Polarization of signal wave radiation generated by parametric four-wave mixing in rubidium vapor: Ultrafast ({approx}150-fs) and nanosecond time scale excitation

Journal Article · Mon Aug 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.023811· OSTI ID:20718210

Zhu, C -J; Senin, A A; Lu, Z -H; Gao, J; Xiao, Y; Eden, J G ^[1]

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1. Laboratory for Optical Physics and Engineering, Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States)

The polarization characteristics of the signal wave produced in Rb vapor by difference-frequency, parametric four-wave mixing (FWM) has been investigated for either ultrafast ({approx}150 fs) or nanosecond time-scale excitation of the 5s{yields}{yields}5d, 7s two photon transitions. The electronic configurations of the 5d {sup 2}D{sub 5/2} and 7s {sup 2}S{sub 1/2} states of Rb, as well as their energy separation ({approx}608 cm{sup -1}), offers the opportunity to examine separately the resonantly enhanced 5s{yields}{yields}7s, 5d{yields}6p{yields}5s FWM pathways on the nanosecond time scale and then to drive both channels simultaneously with an ultrafast pulse of sufficient spectral width. As expected, dye laser ({approx}10 ns) excitation of the 5s{yields}{yields}5d (J=5/2) transition produces a signal wave ({lambda}{sub s}{approx}420 nm) having the same ellipticity as the driving optical field. Two photon excitation of Rb (7s) on the same time scale, however, generates an elliptically polarized signal when the pump is linearly polarized ({epsilon}=1), a result attributed to 7s{yields}6p, 5p amplified spontaneous emission at {approx}4 {mu}m and {approx}741 nm, respectively. Simultaneous excitation of the 5s{yields}{yields}7s, 5d transitions with {approx}150 fs pulses centered at {approx}770 nm yields polarization characteristics that can be approximated as a superposition of those for the individual transitions, thus displaying weak coupling between the two FWM channels. Also, the influence of molecular contributions to the FWM signal is observed for Rb number densities above {approx}5x10{sup 14} cm{sup -3}.

• OSTI ID: 20718210
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 2 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
COUPLING
DYE LASERS
ELECTRONIC STRUCTURE
ENERGY LEVELS
EXCITATION
FREQUENCY MIXING
LASER RADIATION
OPTICAL PUMPING
PHOTON-ATOM COLLISIONS
PHOTONS
POLARIZATION
PULSES
RUBIDIUM
SIGNALS
SUPERRADIANCE
VAPORS