Trimmable nanophotonic devices
Introduction
In the last couple of years many of the basic building blocks required for integrated optic circuits have been successfully demonstrated. However the repeatable fabrication of silicon nano photonic devices such as narrow band filters still remain to be a big challenge because fluctuations in the fabrication process lead to random shifts of the device’s center wavelength which are commonly in the order of a WDM channel [1]. In commercially available hardware the channel filters are usually trimmed individually by electric heating. This is very detrimental to the power budged of the optical circuit. Another technological challenge is the creation of highly resonant cavities with small mode volumes. This is interesting for lasing applications since they may lead to more efficient integrated light sources. We have shown that both of these challenges can be addressed by bleaching a dye doped polymer cladding.
Goals
This project is split into two main goals:
- Demonstration of post fabrication trimming of resonators with high Q-factor (>10k) by bleaching
- Demonstration of photonic crystal cavities with very high Q-factor (>100k) defined by bleaching
Results
We have shown that bleaching can be used to perform a very precise post fabrication trimming of silicon ring resonators. The resonance could be trimmed with a resolution of 12 pm. The Q-factors of the resonators were about 20k [2].
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Figure 1. Light microscope image of silicon ring resonators. The resonators are covered with polymer and have been selectively bleached. The electron dose is increasing from left to right. | Figure 2. Transmission spectrum of ring resonators before and after bleaching. Each dip in the blue spectrum corresponds to one ring resonator. After bleaching all resonators are trimmed to the same wavelength. |
We also have recently demonstrated the first proof of concept for a bleached photonic crystal cavitiy with a Q-factor of 24k. However the simulations suggest that higher Q-factors should be possible with the available structures [3].
List of publications
Prorok, S. Trimming of high-Q-factor silicon ring resonators by electron beam bleaching, Optics Letters 37, 15, 3114–3116 (2012)
Prorok, S. Photonic crystal cavity definition by electron beam bleaching of chromophore doped polymer cladding, Proc. SPIE 8425, Photonic Crystal Materials and Devices X, 842518 (2012)
Responsible
Stefan Prorok
Collaborations:
Prof. Dr. Alex K.-Y. Jen,University of Washington , Department of Materials Science & Engineering, Seattle, Washington
References
1. Zortman, W. Silicon photonics manufacturing, Optics Express 18, 23, 23598-23607 (2010)
2. Prorok, S. Trimming of high-Q-factor silicon ring resonators by electron beam bleaching, Optics Letters 37, 15, 3114–3116 (2012)
3. Prorok, S. Photonic crystal cavity definition by electron beam bleaching of chromophore doped polymer cladding, Proc. SPIE 8425, Photonic Crystal Materials and Devices X, 842518 (2012)