The possibility of using integrated photonics to scale multiple optical components on a single monolithic chip offers transformative advantages in fields such as communications, computing, bioengineering, and sensing. However, today’s integrated photonic circuits are rudimentary compared to the complexity of modern electronic circuits. Any advancements to efficiently integrate new photonic functionalities bring us closer to replicate the enormous impact of electronic integrated circuits.
Slow light propagation in chip-integrated nanophotonic structures with engineered band dispersion is a highly promising approach for controlling the relative phase of light and for enhancing optical nonlinearities on a chip. A primary goal in this field is to achieve devices with large, approximately constant group index (n_g) over the largest possible bandwidth, thereby enabling multimode and pulsed operation. We present an experimental record high group-index-bandwidth product (GBP) in genetically optimized coupled-cavity-waveguides (CCWs) designed by L3 photonic crystal nanocavities. The resulting designs were realized in SOI buckling-free suspended slabs with CCWs integrating up to 800 coupled nanocavities. The samples were characterized by measuring the CCW transmission, the mode dispersion through Fourier-space imaging, and ng via Mach-Zehnder interferometry. Various nanocavity designs were investigated, with theoretical n_g ranging from 37 to 100. Record high GBP = 0.47 was demonstrated over a bandwidth of 19.5 nm with a homogeneous flat-top transmission profile (variations lower than 10 dB) and losses below 56 dB/ns. Our results open the path towards building enhanced slow-light-based devices such as of slow-light-enhanced spectroscopic interferometers and single-photon buffers.
Cavity quantum electrodynamic (QED) effects are studied in semiconductor microcavities embedded with InGaAs
quantum dots. Evidence of weak coupling in the form of lifetime enhancement (the Purcell effect) and inhibition is
found in both oxide-apertured micropillars and photonic crystals. In addition, high-efficiency, low-threshold lasing is
observed in the photonic crystal cavities where only 2-4 quantum dots exist within the cavity mode volume and are not
in general spectrally resonant. The transition to lasing in these soft turn-on devices is explored in a series of nanocavities
by observing the change in photon statistics of the cavity mode with increasing pump power near the threshold.
Defects in photonic crystals (PCs) can support localized light modes with extremely small mode volumes. Depending on the symmetry of the PC, and the means of fabrication of the PC, extremely high quality factors (Q) are also possible. The combination of high Q and small mode volume should allow us to observe strong coupling between the cavity and quantum dot (QD) emitters that are strategically embedded within the cavity. This, in turn, has important implications for a variety of optical phenomena, such as single-photon sources. We describe the fabrication of PCs formed within membranes (180 nm thick) of GaAs, of either triangular or square lattice symmetry. The structures incorporate InAs QDs, grown monolithically with the PC material by Molecular Beam Epitaxy (MBE). We have observed emission from the smallest volume cavities (i.e. single-hole defects) in both the triangular and square lattice structures. The cavities have lattice constants ranging from 0.25 - 0.40 μm, and Q factors as high as 8500. To improve the probability of coupling a single QD to a cavity mode, we have developed a lithographic positioning technique capable of aligning a cavity to a feature on the surface within 50 nm, adequate to overlap a QD with a cavity mode. We will report on the progress achieved thus far with these structures and the challenges remaining to achieve strong coupling with specific QDs.
Conference Committee Involvement (3)
Photonic Crystal Materials and Devices
5 April 2016 | Brussels, Belgium
The Nature of Light: What are Photons? VI
10 August 2015 | San Diego, California, United States