36 ANALYTICAL AND LABORATORY EQUIPMENT
Next-gen silicon photonics
Doris Knauer reports on automatic testing of photonics components
S
ilicon photonics set the pace on the fibre optic data highway. However, a number of challenges must be overcome for production and testing of the latest generation of silicon photonics wafers. Automated solutions must function reliably under industrial conditions and work around-the- clock with great accuracy. With silicon photonics (SiP),
electronic logic circuits (such as those used for computing) and optical transceivers are integrated into the same wafer. Te resulting low-power microchips are then able to transmit data at bandwidths in the Tbit/s range and with low heat generation. However, because the value of a packaged SiP circuit goes up considerably compared to the raw circuit on a wafer, it is critical to introduce wafer-level testing of each circuit before dicing and packaging. Optical inputs and outputs must be tested with highest precision. Tey need to be aligned precisely to the optical fibres connected to the test equipment. Tat is definitely not a trivial matter, because optical waveguides in silicon wafers normally have a core diameter of only 150 to 200nm, and to avoid losses, alignment equipment must have at least 10 times higher resolution.
As a solution supplier for
drive technology and precision positioning systems, PI (Physik Instrumente) has taken a close
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look at this and developed a new complete system for fast fibre alignment, which can align, test and optimise the light input and output at each input and output coupling point in less than one second. Tis guarantees fast data throughput rates during industrial production.
Application-specific controller
Te system consists of two compact identical positioning units that, with a small footprint of 100 × 100mm, require very little installation space. Te heart of the system is the application- specific controller with a variety of built-in alignment and tracking algorithms required for optical alignment and which therefore lightens the burden on the higher level control. Te host computer communicates with the controller via Ethernet, USB 2.0 or an RS-232 interface. Positioning is done in two phases. A three-axis positioning stage driven by closed-loop DC
motors takes care of the initial task of coarse adjustment; it travels to the respective coupling point over travel ranges of several tens of millimetres with an accuracy of up to 50nm. An additional three-axis positioning unit is then responsible for fine positioning of the fibres. Te system is driven by
piezo actuators and achieves resolutions of 1nm with response times in the microsecond range and travel ranges of 100 × 100 × 100 µm. Te high- performance piezo actuators are integrated into guiding systems with FEA-optimised flexure joints and are free of both friction and backlash. Because actuators, guides and
sensor work without wear, the systems are extremely reliable and durable, and are therefore perfectly suitable for industrial requirements in multiple-shift operation (24 hours, seven days a week).
For more information ✔ at
www.scientistlive.com/eurolab
Industry-suited complete systems for wafer probing in silicon photonics
Doris Knauer is with Physik Instrumente (PI).
www.pi.ws
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