1,721,010 research outputs found
Planar waveguide laser optimization and characterization employing real-time beam quality measurement
No full textWe present a methodology for optimizing the output radiance and characterizing a planar waveguide laser utilizing a technique offering "real time" beam quality measurement. This approach is applicable to lasers in general employing the simultaneous measurement and comparison of a re-imaged cavity-mode beam-waist (near-field) and the power distribution in the far-field (specifically in the Fourier plane of a lens). This approach provides the laser’s beam parameter product, and hence M2 beam propagation factor. Exploiting this technique we optimized the performance of a quasi-four-level Nd:YAG planar waveguide laser with an extended stable-cavity configuration, whilst characterizing the in-plane thermal lens. This laser produced a record radiance level of >9 TW/m2/sr for this 946 nm transition, with an effective thermal lens focal length >400 mm at all incident pump powers up to the maximum level of 87 W
Simulation of solid-state lasers with temperature and wavelength dependent absorption and emission
No full textSimulation of diode-pumped solid-state lasers (DPSSL) and amplifiers often do not account for the temperature and spectral dependencies of the absorption and emission cross sections of the gain medium. Typically, to track the pump absorption within the crystal, an average absorption coefficient is applied via a raytracing technique. The outcome, therefore, is an approximation of the pump absorption profile that is independent of the temperature profile within the gain medium. Here an iterative algorithm involving raytracing and Finite Element Analysis (FEA) is demonstrated in the simulation of neodymium(Nd) and ytterbium(Yb) doped yttrium aluminium garnet(YAG) single crystal fiber (SCF) gain media. The algorithm calculates the local temperature, associated absorption coefficient and hence temperature-dependent pump absorption. This allows for a more accurate determination of the distributions of the calculated population inversion and temperature in the crystal. The temperature dependence of the emission spectra can then be taken into account as well, which defines the achievable gain of the amplifying media. The resulting calculations’ influence on the simulated output beam quality and gain for these active media is presented.</p
Multi-watt high efficiency diffraction limited Nd: YAG planar waveguide laser
No full textAn efficient, longitudinally diode-pumped, diffraction-limited, Nd:YAG double-clad planar waveguide laser was operated on four transitions of the Nd3+ ion. Optimised output powers of 4.3W, 3.5W, and 2.7W, were obtained for absorbed pump powers of ~7W, for the transitions at the lasing wavelengths of 1.064µm, 946nm, and 1.3µm, respectively. Operation of the weak 4F3/2 to 4I15/2 transition, lasing at 1.833µm, was demonstrated at an absorbed pump power threshold of 300mW and an output power of 400mW, with a non-optimised output coupling. Diffraction-limited performance was obtained in both the guided and non-guided axes
Temperature-dependent analytical thermal model for end-pumped solid-state lasers
No full textAnalytical expressions for the temperature distribution and thermal-lens power in end-pumped solid-state lasers are reported. Enabled by including a temperature-dependent thermal conductivity, applicable from cryogenic to elevated temperatures, these provide insightful understandings for practical systems
Direct bonding diamond to zinc selenide
Full text linkWe report direct bonding of 5mm dia x 500μm thick polycrystalline CVD-grown diamond to 25mm dia x 4mm ZnSe via a plasma-assisted technique. In addition, diamond to C-cut sapphire bonding is demonstrated via the same approach. Durability of the diamond/ZnSe bond is tested over a temperature range -40 to 150 ºC and under various ramp rates, demonstrating strong adhesion over the majority of the bond up to a temperature of 80 ºC. Optical transmission at a wavelength of 1μm shows near ideal transmission when compared to bare ZnSe. Heatspreading performance of the bonded composite is investigated using a pump-probe arrangement, demonstrating at least two-orders of magnitude reduction in the thermal-lens power compared to ZnSe alone
Direct bonding Nd:YAG to sapphire wafers
No full textWe demonstrate chemical-assisted direct bonding of 450μm-thick neodymium-doped YAG to 660μm-thick sapphire wafers. Diced, polished and AR-coated the composite was trialed in a pump-guided free-space laser. Preliminary performance and future prospects will be discussed
Yellow light generation by frequency doubling of a fiber oscillator
No full textLaser sources with light-emission in the yellow spectral range around 577nm are very favorable for a variety of applications. These include applications in astronomy, in ophthalmology or in quantum optics. The generation and amplification of 1154 nm light is not straight forward when using Yb-doped optical fibers, since lasing occurs preferentially around the gain-maximum of 1030 nm. We generate the radiation within a fiber Bragg grating (FBG) based cavity and focused on reducing the amplified spontaneous emission (ASE). After the cavity, the output is frequency doubled to 577nm by using a second harmonic crystal
Laser operation of a Tm:Y<sub>2</sub>O<sub>3</sub> planar waveguide
No full textWe demonstrate the first Tm-doped yttria planar waveguide laser to our knowledge, grown by pulsed laser deposition. A maximum output power of 35 mW at 1.95 µm with 9% slope efficiency was achieved from a 12 µm-thick film grown on a Y3Al5O12 substrate
Characterisation and laser performance of a Yb:LuAG double-clad planar waveguide grown by pulsed laser deposition
No full textWe report on the fabrication of a crystalline multi-layer lutetium aluminium garnet planar waveguide, with a ytterbium-doped core, via hetero-epitaxial pulsed laser deposition on an undoped yttrium aluminium garnet substrate. Physical and optical characterization of the device revealed good crystallinity of the grown films and mode propagation investigations confirmed waveguiding properties. The measured fluorescence lifetime and calculated absorption and stimulated emission cross section spectra are found to be comparable with those reported for Yb:LuAG crystals grown by traditional methods. When end-pumped by a diode-laser bar, the crystalline double-clad Yb:LuAG planar waveguide lased using a quasi-monolithic cavity configuration. An output power of > 3 W with a 20% slope efficiency was obtained, limited by a waveguide propagation loss of 1.2 dB cm−1. This first demonstration of a multi-layer LuAG double-clad planar waveguide laser shows great potential for realising compact high-power waveguide lasers and amplifiers.</p
Measuring the elevated temperature dependence of up-conversion in Nd:YAG
No full textWe present the measurement of the energy transfer upconversion coefficient temperature-dependence from the main upper laser level (4F3/2) of 1at.% doped Nd:YAG. This is achieved by a very simple method employing the z-scan technique, through monitoring the transmitted power of a probe laser tuned to the main absorption peak at 808 nm. In addition, to fully develop a simple model to support the measurements, we have accurately measured the temperature dependent absorption coefficient for this absorption band, covering the range from 300-450K. The spatially dependent two-level rate equation model is described, which simulates the relationship between the incident pump irradiance and power transmitted by the crystal, in function of its temperature. By comparing the experimental results with the model, we obtain a value for the energy transfer upconversion coefficient of 5.1±0.4 ×10-17 cm3/s, at room temperature, decreasing to 2.0 ×10-17 cm3/s at 450 K
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