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Design and Test of 3D Printed Lenses for sub-THz Design and Test of 3D Printed Lenses for sub-THz

Radiation Radiation

Justin Patterson Portland State University

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Citation Details Citation Details Patterson, Justin, "Design and Test of 3D Printed Lenses for sub-THz Radiation" (2017). Undergraduate Research & Mentoring Program. 13. https://pdxscholar.library.pdx.edu/mcecs_mentoring/13

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Design and Test of 3D Printed Lenses for sub-THz Radiation By Justin Patterson, Prof. Branimir Pejcinovic

Introduction

Lens Design

Measurement Setup

Material Characterization

References

Gaussian Beam Analysis

Acknowledgements

In order to manipulate sub-THz radiation we investigated production of in-

expensive lenses. Production of such lenses were made using additive 3D

printing. With rising 3D printing technology, fabrication of optical compo-

nents transparent to the THz regime is made more accessible. Lenses were

designed using a CAD software, Onshape, and Polypropylene was selected

as the material of choice. The resulting radiation was characterized using

Gaussian beam analysis.

The authors acknowledge the support of the Semiconductor Research Cor-

poration (SRC) Education Alliance (award # 2009-UR-2032G) and of the

Maseeh College of Engineering and Computer Science (MCECS) through

the Undergraduate Research and Mentoring Program (URMP)

The receiving horn was swept

(varying the radial distance) to

observe the E-field amplitude.

MATLAB cftool was used to

fit the Gaussian profile, and the

resulting waveform was then

centered and normalized

Gaussian Beam Theory

Virginia Diodes continuous wave system setup for 150 GHz:

(1): Transmitter (3): Off-axis parabolic mirror

(2): Receiver (4): Plano-convex lens

[1] S.F. Busch, et al. “Optical Properties of 3D Printable Plastics in the

THz Regime and their Application of 3D Printed THz Optics,” J Infrared

Milli Terahz Waves, vol. 35, no. 12, pp. 993-997, Dec. 2014.

[2] Hecht, Eugene. Optics. 4th ed. Reading: Addison-Wesley, 2002. Print.

[3] A. Kazemipour, et al. “The Horn Antenna as Gaussian Source in the

mm-Wave Domain,” J Infrared Milli Terahz Waves, vol. 35, no. 9, pp. 720–

731, Sep. 2014.

Plano-convex lenses were designed using the lens-maker equation.

The beam waist () was calculated at multiple distances (z) by varying the

distance between the lens and the receiving horn. The minimum beam

waist (0) of 7.5 in, corresponds to the focal length of the lens.

(1): 3 inch lens with focal length and

curvature of 5.6 and 2.97 in, respec-

tively. Used with the VDI system

(2): 1.5 inch lens with focal length and

curvature of 3.6 and 1.91 in, respec-

tively. Used with the TDS system

(3): CNC routed Polypropylene lens

Gaussian distribution (left figure): The E-field intensity (I) varies with ra-

dial distance (r) away from the center. The beam waist () is located where

I is 14% of maximum value [2]

Gaussian beam propagation (right figure): Varying as the beam propa-

gates in the z-direction. 0 denotes the minimum beam waist [3]

Polypropylene shows less-loss at THz frequencies compared to ABS.

HDPE carries ideal characteristics; however, it is a challenge to 3D print

due to warping. The absorption coefficient of PP is under 2 cm^(-1) for

frequencies below 1 THz, and the refractive index, n, was approximately

1.53-1.55 for the sub-THz band