36 research outputs found
Focused Ion Beam Nano-structuring for Applications in Photonics
To date, nano- and micro-structuring has commonly been implemented by a combination of specifically optimized processes of electron-beam lithography and reactive ion etching, thus limiting the range of materials that can be structured to only a few. In this talk we will introduce focused ion beam (FIB) milling as an emerging technology that enables fast, reliable and well-controlled nanometer-size feature definition. Since the method involves physical removal of material by a beam of ions, the technique can be adapted and optimized almost for any material system. We will introduce the technique and discuss the basic application areas. In particular, we have investigated the impact of parameters such as ion beam current, dwell time, scanning strategy, and dielectric charging. We will discuss strategies to optimize the nano-structuring processes that are strongly dependent on the geometry of the desired structure. Finally, we will report our recent results on utilization and optimization of the focused ion beam technique for fabrication of nano-structures in integrated photonic devices on several material platforms such as Si, Al2O3, Y2O3, Sc2O3, and KY(WO4)2
Focused ion beam milling strategy for sub-micrometre holes in silicon
Focused ion beam (FIB) milling can be used as a tool to fabricate structures with sub-micrometer details. The slab material can be silicon, for example, which can then be used as a mould for nano-imprint lithography, or in silicon on insulator (SOI) layer configuration suitable for photonic applications. In the latter, additional effort has to be taken to prevent high FIB induced losses, due to ion implantation and material crystal damage. Perfectly vertical sidewalls are, in principle, required for photonic crystal applications to guarantee low-loss propagation; sidewall angles of 5 degrees can already induce a 8 dB/mm propagation loss. We report on optimization of the sidewall angle (FIB) fabricated submicron diameter holes. Our best case results show that sidewall angles as small as 1.5 degree are possible in Si membranes and 5 degree for (bulk) Si and SOI by applying larger doses and using a spiral scan method
Focused-ion-beam processing for photonics
Although focused ion beam (FIB) processing is a well-developed technology for many applications in electronics and physics, it has found limited application to photonics. Due to its very high spatial resolution in the order of 10 nm, and its ability to mill almost any material, it seems to have a good potential for fabricating or modifying nanophotonic structures such as photonic crystals. The two main issues are FIB-induced optical loss, e.g., due to implantation of gallium ions, and the definition of vertical sidewalls, which is affected by redeposition effects. The severity of the loss problem was found to depend on the base material, silicon being rather sensitive to this effect. The optical loss can be significantly reduced by annealing the processed samples. Changing the scanning strategy for the ion beam can both reduce the impact of gallium implantation and the redeposition effect
Silicon based dielectrics : growth, characterization, and applications in integrated optics
Cataloged from PDF version of article.In recent years, growing attention has been paid to silicon based dielectrics, such
as silicon oxynitrides, silicon nitrides, and semiconductor doped silicon oxides, all
combined under the name silica on silicon technology. This attention has been
motivated mainly due to their excellent optical properties such as well controlled
refractive index and high transparency over a wide range of wavelength.
In accordance with the main goal of this study that relied on the utilization of
silicon based dielectrics and their optimization for applications in integrated optics,
an emphasis was given to optimize the compositional and optical properties
of these materials. A detailed quantitative compositional analysis using Fourier
transform infrared spectroscopy resulted in identification of the germanosilicate
dielectrics as the most promising candidates for use in integrated optics. The
first reported systematic study of propagation losses for different-index planar
waveguides by using prism coupling method was correlated with the compositional
analysis. This study had an important outcome for planar waveguides
fabricated with germanosilicate core layers resulting in the lowest propagation
loss values reported so far for as deposited CVD-grown films at λ=1.55 µm, eliminating
the need for costly and cumbersome annealing process.
An improvement of the prism coupling technique led to a new approach for
elasto-optic characterization of thin polymer films. This completely new method
allows one to determine the optical anisotropy and out-of-plane mechanical properties
and to correlate both in order to obtain the elasto-optical properties of thin
polymer films, for the first time.
Of interest as potential electro-optic material, we have concentrated on thermally
poled germanosilicate films deposited on fused-silica substrates by PECVD.
As a result of an optimization study, we demonstrated a record peak nonlinear
coefficient of ∼1.6 pm/V, approximately twice as strong as the highest reliable
value reported in a thermally poled fused silica glass.
Finally, we have demonstrated several applications of this technology in the
field of integrated optics. Since optical waveguides constitute the building blocks
of many integrated optical devices, we had first concentrated on design and optimization
of waveguides employing germanosilicates as the core layers. The final
step of our work concentrated on design and implementation of microring resonator
devices based on germanosilicate layers.Ay, FeridunPh.D
Integrated Al2O3:Er3+ zero-loss optical amplifier and power splitter with 40 nm bandwidth
A combined planar lossless optical amplifier and 1x2 power splitter device has been realized in Al2O3:Er3+ on silicon. Net internal gain was measured over a wavelength range of 40 nm across the complete telecom -band (1525–1565 nm). Calculations predict net gain in a combined amplifier and 1x4 power splitter device over the same wavelength range for a total injected pump power as low as 30 mW
Monolithic integration of erbium-doped amplifiers with silicon-on-insulator waveguides
Monolithic integration of Al2O3:Er3+ amplifier technology with passive silicon-on-insulator waveguides is demonstrated. A signal enhancement of >7 dB at 1533 nm wavelength is obtained. The straightforward wafer-scale fabrication process, which includes reactive co-sputtering and subsequent reactive ion etching, allows for parallel integration of multiple amplifier and laser sections with silicon or other photonic circuits on a chip
Focused Ion Beam Milling Strategies of Photonic Crystal Structures in Silicon
We report on optimisation of the side wall angle of focused ion beam (FIB) fabricated submicron diameter holes in silicon. Two optimisation steps were performed. First, we compare two different FIB scanning procedures and show the advantages of using a spiral scanning method for the definition of holes in photonic crystal slab structures. Secondly, we investigate the effect on the geometry, of parameters for reducing the tapering effect. Furthermore, we report on the initial results regarding effects of ion implantation during FIB milling on optical losses, both before and after an annealing step, showing over a decade reduction of optical loss