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Silicon photonics and hybrid silicon photonics

• [2022] High OMA electro-optic modulation using silicon micro-resonators: 10 mW optical power handling. [Optics Express]
• [2019] A perspective on future 3D Integrated Photonics using lithium niobate thin films. [IEEE Nanotechnology Magazine]
• [2018] Photon-pair generation using spontaneous four-wave mixing in silicon microrings, pumped using a silicon hybrid laser, co-authored with researchers from Intel. [APL Photonics] [CLEO 2017] post-deadline paper
• [2018] Hybrid lithium niobate Mach-Zehnder electro-optic modulator on a silicon photonics platform, exceeding 100 GHz 3-dB electrical bandwidth, co-authored with reseachers from Sandia. [Optics Express]
• [2016] Hybrid Lithium Niobate - Silicon photonic passive devices and circuits. Back-and-forth mode transitions, bends, inter-layer coupling, interferometric circuits. [Scientific Reports]
• [2014] Silicon photonic tunable add/drop/power control (variable optical attenuator, VOA) for four C-band WDM channels. First generation device: thermo-optic tuners on microrings, electro-optic carrier injection VOA, single polarization. [IEEE Conf. PDP]
• [2014] Thermo-optic MZI switch with five cascaded thermo-topic phase-shifters show low power, microsecond-scale cross-bar switching of twenty wavelength channels in UCSD-MORDIA, each carrying 10 Gbit/second data concurrently. [CLEO 2014]
• [2014] Method to extract the electronic carrier-induced loss and coupling coefficients of modern thermo-optic and electro-optic silicon MZI based 2x2 switches (Sandia, IBM and Kotura-Oracle) from the transmission spectra. [CLEO 2014]
• [2013] Demonstrated 100 dB contrast filters (cascade of 2 chips) with 2.8 dB insertion loss, and group delay ripple < 5 ps; built using two > 50 dB extinction filters with 1.4 dB loss, and with thermally-tunable center wavelength and bandwidth (on-chip heaters) [IEEE PTL].
• [2012] Coupling-coefficient dispersion of a silicon-waveguide directional coupler considerably exceeds (by a factor of ~10) the modal refractive-index dispersions of its constituent waveguides [IEEE PTL].

Nonlinear and quantum optics on a chip

QUANTUM

• [2019] Oscilloscopic capture of 100 GHz modulated optical waveforms using a superconducting nanowire single photon detector. [OFC 2019] post-deadline paper
• [2019] Thin-film lithium niobate waveguide entangled photon-pair and heralded single photon generation with CAR > 67,000 and g(2)(0) < 0.025. [FIO 2019] post-deadline paper
• [2017] Silicon photonic entangled photon-pair and heralded single photon generation with CAR > 12,000 and g(2)(0) < 0.006. [URL]
• [2016] Pair generation at 1550 nm using only a few microwatts of optical pump power using a Si microring resonator. [Opt Express].
• [2015] We achieve stable pair generation over 30°C temperature variation by monitoring the microring resonance using a (Ge-free) Si p-i-n photodiode as part of the ring. [Appl. Phys. Lett.].
• [2015] Using two-photon (Franson) interferometry, we measure the entanglement of photon pairs generated from an optically-pumped silicon photonic device operated at room temperature. [Opt. Express].
• [2014] Controlling the joint spectral intensity (2-dimensional photon spectrum) of photon pairs using a silicon chip, and varying the Schmidt degree of entanglement discretely over a wide range without beam-shaping. [Nat Commun]
• [2013] Spectrally-multiplexed ("comb") generated by a coupled-microring silicon pair source, and temperature tuning of the wavelength [Opt Lett] [CLEO 2013 CF2M.4].
• [2012] Heralded single photon generation from a CMOS-compatible silicon nanophotonic chip at room temperature, based on optically-pumped spontaneous four-wave mixing. [Appl Phys Lett].
  
  Press coverage: [NIST Tech Beat], [Photonics.com] [Optics and Photonics News]
  
  "Quantum Light from CMOS-compatible Silicon Microresonators" IEEE Photonics Conference paper TuW2 (2012) [invited].
  
  "Generating photon pairs using silicon photonics" IEEE Group IV Photonics, paper ThC.1, Paris, 27-29 August (2014) [invited].

