Photonic integrated circuit (PIC) is an excellent platform for nonlinear frequency conversion
due to its superior scalability and the capability of integrating linear optics components.
Silicon nitride (SiN), with low intrinsic linear and nonlinear two-photon absorption losses in
the telecommunications window, shows its advantage as a potential material. In this thesis,
we explore high quality factor Si
3N
4 microresonators towards integrated nonlinear and quantum
light sources.
We develop a stress-released stoichiometric silicon nitride (Si
3N
4) fabrication process for
dispersion-engineered integrated silicon photonics. To relax the high tensile stress of a thick
Si
3N
4 film grown by low-pressure chemical vapor deposition (LPCVD) process, we introduce
a dense stress-release pattern prio...[
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Photonic integrated circuit (PIC) is an excellent platform for nonlinear frequency conversion
due to its superior scalability and the capability of integrating linear optics components.
Silicon nitride (SiN), with low intrinsic linear and nonlinear two-photon absorption losses in
the telecommunications window, shows its advantage as a potential material. In this thesis,
we explore high quality factor Si
3N
4 microresonators towards integrated nonlinear and quantum
light sources.
We develop a stress-released stoichiometric silicon nitride (Si
3N
4) fabrication process for
dispersion-engineered integrated silicon photonics. To relax the high tensile stress of a thick
Si
3N
4 film grown by low-pressure chemical vapor deposition (LPCVD) process, we introduce
a dense stress-release pattern prior to the Si
3N
4 film deposition. The pattern is applied either
on the lower-cladding oxide layer, or onto a thin Si
3N
4 film (<400 nm before the cracks start to
generation). Our pattern helps minimize crack formation by releasing the stress of the film
along high-symmetry periodic modulation directions and helps stop cracks from propagating.
We demonstrate crack-free Si
3N
4 films of up to~950nm-thick in a single deposition run on a 4”
silicon wafer.
Our Si
3N
4 photonic platform enables dispersion-engineered, waveguide-coupled microring
and microdisk resonators, with cavity sizes of up to a millimeter. We characterize and analyze
the linear properties through the transmission spectrum measurement. Our 115μm-radius
microring exhibits an intrinsic quality (Q)-factor of ~2.0×10
6 for the TM
00 mode and our
575μm-radius microdisk demonstrates an intrinsic Q of ~4.0×10
6 for TM modes in 1550nm
wavelengths.
We study the simulated nonlinear frequency conversion from our fabricated high-Q
microresonators. By pumping at the high-Q modes, we observe optical parametric oscillation
(OPO). We achieve a threshold power of ~20 mW inside the coupled waveguide on microring
resonators with a loaded Q-factor of ~1×10
6 in TE polarization.
We study the quantum light sources based on the spontaneous four-wave mixing (SFWM)
process. we demonstrate a high-rate and high-purity photon-pair source through pump-degenerated
SFWM using Si
3N
4 whispering-gallery-mode (WGM) microrings. Our 61.5μm-radius
and 8μm-wide microrings, with a typical loaded Q-factor of ~1×10
6, demonstrate a
photon-pair generation rate (PGR) of ~1.03 MHz/mW
2, with spectral brightness of ~5×10
6
pairs/s/mW
2/GHz that is comparable with the state-of-the-art. We study the heralded single-photon
property with the conditional self-correlation measurement, which reveals a low
conditional self-correlation g
H(2)(0) of 0.008 ± 0.003. We explore the radial order degree of
freedom in WGM microrings for photon-pair generations. Our 119μm-radius and 8μm-wide
microrings demonstrate PGRs from tens to hundreds of kHz/mW
2 for the five lowest-radial-order
TM modes.
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