Jared C. Mikkelsen

Polarization rotator-splitters and controllers in a Si 3 N 4 -on-SOI integrated photonics platform

We demonstrate novel polarization management devices in a custom-designed silicon nitride (Si(3)N(4)) on silicon-on-insulator (SOI) integrated photonics platform. In the platform, Si(3)N(4) waveguides are defined atop silicon waveguides. A broadband polarization rotator-splitter using a TM0-TE1 mode converter in a composite Si(3)N(4)-silicon waveguide is demonstrated. The polarization crosstalk, insertion loss, and polarization dependent loss are less than -19 dB, 1.5 dB, and 1.0 dB, respectively, over a bandwidth of 80 nm. A polarization controller composed of polarization rotator-splitters, multimode interference couplers, and thin film heaters is also demonstrated.

Automatic Resonance Alignment of High-Order Microring Filters

Automatic resonance alignment tuning is performed in high-order series coupled microring filters using a feedback system. By inputting only a reference wavelength, the filter transmission is maximized on resonance, passband ripples are dramatically reduced, and the passband becomes centered at the reference. The method is tested on fifth-order microring filters fabricated in a standard silicon photonics foundry process. Repeatable tuning is demonstrated for filters on multiple dies from the wafer and for arbitrary reference wavelengths within the free spectral range of the microrings.

Dimensional variation tolerant silicon-on-insulator directional couplers

We design silicon ridge/rib waveguide directional couplers which are simultaneously tolerant to width, height, coupling gap, and etch depth variations. Using wafer-scale measurements of structures fabricated in the IMEC Standard Passives process, we demonstrate the normalized standard deviation in the per-length coupling coefficient (a metric for the splitting ratio variation) of the variation-tolerant directional couplers is up to 4 times smaller than that of strip waveguide designs. The variation-tolerant couplers are also the most broadband and the deviation in the coupling coefficient shows the lowest spectral dependence.

Silicon photonic transmitter for polarization-encoded quantum key distribution

Silicon (Si) photonics is forming a fabless ecosystem, which is enabling low-cost and densely integrated components for optical communications and quantum information. We present a Si optical transmitter for polarization-encoded quantum key distribution (QKD). The chip was fabricated in a standard Si photonic foundry process and integrated together a pulse generator, intensity modulator, variable optical attenuator, and polarization modulator in a 1.3  mm×3  mm1.3  mm×3  mm die area. The devices in the photonic circuit meet the requirements for QKD. The transmitter was used in a proof-of-concept demonstration of the BB84 QKD protocol over a 5 km long fiber link. This work shows the potential of using foundry Si photonics for low-cost, wafer-scale fabricated components for quantum information.

Adiabatically widened silicon microrings for improved variation tolerance.

We show that silicon microrings with adiabatically widened bends are more tolerant to dimensional variations than conventional microring designs with uniform waveguide widths. Through wafer-scale measurements of test structures fabricated in the IMEC Standard Passives process (193 nm DUV lithography, 200 mm SOI wafer), improvements in the intra-die and wafer-scale variation of the resonance wavelength are demonstrated. A 2.1× reduction in the standard deviation of the resonance wavelength across the wafer was observed.

Microdroplet-etched highly birefringent low-loss fiber tapers

We use hydrofluoric acid microdroplets to directly etch highly birefringent biconical fiber tapers from standard single-mode fibers. The fiber tapers have micrometer-sized cross sections, which are controlled by the etching condition. The characteristic teardrop cross section leads to a high group birefringence of B(G)≈0.017 and insertion losses <0.7 dB over waist lengths of about 2.1 mm.

Tri-layer silicon nitride-on-silicon photonic platform for ultra-low-loss crossings and interlayer transitions

We present a three-layer silicon nitride on silicon platform for constructing very large photonic integrated circuits. Efficient interlayer transitions are enabled by the close spacing between adjacent layers, while ultra-low-loss crossings are enabled by the large spacing between the topmost and bottommost layers. We demonstrate interlayer taper transitions with losses < 0.15 dB for wavelengths spanning from 1480 nm to 1620 nm. Our overpass waveguide crossings exhibit insertion loss < 2.1 mdB and crosstalk below -56 dB in the wavelength range between 1480 nm and 1620 nm with losses as low as 0.28 mdB. Our platform architecture is suited to meet the demands of large-scale photonic circuits which contain hundreds of crossings.

Flip-chip integrated silicon Mach-Zehnder modulator with a 28nm fully depleted silicon-on-insulator CMOS driver

We present a silicon electro-optic transmitter consisting of a 28nm ultra-thin body and buried oxide fully depleted silicon-on-insulator (UTBB FD-SOI) CMOS driver flip-chip integrated onto a Mach-Zehnder modulator. The Mach-Zehnder silicon optical modulator was optimized to have a 3dB bandwidth of around 25 GHz at -1V bias and a 50 Ω impedance. The UTBB FD-SOI CMOS driver provided a large output voltage swing around 5 Vpp to enable a high dynamic extinction ratio and a low device insertion loss. At 44 Gbps, the transmitter achieved a high extinction ratio of 6.4 dB at the modulator quadrature operation point. This result shows open eye diagrams at the highest bit rates and with the largest extinction ratios for silicon electro-optic transmitter using a CMOS driver.

Unidirectional hybrid silicon ring laser with an intracavity S-bend

We demonstrate a hybrid silicon ring laser with an internal amplifying S-bend that couples a fraction of the counter-clockwise circulating light into the the clockwise direction. The device supported single-mode, unidirectional laser oscillation at certain bias conditions. A spatial field distribution model is derived to describe the unidirectional operation. A unidirectional clockwise laser output with a suppression ratio up to 18.6 dB over the counter-clockwise mode was achieved.

Integrated photonic devices and circuits in hybrid silicon platforms

Si3N4-on-SOI and VO2-on-SOI integrated photonic devices and circuits, including an ultra-broadband and efficient grating coupler, adiabatic polarization rotator splitters, and wavelength-scale modulators, are described. Hybrid integration enables functionalities not attainable in each material separately.