Associate Professor Rainer Leonhardt

Dipl. Phys. Dr. rer. nat.

Contact details
Building 303, Room 619
Phone: +64 9 373 7599 ext 88835
Email: r.leonhardt@auckland.ac.nz

• Nonlinear Effects in Optical Fibres
• THz Spectroscopy
• Laser Physics
• Atom Trapping and Quantum Chaos

Holey (PCF) Fibres
Holey fibres are micro-structured fibres where a small glass core is surrounded by an air cladding. Compared to normal single-mode fibres these fibres have a smaller core diameter and different dispersion characteristics. Therefore it is easier to achieve high peak powers, and to observe nonlinear effects that depend on phase matching. Most of our experiments use a mode-locked cavity -dumped Krypton laser (λ=647nm, τp~60ps, Ppeak~1kW) as a pump, and the holey fibres have their zero-GVD around this wavelength. We have used these fibres to generate supercontinua that stretch from 400nm to 1400nm. We also looked at the effect of Modulation Instability (MI) in the normal dispersion regime, generating sidebands at about 471nm and 1055nm. Usually MI can only be observed in the anomalous dispersion regime but taking higher-order dispersion terms into account, MI can also be observed close to the zero-GVD in the normal dispersion regime. Furthermore we utilise a feedback scheme to enhance these nonlinear effects.

THz Spectroscopy
Utilising sub-picosecond laser pulses and photoconductive antennae we are able to generate and detect coherent THz radiation spanning from about 0 .3THz to 1.5THz. At the moment the design of a THz spectrometer that utilises aspherical PE lenses is implemented. As the wavelength of THz radiation is in the order of 0.3mm, the necessary surface quality for the lenses can be achieved with a computer-controlled lathe. One of our projects is to design the 'best' lenses for the spectrometer with the aim to achieve a very high spatial resolution that lies in the order of one wavelength. We expect that the use of these lenses will become quite common as they are much more 'user friendly' than the off-axis parabolic mirrors used at the moment. Another project looks at the feasibility to use diode lasers and fibre optics to build an inexpensive tunable continuous-wave THz spectrometer that operates around 1THz.

Quantum Chaos
The term 'Quantum Chaos' is a misnomer as chaos does not exist in quantum mechanics due to the linearity of the equations. But chaos is a prominent feature of classical physics (eg, the weather pattern), and therefore it is very interesting to study the transition between quantum – and classical physics. One of the simple examples for chaotic behaviour is the δ-kicked rotor that can be realised experimentally by using ultra-cold (5μK) atoms (in our case Caesium) that are exposed to a pulsed laser beam. By changing the experimental parameters (eg, the pulse period or the detuning of the laser beam), one can make the atoms to behave 'more classically' or 'more quantum mechanically'. Also, the addition of spontaneous emission and any kind of noise (eg, period – or amplitude noise) should drive the atoms to behave 'more classically'. Our investigations show that the transition between quantum – and classical physics is not as smooth as one might expect, and that there are resonant features that are susceptible to different kinds of noise in different ways.

