Tunable lasers benefit from precision piezo actuators

Many of today's tunable lasers rely on the performance of a micropositioning or nanopositioning actuator to position a diffraction grating with extreme precision and repeatability. While the virtually unlimited resolution and extremely fast response of piezo stack actuators is highly desirable in these applications, their limited travel (typically

However, these systems cannot provide the ultra-smooth piezo-class motion required for wavelength sweeps. Their precision is also affected by friction and backlash in the mechanical drive screw, and their limited dynamic performance leaves laser designers wanting.

Ceramic linear drive

A novel, ultra-compact linear drive based on the PiezoWalk principle has been developed by PI to overcome the limitations of conventional linear actuators. The system, known as Nexact, combines virtually unlimited travel ranges with high stiffness and bandwidth in a very small package. Furthermore, Nexact actuators provide piezo-class resolution (far below one nanometre) and millisecond response. The special drive design works with a very low operating voltage of 40V or less.

In operation, piezoceramic bending elements act on the ceramic runner, which is connected to the moving part of the application. The length of the runner determines the travel range. Force capacity, resolution and velocity are determined by the piezo geometry and drive electronics, and are scalable. To move the runner over longer distances the stepping mode is used, whereas for smaller distances, the linear sweep mode offers up to 7um of highly dynamic positioning with resolutions far below 1nm and bandwidth in the kHz range. Because the principle is not based on sliding friction (as with ultrasonic or inertial motors) there is virtually no particulate generation. The Nexact drive principle offers very high repeatability and can hold a stable position within nanometres, even when powered down.

Another advantage is the autolocking feature with virtually no heat dissipation at rest, which is a significant improvement over stepper motors, thereby eliminating laser drift. The ceramic actuators require no lubricants, so the Nexact drive principle is high-vacuum compatible, as well as being non-magnetic. Because linear motion is generated in the first place, backlash, friction and wear - as caused by conventional rotating tip actuators - are not an issue.

A compact benchtop controller with high-level command interface and comprehensive software driver package and OEM PCB versions are available to drive the actuators.

In summary, the Nexact drive is a highly suitable precision linear actuator for OEMs. It provides extremely high dynamics, resolution and stability. Its miniature size (only 25 x 25 x 12mm), together with easy control and long lifetime (no wear), allow seamless integration into the final product.