonstrated. The amplifier was end-pumped by a 1890 nm Tm:YLF slab laser and was seeded with a 69 mJ single-frequency Ho:YLF ring laser operating at 50 Hz.
[Show abstract][Hide abstract] ABSTRACT: An HBr master oscillator power amplifier was implemented for the first time which produced up to 9 mJ at 4.2 and 4.34 micrometer wavelength when optically pumped with a single-frequency Ho:YLF slab amplifier.
[Show abstract][Hide abstract] ABSTRACT: We present a novel electronic feedback scheme which allows laser pulse energy control and stabilization by using a custom high speed FPGA digital controller. This scheme was tested on a high-energy fiber-laser-pumped Ho:YLF ring laser. OCIS codes: 140.3425, 140.3538, 140.3070
[Show abstract][Hide abstract] ABSTRACT: A single-frequency double pass Ho:YLF slab amplifier delivering pulses up to 330 mJ at 2064 nm was demonstrated. It was end-pumped with a Tm:YLF slab laser and seeded with 57 mJ of single frequency pulses.
[Show abstract][Hide abstract] ABSTRACT: beam splitter. The oscillator pump path included a plate-polariser which was used together with a quarter-wave plate to prevent optical feedback to the Ho:YLF slab amplifier and oscillator. The 510 mm long HBr oscillator cell was pumped with circularly polarised light in a double-pass configuration, facilitated by a flat 80% reflectivity output coupler at 4 11m which was also a high reflector at 211m. The pump beam size was matched to the HBr resonator fundamental mode size of � 1.5 mm radius, which was formed by a 5 m radius of curvature input coupler mirror, the flat output coupler and a 580 mm long cavity. The 4 11m laser output of the oscillator was coupled into an HBr amplifier cell of length 750 mm in a single-pass configuration for both the residual 2 11m pump light and the 4 11m seed light. Initially all the available pump energy from the Ho:YLF amplifier was coupled into the HBr oscillator which produced up to 5.5 mJ per pulse for 200 mJ incident energy, at which point optical damage of the HBr oscillator cell window was observed due to the high intensity of the pump light in the double-pass configuration. The oscillator was subsequently operated at a reduced input energy of 50 -60 mJ at the point where the HBr laser was most efficient with respect to incident energy, as indicated in the measurements of Fig. la. Approximately 80% of the incident pump light was absorbed in this case where the HBr pressure was 85 mBar.
[Show abstract][Hide abstract] ABSTRACT: Single frequency 2μm sources are useful in varied applications including remote sensing, spectroscopy and non linear conversion to the mid-infrared. However, to generate high energy pulses from a 2 μm oscillator is challenging, which is typically overcome by implementing a master oscillator power amplifier approach. The authors have previously demonstrated a single frequency Ho:YLF laser which produced up to 70 mJ per pulse at 2064nm and subsequently developed a 200W Tm:YLF slab laser to be used as pump source for a power amplifier. To design a high energy amplifier stage a numerical rate equation model was developed in MATLAB and used to determine the optimum system parameters for a Ho:YLF slab amplifier. The model was spatially and temporally resolved and based on a simplification of the travelling wave approximation, implemented so that the gain medium was discretised into three dimensions to accommodate different beam propagation factors for the pump and seed beams in both the horizontal and vertical planes of the slab amplifier.
Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), 2011 Conference on and 12th European Quantum Electronics Conference; 01/2011
[Show abstract][Hide abstract] ABSTRACT: An end-pumped Nd:YLF laser was demonstrated, which delivered 60.3 W continuous-wave and more than 52 W Q-switched average power for all repetition rates from 5 to 30 kHz. To achieve this, an analytical solution to estimate and optimize the unsaturated gain in an end-pumped laser gain medium was derived. The approach presented here should open up the route for scaling end-pumped lasers to even higher power and energy levels.
[Show abstract][Hide abstract] ABSTRACT: Copyright: 2009 IEEE Ho:YLF is an attractive laser material for 2 µm high energy sources since it has a much longer upper laser level lifetime (~14 ms) and higher emission cross section than Ho:YAG. In addition, the very weak thermal lens on the polarisation helps to deliver diffraction limited beams even under intense end-pumping. However, Ho:YLF has a somewhat stronger quasi-three-level nature, which implies that in order to reach transparency at the 2065 nm line, 22% of the Ho ions need to be pumped into the upper laser level (at room temperature), but it already reaches transparency at the 1940 nm pump wavelength with only 56% of the Ho ions in the upper laser level. In addition, the pump absorption cross section at 1940 nm is relatively low and strongly polarised.
[Show abstract][Hide abstract] ABSTRACT: Copyright: 2009 Academy of Science of South Africa South Africa’s first mobile LIDAR (LIght Detection And Ranging) system is being developed at the National Laser Centre (NLC) of the Council for Scientific and Industrial Research (CSIR) in Pretoria (25°45’S; 28°17’E). The system is designed primarily for remote sensing of the atmosphere. At present, the system is being optimised for measuring vertical atmospheric backscatter profiles of aerosols and clouds. In this paper, the authors describe the complete LIDAR system, including laser transmission, telescope configuration, data acquisition, data archival and post-processing.
South African Journal of Science 12/2009; · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a macroscopic laser rate-equation model based on measurable laser parameters, allowing easy system identification. A numerical simulation based on the model is used in the design and testing of electronic laser feedback systems for intensity noise suppression and Q -switched pulse stabilization. A novel pulse energy control scheme is also presented, including experimental results.
IEEE Journal of Quantum Electronics 11/2009; · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A Ho:YLF laser pumped HBr molecular laser was developed that produced up to 2.5 mJ of energy in the 4 micron wavelength region. The Ho:YLF laser was fiber pumped using a commercial Tm:fibre laser. The Ho:YLF laser was operated in a single longitudinal mode via injection seeding with a narrow band diode laser which in turn was locked to one of the HBr transitions. The behavior of the HBr laser was described using a rate equation mathematical model and this was solved numerically. Good agreement both qualitatively and quantitatively between the model and experimental results was obtained.
[Show abstract][Hide abstract] ABSTRACT: A mobile LIDAR (LIght Detection And Ranging) system is being developed and employed for atmosphere remote sensing at the Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25.45 S; 28.16 E), South Africa. In this paper, we describe the results obtained using the CSIR-NLC mobile LIDAR in a 23 hour field campaign at the University of Pretoria.
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present the obtained first scientific results from CSIR-NLC mobile LIDAR (LIght Detection And Ranging) and its validation/comparison with other ground and space-borne measurements. The LIDAR results are compared using aerosol measurements from the Stratosphere Aerosol Gas Experiment (SAGE) and Optical depth derived from sun-photometer employed under AErosol RObotic NETwork (AERONET).
Geoscience and Remote Sensing Symposium,2009 IEEE International,IGARSS 2009; 08/2009
[Show abstract][Hide abstract] ABSTRACT: Nd:GdVO<sub>4</sub> is a relatively new laser material with spectral properties very similar to those of Nd:YVO<sub>4</sub>. It was initially reported that it had almost twice the thermal conductivity of Nd:YVO<sub>4</sub>, and therefore was said to reduce negative thermal effects. In this paper a direct comparison of the thermal lens of the two materials with equal doping concentrations and dimensions was performed. The two materials were compared directly under diode-end-pumping by performing thermal lens measurements during lasing with a HeNe probe beam using identical low-doped (0.15%), 4 times 4 times1 8 mm<sup>3</sup> crystals. The setup was such that it be could separately analyse the dioptric powers in the sigma and pi polarisations.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009