VCSEL Cavity Engineering for High Speed Modulation and Silicon Photonics Integration
Doktorsavhandling, 2018

The GaAs-based vertical-cavity surface-emitting laser (VCSEL) is the standard light source in today's optical interconnects, due to its energy efficiency, low cost, and high speed already at low drive currents. The latest commercial VCSELs operate at data rates of up to 28 Gb/s, but it is expected that higher speeds will be required in the near future.

One important parameter for the speed is the damping of the relaxation oscillations. A higher damping is affordable at low data rates to reduce signal degradation due to overshoot and jitter, while lower damping is required to reach higher data rates. A VCSEL with the damping optimized for high data rates enabled error-free transmission at record-high data rates up to 57 Gb/s.

For future interconnect links it is of interest with tighter integration between the optics and the silicon-based electronics. Techniques to heterogeneously integrate GaAs-based VCSELs on silicon could potentially enable integrated multi-wavelength VCSEL arrays, thus increasing the data rate through wavelength division multiplexing. Heterogeneous integration of GaAs-based VCSELs would also benefit applications that need short-wavelength light sources, such as photonic integrated circuits for life sciences and bio photonics. Silicon-integrated short-wavelength hybrid-cavity VCSELs with up to 2.3 mW optical output power and 12 GHz modulation bandwidth, which enables data transmission at up to 25 Gb/s, are demonstrated by employing ultra-thin adhesive bonding. Further, a vertical-cavity silicon-integrated laser (VCSIL) with in-plane waveguide emission is demonstrated by employing an intra-cavity waveguide with a weak diffraction grating that couples light from the standing wave in the vertical cavity into an in-plane waveguide.

high-speed modulation

on-chip laser source

vertical-cavity surface-emitting laser (VCSEL)

semiconductor lasers

optical interconnects

large signal modulation

laser dynamics

heterogeneous integration

vertical-cavity silicon-integrated laser (VCSIL)

silicon photonics

A423 (Kollektorn), Department of Microtechnology and Nanoscience – MC2, Kemivägen 9, Göteborg
Opponent: Prof. Elyahou (Eli) Kapon, EPFL, Lausanne, Switzerland


Emanuel Haglund

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

High-speed 850 nm VCSELs operating error free up to 57 Gbit/s

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Impact of Damping on High-Speed Large Signal VCSEL Dynamics

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Silicon-integrated short-wavelength hybrid-cavity VCSEL

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20-Gb/s Modulation of Silicon-Integrated Short-Wavelength Hybrid-Cavity VCSELs

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Silicon-Integrated Hybrid-Cavity 850-nm VCSELs by Adhesive Bonding: Impact of Bonding Interface Thickness on Laser Performance

IEEE Journal on Selected Topics in Quantum Electronics,; Vol. 23(2017)p. 1700109-

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Vertical-Cavity Silicon-Integrated Laser with In-Plane Waveguide Emission at 850 nm

Laser and Photonics Reviews,; Vol. 12(2018)p. 1700206-

Artikel i vetenskaplig tidskrift

The Internet has become an important part of our everyday lives. We communicate using social media, listen to music, and watch movies online. As we use these online-based services, much of the complexity have moved from our own devices to the service providers’ data centers. In these data centers, many servers are connected with optical cables. An important component in such optical cables is the light source that transmits the data from one server to another. Typically, this light source is a small laser called VCSEL (vertical-cavity surface-emitting laser). The VCSEL an energy efficient and low cost laser capable of transmitting data at high speeds. However, the Internet data traffic is increasing due to an increased amount of users and the emerging use of more bandwidth demanding applications such as streaming movies in UHD (ultra-high-definition television) quality. These trends are pushing future data center technology to even higher speeds. This thesis deals with how to increase the speed of the VCSEL to meet these demands. The thesis further shows that it is possible to integrate such a laser on optical circuits. Such integrated lasers could be useful to further increase the speed, but also as an important part of sensors with applications in life science and bio photonics.


Informations- och kommunikationsteknik

Nanovetenskap och nanoteknik



Atom- och molekylfysik och optik


Annan elektroteknik och elektronik





Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4421


Chalmers tekniska högskola

A423 (Kollektorn), Department of Microtechnology and Nanoscience – MC2, Kemivägen 9, Göteborg

Opponent: Prof. Elyahou (Eli) Kapon, EPFL, Lausanne, Switzerland