NSF Award 0940380 Principal Investigator: S. R. J Brueck 505-272-7800 / brueck@chtm.unm.edu Period of Performance: September 2009 to August 2011 The infrared spectral region, from 2.5 to about 20 micrometers, is known as the molecular vibration fingerprint region since molecular vibrational absorptions across this region provide a means to indentify and study molecules for both scientific and environmental purposes. Laser spectroscopy of many molecules has been intensively pursued for many years and has led to both scientific breakthroughs (including several Nobel prizes) and important applications in both commercial and defense/security fields. Notwithstanding this progress, a broadly and continuously tunable infrared laser source or sources covering this spectral region has remained elusive. A particularly important spectral region is 3 – 4 micrometers that covers the absorption bands of the important carbon-hydrogen (C-H) stretch that is a signature of all organic molecules. For remote sensing applications a reasonable level of power is a desirable feature. The detection range is directly related to the available power. In this project we have developed a novel tunable laser source that: is continuously tunable over a wide range (so far about 30 nm, but over a 100 nm wavelength range has been demonstrated in a slightly different geometry), is high power (a record power of ~ 1 W from a tunable distributed feedback laser), and with a small number of devices is capable of covering the entire 2.5-20 micrometer range. The unique tuning mechanism we have developed is an optically-pumped, chirped grating (e.g. a grating whose spatial period varies with position) distributed feedback laser. The basic idea is that the local period of the grating at the position of the optical pumping stripe determines the lasing wavelength. Thus, tuning is a simple matter of changing the stripe position. In contrast to many other tunable laser concepts, which often require adjusting two parameters – for example a temperature and laser cavity length, this tuning is rapid and continuous without any spectral jumps or gaps and involves only a single adjustment. Some applications include monitoring of chemical process plants; monitoring of gas pipelines for leaks; medical diagnostics including breathalyzer applications; monitoring of auto exhaust; remote chemical plume investigations, etc. This is a unique laser source well suited for atmospheric monitoring that will find multiple commercial and defense applications. Publications include: L. Xue, S. R. J. Brueck and R. Kaspi, High Power, Continuous Wave, Single Longitudinal Mode Operation of an Opticallly Pumped DFB Laser at l ~ 3.64 mm, Photonics Tech. Lett. 20, 727 (2008). Liang Xue, S. R. J. Brueck and R. Kaspi, Widely Tunable Distributed Feedback Lasers with Chirped Gratings, Appl. Phys. Lett. 94, 161102 (2009). U. S. Patent: 7,656,912 S. R. J. Brueck, L. Xue and R. Kaspi, Tunable infrared lasers for gas-phase spectroscopy
