The worldwide first all-fiber THz time-domain spectrometer for operation at 1.5 microm is presented. Applications up to 3 THz are demonstrated. Key devices are photoconductive antennas based on novel LT InGaAs/InAlAs multi-layer structures.

609In honour of Prof. Dr. Dr. h. c. Y. G~~RLICIX'S 70th birthday The dielectric functions E I ! arid E L of graphite were redetermined by elcct.ron energy loss spectroscopy. At 11 eV a strong maximum in I m (~1 1 ) is obtained, which is in accordance with earlier electron energy loss experiments, but in disagreement with recent reflectance measurements. A detailed discussion of uncertaint.ies in the energy loss function I m (.--1/61!) and in the Kramers-Kronig analysis confirms, t.hat. the 11 eV-maximum of I m (q;) is established beyond experimental error. Our "1 data are in agreement wit.h earlier electron energy loss and optical resu1t.s. Die dielektrischen Funktionen ~, iand E J von Grapliit mirden mit Hilfe von ElektronenEnergieverlusbmessungen neu bestimmt.. I m Gegensatz zu kiirzlich veroffentliehtcri Reflexionsmessungen xeigt die Punktion I m (q) in ubereinstimmung mit fruhcren ElektronenEnergieverlustmessungen ein starkes Maxinium bei 11 eV. Einc genane T;nt.ersuchung der Genauigkeit der Energieverlustfunktion I m (-~/ E I I ) und miiglicher Pehler bci der IfiamersKronig Analyse ergibt, daB die Eixifiteiiz des 11 eV-Maximums als gesichert gelten muB.Der Verlauf der Funktion EL entspricht im wcsentlichen den bereits frtiher mit Elekt.ronenEnergieverlustniessungen und auch optisch bestimmten Resultaten.

No abstract

Excitation spectra of different donor-acceptor pair emission bands and selective pair luminescence spectra were measured on cubic ZnSe crystals with different impurity contents. For the Na and Li acceptor we found the excited states with s symmetry up to 4S, as well as the four 2P excited states. These experiments further demonstrate that the acceptor involved in the A pair band reported in the literature is substitutional Li. The observed excited acceptor states are compared to results of the effective-mass theory of Baldereschi and Lipari, after the theoretical state energies have been scaled by the experimentally determined Rydberg energy of the respective acceptor.