Daniel Jubin

Probe-based ultrahigh-density storage technology

Ultrahigh storage densities can be achieved by using a thermomechanical scanning-probe-based data-storage approach to write, read back, and erase data in very thin polymer films. High data rates are achieved by parallel operation of large two-dimensional arrays of cantilevers that can be batch fabricated by silicon-surface micromachining techniques. The very high precision required to navigate the storage medium relative to the array of probes is achieved by microelectromechanical system (MEMS)- based x and y actuators. The ultrahigh storage densities offered by probe-storage devices pose a significant challenge in terms of both control design for nanoscale positioning and read-channel design for reliable signal detection. Moreover, the high parallelism necessitates new dataflow architectures to ensure high performance and reliability of the system. In this paper, we present a small-scale prototype system of a storage device that we built based on scanning-probe technology. Experimental results of multiple sectors, recorded using multiple levers at 840 Gb/in2 and read back without errors, demonstrate the functionality of the prototype system. This is the first time a scanning-probe recording technology has reached this level of technical maturity, demonstrating the joint operation of all building blocks of a storage device.

Selective Transfer Technology for Microdevice Distribution

We have developed a generic cost-efficient CMOS-compatible heterogeneous device integration method at wafer-scale level. This method enables the distribution of devices from one to numerous wafers using selective transfer technology. We have applied this method for the distribution of atomic force microscopy (AFM) cantilevers and successfully demonstrated the population of multiple wafers from one source wafer. The distribution function has been designed such as to populate 42 wafers with only one source wafer. This CMOS back-end-of-the-line compatible method is particularly suitable for microelectromechanical systems and integrated circuits. Electrical interconnects are compatible with this technology. We present the concept, the selective transfer method, including a laser ablation technique used for the transfer, as well as the process and results of the application for AFM cantilever distribution.

Polymer waveguides for electro-optical integration in data centers and high-performance computers.

To satisfy the intra- and inter-system bandwidth requirements of future data centers and high-performance computers, low-cost low-power high-throughput optical interconnects will become a key enabling technology. To tightly integrate optics with the computing hardware, particularly in the context of CMOS-compatible silicon photonics, optical printed circuit boards using polymer waveguides are considered as a formidable platform. IBM Research has already demonstrated the essential silicon photonics and interconnection building blocks. A remaining challenge is electro-optical packaging, i.e., the connection of the silicon photonics chips with the system. In this paper, we present a new single-mode polymer waveguide technology and a scalable method for building the optical interface between silicon photonics chips and single-mode polymer waveguides.

Development of Versatile Polymer Waveguide Flex Technology for Use in Optical Interconnects

We report on the implementation of novel flexible polymer waveguide interconnects. They are based on newly developed mechanically flexible low-loss silicone waveguides. In addition to meeting the generic requirements of rigid waveguide interconnects, several flex-material challenges were mastered: a) mechanical flexibility permitting waveguide flexing down to radii of 1.0 mm without cracking; b) minimization of waveguide curling induced by the CTE mismatch between flex substrates and polymer layers to enable assembly and connectorization; c) greatly improved cladding adhesion on standard PCB flex substrates, such as polyimide; and d) high environmental stability despite the reduced polymer cross-linking required for better mechanical flexibility. The new waveguides exhibit excellent stability in damp heat (2000 h in 85°C/85% rH) and under thermal shock (500 cycles from -40° to +120°C), and lead-free solder reflow up to 260°C. Using the newly engineered “Dow Corning WG-1017 Optical Waveguide Clad Dev Sample” and the established “Dow Corning WG-1010 Optical Waveguide Core”, we were able to develop a manufacturing process suitable for large areas and offering high process control and stability to produce waveguides having optical loss values of less than 0.05 dB/cm at 850 nm VCSEL wavelength and fulfilling requirements (a) to (d) above. We describe this manufacturing process and how we have overcome the material challenges mentioned. Furthermore, we present characterization and manufacturing results, show demonstrators, and outline the potential of flexible waveguides as versatile electro-optic assembly platform.

Scanning Probes Entering Data Storage: From Promise to Reality

Micro-electro-mechanical-system (MEMS)-based scanning-probe data storage devices are emerging as ultra-high-density, low-access-time, and low-power alternatives to conventional data storage. The probe-storage technique explored at IBM utilizes AFM probes and thermomechanical means to store and retrieve information in thin polymer films. High data rates are achieved by parallel operation of large 2D arrays with thousands of micro/nanomechanical cantilevers/tips that can be batch-fabricated by silicon surface micromachining techniques. The very high precision required to navigate the probe-tips over the storage medium is achieved by MEMS-based x/y actuators that position the large arrays of probe tips for parallel write/read/erase operations. For thermomechanical scanning-probe storage the polymer medium plays a crucial role. Based on a systematic study of different polymers it has been identified that the glass-transition temperature is the most important property that needs to be controlled for indentation writing and erasing at very narrow spacing. A prototype system demonstrating all the basic functions of a storage device based on scanning probes has been built and its main building blocks will be described in this paper. The inherent parallelism, the ultrahigh areal densities and the small form factor that probe storage techniques offer may open up new perspectives and opportunities for application in areas beyond those envisaged today.

Polymer waveguide-based multilayer optical connector

For the realization of a polymer waveguide based optical backplane link for computing applications, we developed a method to passively align multiple layers of polymer waveguide flex sheets in a single MT compatible ferrule. The minimal feature forming the backplane is a 192 channel link. This link is equipped with four MT connector at each end, and is performing a shuffling of the channels. We describe the passive alignment used to realize the connectors. The achieved accuracy demonstrated in a 48 channels connector consisting of 4 polymer sheets carrying 12 waveguides each, is shown to be better than ±5μm. The connection losses between a 48 channel MT fiber connector and the realized polymer waveguide connector were found to be about 2dB. Compared to fiber connectors, the presented concept using polymer waveguides has several advantages. The most relevant are that only few assembly steps are needed, it is based on a totally passive alignment scheme and it can easily be executed by standard pick and place tools.

Optical interconnects for board level applications

Optical link technology will play an increasingly important role for board-level interconnects in servers and supercomputers as a means to keep pace with the increasing intra-system bandwidth requirements. Low-cost and high density optical packaging concepts are required. We describe the development of board-level interconnects based on polymer waveguide technology. In this paper, we focus on flexible optical waveguide sheets and the passive alignment of optical connectors.

Optical interconnects for disaggregated resources in future datacenters

In future datacenters with disaggregation, dynamic allocation and reconfiguration of resources, I/O and networks will become both enabling elements - and bottlenecks. We discuss latency in optical data transmission and photonics integration and packaging, which will become particularly critical.

Optical coupling between polymer waveguides and a silicon photonics chip in the O-band

We present a silicon photonics optical I/O interfacing solution based on adiabatic optical coupling between silicon and polymer waveguides. A transition loss of -0.9 dB and back-reflection <; -45 dB were found at 1310 nm.

Integrated micro-mirrors for compact routing of optical polymer waveguides

We report on micro-mirrors integrated in optical polymer waveguides. The mirrors are fabricated prior to the waveguide core definition step and are based on a selective wet-chemical metallization process.