1,720,969 research outputs found
Deposition and stoichiometry control of Nd-doped gadolinium gallium garnet thin films by combinatorial pulsed laser deposition using two targets of Nd:Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub> and Ga<sub>2</sub>O<sub>3</sub>
No full textWe have demonstrated pulsed laser deposition of Nd-doped gadolinium gallium garnet on Y. Such an approach is of interest as a method of achieving stoichiometry control over films whilst the growth parameters are kept constant and optimal for high quality crystal growth. We show here how the stoichiometry and resultant lattice parameter of a film can be controlled by changing the relative deposition rates from the two targets. Films have been grown with enough extra Ga to compensate for the deficiency that commonly occurs when depositing only from a GGG target. We have also grown crystalline GGG films with an enriched Ga concentration, and this unconventional approach to film stoichiometry control may have potential applications in the fabrication of films with advanced compositionally graded structures
Femtosecond pulsed laser deposition of amorphous gallium lanthanum oxysulphide films
No full textWe report femtosecond and nanosecond pulsed laser deposition (PLD) of gallium lanthanum oxysulphide (GLSO) films. Energy-dispersive X-ray analysis reveals that the atomic percentages of gallium, lanthanum and sulphur are well outside the conventional range for glass formation
Design and performance of a ZnSe tetra-prism for homogeneous substrate heating using a CO<sub>2</sub> laser for pulsed laser deposition experiments
No full textWe report on the design and performance of a ZnSe tetra-prism for homogeneous substrate heating using a continuous wave CO2 laser beam in pulsed laser deposition experiments. We discuss here three potential designs for homogenizing prisms and use ray-tracing modeling to compare their operation to an alternative square-tapered beam-pipe design. A square-pyramidal tetra-prism design was found to be optimal and was subjected to modeling and experimental testing to determine the influence of interference and diffraction effects on the homogeneity of the resultant intensity profile produced at the substrate surface. A heat diffusion model has been used to compare the temperature distributions produced when using various different source intensity profiles. The modeling work has revealed the importance of substrate thickness as a thermal diffuser in producing a resultant homogeneous substrate temperature distribution
Garnet crystal growth by femtosecond pulsed laser deposition
No full textWe have demonstrated heteroepitaxial growth of Nd:Gd (YAG) by femtosecond pulsed laser deposition (PLD). A Ti:sapphire laser was used at a wavelength of 800 nm and pulse length of 130 fs, operating at a repetition rate of 1 kHz. X-ray diffraction analysis shows that epitaxial growth has occurred (figure 1). The effects of various growth conditions have been investigated including fluence, spot-size, target-substrate distance and substrate temperature. The effect of these conditions on crystallinity and optimum conditions will be discussed. An investigation of the plume characteristics using the Langmuir probe technique has revealed that plasmas produced by femtosecond ablation have ions with considerably higher velocities, ~ seven times faster than for nanosecond PLD of the same target material. In our study of growth parameters, we have found that higher ambient gas pressures are required to moderate the ion velocities in the femtosecond-ablated plume to achieve velocities more closely related to the optimum nanosecond conditions. Atomic force microscopy reveals that even at the optimum conditions films suffer from comparatively high surface roughness, with RMS roughness values of 60-70 nm. This level of roughness for films grown by femtosecond PLD could be explained by the presence of highly energetic species formed during femtosecond ablation, which generate defects and thus disturb the smooth growth of crystallites that takes place under the comparatively more controlled nanosecond regime. In this talk, we will discuss the effect on thin film growth of all parameters varied, and conclude that the window for optimum growth is far narrower than for nanosecond growth
A low-loss PLD fabricated garnet planar waveguide laser
No full textPlanar waveguide lasers have attracted increased attention in the recent years, particularly with a view to developing high average power diode-pumped solid state lasers. For diode-pumped schemes, the planar waveguide design can address requirements for optimal laser performance such as efficient coupling of the diode bar pump light into the guide due to both the excellent geometric match of the pump beam to the profile of waveguide facet as well as the possibility to confine non-diffraction limited beams by designing high numerical aperture structures, control of the spatial output of the waveguide by introducing design schemes such as double-cladding, large-mode-area waveguides, multimode interference as well as tapers and unstable resonators. The planar geometry is also ideal for efficient thermal handling and therefore, circumvention of problems such as thermal lensing, birefringence and fracture and in combination with a suitable fabrication technique, such structures can show with low propagation losses
Pulsed laser deposition of thick multilayer garnet films for cladding-pumped planar waveguide laser devices
No full textWe report progress in the pulsed laser deposition of thick multilayer Nd-doped garnet films to be used as high-numerical-aperture cladding-pumped planar waveguide laser devices
A comparative study of gadolinium gallium garnet growth by femtosecond and nanosecond pulsed laser deposition
No full textThe growth of epitaxial Nd:Gd (YAG) by femtosecond pulsed laser deposition is reported. We have used a Ti:sapphire laser at a wavelength of 800 nm and pulse length of 130 fs, operating at a repetition rate of 1 kHz. The film properties have been studied systematically as a function of the deposition parameters of laser fluence, spot-size, oxygen pressure, target-substrate distance and temperature. Scanning electron microscopy, atomic force microscopy and X-ray diffractometry were used to characterise the surface structure and crystallinity of the films. X-ray diffraction analysis shows that epitaxial growth has occurred. A comparison between the ion velocities produced by nanosecond and femtosecond laser ablation of the GGG target material has been investigated by the Langmuir probe technique. The results indicate a large difference in the plasma characteristics between femtosecond and nanosecond ablation, with ion velocities up to eight times faster observed in the femtosecond case
Current state of the art of pulsed laser deposition: existing capabilities and future trends
No full textPulsed laser deposition (PLD) growth of high quality low-loss optical waveguide films of ternary and quaternary doped garnets
No full textMulti-beam pulsed laser deposition for advanced thin-film optical waveguides
No full textWe discuss our progress in the use of multiple laser beams and multiple targets for the pulsed laser deposition of thin films for waveguide laser and magneto-optic applications. In contrast to the more widely used single-beam/single-target geometries, having more than one laser-produced plume can allow tuning of the material properties and complex engineering of the deposited thin films. For optical applications - the majority of the work reported here - dopants can be selectively introduced, lattice mismatch and residual strain can be compensated, which is an important factor for successful growth of thin films of ~ tens of microns thickness, and refractive index values can be adjusted for fabrication of sophisticated waveguiding structures. We discuss mixed, layered, superlattice and Bragg reflector growth, which involve out-of-plane engineering of the film structure, and in-plane engineered geometries for designs relevant to thin-film disc lasing devices. Finally we briefly discuss our most recent use of multi-plume growth for magneto-optic thin films, which involves compositional tuning of final magnetic properties
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