Direct observation of new transitions in the absorption spectra of a V-groove quantum wire waveguide

We report on the direct absorption measurement of the polarization selectio n rules in a V-groove QWR waveguide. Attenuation measurements in a 1 mm lon g waveguide were performed from 10 K up to room temperature. These measurem ents yielded the QWR DOS selection rules for lateral (TE) and vertical (TM) confinement directions. 1D heavy-hole like e(n)h(n) subband features were observed in the TE absorption spectra. Effective mass and 4 x 4 k . p model s have been used to evaluate the band to band absorption. For TM polarizati on, no absorption is observed at the e(1)h(1) transition, but a dominant fe ature appears corresponding to a quasi light-hole transition (e(1)h(7)). An absorption feature is also detected at the e(1)h(2) transition. This is a new genuine QWR transition with no analog in quantum wells: the theoretical analysis shows that it arises both from valence hand mixing at k = 0 and f rom symmetry breaking at the heterostructure level, despite the mirror symm etry of the structure.