Terahertz radiation source is optically steerable

June 28, 2013
Braunschweig, Germany--Researchers at the Physikalisch-Technische Bundesanstalt (PTB) have invented a way to easily steer a terahertz beam generated by a laser exciting a semiconductor.
Selective laser excitation of gallium arsenide (GaAs) leads to different power flows (JP, JS) in the semiconductor. The associated radiated electromagnetic fields overlap, and the sum total field E propagates at an angle (theta) from the surface normal. A change in the polarization of the excitation laser changes the angle of the total field due to a change in the direction of the current JP. (Image: PTB)


Braunschweig, Germany
--Researchers at the Physikalisch-Technische Bundesanstalt (PTB) have invented a way to easily steer a terahertz beam generated by a laser exciting a semiconductor. They demonstrated that exciting different directions of current flow in the semiconductor steers the generated terahertz beam. Rapid steering of terahertz radiation will be useful in, for example, body scanners and other security-based applications.

In the PTB experiments, ultrafast laser pulses produce two different currents flowing parallel and perpendicular to the surface of the semiconductor. The radiated terahertz field results from both currents, because of their polarization properties and areas of mutual gain or attenuation. From these interference effects, directional emission is produced. Because the direction of flow parallel to the surface current can be reversed by changing the polarization of the laser pulse (the vertical flow component is not polarization dependent and remains unchanged), the regions of gain and attenuation of the electromagnetic fields can be reversed, and radiation direction changed.

In initial experiments, a change in direction of the maximum terahertz field strength of up to 8° was measured. The angle of deflection depended on different excitation parameters and could be tailored. The dominant influences were determined, allowing optimization via a theoretical model. As a result, the maximum deflection angle can be increased, for example by using other semiconductor material systems, special silicon lenses, or external magnetic fields.

The researchers' findings are published in Applied Physics Letters.

Source: http://www.ptb.de/de/aktuelles/archiv/presseinfos/pi2013/pitext/pi130627.html

Sponsored Recommendations

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Motion Scan and Data Collection Methods for Electro-Optic System Testing

April 10, 2024
Learn how different scanning patterns and approaches can be used in measuring an electro-optic sensor performance, by reading our whitepaper here!

How Precision Motion Systems are Shaping the Future of Semiconductor Manufacturing

March 28, 2024
This article highlights the pivotal role precision motion systems play in supporting the latest semiconductor manufacturing trends.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!