Spontaneously detected photon echoes in excited molecular ensembles: a probe pulse laser technique for the detection of optical coherence of inhomogeneously broadened electronic transitions

Abstract

We present a simple and versatile laser technique for the detection of photon echoes in molecular excited ensembles. The method utilizes two optical pulses followed by a third probe pulse which converts the optical polarization induced by the laser into a change in excited population that gives rise to spontaneous emission. This way the photon echo burns the spontaneous emission and does not ride on the top of a large laser signal. The observation thus allows one to untangle the inhomogeneous electronic transitions by monitoring the emission into any vibrational level. The technique is capable of measuring as few as 10^6 molecules and should be applicable to a wide variety of problems in gases and solids that echo on the nanosecond (or perhaps picosecond) time scale.

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