1,720,976 research outputs found
Pulsed laser deposition of thick multilayer garnet crystal films for waveguide laser devices
No full textThe main aim of this project was to use the technique of pulsed laser deposition (PLD) to fabricate thick multilayered garnet crystal planar waveguides with rare-earth ion doped cores for use as planar waveguide laser devices. Planar waveguides are of interest because of the implications of their structure, which allows for lasing, pumping and heat dissipation to each have a unique axis of operation, and the confinement properties of planar waveguide lasers result in lower pump power thresholds, higher gains per unit pump power and higher efficiencies than their bulk counterparts. Thick planar waveguide lasers are desirable because they can be pumped by high power diode laser arrays, and suffer less from the detrimental effect of particulates (a practically unavoidable side effect of the PLD technique). The use of multilayers allows a device with a high numerical aperture to be fabricated and the careful choice of the cladding layer thicknesses and refractive indices allows good beam quality output to be produced using diode pumping. Other aims of the project were to fabricate a self-imaging waveguide amplifier and explore other applications of thick garnet crystal films such as the possibility of using a highly doped thick film as a thin-disk laser device. Now that the technique of thick garnet crystal film deposition via multiple growth runs has been established, the potential of thick garnet crystal films needs to be exploited. Multilayer structures with more ideal geometries need to be fabricated to make optimal waveguide laser devices and difficulties resulting from thermal expansion mismatch need to be addressed so that side-pumping can be performed with diode laser arrays
Pulsed laser deposited epitaxial garnet films for efficient low threshold waveguide lasers
No full textPulsed laser deposition is a mature technique capable of producing extremely high quality epitaxial single crystalline films. We have grown doped garnet films (Gd, and the resulting structures yield excellent waveguide lasing
Hybrid garnet crystal growth for thin-disc lasing applications by multi-beam pulsed laser deposition
No full textComposite crystals are of great interest for side-pumped thin-disc laser applications. We present a novel technique for fabricating hybrid films for such applications based upon multi-beam, multi-target Pulsed Laser Deposition (PLD). A two-garnet example was grown as proof of concept, representing the first known demonstration of controlled, continuous horizontal grading in a PLD-grown crystal. The results of shadow masking experiments and the suitability of such a method for growth of the desired structures are also discussed
On the growth and lasing characteristics of thick Nd:GGG waveguiding films fabricated by pulsed laser deposition
No full textPulsed laser deposition of epitaxial, single-crystal Nd:Gd3Ga5O12 (Nd:GGG) films on Y3Al5O12 substrates with thicknesses up to 135 µm and propagation losses as low as 0.1 dB/cm is reported. Rutherford backscattering spectrometry has shown constant stoichiometry for the films throughout their depth. Fluorescence properties were similar to that of the bulk Nd:GGG crystal used as a target material for the deposition and lasing action has been observed at 1059.0 and 1060.6 nm after pumping by a Ti:sapphire laser operating at 808 nm. A laser threshold of 18 mW has been obtained and a slope efficiency of 17.5% has been observed using an output coupler of 4.5%. The low losses in combination with the high numerical aperture (0.75) and the thickness of the structures make them suitable for high-power diode pumping
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 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
The effect of relative plasma plume delay on the properties of complex oxide films grown by multi-laser multi-target combinatorial pulsed laser deposition
Full text linkWe report the effects of relative time delay of plasma plumes on thin garnet crystal films fabricated by dual-beam, combinatorial pulsed laser deposition. Relative plume delay was found to affect both the lattice constant and elemental composition of mixed Gd3Ga5O12 (GGG) and Gd3Sc2Ga5O12 (GSGG) films. Further analysis of the plasmas was undertaken using a Langmuir probe, which revealed that for relative plume delays shorter than ~200 µs, the second plume travels through a partial vacuum created by the first plume, leading to higher energy ion bombardment of the growing film. The resulting in-plane stresses are consistent with the transition to a higher value of lattice constant normal to the film plane that was observed around this delay value. At delays shorter than ~10 µs, plume propagation was found to overlap, leading to scattering of lighter ions from the plume and a change in stoichiometry of the resultant films
Single transverse-mode laser operation of Ti:sapphire rib waveguides
No full textTi:sapphire is an attractive laser medium for the development of miniature lasers with widely tunable output (650-1100 nm). However, due to its low peak emission cross section and short fluorescence lifetime, high pump power densities are required to achieve efficient CW lasing. A route to address this problem is to adopt channel waveguide geometries, which are characterized by lower laser thresholds than their planar waveguide counterparts due to the additional lateral confinement and excellent overlap between the laser and pump modes provided that their fabrication process does not introduce any additional loss. Having already demonstrated laser action from pulsed-laser-deposited (PLD) Ti:sapphire planar waveguides, we report here on the single mode laser operation of Ti:sapphire rib waveguides. They were fabricated in PLD-grown films, using photolithography and ion beam etching and were then coated by a 5µm thick sapphire capping layer to reduce scattering losses
Single-transverse-mode broadband luminescence source based on a PLS grown Ti:sapphire waveguide in rib geometry
No full textRib waveguides have been fabricated in pulsed-laser-deposited Ti:sapphire layers using photolithographic patterning and subsequent Ar-beam milling. Fluorescence output powers up to 0.3 mW have been observed from the ribs following excitation by a 3W multiline argon laser.Mode intensity profiles show high optical confinement and the measured beam propagation factors and of 1.12 and 1.16 respectively, indicate single transverse mode fluorescence emission. Loss measurements using the self-pumped phase conjugation technique have yielded comparable values (1.7dB/cm) for the ribs and the unstructured planar waveguide counterparts.The combination of optimum modal properties and strong optical confinement, together with sufficient levels of fluorescence output, make the single-moded Ti:sapphire rib waveguides a very interesting candidate as a fluorescence source for optical coherence tomography applications
Large mode area multi-trench fiber with delocalization of higher order modes
No full textMulti-trench fiber (MTF) is a novel large mode area fiber design for high power fiber laser applications. This fiber design allows very high suppression of the higher order modes by offering high losses and delocalizing them out of the core. MTFs allow the core refractive index to be higher than the surrounding cladding as compared to other structures such as photonic crystal fibers, photonic bandgap fibers, and Bragg fibers. This feature of MTFs dramatically reduces the complexity associated with doped fiber fabrication. The MTF design is an all-solid structure with cylindrical symmetry, which provides easy cleaving and splicing with other fibers. In this paper, we present the first experimental demonstration of the MTF. S2 measurements indicate single mode operation with very high suppression of the higher order modes
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