From fabrication to mode mapping in silicon nitride microdisks with embedded colloidal quantum dots

Abstract

We report on the fabrication of free-standing and optically active microdisks with cadmium-based colloidal quantum dots embedded directly into silicon nitride. We show that the process optimization results in low-loss silicon nitride microdisks. The Si3N4 matrix provides the stability necessary to preserve the optical properties of the quantum dots and observe efficient coupling of the photoluminescence to the resonating microdisk modes. Using a spectrally and spatially resolved microphotoluminescence measurement, we map the emission pattern from the microdisk. This technique allows us to identify the resonant modes. The results show good agreement with numerical mode simulations.

Fabrication and characterization of on-chip silicon nitride microdisk integrated with colloidal quantum dots

“…This spectrum is dominated by the broad background PL of the QDs and only a few of the WGM, as indicated by the red arrows are vaguely visible. Similar spectra reported in previous work [10,12] show that this background is unavoidable in free-space collection.…”

“…Nevertheless, it should be mentioned that the wavelength-dependent coupling coefficient in the vertical coupling scheme cannot be neglected under some circumstances, for instance, when changing the coupling offset, we also observe a considerable shift in the PL spectra envelopes (not shown here). It is also important to note that, although the absolute intensity may decrease [12], the PL spectra of the QDs after embedding them in the SiN stack exhibits almost the same peak position and overall profile as the original PL spectra of the QDs in solution.…”

“…From a practical viewpoint, it is also important that the active SiN-QD devices should be coupled with on-chip passive waveguides, allowing to combine multiple devices or to couple light in and out of devices. In fact, colloidal QDs have already been integrated with various types of passive SiN building blocks, including photonic crystal nanocavities [10,11] and micro-resonators [12]. In all these demonstrations, the QDs were integrated in an individual component and often experimental results show either weak coupling of QD emission into optical modes or low out coupling efficiency, because either they lack an effective embedding scheme or they lack an efficient coupling scheme.…”

Silicon and silicon nitride photonic circuits for spectroscopic sensing on-a-chip [Invited]

“…Achieving this requires combining an active medium with Si 3 N 4 building blocks such as waveguides and resonators [47,48]. To this end, we have been investigating colloidal quantum dots (QDs), a novel class of materials with efficient and broadly tunable luminescence.…”

Hybrid light-emitting polymer/SiN_x platform for photonic integration

“…SiN x has been widely used in the complementary metal-oxide-semiconductor (CMOS) industry as electrical and chemical isolation [19]. Furthermore, SiN x is transparent from the visible to near-infrared spectral region, making it a high performance solution for PICs [20][21][22].…”