1,720,971 research outputs found
Supercontinuum and frequency comb generation in tantalum pentoxide waveguides
No full textIn this thesis, the design, simulation, fabrication, and characterisation of tantalum pentoxide (Ta2O5) waveguides and micro-resonators on silicon substrates is presented as a potential technology for the generation of supercontinuum and Kerr frequency combs. Vertical external-cavity surface-emitting lasers and membrane external-cavity surface emitting lasers that operate on two frequencies simultaneously are shown for the purposes of either acting as pump sources for the waveguide systems or as sources for generating THz radiation through the beat between the two frequencies. The fabrication process of the Ta2O5 waveguides is discussed in detail, including the relevant fabrication parameters. The Ta2O5 layer is deposited using radio-frequency (RF) sputtering onto a 4 ” diameter silicon wafer, with a 5 µm thick layer of thermal silica on the top surface, using a Ta2O5 powder target. The waveguide and micro-ring structures are realised using photolithography and ion beam milling, and the samples are cladded with a layer of silica using either RF sputtering or plasma-enhanced chemical vapour deposition with a liquid precursor. Linear waveguides in Ta2O5 are presented for the purpose of generating supercontinuum; Experimental outputs from linear Ta2O5 waveguides for a range of pump wavelengths from 900 to 1500 nm are reported with hundreds of nm of spectral broadening being seen for each pump wavelength. The expected spectral broadening emission of the waveguides is shown, which is calculated using a generalised nonlinear Schrodinger equation (GNSLE) solver that is capable of solving for multiple modes. The GNLSE solver is used to estimate which mode is propagating through the waveguide. The propagation losses of linear waveguides, including an investigation into the impact of waveguide width and cladding deposition technique, are presented, with the lowest propagation loss reported to be on the order of 2.5 dB/cm. The dispersion engineering for new Ta2O5 linear waveguide samples is shown with a focus on the waveguide geometry, leading to the finalisation of a waveguide design that corresponds to the optimised dispersion relation for nonlinear broadening. Micro-ring and racetrack resonators are presented for the purpose of generating Kerr frequency combs. The dispersion relations for micro-resonators are calculated and compared to that of linear waveguides, this followed by an investigation into the critical coupling lengths of micro-ring resonators. Racetrack resonator systems are presented as a suitable alternative to micro-ring resonators due to the fact that the critical coupling lengths are larger than the micro-ring geometries. A Lugiato-Lefever equation solver, based on the GNSLE solver, is described and confirmed against the literature, and is used to simulate the expected frequency comb emission from the Ta2O5 micro-resonators. A brief investigation into the effect of propagation loss on the comb generation is presented using the LLE solver. Experimental Q-factor measurements are presented for Ta2O5 micro-ring and racetrack resonators with the highest Q-factor being 1.91×10^5. Frequency comb generation was not observed, this is expected to be due to the propagation losses being too high. Finally, vertical external-cavity surface-emitting lasers and membrane external-cavity surface-emitting lasers operating simultaneously on two distinct spatial modes, and therefore two distinct frequencies, are reported. The laser systems are forced to operate on two modes simultaneously through the inclusion of laser ablated masks on an intracavity high reflectivity mirror that introduces spatially dependent losses on the cavity modes in order to suppress the lasing threshold of the fundamental Hermite Gaussian, HG00, mode and allow the higher order, HG11, mode to operate. Simulated mode losses are calculated, and the lasers are characterised for a range of spatially dependent loss values and pump powers. The spectral emissions of the lasers are shown, with wavelength separations on the order of 5 nm, which corresponds to a beat frequency of 1.41 THz. These laser technologies also represent an exciting potential pump laser system for the micro-resonators with the aim of generating a Kerr frequency comb
Dataset supporting the University of Southampton Doctoral Thesis "Supercontinuum and frequency comb generation in tantalum pentoxide waveguides"
No full textDataset supporting the University of Southampton Doctoral Thesis "Supercontinuum and frequency comb generation in tantalum pentoxide waveguides" by Jake Daykin.
