30

25

20

15

10

5

0

1

2

4

64

256

array elements

Figure 11. Antenna gain (dBi) vs. number of array elements.

4. CONCLUSION

Given the favorable simulation results, the APELC SRR and antenna design presents a viable solution for the

active element of a compact field-deployable THz source. The Manley-Rowe cascade provides an energy efficient

means of frequency up-conversion to enable wall-plug powering of the device. Improvements to the driver circuitry and

conversion process in prototype cycles are expected to allow battery operation for both source and detector modes of

operation.

The SRR array provides quasi-monochromatic radiation, with bandwidth determined by the precision of the

pattern and etch processes. Detuning of geometry dimensions may be used to obtain a wider spectrum. Driving the SRR

array in-phase allows a high degree of partial coherence, thus enabling coherent detection methods for signal extraction

from background noise. The helical antenna elements emit and detect circularly polarized light to enable polarized light

imaging for enhanced contrast.

Fabrication of THz active element in a monolithic unit greatly simplifies the package. The element may be

installed in a modular manner with the driver, power supply and housing to simplify device use and maintenance. The

modularity of the active element also enables interchange of elements to obtain different spectra.

As demonstrated, the gain scales exponentially with number of antenna elements. The HPBW or angular spread

of the radiation places more energy on target and narrows detection sector in receiver mode. Power per unit area, or

intensity, increases exponentially with the number of array components as seen in figure 11. Thus a customer-specified

average power may be obtained through increasing component count. The relatively compact footprint of the active

element allows growth to significant density on a single substrate as compared to discrete emitters and linear antennas.

ACKNOWLEDGMENTS

We extend thanks and gratitude to Raymond Luebbers and Ronn Brourman of Remcom for use of the XFDTD software

used to develop and corroborate geometries in this paper.

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