Steady-State Doppler-Broadened IR–RF Lineshape Theory and Enhancement of Refractive Index in a Three-Level System
✍ Scribed by Sharmistha Ghoshal; Alokmoy Datta
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 229 KB
- Volume
- 181
- Category
- Article
- ISSN
- 0022-2852
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✦ Synopsis
A three-level system with two closely spaced upper levels pumped by an RF field is considered. All three transitions are assumed to be dipole-allowed. An IR field connects the transitions from the upper two levels to the lower one. Steady-state Doppler-broadened IR lineshape theory has been derived from the optical Bloch equations. The effects of multiple coupling and nonlinear response of the RF field on the IR absorption and dispersion lineshapes are investigated. The results show that under a strong RF field, zero or very low absorption is obtained at a slightly off-resonant point for certain values of the ratio of IR transition moments. The dispersion is found to be very high at that point, resulting in a huge enhancement of the refractive index. Thus, from the normal threelevel IR -RF -DR theory, one can predict enhancement of the refractive index if all three transitions are dipoleallowed. The IR lineshape theory also qualitatively explains the ''peculiar dispersive'' structures experimentally observed earlier for the CF 3 I molecule.