Abstract
The dynamics of mutually coupled nano-lasers subject to direct current modulation has been analyzed using rate equations, which include the Purcell cavity-enhanced spontaneous emission factor $F$ and the spontaneous emission coupling factor $\beta $ . Subject to two different modulation frequencies, the mutually coupled nano-lasers display two general types of response. The laser with the lower modulation frequency simply exhibits a response at that modulation frequency. Thus, we term a zero cross-talk response. On the other hand, at higher modulation frequencies the system displays a variety of dynamical responses which, in addition to zero cross-talk, includes a range of behaviors, which are classified from low cross-talk through to a complicated non-linear response. The precise behavior being dependent on the depth of modulation and the laser bias currents. The operational significance of the zero cross-talk regime is that it permits access to a simple periodic response at the modulation frequency. With a view to utilization, it is established that the region of zero cross-talk response enlarges with increasing modulation depth and increasing bias current. In this way, conditions are established, in which the lasers may act independently. The propensity for zero cross-talk response under stronger driving is consistent with previous analysis wherein modulated nano-lasers may have superior characteristics in the large-signal regime.
Highlights
Coupled lasers have been investigated for many decades [1]
At higher modulation frequencies the system displays a variety of dynamical responses which, in addition to zero cross-talk, includes a range of behaviours which are classified from low cross-talk through to a complicated non-linear response
In such work a variety of semiconductor lasers have been utilised with Vertical Cavity Surface Emitting Lasers (VCSELs) providing rich dynamical scenarios [7]
Summary
Coupled lasers have been investigated for many decades [1]. Activity on mutually coupled semiconductor lasers has long antecedents [2], [3] with significant effort having been given to identifying regimes of synchronization and instabilities [4]-[6]. This system is modelled using modified forms of rate equations which incorporate the Purcell enhanced spontaneous emission factor, F and spontaneous emission coupling factor, β have been included as introduced in [21]. A specific recommendation of [34] is that nano-lasers should be operated in a regime where a combination of Purcell enhanced spontaneous emission and Rabi oscillations could provide modulation bandwidths of 350 GHz. The present work does not utilise device parameters allowing entry into that regime but it is considered to be an exciting possibility which will stimulate further nano-laser device development. We focus the attention on the various responses which may be elicited by changing these latter parameters
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