Near-field optical forces arise from evanescent electromagnetic fields and can be advantageously used for on-chip
optical trapping. In this work, we investigate how evanescent fields at the surface of photonic cavities can efficiently trap
micro-objects such as polystyrene particles and bacteria. We study first the influence of trapped particle’s size on the
trapping potential and introduce an original optofluidic near-field optical microscopy technique. Then we analyze the
rotational motion of trapped clusters of microparticles and investigate their possible use as microfluidic micro-tools such
as integrated micro-flow vane. Eventually, we demonstrate efficient on-chip optical trapping of various kinds of bacteria.
Proc. SPIE. 7608, Quantum Sensing and Nanophotonic Devices VII
KEYWORDS: Resonators, Microscopy, Photonic crystals, Near field scanning optical microscopy, Near field, Geometrical optics, Signal detection, Optical microcavities, Near field optics, Photonic nanostructures
The fundamentals of the near-field interaction between a subwavelength tip and a photonic-crystal
nanocavity are investigated experimentally and theoretically. It is shown experimentally that the cavity
resonance is tuned without any degradation by the presence of the tip and that the reported near-field
interaction is strongly related to the field distribution within the nanostructure. From the interaction between
the probe and the cavity, we will show a new kind of microscopy.
Ultrahigh Q/V lineic silicon Fabry Perot (FP) microcavities relying on silica substrate have been fabricated. Two cavities
designs are studied based respectively on cavity mode losses recycling and on mirrors with tapered sections. The
experimental evolution of cavities characteristics are studied as a function of sample temperature. The authors achieve a
quality factor of 58000 for a modal volume of 0.6 (λ/n)3.
Short microcavities consisting of two identical tapered hole mirrors etched into silicon-on-insulator ridge waveguides are investigated. They are designed for operating at telecom wavelength. We describe theoretically and experimentally two different ways to boost quality factors to some thousands. In one hand, we investigate the adaptation of mode profile to suppress mismatch losses. In an other hand, we explore the recycling of the losses. We obtained quality factor up to 3000, which opens the route to WDM applications.
Recently, integrated optic applications on SOI substrate like add-and-drop structures or wavelength filters based on microdisk resonators have been investigated by many research groups. Microdisks exhibiting high quality-factor thanks to the high refractive index contrast between silica and silicon materials have been already reported. However efficient components usually show few micrometers diameter which is huge compared to photonic crystals ones. In this paper, realization and characterization of efficient and compact components are reported. The dropped-wavelength function, composed of a 1.5 μm radius disk and 0.3 μm x 0.3 μm square section waveguides is demonstrated. 22 dB extinction ratio is measured from spectral measurement while keeping a quality factor of 1000. In this structure, the distance between the microdisk and the waveguide is discussed from experimental point of view. Indeed, the efficiency of the add-and-drop strongly depends on this parameter. Moreover, a wavelength filter based on a 4 μm radius microdisk is also shown. Quality-factors of 92,900 ± 5500 were measured showing that these filters are more efficient than equivalent microring filters. A 10 dB extinction ratio of the wavelength rejected signal is reported. For some resonance wavelengths, spectral response degeneracy of the filter appears. An explanation of this effect is given in this paper.
In the past few years, many studies have been carried out to use the ability of light to transport information into silicon-based integrated photonic circuits. The realization of an efficient silicon-based light source is therefore necessary but however challenging. Lasing cannot be easily achieved from silicon emission because of its indirect bandgap. Therefore, one solution proposed is to use other efficient emitters, like rare earth, into silicon or Silicon On Insulator based microcavities. Silica microdisk has been demonstrated to support high-Q whispering-gallery modes, and can be upgraded to ultra-high-Q toroidal microcavities by a CO2 laser melting process. Microdisk high Q-factor balances the low gain generally obtained from the active medium. Thus, those microcavities may be good candidates
for silicon-based laser. In this paper, the fabrication and room
temperature operation of silica microdisk associated with Er-doped silicon rich oxide is presented. Er atoms are excited at the 351 nm wavelength via the silicon clusters, giving to the material a high photonic capture section, and therefore a good photoluminescence efficiency. We demonstrate efficient coupling of erbium atoms to high-Q whispering-gallery modes. The photoluminescence spectrum is then theoretically treated. The WGM resonances are thus identified. We also discuss the contribution of the spot excitation and the weak coupling to the higher radial order modes. Finally, the polarization dependence of the observed modes is investigated, and the experimental results are compared to our analytical model of disk-shape cavities. Those results give us to think that an integrated laser should be soon achieved.
A new kind of substrate called Silicon-On-Mirror has been fabricated for nanophotonics applications. It is composed of a monocrystalline silicon layer separated from the silicon substrate by a buried distributed Bragg reflector. Photoluminescence of silicon at 80 K is used to investigate two-dimensional (2D) photonic crystal hexagonal microcavities etched in the monocrystalline silicon layer. Two types of substrates are compared: silicon-on-insulator (SOI) substrates and the new substrates where the silicon layer is bonded on a buried distributed Bragg reflector (DBR). Quality factors of the in-plane resonant modes are analyzed both experimentally and theoretically when the substrate structure is changing. It is shown that the underlying DBR can enhance the in-plane quality factors by a factor 2.5 by reducing the losses. The out-of-plane light extraction efficiency of the cavities and of defectless photonic crystals are also discussed.
