We demonstrate a novel concept for the fabrication of high Q photonic crystal heterostructure cavities. First, photonic crystal waveguides without cavities are fabricated. The cavities are defined in a later fabrication step by spatially resolved bleaching of a chromophore doped polymer cladding. Bleaching of polymer films either by UV light or by
electron beam illumination is well known to reduce the refractive index of the film. The reduction of the cladding refractive index leads to a reduction of the effective lattice constant of the photonic crystal waveguide. The maximum
refractive index change was found to be 6•10<sup>-2</sup> which corresponds to the effective lattice constant change of 12.2 nm.
With this approach it is also possible to achieve very small effective lattice constant shifts of 0.02 nm which is not possible with state of the art lithography. Being able to precisely define the effective lattice constant at every point of the
photonic crystal waveguide we are able to impose cavity mode profiles which closely resemble a Gaussian envelope.
This leads to a dramatic increase of the Q-factor. In simulations we have obtained Q-factors as high as 3.0•10<sup>6</sup> for a vertically symmetric polymer cladding. First results for non-vertically symmetric structures are presented.
In this letter we demonstrate broadband electro-optic modulation with frequencies up to 40 GHz
in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and
infiltrated with a nonlinear optical polymer. Two dimensional photonic crystal waveguides in
silicon enable integrated optical devices with an extremely small geometrical footprint on the
scale of micrometers. The slotted waveguide design optimizes the overlap of the optical and
electric field in the second order nonlinear optical medium and hence the interaction of the
optical and electric wave.
Racetrack resonators based on the silicon-on-insulator platform are proposed for electro-optical modulation. The
resonators are functionalized by a cladding of a second order nonlinear optical polymer. Two different concepts for the
racetrack design employing different waveguide geometries for quasi-TE and quasi-TM polarization operation are
presented. In both resonator designs the electrical contact is established by fully etched segmented electrode sections to
allow for an easy fabrication process. For quasi-TM polarization the width of the strip waveguide is optimized to 400
nm. The Q factor of 2000 is measured for a sample with segmented electrode. A loss of 0.4 dB per segmented waveguide
is deducted. For the quasi-TE polarization the slot waveguide geometry is optimized to 470 nm total width including a
vertical slot of 90 nm width. Only the straight parts of the racetrack are slotted, while the bends are built from strip
waveguides. To convert the mode from strip to slot geometry stub like couplers of 100 nm length are employed. The
measured Q factor is 550. The in device Pockels coefficient is measured to r<sub>33</sub> = 1 pm/V. This small value indicates a
very low poling induced polar order which needs to be improved. This is a topic of current investigation.
Two dimensional photonic crystal waveguides in high index materials enable integrated optical devices with an extremely small geometrical footprint on the scale of micrometers.1-3 Slotted waveguides are based on the guiding of light in low refractive index materials and a field enhancement in this particular region of the device. Here, we experimentally demonstrate electro-optic modulation in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and infiltrated with highly nonlinear guest host optical polymers.4 A photonic crystal heterostructure is used to create a cavity, while simultaneously serving as an electrical connection from the slot to the metal electrodes that carry the modulation signal.
We report on electrooptical modulation with a sub 1Volt sensititivity in a photonic crystal slab waveguide resonator which contains a nanostructured nonlinear optical polymer. This modulation effect is based on the electronic displacement polarization in a noncentrosymmetric medium (Pockels-effect) and is therefore inherently by more than three orders of magnitude faster than any other reported electrooptic modulation effect in nanophotonics. We also show concepts for extremely high and zero dispersion as well as for time delay in photonic crystal waveguides. Tuning can be achieved by hybrid combination of Si-based PCs and organic EO-materials.
We report on electro-optical modulation with a sub-1-V sensitivity in a photonic crystal slab waveguide resonator which contains a nanostructured second-order nonlinear optical polymer. The electro-optical susceptibility in the core was induced by high electric-field poling. A square lattice of holes carrying a linear defect was transferred into the slab by electron-beam lithography and reactive ion etching, creating a photonic crystal slab-based resonator. Applying an external electric modulation voltage to electrodes leads to a linear electro-optical shift of the resonance spectrum and thus to a modulation of the transmission at a fixed wavelength based on the electronic displacement polarization in a noncentrosymmetric medium (Pockels effect). This effect is therefore inherently faster than other reported electro-optic modulation effects in nanophotonics.