Surface-normal emission of a high-Q resonator using a subwavelength high-contrast grating

Abstract

We report a novel high-quality (Q) factor optical resonator using a subwavelength high-contrast grating (HCG) with in-plane resonance and surface-normal emission. We show that the in-plane resonance is manifested is by a sharp, asymmetric lineshape in the surface-normal reflectivity spectrum. The simulated Q factor of the resonator is shown to be as high as 500,000. A HCG-resonator was fabricated with an InGaAs quantum well active region sandwiched in-between AlGaAs layers and a Q factor of >14,000 was inferred from the photoluminescence linewidth of 0.07 nm, which is currently limited by instrumentation. The novel HCG resonator design will serve as a potential platform for many devices including surface emitting lasers, optical filters, and biological or chemical sensors.

Ultracompact resonator with high quality-factor based on a hybrid grating structure

“…In this paper, we show that an HG-based resonator performs just as well as a resonator based on an HCG structure [10]. The mechanism responsible for achieving the high Q-factor resonance is explained, considering interactions between modes in the grating layer, the cap layer, and the input and output media.…”

“…The reason is that the HG structure inherently does not possess mirror symmetry along the z direction, which results in different decay rates of the electromagnetic energy stored in the HG structure into input and output regions [29]. In contrast, HCG resonators suspended in air have mirror symmetry and the reflectivity varies from 100% to 0% around a resonance peak [10,30]. Figure 4(a) shows the field profile of this high-Q resonance excited by a TM polarized plane wave incident from the air side.…”

“…The broadband nature of the HCG has brought many novel features to vertical-cavity surface-emitting lasers (VCSELs) [2][3][4][5][6][7][8][9]. Also, HCG-resonator lasers with surface normal emission have been demonstrated, with properties of interest for sensing, communication, or display applications [10,11]. Extensive theoretical studies of HCGs have revealed that the high index-contrast between the grating and surrounding materials is essential for achieving the extraordinary properties [12].…”

“…Extensive theoretical studies of HCGs have revealed that the high index-contrast between the grating and surrounding materials is essential for achieving the extraordinary properties [12]. Thus, all HCG designs reported so far employ low refractive index materials such as air and oxides, for the incident as well as exit medium [1][2][3][4][5][6][7][8][9][10][11].…”

“…The HG resonator-based laser (hereafter called HCG resonator laser) structure could have several advantages compared to the HCG resonator laser structure [10]. In the HCG resonator laser structure, a gain material is integrated inside the grating bars while the HG resonator laser structure has a gain material in the cap layer.…”