Femtosecond pulsed laser deposition of amorphous gallium lanthanum oxysulphide films

We 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

Deposition and stoichiometry control of Nd-doped gadolinium gallium garnet thin films by combinatorial pulsed laser deposition using two targets of Nd:Gd₃Ga₅O₁₂ and Ga₂O₃

We 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

Garnet crystal growth by femtosecond pulsed laser deposition

We 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

Pulsed laser deposition of thick multilayer garnet films for cladding-pumped planar waveguide laser devices

We 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

The 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

Ar+ beam etched Ti:sapphire rib waveguides: a route for the development of broadband fluorescence and channel laser sources

Ar-beam-milled rib waveguides were fabricated in pulsed-laser-deposited Ti:sapphire films and overgrown by a 5µm thick sapphire layer to reduce losses. They show broadband single transverse-mode fluorescence emission and potential for development of laser sources

2 - Emerging pulsed laser deposition techniques

The use of lasers for the deposition and processing of electronic and photonic materials is becoming increasingly widespread and advances in processing technology are reducing costs and increasing throughput. Laser deposition of photonic materials and laser processing techniques can produce high quality devices with novel properties. Part one covers laser deposition and growth of materials, including pulsed laser deposition and laser-induced self-assembly of semiconductors. Part two describes laser patterning and lithography techniques, such as 3D laser lithography. Part three looks at laser treatments to manipulate properties of photonic materials for applications such as optical storage, laser components, waveguides and displays

Current state-of-the-art of pulsed laser deposition of optical waveguide structures: existing capabilities and future trends

Pulsed laser deposition (PLD) has now reached a stage of maturity where the growth of thin films is routine. All that is required is a pulsed ultra-violet (UV) wavelength laser, a vacuum chamber, a target, and a substrate placed in near proximity to the plasma plume. Whether the film that you grow is the film that you need, and whether the thickness, uniformity, optical quality, stoichiometry, degree of crystallinity, orientation and much more is what is desired is another question entirely. PLD is both a science and an art and there are many tricks-of-the-trade that need to be considered to ensure that materials grown are the materials wanted. This paper discusses the practicalities of PLD systems, target geometries, heating regimes for successful epitaxial growth of crystalline films, the problem of particulates, laser sources to use, and in the context of our most recent PLD system, the number of independent lasers and targets used. We show that the use of multiple targets permits a combinatorial approach, whereby stoichiometry can be adjusted to grow designer materials, and in particular multilayer systems, ideally suited for active optical waveguides, a truly demanding end application where optical quality and in-plane losses must be reduced to an absolute minimum