Communication Dans Un Congrès Année : 2017

Do micro- and nanolasers actually have thresholds ?

Résumé

Nanolasers are key components of future photonics integrated circuits, and their impact on the rapidly evolving field of information technology is already taking shape in the form of devices which promise ever faster transmission and better integration levels. Yet, the physics of their lasing transition remains comparatively poorly understood. Indeed, their response to pumping combine : a) the memory effects introduced by the slow material response in “Class B” devices [1], b) a high sensitivity to spontaneous emission [2], the fraction of spontaneous emission coupled into the lasing mode ranging from  ~10-4 in microlasers to  ~10-2 in nanolasers, and c) an operation at very low photon flux levels that complicates the exploration of their extended threshold region. We have thus performed, through photon counting measurements in a standard Hanbury-Brown & Twiss (HBT) configuration, a systematic characterization of the threshold region of a commercial VCSEL microlaser (Thorlabs @980 nm). This choice represents a happy compromise between a significant  ~10-4 and a large enough cavity size to also observe the temporal dynamics through fast photodetectors (10 GHz) and detection chain (6 GHz analog bandwidth LeCroy oscilloscope, 106 points per trace). These two combined sets of measurements yield several unexpected observations and conclusions : —Values of g(2)(0) in excess of 2 : while g(2)(0) = 2 is the upper limit for a stationary chaotic signal, small-size lasers sensitivity to spontaneous emission invalidate this approximation by spontaneously inducing a spiked, time-dependent dynamics. Theoretically, g(2)(0) in then inversely proportional to the duration of the pulses, thus unbounded. —The signature of a (fluctuating) coherent signal at very low pump intensities, down to one tenth of the conventionnal, full coherence threshold. This signature is obtained by inserting a Mach-Zender interfererometer before the HBT beamsplitter [3] —Evidence that, while the photon statistics can theoretically be equivalently described either by the probability density function (PDF) of the laser’s output signal or by the measurement of coincidences in the arrival times, the equivalence of these typical “classical” and “quantum” approaches doesn’t hold when measurements are limited to the second moments (g(2)).

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Dates et versions

hal-03566511 , version 1 (11-02-2022)

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  • HAL Id : hal-03566511 , version 1

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Djeylan Aktas, Tao Wang, Olivier Alibart, Gian-Luca Lippi, Éric Picholle, et al.. Do micro- and nanolasers actually have thresholds ?. 8th IQFA colloquium, 2017, Nice, France. ⟨hal-03566511⟩
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