LMI Seminar: Dynamics of Nanoscale Light Emitters

Abstract:

Nanoscale light emitters are ultra-compact light sources, which can be densely integrated on-chip with potential applications ranging from high-speed optical computing and sensing to chemical detection and nonlinear optical microscopy. In recent years, nanolaser research has shifted in direction from proof-of-concept demonstrations of novel nanoresonator architectures to the development and investigation of nanolasers with high spontaneous emission factors (β). High-β lasers can theoretically achieve ultra-low threshold energy since most of the spontaneous emission (SE) is funneled into the lasing mode. Furthermore, applications centered on high-speed on-chip communication and computing demand research focused on nonlinear dynamical phenomena, direct modulation and array architectures. Therefore, nanolasers also provide excellent miniaturized platforms to explore fundamental physics in the field of nonlinear dynamics.

In this presentation, we will review and offer further in-depth analyses in three key aspects of recent nanolaser research, including second order intensity correlation, g2(τ), characterizations, direct modulation and electromagnetic isolation in a dual nanolaser system. For coherence characterization, we will describe a technique exploiting not only the photon bunching peak, but also the g2(τ) pulse width to determine the spontaneous emission (SE), amplified SE and lasing regimes of a nanolaser with a high SE factor, β. We will show that this technique is applicable for lasers with β’s ranging from 10-5 to unity. Specifically, we demonstrate that by employing nanosecond pump pulses, different emission regimes of a nanolaser can be characterized via the full width at half maximum (FWHM) of a g2(τ) peak. We demonstrate the applicability of this technique with a high-β metallo-dielectric nanolaser and further report the first coherence measurement on this type of nanolaser operating at room temperature. We show that while peaks narrow in the spontaneous emission (SE) and amplified spontaneous emission (ASE) regimes as stimulated emission increases in proportion, their FWHMs increase in the lasing regime due to dynamical hysteresis (DH), a phenomenon triggered when a laser is driven across its threshold. The usage of nanosecond pulses is the key to the observation of DH and, therefore, essential to this characterization technique. Additionally, we will discuss direct current modulation of an electrically pumped metallo-dielectric nanolaser followed by the third important aspect concerning nanolaser research for dense integration. Here we investigate nanolasers that can operate without crosstalk. Although coupling between optical cavities when placed in proximity of one another has been widely reported, whether the phenomenon is induced for metal-clad cavities had not been investigated thus far. We discuss coupling between two metallo-dielectric nanolasers by reducing the separation between the two cavities. A split in the resonant wavelength and quality factor is observed, caused by the creation of bonding and anti-bonding supermodes. To preserve the independence of the two closely spaced cavities, the resonance of one of the cavities can be detuned relative to the other, thereby preventing coupling.