Coherent Inhibition of Superfluorescence in a Cascade Three-Level System.
Abstract
The output of a synchronously pumped dye laser is frequency selected at lambda = 8851A and amplified to produce nearly transform-limited 10ps pulses in order to resonantly two-photon excite a coherent superposition between the 6S_{1/2 } and 6D_{3/2} states (two-photon coherence) of Cs atoms. Superfluorescence (SF) at lambda = 8761A, corresponding to the upper 6D_{3/2} -6P_{1/2} transition, is observed in both the forward (parallel to the pump beam) and the backward directions. Superradiance (SR) at lambda = 8944A, corresponding to the lower 6P_{1/2}-6S_ {1/2} transition, is also observed, but only in the forward direction. In addition, SF from the lower transition is observed in the backward direction. The laser excitation pulse exits the sample long before the onset of any superfluorescence pulse. SF in the forward direction is delayed in time compared to SF in the backward direction on the upper transition. SR on the lower transition is generated simultaneously with the SF on the upper transition in the forward direction. These last two observations provide experimental evidence that forward superfluorescence is inhibited by two-photon coherence in a cascade three -level system. More energy is radiated in the backward SF than in the forward SF because of the population competition between the SF in the two directions. To understand the experimental results, we numerically studied the response of a partially inverted three-level system to a weak and short optical pulse resonant with the upper transition. The results of the numerical calculation agree with the experiment qualitatively.
- Publication:
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Ph.D. Thesis
- Pub Date:
- January 1995
- Bibcode:
- 1995PhDT........70L
- Keywords:
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- Physics: Atomic; Physics: Optics