Generic picture of the emission properties of III-nitride polariton laser diodes: Steady state and current modulation response

Abstract

The main emission characteristics of electrically-driven polariton lasers based on planar GaN microcavities with embedded InGaN quantum wells are studied theoretically. The polariton emission dependence on pump current density is first modeled using a set of semi-classical Boltzmann equations for the exciton-polaritons that are coupled to the rate equation describing the electron-hole plasma population. Two experimentally relevant pumping geometries are considered, namely the direct injection of electrons and holes into the strongly coupled microcavity region and intracavity optical pumping via an embedded light-emitting diode. The theoretical framework allows the determination of the minimum threshold current density J thr,min as a function of lattice temperature and exciton-cavity photon detuning for the two pumping schemes. A J thr,min value of 5 Acm −2 and 6 Acm −2 is derived for the direct injection scheme and for the intracavity optical pumping one, respectively, at room temperature at the optimum detuning. Then an approximate quasi-analytical model is introduced to derive solutions for both the steady-state and high-speed current modulation. This analysis makes it possible to show that the exciton population, which acts as a reservoir for the stimulated relaxation process, gets clamped once the condensation threshold is crossed, a behavior analogous to what happens in conventional laser diodes with the carrier density above threshold. Finally the modulation transfer function is calculated for both pumping geometries and the corresponding cutoff frequency is determined.

Holographic arrays based on semiconductor microstructures

“…It is assumed that the conducting layers can be independently connected to control electronics (not shown). 28,31,32 resonances at room temperature. A second conducting layer is placed in the structure between the two quantum wells.…”

“…In principle, this layer could also be made from metal, in which case, the system is similar to the double-metal contact devices that are in development for polariton lasers. 28,31,32 However, it should be pointed out that only a few structures have been successfully grown with metal layers between other layers in the system, for example, in a pioneering paper where organic layers acted as spacers. 33 In GaN-based systems, the use of a transparent conductive oxide (TCO), such as indium tin oxide is perhaps a more-established technique.…”

Optical Bistability in Electrically Driven Polariton Condensates

“…For the description of the observed phenomenon, we exploit a set of standard rate equations, which describe the formation of a polariton condensate from an incoherent electron-hole reservoir, similar to Refs. [1,33]. The difference in our approach, which eventually results in bistability, lies in a feedback mechanism which takes into account an interplay between the persisting electric field of the polariton diode and electrostatic screening.…”

Why do we need polariton lasers?

“…2 The first room-temperature polariton laser with optical pumping was realized in 2007 by a collaboration of the Southampton and Lausanne groups. 3 At present, optimized schemes of electrically pumped polariton lasers based on gallium nitride (GaN) microcavities are discussed in the literature 4 (see Figure 1).…”

“…Polariton lasers are expected to have lower thresholds than conventional semiconductor lasers. 4 Their output power is quite limited, however, because exciton-polaritons dissociate at strong pumping. Consequently, the area of application for polariton lasers still needs to be defined.…”