Jul 29, 2010 – Daylight Solutions has pushed the broad tuning envelope again. We have built a pulsed, single-chip laser that tuned over 525 cm^-1. This ECqcLâ„¢ (External Cavity quantum cascade Laser) tunes so broadly that we had to modify our tuning mechanics in our Ãœber Tuner broad tuning laser platform to cover the entire range in a single scan. Figure 1 is the tuning curve for the performance of this laser. The tuning range covers 3.78 – 4.71 µm (2,122 – 2,647 cm^-1). The chip was successfully designed not only for super broad gain bandwidth, but also to lase below 4 µm as we strive to provide the market with both the broadest tuning in a single laser as well as the most wavelength coverage. This chip encompasses the entire CO₂ absorption band at 4.25 µm. The peak power at the top of the gain curve is just over 200 mW with a 5% duty cycle and 100 kHz pulse repetition rate.

Figure 1. Tuning curve of new ECqcLâ„¢ performance
After obtaining the above tuning curve, we reopened the 1 m path to atmospheric CO₂, decreased the step size, and scanned over the region where CO2 absorbs. The result is shown in Figure 2a. Figure 2b is the same spectrum overlaid by a calculated HITRAN spectrum assuming a laser linewidth of 0.7 cm^-1. When the variation in power of the laser as a function of wavelength (the gain curve of the QCL) is taken into consideration, the agreement between the observed and calculated spectra is quite good.

Figure 2a. Observed spectrum of CO₂ with broad tuning, pulsed ECqcLâ„¢. Inset of laser tuning curve shows range of observed spectrum.

Figure 2b. Observed spectrum overlaid by HITRAN simulated spectrum with an instrument linewidth of 0.7 cm^-1 and a total pressure of 1 atm.

Broad tuning and new wavelength coverage will continue to drive Daylight Solutions’ ECqcL™ development as this will facilitate molecular sensing, imaging, and spectroscopy applications.

What might look like an elephant under a blanket to some, looks like another world’s record to Daylight Solutions.

Daylight Solutions offers a commercial version of our broad-tuning pulsed laser system with over 250 cm^-1 of continuous tuning.  The company provides narrow-band, high-brightness tunability in various ECqcL™ platforms from 3.8-12.2 µm.  For further information, please contact Chris Armacost at carmacost@daylightsolutions.com.