ZnO lasing in complex systems with tetrapods

A ZnO structure in the form of a core–shell wire was grown with a modified vapour transport and condensation method. The wire consists of a dense core which may play the role of a waveguide and a shell formed mainly from tetrapod-type crystallites. The high optical quality of the produced ZnO material is confirmed by continuous wave photoluminescence (PL) analysis demonstrating that low- temperature PL is related to the recombination of bound excitons, while room-temperature PL is due to free excitons. Good quality of the crystal structure is demonstrated also by the Raman spectrum. The shell of the wire exhibits room-temperature laser action due to lasing modes in tetrapods under the excitation by nanosecond laser pulses. The nature of the lasing modes is discussed. A simplified model for one of the possible modes is suggested.