Implementation and Characterization of Imaging Routines into a Continuous-Wave Terahertz Photomixing System

Conclusion and Future Work: In this thesis, a beam profile imaging routine and a sample inspection imaging routine were implemented into a continuous-wave terahertz photomixing system. The beam profile measurement was performed to recognize and characterize the emitter (photomixer) properties and to examine the alignment of the terahertz beam with an opto-mechanic setup. The emitter was whown to form a beam focus in front of its facet, with frequency dependent properties. A similar frequency dependent behaviour was found for the intermediate focus, which is formed by the opto-mechanic setup for sample inspection purposes.

A sample inspection routine was developed based on two scan methods: as step-by-step scan and a continuous scan. Both methods were throughly tested for various parameters.

Finally, both scan methods were used to inspect an envelope, where the teraherzt images of the envelope clearly revealed its content. But, one of the objects could not be identified with terahertz imgaing. Based on its spectral fingerpringts the unknown object's material was identified with an additional spectroscopic analysis.

There are some works left for the future:

- An automatic data analysis is desired for beam profile imaging routine.

- So far there is only one emitter characterized. For statistiscal validations, the beam profile routine should be applied for different emitters.

- The implemented sample inspection routine is compatible with TOPTICA's incoherent photomixing setup. In future, the routine should be extended to a coherent system for phase-sensitive sample inspection.