Subject Area B3: Optical Spectroscopy on Metal-Semiconductor Rolls
Wolfgang Hansen, Christian Heyn, Stefan Mendach
If strained layer systems grown on semiconductor substrates are lifted off by chemical etching,
the self-rolling mechanism leads to small rolls with micron-sized diameters.
Such rolls may yield applications in opto-electro-mechanical devices.
We have embedded a two-dimensional electron system inside a semiconductor microtube and have been
able to investigate the quantum Hall effect in strongly modulated magnetic fields.
In a further experiment we have shown that semiconductor microtubes act as optical ring resonators.
Embedded self-assembled quantum dots have been used as optically active material.
We have also developed a highly reproducible technique for the fabrication of metal-semiconductor
rolls with radii of only a few 100 nm.
(a)-(c) Images of metal-semiconductor rolls taken with a scanning-electron microscope.
(d) Semiconductor microtube ring resonator with optical modes.
The walls of metal-semiconductor microtubes with high winding numbers are radial superlattices that
act as metamaterials.
In this subject area we want to demonstrate that metal-semiconductor microtubes are hyperlenses for
visible light. Hyperlenses provide a better resolution than expected from the Abbe limit.
The imaging properties are studied by scanning near-field optical microscopy.
Embedded quantum systems such as self-organized quantum dots or rings should enhance the optical gain
of the microrolls.
In addition we study spin waves in ferromagnet-semiconductor microtubes.
Spin waves in curved ferromagnetic layers have unique properties that are studied with microwave-absorption
spectroscope and by the spatial- and time-resolved magneto-optical Kerr effect.
O. G. Schmidt and K. Eberl,
"Nanotechnology: Thin solid films roll up into nanotubes",
Nature 410, 168 (2001).
T. Kipp, H. Welsch, Ch. Strelow, Ch. Heyn, and D. Heitmann,
"Optical modes in semiconductor microtube ring resonators",
Phys. Rev. Lett. 96, 077403-1-077403-4 (2006).
S. Schwaiger, M. Bröll, A. Krohn, A. Stemmann, Ch. Heyn, Y. Stark, D. Stickler, D. Heitmann, and
"Rolled-up three-dimensional metamaterials with tunable plasma frequency in the visible regime",
Phys. Rev. Lett. 102,163903-1-163903-4 (2009).
Hyperlenses consisting of radial metamaterials
Quantum systems for optical gain in radial metamaterials
Spin waves in permalloy InGaAs rolls