PT Unknown AU Hübers, HW Pavlov, SG Semenov, AD Tredicucci, A Köhler, R Mahler, L Beere, HE Linfield, EH Ritchie, DA TI Investigation of a 2.5 THz quantum cascade laser as local oscillator SE Proc. 16[super:th] Int. Symp. Space Terahertz Technol. PY 2005 BP 18 PI Göteborg, Sweden ER