• J.D.Harvey, S.G.Murdoch, R.Leonhardt, 'Recent Advances in Fiber Optic Parametric Amplifiers', CFN3, CLEO/QELS (Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science) Baltimore, USA, 978-1-55752-890-2/10 (2010)
• J.D.Harvey, R.Leonhardt, S.G.Murdoch, 'PCF based Optical Parametric Oscillators in the Visible', Nonlinear Photonics Conference, SThB1, invited talk, Karlsruhe (2010)
• J. Anthony, A. Argyros, Y. H. Lo, M. C. J. Large, R. Leonhardt, 'Characterizations of THz microstructured fibers with specially design lenses', International Conference on Plastic Optical Fibers (POF), Sydney (2009)
• R. Leonhardt, B. R. Biedermann, W. Wieser and R. Huber, 'Nonlinear optical frequency conversion of an amplified Fourier Domain Mode Locked (FDML) laser', Optics Express 17 16801-16808 (2009) http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-19-16801
• J. D. Harvey, S. G. Murdoch, and R. Leonhardt, "recent developments in fibre optic parametric amplifiers', ICOCN (International Conference on Optical Communications and Network) 2009, invited paper, Beijing, (2009)
• Y. Q. Xu, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, 'Raman-assisted Continuous-Wave Tunable all-Fiber Optical Parametric Oscillator', J. Opt. Soc. Am. B 56 1351-13 (2009)
• Yiqing Xu, Stuart Murdoch, Rainer Leonhardt,and John Harvey, " All-fiber CW fiber optical parametric oscillator tunable over 240 nm", CLEO Europe 2009, Munich, CD3.4 (2009)
• R. Leonhardt, J. Anthony, Y.H. Lo, A. Argyros, M.C.J. Large, "Efficient coupling into THz PCF fibres using specially designed lenses", CLEO Europe 2009, Munich, JSIV.P.10 (2009)
• Y. Q. Xu, S. G. Murdoch, R. Leonhardt and J. D. Harvey," Widely-Tunable Triply-Resonant Optical Parametric Ring Oscillator", LEOS Winter Topicals: Nonlinear Dynamics in Photonic Systems, Innsbruck WC3.4 (2009)
• A. Argyros, J. Anthony, R. Leonhardt, M.C.J. Large, "Terahertz transmission in Zeonex polymer waveguides", Proc. of the 8th International Photonic & Electromagnetic Crystal Structures Meeting (PECS VIII), p 157, 5-9 April 2009, Sydney (2009)
• J. Anthony and R. Leonhardt, "Characterisation of a Terahertz waveguide", ENZCon Proceedings, ISBN ISBN 978-0-473-14478-4, pp 19-23 (2008)
• Y. H. Lo, R. Leonhardt, "Aspheric Lenses for Terahertz Imaging", Optics Express 16, 15991-15998 (2008) http://www.opticsexpress.org/abstract.cfm?uri=oe-16-20-15991
• Y. Q. Xu, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, "Widely-tunable photonic crystal fiber Fabry-Perot optical parametric amplifier", Optics Letters 33 1351-1353 (2008).
• J. C. C. Wang, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, "Strong signal suppression in single-pump optical parametric amplifiers", Optics Letters 33 935-937 (2008).
• J. D. Harvey, S. G. Murdoch, S. Coen, R. Leonhardt, D. Mechin and G. K. L. Wong, "Parametric processes in microstructured and highly nonlinear optical fibres", Opt. Quant. Electron. 39 1103-1114 (2008)
• M. Sadgrove, S. Wimberger, S. Parkins, R. Leonhardt, "Scaling law and stability for a noisy quantum system", Physical Review E 78, 025206(R) (2008), http://arxiv.org/abs/0808.3824v1
• J. C. C. Wang, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, "Strong signal suppression due to the combined effect of Raman and parametric gain in a fiber parametric amplifier", CLEO San Jose CWJ2 (2008)
• Gordon K. L. Wong, Yiqing Xu, Stuart G. Murdoch, Rainer Leonhardt, John D. Harvey, "An All-Fiber Widely Tunable Photonic Crystal Fiber Optical Parametric Oscillator", OFC/NFOEC, San Diego, USA (2008)
• Y. H. Lo, R. Leonhardt, "Aspheric Lenses for Terahertz Imaging", CLEO San Jose CThD6 (2008)
