Nicholas J. D. Martinez

High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes.

We present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes with varying lateral multiplication regions and different charge implant dimensions are fabricated and their illuminated device characteristics and high-speed performance is measured. We report a record gain-bandwidth product of 432 GHz for our highest performing waveguide-coupled avalanche photodiode operating at 1510nm. Bit error rate measurements show operation with BER< 10-12, in the range from -18.3 dBm to -12 dBm received optical power into a 50 Ω load and open eye diagrams with 13 Gbps pseudo-random data at 1550 nm.

Single photon detection in a waveguide-coupled Ge-on-Si lateral avalanche photodiode

We examine gated-Geiger mode operation of an integrated waveguide-coupled Ge-on-Si lateral avalanche photodiode (APD) and demonstrate single photon detection at low dark count for this mode of operation. Our integrated waveguide-coupled APD is fabricated using a selective epitaxial Ge-on-Si growth process resulting in a separate absorption and charge multiplication (SACM) design compatible with our silicon photonics platform. Single photon detection efficiency and dark count rate is measured as a function of temperature in order to understand and optimize performance characteristics in this device. We report single photon detection of 5.27% at 1310 nm and a dark count rate of 534 kHz at 80 K for a Ge-on-Si single photon avalanche diode. Dark count rate is the lowest for a Ge-on-Si single photon detector in this range of temperatures while maintaining competitive detection efficiency. A jitter of 105 ps was measured for this device.

Characterization of high performance waveguide-coupled linear mode avalanche photodiodes

We present experimental results for a Ge on Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Our linear mode APD has a gain-bandwidth product in excess of 200 GHz. Furthermore, we demonstrate error free operation (BER<; 10-12) with our waveguide coupled linear mode APD using pseudo-random bit sequence (PBRS) data at 10 Gb/s.

Substrate removal for ultra efficient silicon heater-modulators

We present our experimental results of ultra efficient (up to 2.16 nm/mW) thermally tunable modulators with n-type heaters and the Si substrate removed. To our knowledge, this is the most efficient thermally tunable modulator demonstrated at 1550nm to date. We include results of externally heated modulators with commensurate performance enhancements through substrate removal.

Graphene-Insulator-Semiconductor Junction for Hybrid Photodetection Modalities

A sensitive optical detector is presented based on a deeply depleted graphene-insulator-semiconducting (D2GIS) junction, which offers the possibility of simultaneously leveraging the advantages of both charge integration and localized amplification. Direct read-out and built-in amplification are accomplished via photogating of a graphene field-effect transistor (GFET) by carriers generated within a deeply depleted low-doped silicon substrate. Analogous to a depleted metal-oxide-semiconducting junction, photo-generated charge collects in the potential well that forms at the semiconductor/insulator interface and induces charges of opposite polarity within the graphene film modifying its conductivity. This device enables simultaneous photo-induced charge integration with continuous “on detector” readout through use of graphene. The resulting devices exhibit responsivities as high as 2,500 A/W (25,000 S/W) for visible wavelengths and a dynamic range of 30 dB. As both the graphene and device principles are transferrable to arbitrary semiconductor absorbers, D2GIS devices offer a high-performance paradigm for imaging across the electromagnetic spectrum.

Radio frequency silicon photonics at Sandia National Laboratories

Sandia National Laboratories has developed a toolkit of RF photonic devices. These devices have been used in the development of multielement RF photonic circuits and in support of MPW runs. In this talk I will discuss Sandias silicon photonic process and RF photonic device performance.

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.