A sensor based on selective optical absorption allows monitoring of hazardous engine exhaust emissions such as gaseous hydrocarbons and carbon monoxide. The IR components presented here offer the potential to develop a compact, fast and selective sensor reaching the technical and cost requirements for on-board automotive applications. Optical gas monitoring requires light sources above 3 μm since most of the gas species have their fundamental absorption peaks between 3 and 6 μm. We report here on resonant microcavity light sources emitting at room temperature between 3 and 5 μm. The emitter combines a CdxHg1-xTe light emitting heterostructure and two dielectric multilayered mirrors. It is optically pumped by a commercial III-V laser diode. The principle of the resonant microcavity emitter allows tailoring of the emission wavelength and the line width to fit the absorption band of a specific gas, ensuring a very good selectivity between species. Moreover, this kind of emitter allows fast modulation enabling high detectivity and short response time. We report performances of light sources in the range 3 - 5 μm allowing the detection of hydrocarbons and carbon monoxide. Association of emitters peaking at different characteristic wavelengths with a single broad band detector allows designing of an optical sensor for several gas species. Sensitivity and time response issues have been characterized: detection of less than 50 ppm of CH4 on a 15 cm path has been demonstrated on synthetic gas; analysis of exhaust gases from a vehicle has allowed the resolution of a cylinder time. This optical sensor offers the potential of various on-board automotive applications.
A sensor based on selective optical absorption allows monitoring of hazardous engine exhaust emissions such as gaseous hydrocarbons and carbon monoxide. The IR components presented here offer the potential to develop a compact, fast and selective sensor reaching the technical and cost requirements for on-board automotive applications. Optical gas monitoring requires light sources above 3μm since most of the gas species have their fundamental absorption peaks between 3 and 6 μm. We report here on resonant microcavity light sources emitting at room temperature between 3 and 5μm. The emitter combines a CdxHg1-xTe light emitting heterostructure and two dielectric multilayered mirrors. It is optically pumped by a commercial III-V laser diode. The principle of the resonant microcavity emitter allows tailoring of the emission wavelength and the line width to fit the absorption band of a specific gas, ensuring a very good selectivity between species. Moreover, this kind of emitter allows fast modulation enabling high detectivity and short response time. We report performances of light sources in the range 3-5μm allowing the detection of hydrocarbons and carbon monoxide. Association of emitters peaking at different characteristic wavelengths with a single broad band detector allows designing of an optical sensor for several gas species. Sensitivity and time response issues have been characterized: detection of less than 50ppm of CH4 on a 15cm path has been demonstrated on synthetic gas; analysis of exhaust gases from a vehicle has allowed cylinder to cylinder resolution. This optical sensor offers the potential of various on-board automotive applications.
Silicon on insulator (SOI) substrates provide a naturally good template for the introduction of optics at the microelectronics device level, due to the high refractive index contrast between Si and SiO2. If one is able to control the propagation of photons in the material, functional devices like, filters, modulators or resonant detectors can be envisioned. One can even imagine to make light emitters since recent progress showed room temperature light emission from doped silicon material or nano-crystalline silicon. This suggests that combining these new materials with low volume optical resonators will allow to make efficient light sources based on Si and opens a route towards CMOS compatible silicon-based light emitters. A promising way to integrate this functions in compact large-scale photonic circuits is to use photonic crystals (PCs).
In this work we will present the design, fabrication and optical characterization of SOI based PC resonators engineered to change the emissio rate and/or extraction of photons from the Si layer. Different structures have been studied: vertical microcavities, in-plane 2D hexagonal cavities and defect-less structures and results demonstrating strong light extraction enhancement will be shown together with calculations made by plane wave expansion techniques and FDTD.
We report the spectroscopic characterisation of an integrated microcavity designed for the 1.5μm telecommunication wavelength by using both near- and far-field techniques. We show the establishment of the cavity mode for wavelengths ranging from the photonic band gap to the resonance by using a scanning near-field optical microscope in collection mode. The respective contributions of out of plane losses and evanescent field are clearly identified. Transmission measurements on a broad spectral range are performed and results obtained by the two techniques are in very good agreement.
We report in this paper the study of a W1 photonic crystal waveguide which supports two Bloch modes having different parity. A monomode ridge waveguide etched in a Silicon-On-Insulator substrate and connecting to the photonic crystal waveguide allows us to excite the even Bloch mode. Transmission measurements, performed on a broad spectral range, evidence the even mode propagation along the defect line and experimental spectrum is discussed in light of band diagram and FDTD calculations. Then spectrally resolved near-field patterns obtained by using a scanning near field optical microscope in collection mode for wavelengths inside and outside the multimode region of the photonic crystal waveguide clearly demonstrate the even mode parity change along the defect line.