Focus on Ultrafast Optics

Abstract

The establishment of ultrafast optics as an important research field followed the invention of the laser in the late 1950s. However although the generation of ultrashort optical pulses was observed not long after the laser was first invented, it is only in the last few years that ultracompact lasers have been devised which generate picosecond or sub-picosecond sources, making them suitable for widespread use in communication, sensing, machining or medical applications. These in turn have been complemented by the development of new optical amplification, processing and switching technologies.This focus issue in New Journal of Physics reflects the rapid changes that have occurred within the field, incorporating a range of papers. These include reviews of the new generation of compact optical sources now able to generate short optical pulses, switching techniques and applications. Three main classes of mode-locked laser are studied. Two papers are concerned with firstly solid state lasers (Brown et al), and secondly fibre lasers equipped with efficient non-linear SESAM reflectors for passive mode-locking of pulses (Okhotnikov et al). Finally semiconductor diode lasers are reviewed. Both edge emitting and surface emitting devices are reported, the former category allowing compact very high frequency single chip sources (Williams et al, Brown et al), whereas surface emitting devices are shown to provide high power ultrahigh quality pulse generation (Paschotta et al, Brown et al). Laser diodes show particular benefits for direct modulation at very high rates, and hence recent advances in quantum dot lasers and VCSELS are reported by Kuntz et al and Larsson et al respectively.Ultrashort phenomena are not only important in terms of pulse generation, but also in amplification, shaping and switching. As a result, studies of ultrafast nonlinearities in diode laser amplifiers (Berg et al), and the use of fast nonlinearities in photonic crystal fibres for pulse shaping (Konorov et al) are reported. A review by Wada explores the considerable promise for applications in next generation ultrafast systems. Examples of the use of ultrashort pulses in imaging are reviewed by Elson.It has been a privilege to work with the authors and referees in preparing this focus issue and we are most grateful to them. We would also like to express our sincere gratitude to Tim Smith and the New Journal of Physics staff for their support throughout.Focus on Ultrafast Optics ContentsPicosecond pulse sources with multi-GHz repetition rates and high output power R Paschotta, L Krainer, S Lecomte, G J Spühler, S C Zeller, A Aschwanden, D Lorenser, H J Unold, K J Weingarten and U KellerCompact laser-diode-based femtosecond sources C T A Brown, M A Cataluna, A A Lagatsy, E U Rafailov and W SibbettDirect high-frequency modulation of VCSELs and applications in fibre optic RF and microwave links A Larsson, C Carlsson, J Gustavsson, A Haglund, P Modh and J BengtssonUltra-fast fibre laser systems based on SESAM technology: new horizons and applications O Okhotnikov, A Grudinin and M PessaGain dynamics and saturation in semiconductor quantum dot amplifiers T W Berg, J Mork and J M HvamLong wavelength monolithic mode-locked diode lasers K A Williams, M G Thompson and I H WhiteReal-time time-domain fluorescence lifetime imaging including single-shot acquisition with a segmented optical image intensifier D S Elson, I Munro, J Requejo-Isidro, J McGinty, C Dunsby, N Galletly, G W Stamp, M A A Neil, M J Lever, P A Kellett, A Dymoke-Bradshaw, J Hares and P M W FrenchDirect modulation and mode locking of 1.3 µm quantum dot lasers M Kuntz, G Fiol, M Lämmlin, D Bimberg, M G Thompson, K T Tan, C Marinelli, A Wonfor, R Sellin, R V Penty, I H White, V M Ustinov, A E Zhukov, Yu M Shernyakov, A R Kovsh, N N Ledentsov, C Schubert and V MarembertCross-phase-modulation-controlled spectral transformations of ultrashort pulses in photonic-crystal fibres S O Konorov, A A Ivanov, D A Akimov, M V Alfimov, A A Podshivalov, Yu N Kondrat'ev, V S Shevandin, K V Dukel'skii, A V Khokhlov, M Scalora and A M ZheltikovFemtosecond all-optical devices for ultrafast communication and signal processing O WadaMarkus Pessa, Tampere University of Technology, Finland Ian H White, University of Cambridge, UK