Ulagalandha Perumal Dharanipathy

High quality factor two dimensional GaN photonic crystal cavity membranes grown on silicon substrate

We report on the achievement of freestanding GaN photonic crystal L7 nanocavities with embedded InGaN/GaN quantum wells grown by metal organic vapor phase epitaxy on Si (111). GaN was patterned by e-beam lithography, using a SiO2 layer as a hard mask, and usual dry etching techniques. The membrane was released by underetching the Si (111) substrate. Micro-photoluminescence measurements performed at low temperature exhibit a quality factor as high as 5200 at ∼420 nm, a value suitable to expand cavity quantum electrodynamics to the near UV and the visible range and to develop nanophotonic platforms for biofluorescence spectroscopy.

Integrated photonics on silicon with wide bandgap GaN semiconductor

We report on GaN self-supported photonic structures consisting in freestanding waveguides coupled to photonic crystal waveguides and cavities operating in the near-infrared. GaN layers were grown on Si (111) by metal organic vapor phase epitaxy. E-beam lithography and dry etching techniques were employed to pattern the GaN layer and undercut the substrate. The combination of low-absorption in the infrared range and improved etching profiles results in cavities with quality factors as high as ∼5400. The compatibility with standard Si technology should enable the development of low cost photonic devices for optical communications combining wide-bandgap III-nitride semiconductors and silicon.

Single particle detection, manipulation and analysis with resonant optical trapping in photonic crystals

We demonstrate a resonant optical trapping mechanism based on two-dimensional hollow photonic crystal cavities. This approach benefits simultaneously from the resonant nature and unprecedented field overlap with the trapped specimen. The photonic crystal structures are implemented in a 30 mm × 12 mm optofluidic chip consisting of a patterned silicon substrate and an ultrathin microfluidic membrane for particle injection and control. Firstly, we demonstrate permanent trapping of single 250 and 500 nm-sized particles with sub-mW powers. Secondly, the particle induces a large resonance shift of the cavity mode amounting up to several linewidths. This shift is exploited to detect the presence of a particle within the trap and to retrieve information on the trapped particle. The individual addressability of multiple cavities on a single photonic crystal device is also demonstrated.

Statistics of the disorder-induced losses of high-Q photonic crystal cavities

We analyze and compare the effect of fabrication disorder on the quality factor of six well-known high-index photonic crystal cavity designs. The theoretical quality factors for the different nominal structures span more than three orders of magnitude, ranging from 5.4 × 10(4) to 7.5 × 10(7), and the defect responsible for confining light is introduced in a different way for each structure. Nevertheless, among the different designs we observe similar behavior of the statistics of the disorder-induced light losses. In particular, we show that for high enough disorder, such that the quality factor is mainly determined by the disorder-induced losses, the measured quality factors differ marginally - not only on average as commonly acknowledged, but also in their full statistical distributions. This notably shows that optimizing the theoretical quality factor brings little practical improvement if its value is already much larger than what is typically measured, and if this is the case, there is no way to choose an alternative design more robust to disorder.

High-Q silicon photonic crystal cavity for enhanced optical nonlinearities

We fabricate and experimentally characterize an H0 photonic crystal slab nanocavity with a design optimized for maximal quality factor, Q = 1.7 × 106. The cavity, fabricated from a silicon slab, has a resonant mode at λ = 1.59 μm and a measured Q-factor of 400 000. It displays nonlinear effects, including high-contrast optical bistability, at a threshold power among the lowest ever reported for a silicon device. With a theoretical modal volume as small as V = 0.34(λ/n)3, this cavity ranks among those with the highest Q/V ratios ever demonstrated, while having a small footprint suited for integration in photonic circuits.

Fabrication and characterization of integrated photonics structures on GaN-Based photonic crystal membranes grown on silicon

The fabrication and characterization of free-standing hybrid GaN photonic structures operating at 1.55 µm or in the visible range will be discussed. The structures are self-supported by tethers and coupled to photonic crystal waveguides and cavities. The fabrication process is based on the growth of GaN on Si, e-beam lithography and dry etching. W1 PhC waveguides and L3 cavities are investigated. The cavities exhibit quality factors as high as ∼ 5400. In the visible range, L7-type cavity with InGaN/GaN quantum wells exhibit modes with Q factors up to 5200 at ∼ 420 nm at 10 K.

Self-trapping and back-action effects in hollow photonic crystal cavity optical traps

We report on the first experimental demonstration of resonant optical trapping of dielectric particles in a two-dimensional hollow photonic crystal cavity. The cavities are implemented in an optofluidic chip consisting of a silicon-on-insulator substrate and an ultrathin microfluidic membrane, Resonant optical trapping of 500 nm polystyrene beads is achieved using less than 120 μW optical power in the cavity for trapping times reaching over ten minutes.

Single particle detection and self-trapping in hollow photonic crystal cavities integrated in a microfluidic environment

We demonstrate a functional microfluidic hollow photonic crystal cavity chip for single particle detection and optical manipulation. The use of a very thin PDMS membrane atop hollow photonic crystal cavities devices allows accurate monitoring of in-situ cavity-particle interaction as well as particle manipulation simultaneously. The dynamic resonance frequency shift of a particle inside the cavity region is experimentally and theoretically demonstrated. Evidences of a self-trapping of the particle in the resonant field are presented.

Microfluidic integrated hollow photonic crystal cavities for single particle and resonant field interaction

A microfluidic-integrated single particle sensor based on hollow photonic crystal cavities is reported. The interaction relies on the reversible resonance frequency shift induced by a dielectric particle near the cavity.