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Jonathan Lawrence - One of the best experts on this subject based on the ideXlab platform.
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mathematical modelling of the Fibre Laser surface processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a ZrO2 engineering ceramic were studied using a computational finite element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the Fibre Laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5% with the surface and 18% within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed; power density; time; depth and the temperature during various stages of the Fibre Laser surface treatment of the ZrO2. By utilizing data obtained from a thermo, gravimetry- differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the ZrO2. The mapping revealed that the Fibre Laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the paper.
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mathematical modelling of the Fibre Laser surface processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a ZrO2 engineering ceramic were studied using a computational finite-element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the Fibre Laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the Fibre Laser surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the ZrO2. The mapping revealed that the Fibre Laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.
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distribution of temperature during Fibre Laser radiation and effects thereon phase transformation of zro2 engineering ceramic
Surface Engineering, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:Distribution of surface and the bulk temperature was recorded during Fibre Laser surface treatment of ZrO2 engineering ceramic. The experimental readings were then compared with a finite element model which showed the flow and distribution of the Laser induced heat as a result of the Fibre Laser surface treatment. Moreover, thermogravimetry–differential scanning calorimetry was used to collect data with respect to physical changes during heating and cooling of the ZrO2 engineering ceramic. The thermogravimetry–differential scanning calorimetry data and the finite element model predictions were then used to map the phase transitions within the ZrO2 engineering ceramic resulting from Fibre Laser surface treatment. The mapping revealed that the Fibre Laser surface treatment had generally resulted in a phase transformation of the ZrO2 engineering ceramic from the monoclinic (M) state to a mixture of tetragonal and cubic (T+C) followed by partially formed liquid (L) phase during Fibre Laser surface treatment a...
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evaluation of fracture toughness of zro2 and si3n4 engineering ceramics following co2 and Fibre Laser surface treatment
Optics and Lasers in Engineering, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The fracture toughness property (K1c) of Si3N4 and ZrO2 engineering ceramics was investigated by means of CO2 and a Fibre Laser surface treatment. Near surface modifications in the hardness was investigated by employing the Vickers indentation method. Crack lengths and geometry were then measured by using the optical. A co-ordinate measuring machine was used to investigate the diamond indentations and to measure the lengths of the cracks. Thereafter, computational and analytical methods were employed to determine the K1C. An increase in the K1C of both ceramics was found by the CO2 and the Fibre Laser surface treatment in comparison to the as-received surfaces. The K1C of the CO2 Laser radiated surface of the Si3N4 was over 3 % higher in comparison to that of the Fibre Laser treated surface. This was by softening of the near surface layer of the Si3N4 which comprised of lower in hardness, which in turn increased the crack resistance. The effects were not similar with the ZrO2 ceramic to that of the Si3N4 as the Fibre Laser radiation in this case had produced a rise of 34% compared to that of the CO2 Laser radiation. This occurred due to propagation of lower crack resulting from the Vickers indentation test during the Fibre Laser surface treatment which inherently affected the end K1C though an induced compressive stress layer. The K1C modification of the two ceramics treated by the CO2 and the Fibre Laser was also believed to be influenced by the different Laser wavelength and its absorption co-efficient, the beam delivery system as well as the differences in the brightness of the two Lasers used.
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Examination of temperature distribution and the thermal effects on Si3N4 engineering ceramics during Fibre Laser surface treatment
Optics and Lasers in Engineering, 2011Co-Authors: P P Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a Si3N4 engineering ceramic were studied using a computational finite element analysis (FEA). Temperature increases on the surface of the Si3N4 during Fibre Laser processing were measured using an infra-red thermometer; temperature distributions in the bulk were measured with specifically located thermocouples. A computational model by using FEA was then developed to model the flow and the distribution of the radiated heat resulting from the Fibre Laser treatment of the Si3N4 ceramic. By utilising data obtained from a TG-DSC analysis the FEA model predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the Si3N4. The TG-DSC analysis also indicated that the Fibre Laser surface treatment generally resulted in a phase transformation of the Si3N4 from α-phase to β-phase modification as elongated rod-like grains were found.
Stuart D. Jackson - One of the best experts on this subject based on the ideXlab platform.
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mode locked mid ir Fibre Laser based on 2d nanomaterials
Australian Conference on Optical Fibre Technology, 2019Co-Authors: Gayathri Bharathan, Stuart D. Jackson, Xiantao Jiang, Han Zhang, Feng Chen, Alexander FuerbachAbstract:We demonstrate the first stable mode-locking from an Er3+ doped fluoride Fibre Laser cavity using various novel two-dimensional saturable absorber materials such as PtSe2 and MXene operating near 2.8 μm wavelength to the best of our knowledge. The linear cavity includes a high reflective chirped Fibre Bragg grating to provide wavelength stability. The observed mode-locked pulse train has a 30 MHz repetition rate and an average power of 223 mW. Our results demonstrate the feasibility of using the novel two-dimensional nanomaterials such as PtSe2 and MXene into the Fibre Laser cavity for the application in mid-infrared wavelength regime.
