The Optical Hall Effect (OHE) is the birefringence induced by the interaction of incident electromagnetic radiation with the free carriers in a material under a magnetic field. One of the uses of the OHE is the probing of electronic structures in semiconductors.
The authors demonstrate amplified OHE in the Terahertz range in a two dimensional electron gas generated at the interface of two semiconductors. The amplification of the OHE is performed by a Fabry-Perrot optical cavity and is the consequence of the multiple path of light at the multiple interfaces in the cavity. This amplification is up to one order of magnitude, allowing the use a permanent neodymium magnet generating a magnetic field of 0.55T amplitude to induce the effect.
The OHE is characterized by the difference of the off-diagonal terms of the Mueller Matrix (which characterizes the birefringence of a material) for opposite direction of the magnetic field. Experimentally, a difference as strong as 0.15 is measured for ΔM13,31
for a gap layer in the cavity of dgap
= 194.5 μm. The measure is made by a commercially available mid-infrared ellipsometer.
The use of simple permanent magnets and tunable optical cavities will offer the possibility of large-scale measures of OHE for various sets of semi-conductors and thus help improve measures and modelling of free carrier charges in complex heterostructures.
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