Acoustic Phonon-Induced Dephasing in Gallium Nitride Defect-Based Quantum Emitters

TL;DR

This study investigates how acoustic phonons cause dephasing in GaN defect-based quantum emitters, revealing temperature-dependent spectral broadening mechanisms that impact their use in quantum information technologies.

Contribution

The paper provides the first detailed experimental and theoretical analysis of acoustic phonon-induced dephasing in GaN defect quantum emitters, highlighting the role of both acoustic and optical phonons.

Findings

PL linewidth remains constant at low temperatures due to spectral diffusion

Line shape transitions from Gaussian to Lorentzian with increasing temperature

Dephasing modeled by quadratic Stark effect modulated by acoustic phonons

Abstract

GaN defect based quantum emitters have recently gained attention as promising single photon sources for quantum information applications. However, dephasing processes, manifested as photoluminescence (PL) linewidth broadening, pose a limitation to photon indistinguishability. In this study, we use a custom built confocal scanning microscope to examine the temperature dependent PL spectra of GaN defect quantum emitters integrated with solid immersion lenses, with the goal of elucidating their dephasing mechanisms. Our experimental findings show that at low temperatures, the PL lineshape exhibits a Gaussian profile with a constant, temperature independent linewidth, consistent with spectral diffusion. As the temperature increases, the PL lineshape evolves into a Lorentzian, and the temperature dependent linewidth deviates from the common T3 law. Considering the Debye temperature of GaN (about 600 K), the experimentally observed temperature dependent linewidth can be modeled by the quadratic Stark effect modulated by acoustic phonons in defect rich crystals. Furthermore, this model exhibits a level of accuracy comparable to that of the defect-E2(low) optical phonon coupling model previously reported in the literature. Our work reveals the mechanism of acoustic phonon induced dephasing in GaN defect emitters and demonstrates that both acoustic and optical phonons can contribute to their dephasing.