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Generalized ultrafast dispersion scans of continuum generation induced by sub-50fs chirped pulses in highly nonlinear tapered planar waveguides

Matthew Praeger, William S. Brocklesby, Ana M. de Paula, Jeremy Frey, Jeremy J. Baumberg, Caterina M. Netti, Majd E. Zoorob, Nicolas M. B. Perney, Martin D. B. Charlton, Stephen W. Roberts, James S. Wilkinson, Greg J. Parker (+5 others)
2005 Commercial and Biomedical Applications of Ultrafast Lasers V  

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Ultra-high bandwidth continua generated by ultrashort fs pulses have been attracting enormous interest for applications such as general spectroscopy, Optical Coherence Tomography and metrology. Dispersion engineering is one of the key aspects of optimised continuum generation in optical waveguides. However in addition, the dispersion of the pump pulse can be continuously adapted to control bandwidth and spectral characteristics of the generated continua. In this work we report on a systematic
more » ... vestigation of how 2 nd ,and 3 rd order dispersion affects the continuum generated in strongly non linear planar waveguides. A ∼30 fs Ti:Sapphire tuned to 800 nm was used as a pump source delivering ∼3 nJ pulses. The chirp of the pulses was controlled completely-arbitrarily by an acousto-optic programmable dispersive filter (Dazzler). The power launched into the structures was kept constant to compare the generated continua as the pulse dispersion is varied. High refractive index tantalum pentoxide (T a 2 O 5 ) waveguides grown by standard silicon processing techniques were used. The devices investigated were specially designed tapered ridges with ∼5 mm 2 input modal volume and zero group velocity dispersion at ∼l-3.7 mm. Self-phase modulation, which is responsible for the spectral broadening of the continua, is tracked by finely tuning the both 2 nd and 3 rd order dispersions. The nonlinear propagation is dramatically influenced by the simultaneous presence of these dispersive effects resulting in a change of bandwidth and spectral shape. Pulse widths of up to Dl > 100 nm for launched powers as low as 300 pJ. Spectral peak intensity can also be systematically modulated by simply scanning the 2 nd and 3 rd order dispersion around their relative zeros. Specific combinations of high order dispersion contribution are currently targeted as a route to control and optimise the continua bandwidths and to control dispersion lengths in specifically engineered waveguides.
doi:10.1117/12.589346 fatcat:z3anlwo7bfalvfhb6tsxhetd5q
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Matthew Praeger, William S. Brocklesby, Ana M. de Paula, Jeremy Frey, Jeremy J. Baumberg, Caterina M. Netti, Majd E. Zoorob, Nicolas M. B. Perney, Martin D. B. Charlton, Stephen W. Roberts, James S. Wilkinson, Greg J. Parker, John R. Lincoln, Joseph Neev, Christopher B. Schaffer, Andreas Ostendorf, Stefan Nolte. "Generalized ultrafast dispersion scans of continuum generation induced by sub-50fs chirped pulses in highly nonlinear tapered planar waveguides." Commercial and Biomedical Applications of Ultrafast Lasers V (2005)