Broadband, background-free, single-laser-shot absorption
Abstract
A robust approach for acquiring background-free, multitransition absorption spectra under single-laser-shot conditions is demonstrated using broadband, ultrashort laser pulses. This technique—referred to as time-resolved optically gated absorption (TOGA)—exploits the inherent differences in timescales between broadband, femtosecond-duration light sources and the longer-duration responses of narrowband atomic or molecular absorption features. An optical temporal gate, based on frequency mixing via sum-frequency generation or difference-frequency generation, is used to isolate these long-lived time-domain absorption features from the ultrashort component associated with the broadband absorption light source. A proof-of-principle demonstration of TOGA is provided using atomic Rb as an absorbing medium. Application of this technique toward single-laser-shot simultaneous detection of hydroxyl radical concentration and the corresponding local temperature is also demonstrated in a reacting flow. These results indicate that TOGA can provide spectrally resolved, broadband, background-free absorption measurements at laser-source repetition rates.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 15, 2020
- Source ID
- 10.1364/optica.394469
Entities
People
- Hans U. Stauffer
- Patrick S. Walsh
- S. Alexander Schumaker
- Sukesh Roy
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory