Hollow Photonic Crystal Cavities Research Articles

Gram-type differentiation of bacteria with 2D hollow photonic crystal cavities

Fast and label-free techniques to analyze viruses and bacteria are of crucial interest in biological and bio-medical applications. For this purpose, optofluidic systems based on the integration of photonic structures with microfluidic layers were shown to be promising tools for biological analysis, thanks to their small footprint and to their ability to manipulate objects using low powers. In this letter, we report on the optical trapping of living bacteria in a 2D silicon hollow photonic crystal cavity. This structure allows for the Gram-type differentiation of bacteria at the single cell scale, in a fast, label-free, and non-destructive way.

Thermal fluctuation analysis of singly optically trapped spheres in hollow photonic crystal cavities

We report on the behaviour of singly optically trapped nanospheres inside a hollow, resonant photonic crystal cavity and measure experimentally the trapping constant using back-focal plane interferometry. We observe two trapping regimes arising from the back-action effect on the motion of the nanosphere in the optical cavity. The specific force profiles from these trapping regimes is measured.

Observation of backaction and self-induced trapping in a planar hollow photonic crystal cavity.

The optomechanical coupling between a resonant optical field and a nanoparticle through trapping forces is demonstrated. Resonant optical trapping, when achieved in a hollow photonic crystal cavity is accompanied by cavity backaction effects that result from two mechanisms. First, the effect of the particle on the resonant field is measured as a shift in the cavity eigenfrequency. Second, the effect of the resonant field on the particle is shown as a wavelength-dependent trapping strength. The existence of two distinct trapping regimes, intrinsically particle specific, is also revealed. Long optical trapping (>10 min) of 500 nm dielectric particles is achieved with very low intracavity powers (<120 μW).

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.

Numerical modelling of optical trapping in hollow photonic crystal cavities

Photonic crystal (PhC) devices owing to their strong confinement of electromagnetic energy are considered to be excellent candidates for on chip optical trapping of dielectric or biological particles in the nanometer range. In this work, we study and present hollow PhC cavities and characterize them for their trapping stiffness, trapping stability and variation of resonance wavelength due to the presence of various sized single particles in the cavity.