Stabilization techniques and silicon-germanium saturable absorbers for high repetition rate mode-locked lasers

The monolithic integration of passively mode-locked solid-state lasers at highest repetition rates has been prevented by Q-switching instabilities and the lack of integrable saturable absorbers to date. In this thesis we demonstrate in theory and experiment that active feedback electronics controlling the intracavity loss of the laser is capable of suppressing the Q-switching instability. We introduce a control system's perspective to the stability of saturable absorber mode-locked lasers. This approach unifies the existing methods of laser stabilization and identifies feedback control with an intracavity loss modulator as a universal stabilization scheme, applicable without restrictions to lasers at the highest repetition rates. This finding is validated in laboratory experiments by showing that a laser which is unstable without feedback control can reach a noise performance equivalent to that of a, passively stabilized laser, once the feedback controller is engaged. The addition of feedback stabilization does not negatively affect the pulse shaping dynamics, since controller and mode-locking dynamics occur on vastly different timescales. Furthermore, we address the materials challenge of manufacturing a CMOS-compatible saturable Bragg reflector in the Si-SiO2-Ge materials system, enabling the monolithic integration of the absorber with the laser gain medium of future compact mode-locked lasers. A wafer-scale Si-SiO2 high reflector with 99.8% peak reflectance and an unprecedented bandwidth of 700 nm in the near-infrared serves as the substrate of a saturable Bragg reflector, while a germanium layer grown on top provides saturable loss.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Grawert, Felix Jan

Advisor dc:contributor.advisor

• Frans X. Kärtner.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34641

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34641