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towards high power mid infrared emission from a Fibre Laser
Nature Photonics, 2012Co-Authors: Stuart D. JacksonAbstract:Fibre Lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared Fibre Laser technology, and discusses the future applications and challenges for the field.
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gain switched holmium doped Fibre Laser
Optics Express, 2009Co-Authors: D J Ottaway, David G Lancaster, J Munch, Shayne Bennetts, Stuart D. JacksonAbstract:We demonstrate the first gain-switched, singly doped, single-mode holmium-doped silicate glass Fibre Laser that operates at 2.106µm. Using a gain-switched 1.909-µm thulium-doped Fibre Laser as the pump source, output pulses of energy 3.2 µJ and pulse duration of 150 ns were generated at 80 kHz and slope efficiency of 44%. Pulse stacking within the holmium-doped Fibre Laser resulted in significantly shorter 70 ns pulses.
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85 w tm3 doped silica Fibre Laser
Electronics Letters, 2005Co-Authors: G P Frith, David G Lancaster, Stuart D. JacksonAbstract:An 85 W Tm/sup 3+/-doped silica Fibre Laser is presented. To the best of the authors' knowledge this is the highest output power achieved by pumping with 793 nm. The slope efficiency was 56%, the threshold 11 W and the output wavelength centred at 2.04 /spl mu/m. The high rate of cross relaxation in this Laser provided a quantum efficiency of >130%.
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high power broadly tunable ho3 doped silica Fibre Laser
Electronics Letters, 2004Co-Authors: Stuart D. Jackson, Yonghui LiAbstract:Tuning of the 2.1 μm Ho 3+ -doped silica Fibre Laser is demonstrated for the first time. The 5 I 7 → 5 I 8 transition provides tuning over 144 nm, from 2019 to 2163 nm, and a maximum pump-limited output power of 1.58 W at 2100 nm was produced.
Pratik Shukla - One of the best experts on this subject based on the ideXlab platform.
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mathematical modelling of the Fibre Laser surface processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a ZrO2 engineering ceramic were studied using a computational finite-element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the Fibre Laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the Fibre Laser surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the ZrO2. The mapping revealed that the Fibre Laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.
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mathematical modelling of the Fibre Laser surface processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a ZrO2 engineering ceramic were studied using a computational finite element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the Fibre Laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5% with the surface and 18% within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed; power density; time; depth and the temperature during various stages of the Fibre Laser surface treatment of the ZrO2. By utilizing data obtained from a thermo, gravimetry- differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the ZrO2. The mapping revealed that the Fibre Laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the paper.
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distribution of temperature during Fibre Laser radiation and effects thereon phase transformation of zro2 engineering ceramic
Surface Engineering, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:Distribution of surface and the bulk temperature was recorded during Fibre Laser surface treatment of ZrO2 engineering ceramic. The experimental readings were then compared with a finite element model which showed the flow and distribution of the Laser induced heat as a result of the Fibre Laser surface treatment. Moreover, thermogravimetry–differential scanning calorimetry was used to collect data with respect to physical changes during heating and cooling of the ZrO2 engineering ceramic. The thermogravimetry–differential scanning calorimetry data and the finite element model predictions were then used to map the phase transitions within the ZrO2 engineering ceramic resulting from Fibre Laser surface treatment. The mapping revealed that the Fibre Laser surface treatment had generally resulted in a phase transformation of the ZrO2 engineering ceramic from the monoclinic (M) state to a mixture of tetragonal and cubic (T+C) followed by partially formed liquid (L) phase during Fibre Laser surface treatment a...
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evaluation of fracture toughness of zro2 and si3n4 engineering ceramics following co2 and Fibre Laser surface treatment
Optics and Lasers in Engineering, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The fracture toughness property (K1c) of Si3N4 and ZrO2 engineering ceramics was investigated by means of CO2 and a Fibre Laser surface treatment. Near surface modifications in the hardness was investigated by employing the Vickers indentation method. Crack lengths and geometry were then measured by using the optical. A co-ordinate measuring machine was used to investigate the diamond indentations and to measure the lengths of the cracks. Thereafter, computational and analytical methods were employed to determine the K1C. An increase in the K1C of both ceramics was found by the CO2 and the Fibre Laser surface treatment in comparison to the as-received surfaces. The K1C of the CO2 Laser radiated surface of the Si3N4 was over 3 % higher in comparison to that of the Fibre Laser treated surface. This was by softening of the near surface layer of the Si3N4 which comprised of lower in hardness, which in turn increased the crack resistance. The effects were not similar with the ZrO2 ceramic to that of the Si3N4 as the Fibre Laser radiation in this case had produced a rise of 34% compared to that of the CO2 Laser radiation. This occurred due to propagation of lower crack resulting from the Vickers indentation test during the Fibre Laser surface treatment which inherently affected the end K1C though an induced compressive stress layer. The K1C modification of the two ceramics treated by the CO2 and the Fibre Laser was also believed to be influenced by the different Laser wavelength and its absorption co-efficient, the beam delivery system as well as the differences in the brightness of the two Lasers used.
