title: High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers.
abstract: Lasing characteristics were evaluated for distributed-feedback quantum-cascade (QC) lasers operating in a continuous mode at cryogenic temperatures. These tests were performed to determine the QC lasers' suitability for use in high-resolution spectroscopic applications, including Doppler-limited molecular absorption and pressure-limited lidar applications. By use of a rapid-scan technique, direct absorbance measurements of nitric oxide (NO) and ammonia (NH>(3)) were performed with several QC lasers, operating at either 5.2 or 8.5 microm. Results include time-averaged linewidths of better than 40 MHz and long-term laser frequency reproducibility, even after numerous temperature cycles, of 80 MHz or better. Tuning rates of 2.5 cm(-1) in 0.6 ms can be easily achieved. Noise-equivalent absorbance of 3 x 10(-6) was also obtained without optimizing the optical arrangement.
authors: S W
authors: SW
authors: Sharpe
authors: J F
authors: JF
authors: Kelly
authors: J S
authors: JS
authors: Hartman
authors: C
authors: C
authors: Gmachl
authors: F
authors: F
authors: Capasso
authors: D L
authors: DL
authors: Sivco
authors: J N
authors: JN
authors: Baillargeon
authors: A Y
authors: AY
authors: Cho