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Southampton University’s Optoelectronics Research Centre is studying the direct UV laser writing of integrated optical circuits on specialised glass substrates and on its own ‘flat’ optical cable.

With application potential from telecom network components through to lab-on-a-chip (LOC) biological and chemical sensors, the photonic circuits are produced with the help of nanometre-level precision positioning systems and motion controls from Aerotech.

The types of optical components that are typically written into the substrates include curved or straight waveguides and splitters that channel light around the circuit; and Bragg gratings that can be used to measure the refractive index of fluids or other materials.

These refractive index sensors are now built into complete optical microchip solutions for bio/chemical sensing by Stratophase.

The basis principle involves passing a sample material over a sensing window and the wavelength of the light reflected from the Bragg grating confirms that its refractive index is within a certain band.

With a typical sensitivity of one part in a million, these devices are providing a solution for a range of commercial bio/chemical-detection applications, from sugar concentrations in foods to toxin, virus and bacteria discovery for pharmaceuticals and petro-chemical quality-control processing.

When a similar UV writing process is directly applied to the flat optical cable, the potential for these types of sensors may be produced without the need to connect high-loss pigtail connections between optical-fibre and optical-material substrates – and may be applied for multiple sensor solutions over long distances for applications that could include biological and chemical monitoring in supply pipes and rivers.

The work in this area is at an early stage but the potential outcome using such techniques may also lead to the production of complete active switching circuits for optical computing.

As opposed to more traditional photolithography mask processing methods for these types of devices, the direct-write approach benefits from single-step integration and is said to be much faster and adaptable for rapid prototyping/short production runs at reasonable costs.

The basis of the direct writing process involves modifying the core layer material by manipulating the substrate under the focused UV laser, so the precision and dynamic performance of the positioning system is fundamental and an intrinsic ‘enabling technology’ for the success of the process.

The high-power UV laser is directed through an interferometer to produce an intense dual-beam interference pattern at the target area.

During the writing process, its focal length is held constant and the overall positioning system flatness, derived from pitch, roll, yaw and Abbe errors from both X and Y axes, must maintain sub-micron tolerances.

The writing process needs to be continuous as the core materials are adversely affected by heating, so the control of the UV lasers’ power and firing pattern is completely synchronised with the on-the-fly compound translation of the X and Y axes.

This synchronisation is another key factor for the process and is carried out within the Aerotech controller by an advanced software feature called PSO or Position Synchronised Output.

PSO triggers the UV laser in real time during continuous motion, processing high-speed encoder feedback in conjunction with XY position array information for the particular feature being written.

In this way, each feature is held to nanometre-level tolerances in all planes and the accuracy and repeatability from feature to feature and the distance between them is realised with high precision.

The positioning system used at the ORC is an Aerotech ABL9000 series air-bearing stage, complete with the A3200 Digital Automation Platform motion-control system with Firewire networked Ndrive linear-stage amplifiers.

With a 300 x 300mm travel range, this brushless linear-servomotor-driven, ultra-high precision stage features a balanced air-on-air preload system for maximum stiffness and glass-scale encoder feedback with an encoder resolution of 1nm.

The H-bridge design maintains both axes and their respective encoders at the same level, which co-locates the centrelines of mass, force and feedback – effectively ensuring that errors are minimised for best performance straightness and flatness.

With dual linear motor-driven Y axes and active yaw control, the ABL9000 is able to produce perfectly parallel scans, straight lines and interpolated curves over its entire working surface.

Each axis is also factory calibrated by Aerotech against a laser interferometer with the error map information added to the controller.

In operation this ensures optimum translation-stage accuracy.

The combination of Aerotech’s BLM series brushless linear servomotors and HLe series linear servo amplifiers provide the smoothness and stability required for nanometre-resolution positioning, while ensuring the required high-bandwidth, zero-crossover distortion and ultra-quiet EMC characteristics that are essential for this application.

Aerotech’s A3200 Digital Automation Platform provides fully deterministic PC-based motion control with advanced diagnostics, setup and tuning features.

As well as the PSO feature, the A3200 includes trajectory generation with multi-block look ahead to minimise geometry errors in tight profiles by regulating the speed and/or the position on each axis.

The ORC uses G-code programming for its application, but the A3200 is also equipped for programming in Aerotech’s own Aerobasic or in C, C++ and Visual Basic.

For complete application integration, the optional Ncontrol SDK software development kit may be used with Windows-based ActiveX components, C++, VB and .NET class libraries.

There are also a number of advanced software and hardware features available to optimise throughput performance and further improve overall machine operation.

The complete system was supplied to the ORC on a customised granite base with an additional fixed-bridge arrangement that provides a stable platform for the ORC-supplied interferometer optical system.

The scope of supply also includes direct drive rotary and vertical lift stages with comparable resolution and precision that are used together for pre-alignment of the substrate.

Full cable management was included in the design, which assisted commissioning at the ORC.

The performance of the ABL9000 series has been enhanced with Aerotech’s PlanarHD air-bearing stage.

The stage is aimed at high-throughput scanning and ultra-high precision step-and-settle applications found in semiconductor processing and other emerging MEMS/Nano technologies.

The design features larger air-bearing surfaces for improved load carrying and higher dynamic characteristics.

A brief performance specification includes 2m/sec scan velocity and peak acceleration to 5G – with a positioning resolution of up to 0.25nm, repeatability to 50nm and accuracy to +/-300nm.


Aerotech — manufacturer of high-precision motion control components and systems

Aerotech — manufacturer of high-precision motion control components and systems

Aerotech manufactures the highest-performance motion control components and systems for our customers in industry, government, science and research institutions around the world. Our products include automated nanopositioners; planar and rotary air-bearing stages; high-speed gantries; mechanical-bearing linear, rotary and lift stages; brushless linear and rotary servomotors and drives; standalone and software-based motion controllers; goniometers; and gimbals/optical mounts. Custom, vacuum-prepped and cleanroom-ready positioning systems and components are available. Aerotech’s precision motion control products provide the critical performance for demanding applications in markets including medical devices and life sciences, semiconductors and flat panels, photonics, automotive, data storage, laser processing, military and aerospace, electronic manufacturing and test, assembly, research and development and others requiring high-precision, high-throughput motion solutions.

Motion controls, drives and motors

From our award-winning Automation 3200 32-axis machine controller to our Soloist series single-axis and Ensemble series multi-axis standalone motion controllers, Aerotech provides a controller solution to fit almost any need. Aerotech complements our controllers with our large selection of high-performance brushless linear and rotary servomotors and PWM and linear drives.

Linear and rotary stages, nanopositioners and gantries

Aerotech positioning stages range from economical ballscrew and gear-driven linear and rotary stages to the highest-performance direct-drive linear and rotary stages available, linear-motor-based Cartesian gantry systems, single- and multi-axis air-bearing systems and our complete range of ANT series long-travel nanopositioners.

Custom, vacuum and cleanroom-ready motion systems

If you don’t find a standard product suitable for your application, our expertise and ability to provide custom motion components and systems is unmatched. Our custom manufacturing capability is further augmented by our long history of providing systems for vacuum and cleanroom operation.

Since 1970, Aerotech has been committed to supporting our customers worldwide. We maintain a growing number of direct field sales and engineering offices throughout the US, as well as representatives across the globe. We also operate full sales and service facilities in the UK, Germany, Japan, Taiwan and China.

We’d be happy to assist you with your motion control application. Please use the contact information below to enquire about our services.

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