W. R. Babbitt

Real‐time optical waveform convolver/cross correlator

We show that an inhomogeneously broadened sample, excited by a series of three resonant optical pulses, emits an optical signal whose electric field envelope closely approximates the convolution or cross correlation of the field envelopes belonging to two of the three excitation pulses. The convolution (cross correlation) function is obtained when the first (second) pulse in the excitation sequence is short compared to the temporal structure of the other two excitation pulses.

Storage and time reversal of light pulses using photon echoes

We have studied the temporal profile of photon-echo signals generated by combined gated cw and pulsed dye-laser excitation of the inhomogeneously broadened, 555.6-nm absorption line of (174)Yb vapor. We find that the echo profile is, after time reversal, essentially identical with that of the first excitation pulse. We give a new analysis of this effect. Since time-reversed pulse reproduction should also occur in inhomogeneously broadened solid samples, and since we observe time-reversed reproduced pulses up to 4% as intense as the input pulse, this effect may have important applications in optical signal-processing systems.

Coherent transient optical pulse-shape storage/recall using frequency-swept excitation pulses

We demonstrate that frequency-chirped laser excitation pulses may be employed to generate coherent transient signals possessing the same temporal profile as a particular excitation pulse. In comparison with the short, fixedfrequency pulses used in previous studies of this effect, chirped pulses can be temporally longer, of lower intensity, and hence easier to generate. The experiment was performed on the 555.6-nm transition of vapor-phase atomic ytterbium, and pulse-shape information was stored in a coherence between excited-state Zeeman levels. A simple theoretical analysis of our results is presented.

Storage and phase conjugation of light pulses using stimulated photon echoes.

We experimentally demonstrate that three-excitation-pulse (i.e., stimulated) photon echo signals can be backward-propagating, phase-conjugate replicas of the second echo-excitation pulse. Working on the 555.6-nm absorption line of atomic Yb vapor, echo signals, effectively 0.5% as intense as the second excitation pulse, are shown to reproduce image information carried by the second excitation pulse even when wave-front distorters are employed.

Field-inhibited optical dephasing and shape locking of photon echoes

Using an acousto-optically gated cw dye laser and working on the 555.6-nm absorption line of atomic(174)Yb, we have studied the shape of two-excitation-pulse photon echoes as a function of the duration and intensity of the second excitation pulse. Surprisingly, a long and intense second excitation pulse is found to generate an echo having a shape highly correlated with that of the first excitation pulse. This occurs because the high field of pulse 2 effectively stops dephasing processes throughout its duration.

Convolution, Correlation, And Storage Of Optical Data In Inhomogeneously Broadened Absorbing Materials

We discuss the light signals that are coherently emitted by some optical absorbers sub-sequent to excitation by a series of three laser excitation pulses. In some cases, the light signal emitted by the material duplicates the temporal shape of one of the laser in-put pulses. In other cases, the emitted signal represents the convolution or cross-correlation of two of the laser input pulses. In principle, digitally encoded signals of multi-gigahertz bandwidth can be convolved in real time, or, in suitable materials, stored for long periods. Output signals on the order of a few percent as intense as the inputs are possible. We provide experimental demonstrations of these effects, and discuss their implementation in optical signal processing and data storage systems.

Interaction of transient temporally modulated laser radiation with simple atomic systems

We point out that the frequency‐selective nature of the light‐matter interaction can be utilized to effect the storage of a spectral image (Fourier transform) of a temporally structured light pulse in the absorption profile of an inhomogeneously broadened atomic ensemble, and that the stored information can be subsequently recalled in the form of a free‐induction‐decay signal. Applications of this process to optical data storage are discussed. We also consider the interaction of a phase‐controlled, amplitude‐grated, resonant laser field with the atoms in a collimated atomic beam. We describe experiments wherein suitably prepared atoms are placed in pure stationary‐states (dressed states) of the atom + laser‐field system, and note that atoms in pure dressed states should have interesting spectral and dynamical properties.