We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.

We consider group delay and broadening using two strongly absorbing and widely spaced resonances. We derive relations which show that very large pulse bandwidths coupled with large group delays and small broadening can be achieved. Unlike single resonance systems the dispersive broadening dominates the absorptive broadening which leads to a dramatic increase in the possible group delay. We show that the double resonance systems are excellent candidates for realizing all-optical delay lines. We report on an experiment which achieved up to 50 pulse delays with 40% broadening.A variety of applications in telecommunications and quantum information have been driving recent interest in slow group velocities of light pulses. Among these applications are continuously tunable delay lines, all-optical buffers [1], optical pattern correlation, ultra-strong crossphase modulation [2], low light level nonlinear optics [3,4,5], and numerous others. The means for obtaining ultra-slow group velocities have usually involved a Lorentzian transparency or gain resonance: electromagnetically induced transparency (EIT) [6,7,8,9,10], coherent population oscillations (CPO) [11,12,13], stimulated Brillouin scattering (SBS) [14,15,16], stimulated Raman scattering (SRS) [17,18] etc..In this paper we discuss delaying pulses whose center frequency lies between two strongly absorbing resonances. Many researchers have considered using gain doublets in the context of pulse advancement [19,20,21,22,23], and Macke and Segard [22] have discussed pulse advancements for absorptive doublets. Grischkowsky [24] measured the delay of a pulse between two Zeemanshifted absorbing resonances, and Tanaka et al. [25] performed initial measurements of the delay of a pulse between two atomic hyperfine resonances. This work considers both delay and broadening with an emphasis on the suitability of the delay and broadening characteristics for practical applications.In the context of optical delay lines, several criteria must be satisfied for slow light to be useful. First, the slowed light pulses must meet system bandwidth specifications. Second, the delay-bandwidth product must be much larger than unity. Third, the delay re-configuration rate should be faster than the inverse pulse propagation time through the medium. Fourth, pulse absorption must be kept to a minimum. Fifth, the pulse broadening should also be minimal. The exact requirements for practical optical buffers are application dependant. A typical system operating at 10 Gb/sec with return-tozero coding and a 50 % duty cycle might require 7.5 GHz signal bandwidth, a delay bandwidth product of 1000, a re-configuration rate in excess of 7.5 MHz with less than 90% absorption and pulse broadening of less than 2.Despite widespread interest in large pulse delays, simultaneously satisfying all five criteria for most applications has proven difficult. In this paper we show that double Lorentzian systems manages four of these criteria well: large bandwidth, large delay bandwidth product, minimal absorption and ...

We use the separated-beams method to measure the second-order nonlinear optical tensors of the crystals KTiOPO4, KTiOAsO4, RbTiOPO4, and RbTiOAsO4 for second-harmonic generation of 1064-nm light. Our results agree well with most previous measurements but have improved precision.

We report on the experimental realization of large fractional pulse delays in a hot, Doppler-broadened rubidium vapor. A pump laser burns a deep spectral hole in the inhomogeneously broadened vapor. The delay is shown to be widely tunable by both power broadening the resonance and frequency modulating the pump laser. The simplicity of the scheme opens up the possibility for practical optical delays and buffers.

We report observations of the dynamics of electromagnetically induced transparency ͑EIT͒ in a ⌳ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well with theory.

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