Rohan D. Kekatpure

Electronically controlled optical beam-steering by an active phased array of metallic nanoantennas

An optical phased array of nanoantenna fabricated in a CMOS compatible silicon photonics process is presented. The optical phased array is fed by low loss silicon waveguides with integrated ohmic thermo-optic phase shifters capable of 2π phase shift with ∼ 15 mW of applied electrical power. By controlling the electrical power to the individual integrated phase shifters fixed wavelength steering of the beam emitted normal to the surface of the wafer of 8° is demonstrated for 1 × 8 phased arrays with periods of both 6 and 9 μm.

The suitability of SiGe multiple quantum well modulators for short reach DWDM optical interconnects.

We describe calculations that address the suitability at using silicon-germanium multiple quantum well (MQW) modulators in dense wavelength division multiplexed (DWDM) short reach optical interconnects that vary over a significant temperature range. Our calculations indicate that there is a tradeoff between the number of channels, the temperature range and laser power required. Twenty to forty DWDM channels at 100 GHz and 50 GHz channel spacing is possible in DWDM links with a ~ 12° temperature range with less than a 1 dB laser power penalty compared to the optimum single channel, single temperature case. The same number of channels can be operated over a wider 37° temperature range with laser power penalties of 3 dB. It shows that, even for DWDM systems, silicon-germanium modulators might provide an alternative to ring and disk resonant modulators without the need for stringent (<< 1 °C) temperature control.

First-Principles Full-Vectorial Eigenfrequency Computations for Axially Symmetric Resonators

Starting from the time-harmonic Maxwells equations in cylindrical coordinates, we derive and solve the finite-difference (FD) eigenvalue equations for determining vector modes of axially symmetric resonator structures such as disks, rings, spheres and toroids. Contrary to the most existing implementations, our FD scheme is readily adapted for both eigenmode and eigenfrequency calculations. An excellent match of the FD solutions with the analytically calculated mode indices of a microsphere resonator provides a numerical confirmation of the mode-solver accuracy. The comparison of the presented FD technique with the finite-element method highlights the relative strengths of both techniques and advances the FD mode-solver as an important tool for cylindrical resonator design.

A CMOS compatible external heater-modulator

We present simulation and experimental results of a novel external heater-modulator structure. A heater efficiency of 21.3 μW/GHz is measured with no power penalty between heater off and heater on states observed at 10 Gbps.

Thermal crosstalk limits for silicon photonic DWDM interconnects

We present theoretical modeling and experimental results of the thermal crosstalk and time constants of micro-disk modulators as a function of the spacing between nearby devices, taking into consideration the effects of dense metallic interconnects.

Evaluation of SiGe multiple quantum well modulators for short-reach, dense wavelength division multiplexed optical interconnects

By modeling temperature-dependent SiGe MQW electroabsorption, we calculate the number of allowed DWDM channels as a function of operating temperature, applied voltage, and a figure of merit related to the laser power penalty. We find that 20 to 40 DWDM channels at 100 GHz and 50 GHz channel spacing is possible in DWDM links with a ~12° temperature range with less than a 1 dB laser power penalty compared to the optimum single channel, single temperature case. The same number of channels can be supported over a 37° temperature range with a 3 dB power penalty.

Thermal infrared plasmonics

We examine a new class of infrared (IR) plasmonic devices that convert thermal radiation into bound surface plasmon polaritons (SPPs). The coupling of these SPPs into nanometer scale metal insulator metal (MIM) channels is investigated both theoretically and experimentally. A new mechanism for detection of the IR radiation is examined that is based on direct rectification of a traveling MIM surface plasmon mode.