The ability to induce, observe and control quantum coherent interactions inroom temperature, electrically driven optoelectronic devices is of outmostsignificance for advancing quantum science and engineering towards practicalapplications. We demonstrate here a quantum interference phenomena, Ramseyfringes, in an inhomogeneously broadened InAs/InP quantum dot (QD) ensemble inthe form of a 1.5 mm long optical amplifier operating at room temperature.Observation of Ramsey fringes in semiconductor QD was previously achieved onlyat cryogenic temperatures and only in isolated single dot systems. Ahigh-resolution pump probe scheme where both pulses are characterized by crossfrequency resolved optical gating (X-FROG) reveals a clear oscillatory behaviorboth in the amplitude and the instantaneous frequency of the probe pulse with aperiod that equals one optical cycle at operational wavelength. Using nominalinput delays of 600 to 900 fs and scanning the separation around each delay in1 fs steps, we map the evolution of the material de-coherence and extract acoherence time. Moreover we notice a unique phenomenon, which can not beobserved in single dot systems, that the temporal position of the output probepulse also oscillates with the same periodicity but with a quarter cycle delayrelative to the intensity variations. This delay is the time domainmanifestation of coupling between the real and imaginary parts of the complexsusceptibility.
展开▼
