Abstract
The main drawback of the rapidly evolving field of silicon photonics lies in the absence of efficient monolithically integrated radiation sources as a consequence of the indirect bandgap of Si and Ge. Relevant alternatives based on the hybrid combination of Si with optically active materials have to be technologically simple, temporally stable, and provide efficient coupling to the Si waveguides. Lead-sulfide nanocrystals (NCs) were blended into a polymer resist suitable for deep-UV- and electron-beam lithography and integrated into Si-based vertically slotted waveguides and ring resonators. The polymer both stabilizes the NC’s photoluminescence emission against degradation under ambient conditions and allows lithographic patterning of this compound material. After integration into the optoelectronic structures and upon optical pumping, intense photoluminescence emission from ring resonators was recorded at the output of bus-waveguides. The resonator quality factors were investigated for polymer-NC compounds with NC concentrations in the range between 0.1 and 8 vol%. The spontaneous emission rate enhancement for vertically slotted resonators was estimated to be a factor of two higher as compared to unslotted ones. The stable integration of colloidal NCs as well as the improved light coupling to silicon circuits is an important step in the development of silicon-based hybrid photonics.
Highlights
The field of integrated Si-based photonics has been emerging as a promising alternative to electronics over the last years, a trend that can be explained by the rapid advancements in terms of device design and compatibility with complementary metal-oxide semiconductor technology.[1]
This paper is substantially based on the paper titled “Colloidal PbS nanocrystals integrated to Si-based photonics for applications at telecom wavelengths,” presented at the SPIE Conference 8767 Integrated Photonics: Materials, Devices, and Applications II, held April 24-26, 2013, in Grenoble, Rhône-Alpes, France
We experimentally demonstrate the integration of polymer-embedded PbS nanocrystal quantum dots (NCs) into all-integrated Si-based vertically slotted ring resonators and waveguides as optically pumped emitters for room temperature applications
Summary
The field of integrated Si-based photonics has been emerging as a promising alternative to electronics over the last years, a trend that can be explained by the rapid advancements in terms of device design and compatibility with complementary metal-oxide semiconductor technology.[1]. The absorption and emission wavelengths of these NCs depend on the materials used during synthesis and on their size, and especially lead-sulfide (PbS) NCs are very attractive for applications in the telecom wavelength regime.[2,3,4] Recent studies on NCs coupled to Si-based photonic crystal cavities have shown promising results toward the spectroscopy of single NCs5 as well as electrically pumped light-emitting devices.[6]. As the fabrication of such NCs is based on colloidal chemistry, their on-chip integration can be carried out after synthesis using well-established methods like drop casting, spin coating, or inkjet printing. We experimentally demonstrate the integration of polymer-embedded PbS NCs into all-integrated Si-based vertically slotted ring resonators and waveguides as optically pumped emitters for room temperature applications. The compound shows unaltered optical properties weeks after sample preparation, pointing out the high stability of this material and its suitability for device applications
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