Nicolas Descharmes

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.

Hybrid PDMS/glass microfluidics for high resolution imaging and application to sub-wavelength particle trapping

We demonstrate the fabrication of a hybrid PDMS/glass microfluidic layer that can be placed on top of non-transparent samples and allows high-resolution optical microscopy through it. The layer mimics a glass coverslip to limit optical aberrations and can be applied on the sample without the use of permanent bonding. The bonding strength can withstand to hold up to 7 bars of injected pressure in the channel without leaking or breaking. We show that this process is compatible with multilayer soft lithography for the implementation of flexible valves. The benefits of this application is illustrated by optically trapping sub-wavelength particles and manipulate them around photonic nano-structures. Among others, we achieve close to diffraction limited imaging through the microfluidic assembly, full control on the flow with no dynamical deformations of the membrane and a 20-fold improvement on the stiffness of the trap at equivalent trapping power.

Dynamic optics for digital projection applications

We present a projection optical system incoporating a dynamic optical element and we outline some of its potentional applications for digital projections. We describe experiments undertaken to validate a variety of these applications, in particular: change of focus without mechanical motion of the focus group; correction of chromatic aberration; and correction of a variety of other aberrations. We conclude that dynamic optical element can be used to improve the quality of image achieved from a very simple digital projection optical system.

Dynamic optics for projection displays

We present a projection optical system incorporating a dynamic optical element and we outline some of its potential applications for digital projection displays. We describe experiments undertaken to validate one of these applications, the correction aberrations in a rear-projection television (RPTV) optical module where the original fold mirror is replaced by a simple MEMS deformable mirror.

Observation of Bloch Surface Waves in the Mid-Infrared Spectral Range, 2018 International Conference on Optical MEMS and Nanophotonics (OMN)

We present the observation of Bloch Surface Waves in the mid-infrared spectral range. A dielectric multi-layer coating made of ZnSe and YbF3 deposited on a CaF2 substrate is designed and fabricated specifically for that purpose. The structure supports the propagation of surface waves between 6.6 and 10.6 micrometres wavelength. A tunable quantum cascade laser setup is used to characterize the fabricated structure.

Investigation of the Propagation Length of Bloch Surface Waves on One Dimensional Photonic Crystals, 2018 International Conference on Optical MEMS and Nanophotonics (OMN)

A 1D photonic crystal structure sustaining optical surface waves is investigated. The propagation length of the surface mode is studied both using an eigenmode model and a rigorous time domain solver. The two models show good convergence. Our results demonstrate that by a carefully designed 1D photonic crystal, dielectric surface waves may propagate over several millimeters, even if a Kretschmann-type coupling configuration is used.

Bloch Surface Waves Fabry- Pérot Nanocavity

We demonstrate the first cavity confinement of Bloch surface waves in the fundamental mode of a Fabry–Perot cavity. The cavity consists of two distributed Bragg mirrors separated by a spacer of dimensions smaller than the wavelength (633nm). The cavity mode exhibits quality factor of 400. This quality factor is the highest recorded thus far for a subwavelength optical surface waves cavity.

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.