A quantum optical study of thresholdless lasing features in high-β nitride nanobeam cavities

Abstract

Exploring the limits of spontaneous emission coupling is not only one of the central goals in the development of nanolasers, it is also highly relevant regarding future large-scale photonic integration requiring energy-efficient coherent light sources with a small footprint. Recent studies in this field have triggered a vivid debate on how to prove and interpret lasing in the high-β regime. We investigate close-to-ideal spontaneous emission coupling in GaN nanobeam lasers grown on silicon. Such nanobeam cavities allow for efficient funneling of spontaneous emission from the quantum well gain material into the laser mode. By performing a comprehensive optical and quantum-optical characterization, supported by microscopic modeling of the nanolasers, we identify high-β lasing at room temperature and show a lasing transition in the absence of a threshold nonlinearity at 156 K. This peculiar characteristic is explained in terms of a temperature and excitation power-dependent interplay between zero-dimensional and two-dimensional gain contributions.

Delayed Transition to Coherent Emission in Nanolasers with Extended Gain Media

“…The only available g (2) (0) measurements performed in the parameter regime we associate with nanolasers with extended gain media are published in Ref. [26]. Upon close inspection, the results shown there indicate that the coherence threshold is also offset to the intensity threshold thereby confirming our prediction.…”

“…In this picture, a coherent (thermal) state of the light field is characterized by a Poissonian (Bose-Einstein) photon distribution function p n . This quantity can be accessed both in theory by using master-equation approaches [25][26][27][28], and in experiment by using photon-number-resolved detection schemes [29,30]. In practice, it is much easier to use the second-order photon autocorrelation function g (2) (0) to characterize the emission, as it can be readily mea-sured using Hanbury Brown and Twiss setups [31].…”

“…Assuming an active region of 0.3 µm 2 and a typical carrier density of 10 13 cm −2 yields an estimate for the maximum number of excitons of N = 3 × 10 4 . The parameters we use in the following correspond to that of the nanobeam-quantum-well laser investigated by Jagsch et al [26]. In addition to much larger N , reported Q factors for both the nanobeam and TMD nanolasers are significantly lower and are typically around 2500 [26,[33][34][35][36].…”

Ultrafast spin-lasers

“…We have revealed a new approach to overcome the bandwidth bottleneck by utilizing polarization as the information carrier in highly birefringent spinlasers. Even faster operation and lower energy-to-data ratios can be expected if PM is combined with high spontanous emission coupling or threshold-less nanolasers in future optical interconnects [33]. Lasers based on two-dimensional materials [34] which support very large strain and thus high birefringence [18] may offer unprecedented bandwidths.…”

Demonstration of critical coupling in an active III-nitride microdisk photonic circuit on silicon

“…III-nitride on silicon microdisks critically coupled to waveguides pose an important building block for more complex integrated photonic circuits that will greatly benefit the fields of both III-nitride and silicon photonics 28 . Potential applications range from visible-light communication 29 , to optical interconnects 30 , to on-chip quantum optics 31 and lab-on-chip applications, such as bio-sensing 32 and gene activation 33 .…”