Design and Fabrication of VCSELs for 3D Sensing

Kevin Cook

EECS Department, University of California, Berkeley

Technical Report No. UCB/EECS-2021-228

December 1, 2021

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2021/EECS-2021-228.pdf

Vertical-cavity surface-emitting lasers (VCSELs) are critical components in many optical systems. They already drive the transmission of data in massive datacenters and supercomputers, and they are becoming the state of the art in 3D sensing systems that allow computers to perceive the world more like humans. These systems have important applications in medicine, autonomous vehicles, facial recognition, and gesture detection. VCSELs have shown the promise of improving resolution while decreasing module cost due to their extremely scalable fabrication process.

The first 3D sensing mechanisms that VCSELs promise to improve are swept-source optical coherence tomography and frequency-modulated continuous-wave LIDAR. These techniques use a wavelength tunable source to probe the distance to reflectors in the beam path. The resolution of these systems is limited by the fractional tuning range of the source. This work presents a method to increase the fractional tuning range of tunable VCSELs by coupling the energy in the cavity out of the gain medium and into the tuning gap. The design is demonstrated experimentally to increase the tuning range by a factor of two over a comparable tunable VCSEL.

The second family of 3D sensing mechanisms demand high-power, high-efficiency VCSEL arrays to illuminate an entire scene to identify gestures and faces. The final chapter of this dissertation describes a novel fabrication method leveraging the oxidation of AlGaAs to form a high-contrast grating (HCG) reflector in a VCSEL array. The process is scaled from a proof of concept, to the first high-efficiency HCG VCSEL, and finally to an array of HCG VCSELs. The introduction of an HCG to the device reduces the fabrication cost and introduces polarization control to the array, creating a platform for new possibilities in 3D sensing.

Advisors: Constance Chang-Hasnain

BibTeX citation:

@phdthesis{Cook:EECS-2021-228,
    Author= {Cook, Kevin},
    Title= {Design and Fabrication of VCSELs for 3D Sensing},
    School= {EECS Department, University of California, Berkeley},
    Year= {2021},
    Month= {Dec},
    Url= {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2021/EECS-2021-228.html},
    Number= {UCB/EECS-2021-228},
    Abstract= {Vertical-cavity surface-emitting lasers (VCSELs) are critical components in many optical systems. They already drive the transmission of data in massive datacenters and supercomputers, and they are becoming the state of the art in 3D sensing systems that allow computers to perceive the world more like humans. These systems have important applications in medicine, autonomous vehicles, facial recognition, and gesture detection. VCSELs have shown the promise of improving resolution while decreasing module cost due to their extremely scalable fabrication process.

The first 3D sensing mechanisms that VCSELs promise to improve are swept-source optical coherence tomography and frequency-modulated continuous-wave LIDAR. These techniques use a wavelength tunable source to probe the distance to reflectors in the beam path. The resolution of these systems is limited by the fractional tuning range of the source. This work presents a method to increase the fractional tuning range of tunable VCSELs by coupling the energy in the cavity out of the gain medium and into the tuning gap. The design is demonstrated experimentally to increase the tuning range by a factor of two over a comparable tunable VCSEL.

The second family of 3D sensing mechanisms demand high-power, high-efficiency VCSEL arrays to illuminate an entire scene to identify gestures and faces. The final chapter of this dissertation describes a novel fabrication method leveraging the oxidation of AlGaAs to form a high-contrast grating (HCG) reflector in a VCSEL array. The process is scaled from a proof of concept, to the first high-efficiency HCG VCSEL, and finally to an array of HCG VCSELs. The introduction of an HCG to the device reduces the fabrication cost and introduces polarization control to the array, creating a platform for new possibilities in 3D sensing.},
}

EndNote citation:

%0 Thesis
%A Cook, Kevin 
%T Design and Fabrication of VCSELs for 3D Sensing
%I EECS Department, University of California, Berkeley
%D 2021
%8 December 1
%@ UCB/EECS-2021-228
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2021/EECS-2021-228.html
%F Cook:EECS-2021-228