Lasing from a circular Bragg nanocavity with an ultrasmall modal volume

Abstract

We demonstrate single-mode lasing at telecommunication wavelengths from a circular nanocavity employing a radial Bragg reflector. Ultrasmall modal volumes and submilliwatt pump thresholds level are observed for lasers with InGaAsP quantum well active membrane. The electromagnetic field is shown to be tightly confined within the 300 nm central pillar of the cavity. The quality factors of the resonator modal fields are estimated to be on the order of a few thousands. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1947375͔The quest for the ultimate localization of light has been one of the central directions in contemporary research in many fields, such as integrated optics, quantum communication and computation, sensing, and more. 1-3 Optical nanocavities with high-quality factors ͑Q͒ and small modal volume ͑V mode ͒ are key elements for a wide variety of applications, such as functional building blocks for integrated optical circuits, lasers, optical traps, and optical logic. 4,5 In the past few years, much attention was focused on decreasing the modal volume and improving the Q of photonic crystal ͑PC͒ defect cavities by carefully optimizing the position, dimensions, and shape of the holes composing the crystal. [6][7][8][9] This optimization procedure attempts to tune the effective length of the cavity to the maximal reflection frequency of the PC reflector and is generally conducted numerically. The main disadvantage of this process is the enormous number of parameters to be optimized and the endless number of configurations that potentially need to be considered.Recently, we have proposed and demonstrated a novel class of circular resonators that are based on optimally designed radial Bragg reflectors. 9-11 These devices, known as annular Bragg resonators ͑ABRs͒, are designed to support azimuthally propagating modes, with energy concentrated within a radial defect region or in a central pillar by radial Bragg reflection. Compared to conventional resonators based on total-internal reflection ͑TIR͒, the employment of the Bragg reflection mechanism offers improved control over the resonator parameters ͑Q, V mode , etc.͒ and allows for engineering unique mode profiles. Compared to PC defect resonators, the radial symmetry of ABRs allows for analytical engineering the Bragg reflector for optimized Q and smaller modal volume. These properties make the ABR structure highly suitable for realizing ultracompact cavities, especially if they are designed for the mode with angular modal number m = 0. The m = 0 mode is an interesting solution of a disk Bragg resonator consisting of a disk surrounded by a radial Bragg stack ͑see Fig. 1͒. Unlike other solutions with nonzero angular modal numbers, the m = 0 mode is nondegenerate and features maximum intensity at the center of the device. This mode cannot be supported in conventional cavities because the propagation direction of the waves is perpendicular to the cavity interfaces.In this letter, we report on the observation of single mode lasing from a Bragg-based dis...

A comparative study of modal properties of surface-emitting circular bragg micro-lasers

“…This is not surprising and can be inferred from their unique modal profiles listed in Table I. Actually our prior experimental work has demonstrated single-mode lasing with ultrasmall modal volume in a nanosized disk CBML fabricated in InGaAsP [3]. Clearly, a disk configuration is preferable in ultracompact laser design.…”

“…Surface-emitting lasers with a circular emission aperture are particularly useful in optical communications because they can produce circularly-symmetric, narrow-divergence laser beams [1][2][3]. With optical gain, circular Bragg microresonators can be engineered for such applications -the radial Bragg reflector not only provides feedback for the in-plane fields but also couples the laser radiation out of the plane vertically.…”

Programming of inhomogeneous resonant guided wave networks

“…metamaterials). The discovery of photonic crystals [1,2] led to extremely high quality factor cavities using all dielectric materials based on the idea of Bragg wave physics [3,4]. The field of metamaterials [5,6] enabled the exciting research area of transformation optics [7] based on the ability to locally tune the material electromagnetic properties.…”

Optimization of circular photonic crystal cavities - beyond coupled mode theory

“…Recently, it was suggested to employ radial Bragg layers instead of PC to confine light in small cavities [24]. The radial structure offers significant advantages for optimal cavity design, primarily because it enables analytic design of the layer structure and optimal tailoring of the cavity size and the reflector periodicity.…”