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Free carrier absorption modulation in polymer waveguides doped with Si nanocrystals
KTH, School of Engineering Sciences (SCI).
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

This work demonstrates all-optical intensity modulation in integrated optical polymer waveguides doped with Si nanocrystals. The modulation here is based on free carrier absorption of 1550 nm probe signal in Si nanocrystals with excited carriers. Optical 405 nm pump was used to increase free carrier concentration. By applying pulsed pump excitation, -1.55 dB deep intensity modulation was achieved in 5 mm long waveguides. The modulation bandwidth is limited to few kHz due to excited carrier relaxation time (τ ~ 100 μs). Demonstrated all-optical reconfigurable polymer waveguides are a promising potential alternative to thermo-optical switches.

National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-219568OAI: oai:DiVA.org:kth-219568DiVA, id: diva2:1163658
Note

QC 20171211

Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2022-09-06
In thesis
1. Polymer Components for Photonic Integrated Circuits
Open this publication in new window or tab >>Polymer Components for Photonic Integrated Circuits
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optical polymers are a subject of research and industry implementation for many decades. Optical polymers are inexpensive, easy to process and flexible enough to meet a broad range of application-specific requirements. These advantages allow a development of cost-efficient polymer photonic integrated circuits for on-chip optical communications. However, low refractive index contrast between core and cladding limits light confinement in a core and, consequently, integrated polymer device miniaturization. Also, polymers lack active functionality like light emission, amplification, modulation, etc. In this work, we improved a performance of integrated polymer waveguides and demonstrated active waveguide devices. Also, we present novel Si QD/polymer optical materials.

In the integrated device part, we demonstrate optical waveguides with enhanced performance. Decreased radiation losses in air-suspended curved waveguides allow low-loss bending with radii of only 15 µm, which is far better than >100 µm for typical polymer waveguides. Another study shows a positive effect of thermal treatment on acrylate waveguides. By heating higher than polymer glass transition temperature, surface roughness is reflown, minimizing scattering losses. This treatment method enhances microring resonator Q factor more than 2 times. We also fabricated and evaluated all-optical intensity modulator based on PMMA waveguides doped with Si QDs.

We developed novel hybrid optical materials. Si QDs are encapsulated into PMMA and OSTE polymers. Obtained materials show stable photoluminescence with high quantum yield. We achieved the highest up to date ~65% QY for solid-state Si QD composites. Demonstrated materials are a step towards Si light sources and active devices.

Integrated devices and materials presented in this work enhance the performance and expand functionality of polymer PICs. The components described here can also serve as building blocks for on-chip sensing applications, microfluidics, etc.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 60
Series
TRITA-FYS, ISSN 0280-316X ; 2017:66
Keywords
integrated photonics, polymers, optical communications, microfabrication, optical waveguides, microring resonators, silicon, Si nanocrystals, photoluminescence
National Category
Engineering and Technology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-219556 (URN)978-91-7729-576-1 (ISBN)
Public defence
2017-11-24, Sal C, Isafjordsgatan 22, Stockholm, 14:00 (English)
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Supervisors
Note

QC 20171207

Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2022-06-26Bibliographically approved

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