A quantum optical study of thresholdless lasing features in high-\u03b2 nitride nanobeam cavities

Stefan T Jagsch,Jean-François Carlin,Stephan Reitzenstein,Frederik Lohof,Christopher Gies,Frank Jahnke,Nicolas Grandjean,Axel Hoffmann,Stefan Kalinowski,Ian M Rousseau,Noelia Vico Triviño,Gordon Callsen,Roy Barzel,Raphaël Butté

doi:10.1038/s41467-018-02999-2

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.

Highlights

Exploring the limits of spontaneous emission coupling is one of the central goals in the development of nanolasers, it is highly relevant regarding future large-scale photonic integration requiring energy-efficient coherent light sources with a small footprint
The second-order autocorrelation function g(2) (τ) = hIðtÞIðt À τÞi=hIðtÞi2, where τ is the delay between photon counting events in both arms of a Hanbury-Brown and Twiss (HBT) interferometer, is expected to show an excitation powerdependent transition from thermal emission (ideally g(2)(0) = 2) to the Poisson limit with g(2)(0) = 1 at the onset of lasing
A convolution of the correlation function with the detector response function is measured and the thermal emission statistic can only be resolved if the coherence time approaches the detector resolution

Summary

Introduction

Exploring the limits of spontaneous emission coupling is one of the central goals in the development of nanolasers, it is 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. 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. Second-order (intensity) autocorrelation measurements evidence the onset of lasing via an excitation-power-density dependent transition in emission statistics from thermal bunching towards the Poisson limit, associated with the stimulated emission of photons, i.e. coherent light. Our results provide a comprehensive analysis of high-β lasing and possible pitfalls in its interpretation

Methods

Results

Conclusion