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fracture toughness modification by using a Fibre Laser surface treatment of a silicon nitride engineering ceramic
Journal of Materials Science, 2010Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:Surface treatment of a silicon nitride (Si3N4) engineering ceramic with Fibre Laser radiation was conducted to identify changes in the fracture toughness as measured by K1c. A Vickers macro-hardness indentation method was adopted to determine the K1c of the Si3N4 before and after Fibre Laser surface treatment. Optical and a scanning electron microscopy (SEM), a co-ordinate measuring machine and a focus variation technique were used to observe and measure the dimensions of the Vickers indentation, the resulting crack lengths, as well as the crack geometry within the as-received and Fibre Laser-treated Si3N4. Thereafter, computational and analytical methods were employed to determine the K1c using various empirical equations. The equation K1c = 0.016 (E/Hv)1/2 (P/c3/2) produced most accurate results in generating K1c values within the range from 4 to 6 MPa m1/2. From this it was found that the indentation load, hardness, along with the resulting crack lengths in particular, were the most influential parameters within the K1c equation used. An increase in the near surface hardness of 4% was found with the Si3N4 in comparison with the as-received surface, which meant that the Fibre Laser-treated surface of the Si3N4 became harder and more brittle, indicating that the surface was more prone to cracking after the Fibre Laser treatment. Yet, the resulting crack lengths from the Vickers indentation tests were reduced by 37% for the Si3N4 which in turn led to increase in the K1c by 47% in comparison with the as-received surface. It is postulated that the Fibre Laser treatment induced a compressive stress layer by gaining an increase in the dislocation movement during elevated temperatures from the Fibre Laser surface processing. This inherently increased the compressive stress within the Si3N4 and minimized the crack propagation during the Vickers indentation test, which led to the Fibre Laser-radiated surface of the Si3N4 engineering ceramic to have more resistance to crack propagation.
W. Andrew Clarkson - One of the best experts on this subject based on the ideXlab platform.
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ultra short wavelength operation of a thulium Fibre Laser in the 1660 1750 nm wavelength band
Optics Express, 2015Co-Authors: J M O Daniel, Nikita Simakov, Masaki Tokurakawa, Michael Ibsen, W. Andrew ClarksonAbstract:Ultra-short wavelength operation of a thulium Fibre Laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable Fibre Laser source operating from 1660 nm to 1720 nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium Fibre Lasers in this band, fixed wavelength operation at 1726 nm with output power up 12.6 W and with slope efficiency > 60% is also shown.
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ho doped silica Fibre Laser in band pumped by a tm doped Fibre Laser
European Quantum Electronics Conference, 2009Co-Authors: A. Boyland, J K Sahu, W. Andrew ClarksonAbstract:Over the last few years there has been increasing interest in power-scaling of Fibre-based sources operating in the eyesafe two-micron wavelength regime driven by a range of applications. Much of this interest has focussed on Tm-doped silica Fibres which offer wide spectral coverage from ∼1.7 µm to ∼2.1 µm [1], a range of pump wavelengths and the potential to be scaled to very high powers [2]. By contrast, far less attention has been directed towards Ho-doped silica Fibres which also offer a very wide range of emission wavelengths extending well beyond 2.1 µm. However, scaling the output power from Ho-doped silica Fibres is hindered by the fact that there is no absorption band that coincides with the emission wavelengths available from high-power (near-infrared) commercially available diode pump sources. One solution to this problem is to add Tm to the core to act as a sensitiser. In this way pump light from high-power Laser diodes at ∼0.8 µm is absorbed by the Tm ions and the Ho ions in-directly excited by energy-transfer from the Tm ions. Using this approach, Jackson et al. recently reported 83 W of output from a cladding-pumped Tm, Ho co-doped Fibre Laser [2]. Co-doping with Tm however leads to very strong energy-transfer-upconversion and hence a reduction in the effective upper-state lifetime. The net result is additional heat loading leading, lower efficiency and limited flexibility in mode of operation. An alternative approach is to use a high-power cladding-pumped Tm Fibre Laser to pump a Ho-doped Fibre Laser avoiding the need for co-doping with Tm [4]. This has the attraction a very low quantum defect pumping scheme can be employed in the Ho Fibre Laser allowing very high lasing efficiencies to be achieved and offering the potential to be scaled to very high power levels. In this paper, we report preliminary results for a Ho silica Fibre Laser operating at 2090 nm in-band pumped by a cladding-pumped Tm doped Fibre Laser at 1980 nm.
