“Amplified Spontaneous Emission” in Micro- and Nanolasers

Abstract

Amplified Spontaneous Emission is ubiquitous in systems with optical gain and is responsible for many opportunities and shortcomings. Its role in the progression from the simplest form of thermal radiation (single emitter spontaneous emission) all the way to coherent radiation from inverted systems is still an open question. We critically review observations of photon bursts in micro- and nanolasers, in the perspective of currently used measurement techniques, in relation to threshold-related questions for small devices. Corresponding stochastic predictions are analyzed, and contrasted with burst absence in differential models, in light of general phase space properties. A brief discussion on perspectives is offered in the conclusions.

Nanolasers with Feedback as Low-Coherence Illumination Sources for Speckle-Free Imaging: A Numerical Analysis of the Superthermal Emission Regime

“…In order to properly account for the statistical properties of the emission in the transition region, characterized by photon bursts [42,43], we make use of a Stochastic Simulator [44] (or Stochastic Laser Simulator, SLS), based on a semiclassical description [45] of lasing. The intrinsic advantage of the SLS is the rapid prediction of trajectories, and their statistics, without any hypotheses on the noise structure: all physical processes (including spontaneous emission, relaxations and photon transmission and reinjection) are modeled as probabilistic processes based on their characteristic time constants.…”

“…Thermal (or chaotic) radiation, described by Gaussian statistics, gives g (2) (0) = 2, which decays towards g (2) (τ) → 1 as τ → ∞: photons that are progressively distant in time become gradually independent; thus, converging towards a Poisson probability distribution. Superthermal statistics, g (2) (0) > 2, correspond to highly bunched photons, whose mutual, zero-delay (τ = 0) correlation is a representation of pulsing behavior [36,42,43,51]. The physical origin of the pulses is the rapid amplification of a fluctuation through stimulated emission due to an excess of accumulated energy in the material (population inversion) [43].…”

“…Superthermal statistics, g (2) (0) > 2, correspond to highly bunched photons, whose mutual, zero-delay (τ = 0) correlation is a representation of pulsing behavior [36,42,43,51]. The physical origin of the pulses is the rapid amplification of a fluctuation through stimulated emission due to an excess of accumulated energy in the material (population inversion) [43]. The phenomenon is the extreme form of the depletion that occurs when switching up the pump in a class B laser [52], where coupled oscillations take hold between population and photon number (e.g., spiraling trajectories in phase space [53]).…”

“…In a nanolaser, the large photon bursts that precede the nanolaser threshold deplete the energy reservoir, causing their own extinction [43]. Since coherence is established and maintained by the action of stimulated emission-even though each photon burst is (partially) coherent with itself (due to the broadband properties of ASE [55][56][57][58]), subsequent pulses are mutually incoherent as they start from a different initiating (spontaneous) photons.…”

Physics and Applications of High‐β Micro‐ and Nanolasers

“…Photon‐statistical work on early lasers [ 80,103 ] established that the transition between incoherent and coherent emission takes place through a statistical mixture of the two kinds of radiations. [ 102 ] Photon bursts may enlarge the picture by describing the temporal evolution which was summarized in those statistical considerations. [ 102 ]…”