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Associate Professor Rainer Leonhardt

Dipl. Phys. Dr. rer. nat.

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Associate Professor

Research | Current

  • 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.


Areas of expertise

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


Selected publications and creative works (Research Outputs)

  • Vogt, D. W., & Leonhardt, R. (2018). Mode identification for ultra high-Q terahertz whispering-gallery modes. 2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings.
  • Vogt, D. W., Jones, A. H., & Leonhardt, R. (2018). Thermal tuning of silicon terahertz whispering-gallery mode resonators. Applied Physics Letters, 113 (1), 011101-011101. 10.1063/1.5036539
  • Vogt, D. W., & Leonhardt, R. (2018). Ultra-high Q terahertz whispering-gallery modes in a silicon resonator. APL Photonics, 3 (5), 051702-051702. 10.1063/1.5010364
  • Rana, S., Rakin, A. S., Hasan, M. R., Reza, M. S., Leonhardt, R., Abbott, D., & Subbaraman, H. (2018). Low loss and flat dispersion Kagome photonic crystal fiber in the terahertz regime. Optics Communications, 410, 452-456. 10.1016/j.optcom.2017.10.073
  • Vogt, D. W., & Leonhardt, R. (2018). Mode identification for ultra high-Q terahertz whispering-gallery modes. Optics InfoBase Conference Papers. 10.1364/CLEO_AT.2018.JW2A.74
  • Vogt, D. W., & Leonhardt, R. (2017). Fano resonances in a high-Q terahertz whispering-gallery mode resonator coupled to a multi-mode waveguide. Optics Letters, 42 (21), 4359-4362. 10.1364/OL.42.004359
  • Vogt, D. W., & Leonhardt, R. (2017). Terahertz whispering gallery mode bubble resonator. Optica, 4 (7), 809-812. 10.1364/OPTICA.4.000809
  • Vogt, D. W., & Leonhardt, R. (2017). High resolution terahertz spectroscopy of a whispering gallery mode bubble resonator using Hilbert analysis. Optics Express, 25 (14), 16860-16866. 10.1364/OE.25.016860

Contact details

Primary office location

Level 6, Room 619
New Zealand