Intrasubband magnetoplasmon lo-phonon coupling in an InAs antidot array

We present far-infrared photoconductivity measurements for InAs antidot arrays grown on a GaAs substrate. By applying a magnetic field, we have tuned the intraband-magnetoplasmon mode across the reststrahlen band of InAs. We have observed an anticrossing in the vicinity of the LO phonon of InAs arising from the intraband-magnetoplasmon-LO-phonon coupling. This coupling was so far only theoretically predicted. The experimentally observed splitting can be directly reproduced by the theory without any fitting parameters.