• Y. H. Lo, R. Leonhardt, "Aspherical lenses for Terahertz spectroscopy", Proc. of SPIE Vol. 6801, 68011R, Canberra, Australia (2008)
• J.D.Harvey, S. G. Murdoch, S. Coen, R. Leonhardt, D. Mechin, G. K. L. Wong, "Parametric processes in microstructured and highly nonlinear optical fibres", Opt Quant Electron 39, 1103-1114 (2007)
• Y. H. Lo, R. Leonhardt, "Numerical Design and Analysis of Lens Performances for Use with Terahertz Imaging", ENZCon, Wellington NZ (2007)
• G. K. L. Wong, S. G. Murdoch, R. Leonhardt, J. D. Harvey, and V. Marie, "High-conversion-efficiency widely-tunable all-fiber optical parametric oscillator," Opt. Express Vol. 15, 2947-2952 (2007)
• A. S. Y. Hsieh, G. K. L. Wong, S. G. Murdoch, S. Coen, F. Vanholsbeeck, R. Leonhardt, and J. D. Harvey, "Combined effect of Raman and parametric gain on single-pump parametric amplifiers," Opt. Express Vol.15, 8104-8114 (2007)
• G. K. L. Wong, S. G. Murdoch, R. Leonhardt, J. D. Harvey, and V. Marie, "Fiber optical parametric oscillator with 560 nm tuning range using dispersion-shifted fiber," The Optical Fiber Communication Conference & Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), Anaheim, California, USA, paper OWQ3 (2007)
• G. K. L. Wong, S. G. Murdoch, R. Leonhardt, and J. D. Harvey, "Widely-tunable high-conversion-efficiency chi(3) parametric oscillator," Australian Conference on Optical Fibre Technology, Canberra Australia (ACOFT), WeB2-2, Melbourne, Australia (2007)
• A. S. Y. Hsieh, S. G. Murdoch, S. Coen, R. Leonhardt, and J. D. Harvey, "Influence of Raman susceptibility on optical parametric amplification in optical fibers," Optics Letters 32, 521-523 (2007)
• A. S. Y. Hsieh, S. G. Murdoch, S. Coen, R. Leonhardt, and J. D. Harvey, "Effect of Raman susceptibility on single-pump optical parametric amplifiers", Conference on Lasers and Electro-Optics (CLEO 2007), Baltimore USA, May 2007, paper CFD1 (2007)
• J.S.Y. Chen, S.G. Murdoch, R. Leonhardt, and J.D. Harvey, "Effect of dispersion fluctuations on widely tunable optical parametric amplification in photonic crystal fibers," Opt. Express Vol.14, pp 9491-9501 (2006)
• R.J. Kruhlak, G.K.L. Wong, J.S.Y. Chen, S.G. Murdoch, R. Leonhardt, J.D. Harvey, N.Y. Joly, and J.C. Knight, "Polarisation modulation instability in photonic crystal fibers," Optics Letters 31, No. 10, pp 1379-1381 ( 2006)
• J.S.Y. Chen, G.K.L. Wong, S.G. Murdoch, R.J. Kruhlak, R. Leonhardt, J.D. Harvey, N.Y. Joly, and J.C. Knight, "Cross-phase modulation instability in photonic crystal fibers," Optics Letters 31, No. 7, pp 873-875 (2006)
• J. S. Y. Chen, G. K.L. Wong, S. G. Murdoch, R. J. Kruhlak, R. Leonhardt, and J. D. Harvey, "Vector modulation instabilities in a photonic crystal fiber," OptoElectronics and Communications Conference (OECC). Kaohsiung, Taiwan. 3 July 2006 [post-deadline] (2006)
• G. K. L. Wong, J. S. Y. Chen, S. G. Murdoch, R. J. Kruhlak, R. Leonhardt, J. D. Harvey, "Vector Modulational Instabilities in Photonic Crystal Fiber" European conference on Optical Communications (ECOC 2006) Cannes, France, Paper Tu4.3.5 ECOC proceedings Vol. 2 pg 137-138 (2006)
• J. S. Y. Chen, S. G. Murdoch, R. Leonhardt, J. D. Harvey, "Effect of Dispersion Fluctuations on Large Frequency Shift Parametric Amplification in Photonic Crystal Fiber." European conference on Optical Communications (ECOC 2006), Cannes, France, Paper Th1.3.4 ECOC proceedings Vol. 4 pg 19-20 (2006)
• G. K. L. Wong, J. S. Y. Chen, S. G. Murdoch, R. J. Kruhlak, R. Leonhardt, J. D. Harvey, N. Y. Joly, J. C. Knight, "Cross-phase modulation instability in photonic crystal fiber", CLEO/QELS 2006 Long Beach, USA, CTuA3 (2006)