Katarzyna Komorowska

Performance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulators

Carrier-depletion based silicon modulators with lateral and interdigitated PN junctions are compared systematically on the same fabrication platform. The interdigitated diode is shown to outperform the lateral diode in achieving a low VπLπ of 0.62 V∙cm with comparable propagation loss at the expense of a higher depletion capacitance. The low VπLπ of the interdigitated PN junction is employed to demonstrate 10 Gbit/s modulation with 7.5 dB extinction ration from a 500 µm long device whose static insertion loss is 2.8 dB. In addition, up to 40 Gbit/s modulation is demonstrated for a 3 mm long device comprising a lateral diode and a co-designed traveling wave electrode.

Using carrier-depletion silicon modulators for optical power monitoring

Defect-mediated subbandgap absorption is observed in ion-implanted silicon-on-oxide waveguides that experience a rapid thermal annealing at 1075°C. With this effect, general carrier-depletion silicon modulators exhibit the capability of optical power monitoring. Responsivity is measured to be 22 mA/W for a 3 mm long Mach-Zehnder modulator of 2×10(18) cm(-3) doping concentration at -7.1 V bias voltage and 5.9 mA/W for a ring modulator of 1×10(18) cm(-3) doping concentration at -10 V bias voltage. The former is used to demonstrate data detection of up to 35 Gbits/s.

Near-Infrared Grating Couplers for Silicon Nitride Photonic Wires

Silicon nitride is a promising high-index material for dense photonic circuits and applications in the visible-midinfrared wavelength regime. Design, fabrication, and optical characterization of silicon nitride waveguides at visible-near-infrared wavelength are presented. Finally, design and experimental results are presented for the first time for linear and focused grating couplers (GCs) at near-infrared wavelength (900 nm) for plasma-enhanced chemical vapor deposition silicon nitride wires (220 × 500 nm) and compared with theoretical simulations. An experimental efficiency of 5.7 and 6.5 dB and 1-dB bandwidth of 26 and 40 nm are reported for the linear and focused GCs, respectively.

Silicon-on-Insulator Microring Resonator Sensor Integrated on an Optical Fiber Facet

In recent years, portable, sensitive, and cheap sensors have gained interest in fields such as medical diagnostics, food quality control, environmental monitoring, and drug development. Especially optical sensors in silicon-on-insulator (SOI) have proven to be very promising, because they have a low limit of detection, are very compact, and can be made with cheap mass fabrication techniques. While a lot of progress has been made to implement such sensors in small and easy-to-use cartridges, many applications require a sensor probe that can perform measurements at locations that are hard to reach. We introduce a method to integrate an SOI photonic sensor on the facet of a standard single-mode optical fiber, and apply this method to a well-known ring resonator refractive index sensor without deteriorating its sensitivity. We thus combined the good performance of SOI sensors with the high mobility of optical fibers.

From fabrication to mode mapping in silicon nitride microdisks with embedded colloidal quantum dots

We report on the fabrication of free-standing and optically active microdisks with cadmium-based colloidal quantum dots embedded directly into silicon nitride. We show that the process optimization results in low-loss silicon nitride microdisks. The Si3N4 matrix provides the stability necessary to preserve the optical properties of the quantum dots and observe efficient coupling of the photoluminescence to the resonating microdisk modes. Using a spectrally and spatially resolved microphotoluminescence measurement, we map the emission pattern from the microdisk. This technique allows us to identify the resonant modes. The results show good agreement with numerical mode simulations.

One-Dimensional Off-Chip Beam Steering and Shaping Using Optical Phased Arrays on Silicon-on-Insulator

Optical beam steering can find applications in several domains such as laser scanning, LiDAR (Light Detection And Ranging), wireless data transfer and optical switches and interconnects. As present beam steering approaches use mechanical motion such as moving mirrors or MEMS (MicroElectroMechanical Systems) or molecular movement using liquid crystals, they are usually limited in speed and/or performance. Therefore we have studied the possibilities of the integrated silicon photonics platform in beam steering applications. In this paper, we have investigated a 16 element one-dimensional optical phased array on silicon-on-insulator with a field-of-view of 23. Using thermo-optic phase tuners, we have shown beam steering over the complete field-of-view. By programming the phase tuners as a lens, we have also shown the focusing capabilities of this one-dimensional optical phased array. The field-of-view can easily be increased by decreasing the width of the waveguides. This clearly shows the potential of silicon photonics in beam steering and scanning applications.

Doping geometries for 40G carrier-depletion-based silicon optical modulators

A comparison is preformed between carrier-depletion modulators with different doping patterns to reach low V_πL_π = 0.62 V·cm at DC with interdigitated and lateral PN junctions respectively, but also show modulation at 35 Gbit/s (errorfree).

Reaction tubes: A new platform for silicon nanophotonic ring resonator sensors

Label-free biosensing with silicon nanophotonic ring resonator sensors has proven to be an excellent sensing technique for achieving high throughput and high sensitivity, comparing favorably with other labeled and label-free sensing techniques. However, as in any biosensing platform, silicon nanophotonic ring resonator sensors require a fluidic component that allows the continuous delivery of the sample to the sensor surface. This is the big disadvantage of this platform since this type of microfluidic system is very much removed from the daily practice in, e.g., hospital labs, which still relies to a large degree on platforms like 96-well microtiter plates or reaction tubes. To address this major drawback, we propose the combination of a simple and lab-compatible reaction tube platform, with label-free nanophotonic biosensors with a special microfluidic system imbedded into the same chip, where the flow is through the chip rather than over the chip as in more traditional approaches. This shows that label-free nanophotonic ring resonators can be also used in the user-friendly platform like reaction tubes or well microtiter plates, conserving their excellent performance.

Single-mode air-clad liquid-core waveguides on a surface energy patterned substrate

We demonstrate a new kind of single-mode micro-optical waveguide based on a liquid core on top of solid substrate and air cladding. The liquid is held in place by surface tension and patterned surface energy on the substrate. Due to the smooth nature of the liquid/air interface down to the molecular level, low scattering losses are expected. Losses were measured to be -6.0 and -7.8 dB/cm for, respectively, 12 and 9 μm wide waveguides.

Low dispersion integrated Michelson interferometer on silicon on insulator for optical coherence tomography

We present an integrated silicon Michelson interferometer for OCT fabricated with wafer scale deep UV lithography. Silicon waveguides of the interferometer are designed with GVD less than 50 ps/nm.km. The footprint of the device is 0.5 mm x 3 mm. The effect of sidewall roughness of silicon waveguides has been observed, possible solutions are discussed.