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

Abstract

Lasers distinguish themselves for the high coherence and high brightness of their radiation, features which have been exploited both in fundamental research and a broad range of technologies. However, emerging applications in the field of imaging, which can benefit from brightness, directionality and efficiency, are impaired by the speckle noise superimposed onto the picture by the interference of coherent scattered fields. We contribute a novel approach to the longstanding efforts in speckle noise reduction by exploiting a new emission regime typical of nanolasers, where low-coherence laser pulses are spontaneously emitted below the laser threshold. Exploring the dynamic properties of this kind of emission in the presence of optical reinjection we show, through the numerical analysis of a fully stochastic approach, that it is possible to tailor some of the properties of the emitted radiation, in addition to exploiting this naturally existing regime. This investigation, therefore, proposes semiconductor nanolasers as potential attractive, miniaturized and versatile future sources of low-coherence radiation for imaging.

Reservoir Computing and Task Performing through Using High-β Lasers with Delayed Optical Feedback

“…In order to properly simulate the proposed TDRC system based on a semiconductor microcavity laser with β = 10 −2 , we adopt a newly developed Stochastic Simulator (S-S) [38] by inserting the function modulation and feedback terms. S-S is specified as a semiclassical model, which can efficiently describe the dynamics for the lasers from macro-to microscale [36]. This model is unique in that it allows for the separate characterization of stimulated and spontaneous emission, which is different from the non-stochastic approaches.…”

“…In terms of model, the detail recurrence relations between different physical processes have been well defined in [38] with the optical feedback added as in [36]. In addition to the parameters detailed in previous work [36,38], we set the spontaneous emission coupling factor β of semiconductor laser to 10 −2 and ideally make the delay length to 0.6 m, which is corresponding to τ = 4 ns time delay. For the Mackey-Glass chaotic sequences prediction, the input signal is composed of 2.5P th + 5 × Mackey-Glass chaotic sequences (P th is the so-called threshold pump [40]).…”

“…High-β lasers possess small footprint and high efficiency for information processing [33], favoring the development of RC-based neuromorphic visual systems towards high speed, low consumption, and easy integration [34]. The main idea of this work is based on the delayed optical feedback and external carrier modulation, and considers the lasing transition region where the amplified spontaneous emission photons enable spiking dynamics in temporal [35,36]. We prove that the novel TDRC is not only efficient in dealing with several bench-marking tasks, including pattern recognition and Mackey-Glass chaotic sequences prediction, but the power consuming is also much lower than the previous ones by using low-β lasers.…”

Low-coherence semiconductor light sources: devices and applications

“…Their applications have also expanded in many scenarios; for example, chaotic-cavity lasers serve as a special type of broad-area lasers, have shown their promise in reducing coherence artifacts 33,34 , which benefits the display industries. Other potential applications in diverse fields are being explored, including instability suppression 35 , illumination 36 , communication 37 , and random number generation 38 . Collectively, these innovations play a pivotal role in driving breakthroughs across diverse scientific and technological fields.…”

Spontaneous emission noise resilience of coupled nanolasers

“…Here, we focus on the effect of spontaneous emission noise and derive insights about optimal conditions for the noise-resilient phase-locked operation of the two delay-coupled lasers. For our purpose, the exact noise distribution, e.g., as can be obtained via a stochastic simulator approach (Puccioni and Lippi, 2015;Wang et al, 2021), is less important. Hence, we use a simplified Langevin stochastic noise source.…”