Dataset includes data and scripts required for reproducing the majority of figures present in the thesis. The dataset does not include versions of simulation code such as the GNLSE or LLE models.</span
High power 739 nm VECSELs for future Yb<sup>+</sup> ion cooling
No full textWe present an operational characterization of a vertical-external-cavity surface-emitting laser emitting around 739 nm with over 150 mW in a single fundamental spatial mode. Results show that the laser is capable of oscillating on a single cavity axial mode at 740 nm for up to 22 mW. Tuning of the optical emission is shown to reach 737.3 nm. Furthermore, at best performance, the laser exhibits a slope efficiency of 8.3% and a threshold power of 1.27 W for an output coupler reflectivity of 98%.</p
Dataset for "Membrane Quantum Well Lasers and Tantalum Pentoxide Optical Waveguides"
No full textThis dataset includes data presented in Stephen Richardson's PhD project titled "Membrane Quantum Well Lasers and Tantalum Pentoxide Optical Waveguides".</span
Dataset for "Supercontinuum generation in tantalum pentoxide waveguides for pump wavelengths in the 900 nm to 1500 nm spectral region"
No full textData supports article "Supercontinuum generation in tantalum pentoxide waveguides for pump wavelengths in the 900 nm to 1500 nm spectral region" by Jonathan R. C. Woods, Jake Daykin, Amy S. K. Tong, Cosimo Lacava, Periklis Petropoulos, Anne C. Tropper, Peter Horak, James S. Wilkinson, and Vasilis Apostolopoulos in Optics Express, OSA, 10.1364/OE.403089. Includes data and instructions for the recreation of figures included in the above publication.</span
Dataset for "High power 739 nm VECSELs for future Yb+ ion cooling"
No full textThis is the dataset for "High power 739 nm VECSELs for future Yb+ ion cooling", authored by Jonathan Woods, Hermann Kahle, Alan Gray, Jake Daykin, Anne Tropper, Corin Gawith, Mircea Guina, and Vasilis Apostolopoulos in Applied Optics, DOI: 10.1364/AO.409970
Dataset contains raw data and instructions of recreating figures in the publication. The figures and process in required detail for recreation are described in the readme file.
The figures are as follows:
Fig. 2 Optical spectra
Fig. 3 Efficiency curves
Fig. 4 Spatial mode profile and fitting
Fig. 5 RF spectra</span
Dataset supporting the publication "Bi-frequency operation in a membrane external-cavity surface-emitting laser"
No full textThis dataset supporting the article "Bi-frequency operation in a membrane external-cavity surface-emitting laser", by J Daykin, J Woods, R Bek, M Jetter, P Michler, B Mills, P Horak, J Wilkinson and V Apostolopoulos. PLOS One
The dataset contains the raw data and MATLAB scripts required for recreating figures in the publication. The figures are as follows:
Figures 3B - Simulated mode losses for a range of mask widths
Figure 4 - MECSEL output power and spectrum while off-mask
Figure 5 - Spectral emission from MECSEL while operating on each of the spatial loss masks and while on an unablated area. Requires the running of individual .m files from subfolders
Figure 6 - Calculated etalon transmission plotted with spectral emission from MECSEL while centred on the 10µm mask
Figure 7C - Spectral profile from MECSEL while operating on the 50µm mask at a pump power of 3.96W
Figure 8 - RF spectral data for MECSEL operating on mask with detector both blocked and unblocked, as well as the residual of the two plots.
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Bi-frequency operation in a membrane external-cavity surface-emitting laser
No full textWe report on the achievement of continuous wave bi-frequency operation in a membrane external-cavity surface-emitting laser (MECSEL), which is optically pumped with up to 4 W of 808 nm pump light. The presence of spatially specific loss of the intra-cavity high reflectivity mirror allows loss to be controlled on certain transverse cavity modes. The regions of spatially specific loss are defined through the removal of Bragg layers from the surface of the cavity high reflectivity mirror in the form of crosshair patterns with undamaged central regions, which are created using a laser ablation system incorporating a digital micromirror device (DMD). By aligning the laser cavity mode with the geometric centre of the loss patterns, the laser simultaneously operated on two Hermite-Gaussian spatial modes: the fundamental HG00 and the higher order HG11 mode. We demonstrate bi-frequency operation over a range of pump powers and sizes of spatial loss features, with a wavelength separation of approximately 5 nm centred at 1005 nm
Membrane quantum well waveguide lasers
No full textWe study coherent laser arrays operating in epitaxially grown semiconductor membrane quantum wells. The samples are deposited by transfer on substrates of oxidized silicon and we record the real and reciprocal space of the laser emission. The Laser arrays are in a lateral emission geometry and are waveguides lasers where the end mirrors are the end-facets of the cleaved membranes which usually form cavities in the order of 100 microns. We are able to create waveguide laser arrays with modal widths of approximately 5-10 microns separated by 10-20 microns. We use real and reciprocal space imaging to examine the emission characteristics of the lasing cavity. Remarkably, we discover that the mutual coherence is preserved whether the cavity operates on a single longitudinal mode or multiple modes. We will show how their emission and coherence can be controlled using a digital micromirror device to control the position and shape of the pump illumination studying threshold, coherence and frequency
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