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highly efficient ho ylf and ho yag Lasers pumped by tm doped silica Fibre Laser
2004Co-Authors: Deyuan Shen, L.j. Cooper, W. Andrew ClarksonAbstract:Efficient operation Ho:YLF and Ho:YAG Lasers end-pumped by a tunable cladding-pumped Tm-doped silica Fibre Laser is reported. Output powers of 4.8W at 2066nm and 6.4W at 2097nm were obtained from the Ho:YLF and Ho:YAG Lasers for < 9.6W of incident pump at 1940nm and 1905nm respectively.
P P Shukla - One of the best experts on this subject based on the ideXlab platform.
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Examination of temperature distribution and the thermal effects on Si3N4 engineering ceramics during Fibre Laser surface treatment
Optics and Lasers in Engineering, 2011Co-Authors: P P Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment on a Si3N4 engineering ceramic were studied using a computational finite element analysis (FEA). Temperature increases on the surface of the Si3N4 during Fibre Laser processing were measured using an infra-red thermometer; temperature distributions in the bulk were measured with specifically located thermocouples. A computational model by using FEA was then developed to model the flow and the distribution of the radiated heat resulting from the Fibre Laser treatment of the Si3N4 ceramic. By utilising data obtained from a TG-DSC analysis the FEA model predictions of the temperature distribution were used to map phase transformations and significant events occurring during the Fibre Laser surface treatment of the Si3N4. The TG-DSC analysis also indicated that the Fibre Laser surface treatment generally resulted in a phase transformation of the Si3N4 from α-phase to β-phase modification as elongated rod-like grains were found.
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Analysis of temperature distribution during Fibre Laser surface treatment of a zirconia engineering ceramic
Proceedings of the 36th International MATADOR Conference, 2010Co-Authors: P P Shukla, Jonathan LawrenceAbstract:The thermal effects of Fibre Laser surface treatment of a ZrO2 engineering ceramic were studied using finite element analysis (FEA). Temperature increases on the surface and in the bulk of the ZrO2 during Fibre Laser processing were measured. FEA was then used to model the flow and distribution of the radiated heat resulting from the Fibre Laser surface treatment. Data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC) analysis and the FEA model predictions was used to map the phase transformations in the ZrO2 resulting from Fibre Laser surface treatment. The mapping revealed that the Fibre Laser surface treatment generally resulted in a phase transformation of the ZrO2 from the M state to a mixture of T+C during Fibre Laser irradiation and from T+C to T followed by the M state during solidification.
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Fracture toughness of a zirconia engineering ceramic and the effects thereon of surface processing with Fibre Laser radiation
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2010Co-Authors: H. Wu, P P Shukla, Jonathan LawrenceAbstract:Vickers hardness indentation tests were employed to investigate the near-surface changes in the hardness of a Fibre Laser-treated and an as-received ZrO2 engineering ceramic. Indents were created using 5, 20, and 30 kg loads to obtain the hardness. Optical microscopy, white-light interferometry, and a coordinate measuring machine were then used to observe the crack lengths and crack geometry. Palmqvist and half-penny median crack profiles were found, which dictated the selection of the group of equations used herein. Computational and analytical approaches were then adapted to determine the K1c of ZrO2. It was found that the best applicable equation was: K1c = 0.016 (E/H)1/2 (P/c3/2), which was confirmed to be 42 per cent accurate in producing K1c values within the range of 8 to 12 MPa m1/2 for ZrO2. Fibre Laser surface treatment reduced the surface hardness and produced smaller crack lengths in comparison with the as-received surface. The surface crack lengths, hardness, and indentation loads were found to be important, particularly the crack length, which significantly influenced the end K1c value when K1c = 0.016 (E/H)1/2 (P/c3/2) was used. This is because, the longer the crack lengths, the lower the ceramic's resistance to indentation. This, in turn, increased the end K1c value. Also, the hardness influences the K1c, and a softer surface was produced by the Fibre Laser treatment; this resulted in higher resistance to crack propagation and enhanced the ceramic's K1c. Increasing the indentation load also varied the end K1c value, as higher indentation loads resulted in a bigger diamond footprint, and the ceramic exhibited longer crack lengths.