Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences

COLLEGE OF ENGINEERING

UC Berkeley

Nano-Electromechanical Optoelectronic Tunable Lasers

Michael Chung-Yi Huang

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2008-2
January 7, 2008

http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-2.pdf

Semiconductor diode lasers can be used in a variety of applications including telecommunications, displays, optical data storage, solid-state lighting, sensing and printing. Among them, vertical-cavity surface-emitting lasers (VCSELs) are particularly promising. Because they emit light normal to the constituent wafer surface, it is possible to extract light more efficiently and to fabricate two-dimensional device arrays. A VCSEL contains two distributed Bragg reflector (DBR) mirrors for optical feedback, separated by a very short active gain region. Typically, the reflectivity of the DBRs must exceed 99.5% in order for the VCSEL to reach lasing operation. However, the realization of practical VCSELs that can be used over a wide range of wavelengths has been hindered by the poor optical and thermal properties of candidate DBR materials. In this dissertation, we present a novel design of surface emitting lasers utilizing a revolutionary, single-layer, high-index-contrast subwavelength grating (HCG), instead of conventional a distributed Bragg reflector (DBRs). The HCG provides both efficient optical feedback and control over the wavelength and polarization of the emitted light. Such integration drastically reduces the required VCSEL epitaxial thickness and greatly increases the tolerance toward variations in fabrication. Furthermore by integrating a movable actuator with the lightweight, single-layer HCG, a nano-electromechanical optoelectronic (NEMO) tunable laser with precise and continuous wavelength tuning is experimentally demonstrated. The small footprint of HCG enables the scaling down of the mechanical actuator¿s structural geometry by at least a factor of 10, leading to >1000 times reduction in the overall structural mass and a huge increase in the mechanical resonant frequency. Thus, a compact and efficient NEMO tunable VCSEL with tens of nanoseconds tuning speed is obtained experimentally. Furthermore, to improve the mechanical actuation design, we present a monolithic piezoelectric actuated MEM tunable VCSEL that exploits the inherent piezoelectric properties of the AlxGa1-xAs compounds. Such mechanical movement is not limited by the pull-in effect, as opposed to the 1/3 gap limit known for electrostatic actuation and consequently the possibility of catastrophic damages due to capacitor discharge. Lastly, we discuss a novel label-free, compact, and highly sensitive VCSEL optoelectronic biosensor for the detection and monitoring of biomolecular interactions. Experimentally, the biosensor has demonstrated its high sensitivity and clinical practicality for the detection of infectious diseases, where the biosensor can accurately monitor the biomolecular binding between antibodies against dengue virus.

Advisor: Constance Chang-Hasnain


BibTeX citation:

@phdthesis{Huang:EECS-2008-2,
    Author = {Huang, Michael Chung-Yi},
    Title = {Nano-Electromechanical Optoelectronic Tunable Lasers},
    School = {EECS Department, University of California, Berkeley},
    Year = {2008},
    Month = {Jan},
    URL = {http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-2.html},
    Number = {UCB/EECS-2008-2},
    Abstract = {Semiconductor diode lasers can be used in a variety of applications including telecommunications, displays, optical data storage, solid-state lighting, sensing and printing. Among them, vertical-cavity surface-emitting lasers (VCSELs) are particularly promising. Because they emit light normal to the constituent wafer surface, it is possible to extract light more efficiently and to fabricate two-dimensional device arrays. A VCSEL contains two distributed Bragg reflector (DBR) mirrors for optical feedback, separated by a very short active gain region. Typically, the reflectivity of the DBRs must exceed 99.5% in order for the VCSEL to reach lasing operation. However, the realization of practical VCSELs that can be used over a wide range of wavelengths has been hindered by the poor optical and thermal properties of candidate DBR materials.  
In this dissertation, we present a novel design of surface emitting lasers utilizing a revolutionary, single-layer, high-index-contrast subwavelength grating (HCG), instead of conventional a distributed Bragg reflector (DBRs). The HCG provides both efficient optical feedback and control over the wavelength and polarization of the emitted light. Such integration drastically reduces the required VCSEL epitaxial thickness and greatly increases the tolerance toward variations in fabrication. Furthermore by integrating a movable actuator with the lightweight, single-layer HCG, a nano-electromechanical optoelectronic (NEMO) tunable laser with precise and continuous wavelength tuning is experimentally demonstrated. The small footprint of HCG enables the scaling down of the mechanical actuator¿s structural geometry by at least a factor of 10, leading to >1000 times reduction in the overall structural mass and a huge increase in the mechanical resonant frequency. Thus, a compact and efficient NEMO tunable VCSEL with tens of nanoseconds tuning speed is obtained experimentally.
Furthermore, to improve the mechanical actuation design, we present a monolithic piezoelectric actuated MEM tunable VCSEL that exploits the inherent piezoelectric properties of the AlxGa1-xAs compounds. Such mechanical movement is not limited by the pull-in effect, as opposed to the 1/3 gap limit known for electrostatic actuation and consequently the possibility of catastrophic damages due to capacitor discharge. 
Lastly, we discuss a novel label-free, compact, and highly sensitive VCSEL optoelectronic biosensor for the detection and monitoring of biomolecular interactions. Experimentally, the biosensor has demonstrated its high sensitivity and clinical practicality for the detection of infectious diseases, where the biosensor can accurately monitor the biomolecular binding between antibodies against dengue virus.}
}

EndNote citation:

%0 Thesis
%A Huang, Michael Chung-Yi
%T Nano-Electromechanical Optoelectronic Tunable Lasers
%I EECS Department, University of California, Berkeley
%D 2008
%8 January 7
%@ UCB/EECS-2008-2
%U http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-2.html
%F Huang:EECS-2008-2