Research round-up

30 Aug 2005

A look at some of innovations in optics this month including a terahertz study of imflammable liquids in plastic bottles.

Terahertz spectroscopy

Scientists at Osaka University in Japan have teamed up with the city's police forensic laboratory to assess the potential of terahertz time-domain spectroscopy (THz-TDS) for screening for inflammable liquids stored in common plastic bottles. (Applied Physics Letters 87 034105)

The team investigated liquids such as gasoline, benzene and kerosene which were stored in plastic bottles made of polyethylene (PE) and polyethylene terephthalate (PET). Water, which does not transmit THz waves, was also included in the study. "The transmittances and the refractive indices in the THz region allow us to distinguish these liquids even in plastic bottles," say the researchers.

Sources

A diode-end-pumped continuous wave Nd:YVO₄ laser emitting at 1386 nm has been unveiled by scientists at Tianjin University in China. The researchers say their laser has a maximum output power of 305 mW at an incident pump power of 4.24 W and a slope efficiency of 13.9%. (Optics Express 13 5819)

"To the best of our knowledge, this is the first time that CW operation at 1386 nm transition of Nd:YVO₄ crystal is reported," say the authors. "We believe that if better output couplers are used, an output power of several watts should be obtained."

Spectroscopy

Researchers at the University of Glasgow have developed a tunable diode laser spectroscopy (TDLS) system capable of measuring ethane in real-time to sub-ppb levels. Designed to offer a fast response ethane breath-test, the team has carried out preliminary tests on exhaled ethane in humans and horses. (Applied Optics 44 4712)

The presence of increased ethane on the breath can indicate problems such as chronic obstructive pulmonary disease in humans and recurrent airway obstruction in horses. Based on a lead-salt diode laser emitting around 0.25 mW at 3.4 microns, the researchers believe their instrument has monitoring and diagnostic potential.

"We believe our present configuration offers the best reported combination of sensitivity and response time in an instrument that is portable, requires no pre-processing of the breath sample and is insensitive to mirror degradation," conclude the authors.