In this study we will design photonic structures whose spectral properties are particularly sensitive to the environmental modifications, and we will present measurement system that allows to detect these small variations. For this purpose, we will focus on the phase at the reflection on periodic structures, in particular for the critical coupling points for which the phase variation is abrupt. The measurement method that we develop consists in an original holographic interferometric setup based on wavefront shaping that allow a very stable phase measurement.The fabrication of a temperature sensor based on these two principles has allowed us to experimentally reach phase sensitivities up to 39°/°C.
Many applications require colored surfaces while maximizing photons to pass through with no optical losses. As the perceived color depends on the spectral content and the number of reflected photons for each wavelength, it is necessary to consider not only the chromatic content but also the brightness. As a first application example, photovoltaic modules could see their acceptance in urban situations greatly improved if their color could be controlled while maximizing the number of photons used for energy conversion. In this case, it is important to limit light brightness to avoid glare when light coming from the sun is reflected directly. As another example, a colored and semi-transparent glass layer in the infrared could efficiently protect sensors while camouflaging them, such as lidar in automotive applications. We propose a theoretical study for multicolor applications, considering 2D partially etched grating waveguide structures that behave as a perfect broadband antireflection coating while the residual layer couples light in a waveguided mode in order to reflect only a particular photon band. This strategy allows to produce a large variety of colors and the use of non-absorbing materials avoids any optical loss. The width of the resonance peak is a crucial parameter for balancing brightness in multicolor applications. In the second part, we developed a method for a fast optimization of the geometrical parameters and we applied it to obtain the three primary colors with strong geometrical constraints, so that such structures could be manufactured in a single step by nano-imprint. Finally, we propose some improvements of these structures, in particular by reducing broadband reflection to obtain more saturated colors, or to improve the angular behavior of these structures.
In this communication, we present the potentialities offered by 2D photonic crystals to trap and absorb photons in thin silicon layers. We will specifically focus on the impact of the photonic crystal unit cells symmetry, and the possibility to increase light absorption and generated photocurrent using multi-periodic and pseudo-disordered photonic nanostructures.
The on-coming photonic layer of CMOS integrated circuits needs efficient light sources to treat and transmit the flow of
data. We develop new configurations of III-V/Si vertical cavity lasers coupled to silicon optical waveguides using
mirror/coupler based on photonic crystals. These devices can be fabricated using fully CMOS-compatible technological
steps. Using this approach, the optical gain is provided by the III-V material, while all the remaining part of the optical
cavity is in silicon. The output coupling to the sub-µm waveguides of the CMOS optical layer can then be inherently
optimised since the laser mirror/coupler and the Si output waveguides will be realised together during the same
fabrication step.
It has been demonstrated that photonic crystals membrane can act as very efficient reflectors (PCM-mirrors) for vertical
microresonators. In this communication, the design of a vertical cavity microlaser based on these PCM-mirrors will
be presented. We will show that high Q-factors (>10000) along with strong vertical and lateral confinements can be
achieved. As a first demonstration, experimental results on silicon PhC-mirrors and associated vertical cavities will be
discussed, showing Q factors larger than 2000. Finally, theoretical results on the coupling between such cavities and a
silicon micro-waveguide will be presented.
Low cost, robust and efficient light sources are suitable for optical high speed communications in integrated circuits.
Microdisk resonator lasers correspond to one of the most adapted solution in regard to their performances and their
processing easiness. They mix low space dimension and low power consumption (threshold<50 μW). The use of dies
of InP membranes bonded onto 200 mm SOI wafers allows the fabrication of a complete optical link, with an
optical InP based microsource, Si waveguides and sensors for signal collection. Contacting such sources complies with
the necessity of using metals - more generally optical absorbing elements - and the necessary low power consumption to
stand up traditional electrical circuits. In this paper, we investigate design rules of contacts using a simple model for fast
estimated results which are compared to 3D FDTD simulations. In a second part, we will discuss the coupling between a
microdisk resonator and a Si waveguide. Then we will describe the fabrication of such devices with a 200mm CMOS
pilot line and point out the technological induced limitations.
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