Stabilizing nanolasers via polarization lifetime tuning

Abstract

We investigate the emission dynamics of mutually coupled nanolasers and predict ways to optimize their stability, i.e., maximize their locking range. We find that tuning the cavity lifetime to the same order of magnitude as the dephasing time of the microscopic polarization yields optimal operation conditions, which allow for wider tuning ranges than usually observed in conventional semiconductor lasers. The lasers are modeled by Maxwell–Bloch type class-C equations. For our analysis, we analytically determine the steady state solutions, analyze the symmetries of the system and numerically characterize the emission dynamics via the underlying bifurcation structure. The polarization lifetime is found to be a crucial parameter, which impacts the observed dynamics in the parameter space spanned by frequency detuning, coupling strength and coupling phase.

Spontaneous emission noise resilience of coupled nanolasers

“…The delay-coupled nanolasers are shown in Figure 1 and are described by the following set of macroscopic Maxwell-Bloch equations [class-C laser model, also used in (Roos et al, 2021)]:…”

“…For all parameter choices, the first laser threshold is at p (1) thr 0.5 due to the scaling with c ((2Δω)/(T 2 + 2)) 2 + 1. The detuning between the two lasers is 2δω, and it is implemented such that the rotating frame used for the fields is located equidistantly between the two laser frequencies (Roos et al, 2021). In addition to detuning, the lasers are modeled with identical parameters.…”

“…The coupling setup of the lasers is characterized by three parameters: the coupling strength K [we use a value of K = 0.1 corresponding to an intensity reflectivity of ≈ 20% (Roos et al, 2021), where effects due to back-reflected light are negligible (Schelte et al, 2019)], the coupling phase θ describing an additional phase shift between the interfering fields, and the time delay τ of the two laser fields due to the finite propagation speed of the signals [we consider a time delay of τ = 10 that refers to an onchip coupling distance of 800 μm and can experimentally be realized; see e.g., (Deka et al, 2020)]. Spontaneous emission is included via a stochastic Langevin term added to the field equation, given in Eq.…”

“…Frontiers in Photonics frontiersin.org emission states with complex dynamics even below the second threshold. Recently, the polarization lifetime T 2 was found to fundamentally influence the locking structure of two coupled class-C lasers (Roos et al, 2021). A scan of the dynamics found in the parameter plane of the coupling phase and the detuning is shown in Figure 2A for a dephasing time of T 2 = 1.…”

“…A scan of the dynamics found in the parameter plane of the coupling phase and the detuning is shown in Figure 2A for a dephasing time of T 2 = 1. The steady-state solutions, commonly referred to as compound laser modes (CLMs) (Erzgräber et al, 2006;Roos et al, 2021), can be followed in parameter space and are plotted in yellow/pink colors, as shown in Figure 2A. The color encodes the constant phase shift Δϕ between the emission of the two lasers, E j (t) E j (t)e iϕ j (t) , which is defined as follows (j = 1, 2 enumerates the lasers):…”