The comprehension and manipulation of the spectral characteristics of photonic structures is of great interest for a vast bunch of applications, in particular for energy efficiency. In this paper we focus on a perturbation model capable of providing insight and control on the resonances that are supported by high index contrast gratings.
The mid-infrared (mid-IR, wavelength range between 2 and 10 μm) is of great interest for a huge range of applications
such as medical and environment sensors, security, defense and astronomy. I will give a broad overview of the different
activities recently launched in INL Lyon, in close collaboration with several French and Australian institutions, under
the umbrella of “Mid-IR integrated photonics” with a particular focus on novel integrated sources for the Mid-IR
including hybrid III-V semiconductors on SiGe sources, thermal sources and nonlinear sources.
The linear and nonlinear optical response of SiGe waveguides in the mid-infrared are experimentally measured. By cutback measurements we find the linear losses to be less than 1.5dB/cm between 3μm and 5μm, with a record low loss of 0.5dB/cm at a wavelength of 4.75μm. By launching picosecond pulses between 3.25μm and 4.75μm into the waveguides and measuring both their self-phase modulation and nonlinear transmission we find that nonlinear losses can be significant in this wavelength range due to free-carrier absorption induced by multi-photon absorption. This should be considered when engineering SiGe photonic devices for nonlinear applications in the mid-IR.
The nonlinear characteristics of hydrogenated amorphous silicon nanowires are experimentally measured. A nonlinear coefficient, γ, with a high real part Real(γ)= 690W-1m-1, combined with a low imaginary part Im(γ)= 10 W-1m-1, resulted in a high nonlinear FOM of 5.5. Furthermore, systematic studies over hours of operational time under 2.2W of pulse peak power revealed no degradation of the optical response.
The marriage of photonics and microfluidics ("optofluidics") uses the inherent mobility of fluids to reversibly tune
photonic structures beyond traditional fabrication methods by infiltrating voids in said structures. Photonic crystals
(PhCs) strongly control light on the wavelength scale and are well suited to optofluidic tuning because their periodic airhole
microstructure is a natural candidate for housing liquids.
The infiltration of a single row of holes in the PhC matrix modifies the effective refractive index allowing optical modes
to be guided by the PhC bandgap. In this work we present the first experimental demonstration of a reconfigurable single
mode W1 photonic crystal defect waveguide created by selective liquid infiltration. We modified a hexagonal silicon
planar photonic crystal membrane by selectively filling a single row of air holes with ~300nm resolution, using high
refractive index ionic liquid. The modification creates optical confinement in the infiltrated region and allows
propagation of a single optical waveguide mode. We describe the challenges arising from the infiltration process and the
liquid/solid surface interaction in the photonic crystal. We include a detailed comparison between analytic and numerical
modeling and experimental results, and introduce a new approach to create an offset photonic crystal cavity by varying
the nature of the selective infiltration process.
The results of a detailed investigation of light transmission behavior of a centric marine diatom species Coscinodiscus
wailesii are reported. We measured 3-dimentional intensity distributions of both broadband and monochromatic light
transmitted through individual valves of the diatom in air and water. Cross-sectional intensity profiles of transmitted
light indicates valves of C. wailesii can concentrate light into certain regions. At a distance from the valve shorter than its
diameter, light intensities close to the optical axis are relatively higher than those in the surrounds; at a longer distance,
transmitted light intensities display ring-shaped profiles. The distance showing this light concentration characteristic
becomes shorter as the wavelength of incoming light goes up. These results may offer insight into the understanding of
biological functions of diatom frustules' intricate structures and inspire new optical biomimetic applications.
Optofluidics, the marriage of photonics and microfluidics, uses the inherent flexibility of confined fluids to reversibly
tune photonic structures beyond traditional fabrication methods. Photonic crystals (PhCs) are well suited to optofluidic
tuning; their periodic air-hole microstructure is a natural candidate for housing liquids. This microstructure enables PhCs
to strongly control light on the wavelength scale.
Defects purposefully introduced during PhC fabrication can support guided optical modes, forming waveguides or
cavities; their dispersion can be engineered by fine alteration of individual PhC holes in or around the structure. This
engineering requires very high fabrication tolerances and is irreversible once performed. Optofluidic tuning of PhC
waveguides, however, is completely reversible and only limited by the properties of available fluids. Infiltration of the
PhC microstructure surrounding a waveguide modifies the local refractive index profile through the liquid used and the
amount of microstructure filled.
In this paper we demonstrate experimentally for the first time, optofluidics dispersion engineer of photonic crystals
waveguides. We have modified the group velocity dispersion using a technique based on selective liquid infiltrations to
precisely and reversibly change our structures. We also present how the amount of fluid infiltrated into the photonic
crystal microstructure strongly influences the waveguide dispersion.
In this review, we discuss the progress and prospects offered by chalcogenide glass photonic crystals. We show that by
making photonic crystals from a highly-nonlinear chalcogenide glass, we have the potential to integrate a variety of
active devices into a photonic chip. We describe the testing of two-dimensional Ge33As12Se55 chalcogenide glass
photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to not only post-tune
the devices properties but also create high Q cavities by using the material photosensitivity.
