Optical manipulation of quantum-degenerate excitonic particles Makoto Kuwata-Gonokami Department of Applied Physics, the University of Tokyo, and CREST-JST 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, Tel: +81-3-5841-6836, Fax: +81-3-5841-8809, [email protected] Collective quantum mechanical phenomena such as superfluidity and superconductivity are observed for particles at a high density and low temperature. These collective effects can also take place in optically manipulated materials through a precise control of light-matter interactions. We have performed several experiments in order to obtain high particle density, low temperature photo-controlled matter states, including Bose-Einstein condensates of excitonic particles, electron-hole liquids and laser-cooled neutral atoms. In particular, photo-generated electrons and holes in semiconductors provide a unique opportunity to examine macroscopic quantum phenomena such as the crossover from quantum degenerate bosonic ensembles (Bose-Einstein condensate states of excitons) to Fermi-degenerate electron-hole ensembles. In this talk, several topics shown below on the creation and detection of high density and cold excitonic particles will be presented and novel experimental aspects of collective quantum phenomena with electron-hole ensembles in semiconductors will be discussed. (1) Generation of highly quantum-degenerate excitonic particles by pulsed two-photon excitation with phase space compression [1-3] (2) Observation of cold para-excitons in Cu2O by excitonic Lyman spectroscopy [4-8] (3) Dynamics of cold and dense electron-hole ensembles in semiconductors [9-12]  M. Kuwata-Gonokami, R. Shimano and A. Mysyrowicz,, J. Phys. Soc. Jpn, 71 (2002) 1257.  R. Shimano, Yu. P. Svirko, A. Mysyrowicz, and M. Kuwata-Gonokami, Phys. Rev. Lett. 89 (2002) 233601.  K. Yoshioka and M.Kuwata-Gonokami, Phys. Rev. B, 73 (2006) 081202 (R).  M. Kuwata-Gonokami , M. Kubouchi, R. Shimano, A. Mysyrowicz, J. Phys. Soc. Jpn. 73 (2004) 1065; M. Kuwata-Gonokami, Solid State Commun. 134 (2005) 127.  M. Kubouchi , K. Yoshioka, R. Shimano, A. Mysyrowicz and M. Kuwata-Gonokami, Phys. Rev. Lett. 94 (2005) 016403.  T. Tayagaki , A. Mysyrowicz and M. Kuwata-Gonokami J. Phys. Soc. Jpn. 74 (2005) 1423. T. Tayagaki, A. Mysyrowicz, and M. Kuwata-Gonokami,Phys. Rev. B, 74, (2006) 245127.  K. Yoshioka, T. Ideguchi, and M. Kuwata-Gonokami,Phys. Rev. B, 76 (2007) 033204.  R. Shimano, M. Nagai, K. Horiuchi and M. Kuwata-Gonokami, Phys. Rev. Lett. 88 (2002) 057404.  M. Nagai, R. Shimano and M. Kuwata-Gonokami, Phys. Rev. Lett. 86 (2001) 5796.  M.Nagai and M. Kuwata-Gonokami. J. Lumi. 100 (2002) 233.  N. Naka, J. Omathi, M. Kuwata-Gonokami, Phys. Rev. B, in press.