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CLEO News: Research highlights (2)

21 May 2004

Advances in RGB lasers, terahertz spectroscopy and NASA's laser altimeter pull in the crowds.

This year’s CLEO, IQEC and the newly launched PhAST conference attracted a total of 1651 papers. Judging by the busy rooms at all the CLEO and IQEC oral presentations, it’s safe to say that both conferences upheld their reputation of showcasing all the latest breakthroughs in fundamental optics. PhAST was also well attended, especially the keynote sessions which were standing-room only. Here are a few of the papers that caught our eye:

•  This summer NASA will send its first unmanned probe to the planet Mercury. Dubbed MESSENGER, Mercury Surface Space Environment Geochemistry and Ranging, it is due to blast off on July 30 and will take 7 years to reach Mercury.

Xiaoli Sun and his colleagues from NASA’s Goddard Space Flight Center described the laser altimeter that will be onboard. It is based on a diode-pumped, Q-switched Nd:YAG laser. Operating at 1064 nm, it will emit 20 mJ 6 ns pulses at a repetition rate of 8 Hz. Along with a variety of other instruments such as X-ray, gamma-ray and neutron spectrometers, NASA plans to map the northern hemisphere of the planet, accurately measure Mercury’s shape and study how the planet wobbles on its axis.

•  In a packed session on terahertz spectroscopy, Kohji Yamamoto from Osaka University told delegates about his work using THz rays to detect the chemical explosive C-4 in mail and parcel bombs. The Osaka group has successfully used to THz spectroscopy to identify a small 13 mm pellet of C-4 hidden in envelopes and parcels. The approach involves firing THz rays at the envelope and looking for C-4’s characteristic absorption spectrum in the transmitted signal.

•  In CLEO’s femtosecond down-conversion conference, Edith Innerhofer from ETH Zurich in Switzerland told attendees about an RGB laser source for projection displays. The main advantage of the system is that all the pump power is provided by a single source: a passively modelocked Yb:YAG thin disk laser. Innerhofer stressed that no synchronously-pumped parametric oscillators or laser amplifiers are required.

The disk laser has an average power of 79 W and emits 780 fs pulses at 1.4 µm. This beam is then passed through a frequency doubler, a two-stage parametric generator and two sum-frequency mixers. The end result is 8 W of 603 nm light, 23 W at 515 nm and 10.1 W at 450 nm. The team is now optimizing the system and hopes to achieve in excess of 10 W per colour.

Jacqueline Hewett is technology editor on Optics.org and Opto & Laser Europe magazine.

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