Optofluidic devices exploit the characteristics of liquids to achieve a dynamic adaptation of their optical properties. The
use of liquids allows for functionalities of optical elements to be created, reconfigured or tuned. We present an overview
of our work on fluid-control of optical elements and highlight the benefits of an optofluidic approach, focusing on
optofluidic cavities created in silicon photonic crystal (PhC) waveguide platforms. These cavities can be spatially and
spectrally reconfigured, thus allowing a dynamic control of their optical characteristics. PhC cavities are major building
blocks in many applications, from microlasers and biomedical sensor systems to optical switches and integrated circuits.
In this paper, we show that PhC microcavities can be formed by infusing a liquid into a selected section of a uniform
PhC waveguide and that the optical properties of these cavities can be tuned and adapted. By taking advantage of the
negative thermo-optic coefficient of liquids, we describe a method which renders PhC cavities insensitive to temperature
changes in the environment. This is only one example where the fluid-control of optical elements results in a
functionality that would be very hard to realize with other methods and techniques.
We report reconfigurable optofluidic photonic crystal components in silicon-based membranes by controllably
infiltrating and removing fluid from holes of the photonic crystal lattice. Systematic characterizations of our fluidically defined
microcavities are presented, corresponding with the capability to increase or decrease the span of the fluid-filled
regions and thus alter their optical properties. We show initial images of single-pore fluid infiltration for holes of
diameter 265 nm. Furthermore, the infiltration process may employ a large range of optical fluids, adding more
flexibility to engineer device functionality. We discuss the great potential offered by this optofluidic scheme for
integrated optofluidic circuits, sensing, fluorescence and plasmonic applications.
We demonstrate post-processed and reconfigurable photonic crystal double-heterostructure nanocavities via selective fluid infiltration. We experimentally investigate the microfluidic structures via evanescent probing from a tapered fiber at telecommunications wavelengths. We demonstrate a cavity with quality factor Q = 4,300. The defect-writing technique we present does not require nanometer-scale alterations in lattice geometry and may be undertaken at any time after photonic crystal waveguide fabrication.
Optofluidics offers new functionalities that can be useful for a large range of applications. What microfluidics can bring
to microphotonics is the ability to tune and reconfigure ultra-compact optical devices. This flexibility is essentially
provided by three characteristics of fluids that are scalable at the micron-scale: fluid mobility, large ranges of index
modulation, and adaptable interfaces. Several examples of optofluidic devices are presented to illustrate the achievement
of new functionalities onto (semi)planar and compact platforms. First, we report an ultra-compact and tunable
interferometer that exploits a sharp and mobile air/water interface. We describe then a novel class of optically controlled
switches and routers that rely on the actuation of optically trapped lens microspheres within fluid environment. A tunable
optical switch device can alternatively be built from a transversely probed photonic crystal fiber infused with mobile
fluids. The last reported optofluidic device relies on strong fluid/ light interaction to produce either a sensitive index
sensor or a tunable optical filter. The common feature of these various devices is their significant flexibility. Higher
degrees of functionality could be achieved in the future with fully integrated optofluidic platforms that associate complex
microfluidic delivery and mixing schemes with microphotonic devices.
We report integrated devices in chalcogenide glass for all-optical signal processing, based on pure Kerr (near instantaneous) optical nonlinearities. We demonstrate an integrated 2R optical regenerator operating through a combination of nonlinear self-phase modulation followed by spectral filtering, with a potential to reach bit rates in excess of 1Tb/s. It consists of a low loss As2S3 chalcogenide rib waveguide incorporating a high quality Bragg grating written by an ultra-stable Sagnac interferometer. We achieve a nonlinear power transfer curve using 1.4ps pulses, sufficient for suppressing noise in an amplified link. In addition, we report photonic crystal structures fabricated by focused ion beam (FIB) milling in AMTIR-1 (Ge33As12Se55) chalcogenide glass. We realize high quality free-standing photonic crystal membranes, and observe optical "Fano" resonances in the transmission spectra at normal incidence. We achieve good agreement with theoretical results based on 3D finite difference time-domain calculations. Finally, we achieve resonant evanescent coupling to photonic crystal waveguides via tapered microstructured optical fibre (MOF) nanowires.
All optical switching devices based on kerr-effect, where light switches light, are enjoying renewed interest. The dream of ultra compact devices operating at very low power and integrable on a chip is entering the realm of reality thanks to the advent of photonic crystal, enabling high Q/V ratio. We show that marrying photonic crystal and a new class of highly non linear material, Chalcogenide glasses, is a very promising way to achieve an all-optical chip. We describe the fabrication techniques we have developed for manufacturing two-dimensional Chalcogenide photonic crystal. Different types of photonic crystal resonances are investigated. Coupling technique to chalcogenide based photonic crystal waveguides and cavities via tapered nanowires is thoroughly described. We demonstrate resonant guiding in a chalcogenide glass photonic crystal membrane using a fano probe technique. We observe strong resonances in the optical transmission spectra at normal incidence, associated with Fano coupling between free space and guided modes. We obtain good agreement with modeling results based on three-dimensional finite-difference time-domain simulations, and identify the guided modes near the centre of the first Brillouin zone responsible for the main spectral features.