NONLINEAR

• [2019] Periodic poling and non-destructive diagnostic techniques of x-cut thin-film lithium niobate on insulator (LNOI) for second-harmonic generation. [Opt. Express 2019] [J. Applied Phys. 2019]
• [2014] Tunable higher-order microring filters were integrated on the same chip as a carrier-swept ring mixer, to separate the generated idler wavelength from the residual pump and unconverted signal [Opt Lett 2014].
• [2013] Using reverse-biased silicon microrings, CW four-wave mixing conversion efficiency of -13.4 dB is achieved using 20 um radius micro-ring resonators with only 2.5 mW pump power [IEEE PTL 2013]. Silicon rib waveguides (passive loss of 0.74 dB/cm) with free-carrier lifetime reduction via reverse biased PIN diodes show CW four-wave mixing efficiency of -8.2 dB (-4.4 dB if both signal and idler are measured at the output) with 160 mW pump power (about 2X reduction compared to other reports in literature) [CLEO 2013].
• [2014] Triply-resonant four-wave mixing using coupled silicon microresonators. Wavelength conversion efficiency was improved by 20 dB, enough to demonstrate open eyes at 10 Gbps for converted wavelengths using a CW pump [Opt Lett 2014]
• [2011] Low-power CW four-wave mixing in silicon CROWs, demonstrating +16 dB conversion enhancement relative to a conventional silicon waveguide of equivalent length, a nonlinear coefficient g_eff=3720 /(W.m) and flat conversion in channels spanning more than 10 THz bandwidth (signal to idler) [Opt Lett 2011]. Intra-band and inter-band four-wave mixing using a continuous-wave (CW) pump in silicon CROWs [CLEO].
• [2010] Four-wave mixing in silicon waveguides at wavelengths above 2 um, demonstrating a nonlinear coefficient g=103 /(W.m) and flat conversion over more than 220 nm bandwidth (signal to idler) [Nat Photon] [Frontiers in Optics, 2009]
• [2010] Two pump four-wave mixing in silicon waveguides, showing multicasting of a pulsed signal into several idler wavelengths [Fronters in Optics, 2010].

Coupled micro-resonators: science and applications

• [2014] Electronic on-off switching control over optical Anderson localized modes using a lithographically-fabricated silicon photonic waveguide infiltrated by about 100 sub-micron-scale p-n junction diodes. [Nat Nano]
• [2010] Silicon microring coupled-resonator optical waveguides (CROWs) consisting of upto 235 coupled microring resonators [Opt Lett].
• [2010] Statistical measurements of intensity and group delay, showing scaling behavior with length, and evidence of non-localized propagation through 235-ring silicon CROWs [OpEx].
• [2007] Effect of disorder on slow-wave waveguides, deriving a simple expression for the maximum achievable slowing factor (S=c/v_g) [Opt Lett].
• [2011] How many rings can be coupled in a CROW before disorder-induced bandwidth collapse occurs? Theoretical and experimental studies in silicon microring CROWs [Opt Lett].
• [2008] Light localization in SOI coupled resonator optical waveguides, demonstrating strong localization of Bloch excitations in a disordered 1D chain of 100 resonators [Nat Photon].
• [2011] Accurate transfer matrix modeling of long CROWs, including silicon waveguide dispersion and disorder effects [PTL].
• [2014] 20 dB improvement in CW four-wave mixing in silicon CROWs with electronic free-carrier removal [Opt Lett]
• [2001-2004) Earlier tight-binding [OpEx, 2001] and transfer-matrix analysis [OpEx, 2004] of CROWs. Tight-binding analysis of holographic pulse storage in CROWs [PRE, 2001]. Nonlinear interactions in CROWs [PRE, 2002]. "Frozen" light CROW soliton theory [PRE, 2002].

Experimental and theoretical methods

• [2019] Oscilloscopic capture of 100 GHz modulated optical waveforms at femtowatt power levels. [OFC 2019] post-deadline paper
• [2012] Static rerouting of the optical light path on a silicon chip, using tip-induced nano-oxidation of 2x2 components: microring add/drop filter and Mach-Zehnder interferometer [CLEO/QELS 2012].
• [2011] 0.002 nm precision set-and-forget alignment of silicon photonic microring resonators and Mach Zehnder interferometers using nano-oxidation [OFC PDP, 2011] and [Opt Lett]
• [2011] Measuring statistical distributions of group delay in silicon nanophotonic waveguides rapidly and accurately using the Luna OVA5000 and unfiltered optical amplification [IEEE PTL].
• [2010] Infrared imaging and diagnostics of multi-resonator optical circuits, extracting individual resonator eigen-frequencies and coupling coefficients in a rapid and non-invasive way [Opt Lett].
  
  Spotlight on Optics, commentary by Dr. J. E. Heebner.
• [2012] High dynamic range infrared microscope imaging of silicon nanophotonic devices, overcoming conventional signal-to-noise ratio limitations in dB-scale imaging, by stitching together several images taken at different integration time, using a commercial 12-bit InGaAs infrared (1550 nm wavelength) camera [Opt Lett].
• [2009] Numerically-assisted coupled mode theory for more accurate design of strongly-coupled and compact silicon-on-insulator waveguide couplers and waveguide arrays [OpEx].

Other work in chip-scale photonics

• [2008] Giant birefringence in multi-slot SOI waveguides. We demonstrate record giant birefringence, nearly twice as large as has previously been achieved (Dn_group = 1.5 over more than 60 nm of bandwidth near 1550 nm) using a multi-slotted silicon nanophotonic waveguide [OpEx].
• [2006] Microfluidically-tuned polymeric microring resonator with microfluidic chip for sensing small changes in fluidic composition by refractive index monitoring of a flow [Appl Phys Lett]. This work was one of the earliest "opto-fluidic" micro-resonator demonstrations.