Lasing from a Quantum-Dot-Like Buried Heterostructure in an InP Nanobeam Cavity

Abstract

We report lasing from a lithographically defined buried heterostructure with an estimated lateral footprint of (107 nm)^2, embedded in an InP photonic-crystal nanobeam cavity. This represents the smallest laterally confined buried heterostructure gain region from which lasing has been observed. Despite etching of the active region during cavity definition and the associated risk of surface-related nonradiative recombination, optically pumped devices exhibit a clear lasing threshold and a narrow linewidth. By systematically varying the BH size, we investigate how the lasing threshold depends on the active volume under optical pumping. The estimated intrinsic threshold under ideal carrier injection is 57 nW, comparable to values reported for single quantum-dot nanolasers, highlighting the potential of quantum-dot-scale buried heterostructures as deterministic, scalable gain media for nanophotonic lasers.

Figures (5)

• Figure 1: Scanning electron microscope image of a fabricated nanobeam laser. A sketch of the central region is shown below, highlighting the scale of two different BH lengths $l_\mathrm{BH}$ as compared to the holes. At the bottom, the cross-section of the BH is illustrated.
• Figure 2: (a) Emission spectra around the lasing wavelength measured far below, near, and above threshold. The spectrometer's exposure time is greatly reduced above the threshold, leading to increased noise. (b) Pump power dependent peak emission intensity of the lasing mode compared to the emission around $1446\, \mathrm{nm}$ and the background, which is taken at $1460\, \mathrm{nm}$.
• Figure 3: Output versus external pump power for the smallest BH laser. Three repeated measurements, the average curve, and the extracted thresholds (vertical dashed lines) are shown.
• Figure 4: The laser with $l_\mathrm{BH,eff}=107$ nm as measured in setup 2. (a): The fitted emission spectra at different pump powers. (b): From the fit of the spectra, peak wavelengths and widths are extracted and plotted as a function of the pump power. The pump powers in this figure cannot be directly compared to those in Figs. \ref{['fig:lasing']}-\ref{['fig:LL-repeated']}, as the injection efficiencies between the setups will differ.
• Figure 5: The extracted thresholds are plotted as a function of the BH size, and with a steady-state rate-equation model. The error bars indicate the standard deviation as found in figure \ref{['fig:LL-repeated']}. In the lower part of the plot, the internal threshold is estimated assuming pumping with unity quantum efficiency ($\eta_\mathrm{abs}=1$).