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A planar and thin‐grooved Fresnel lens is a great candidate for gain enhancement in millimetre wave communication, imaging systems, and wireless power transfer applications. The authors report the design, fabrication, and measurement of a 3D‐printed Fresnel lens, using a single material. A low‐profile (1.2λthick) 4‐zone Fresnel lens with 16 annular rings is designed with a focal length of 40 mm (≃4λ) operating at 30 GHz. Authors’ design consists of four‐step heights with outer radius of 69 mm (6.9λ). Permittivity and loss tangent of polylactic acid are measured to be 2.79 and 0.0048 at 30 GHz, respectively. Focusing ability of the lens is studied using full‐wave simulation. The lens is fabricated using a table‐top commercial fused deposition modelling printer. The surface roughness, step heights, and radii of each zone are measured and verified using a 3D optical profilometer. Impact of the 3D‐printed limitation on performance of the device is discussed. The gain of the fabricated prototype is measured, in conjunction with a horn antenna, in an anechoic chamber. Pattern measurement results illustrate 6.6 dB gain enhancement at broadside at 30 GHz. Gain enhancing behaviour is studied at three different focal lengths and frequencies of 29–31 GHz.
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Telephoto-lens-based Optical Differentiation Wavefront Sensor for freeform metrology
We report an Optical Differentiation Wavefront Sensor based on a telephoto lens system and binary pixelated filters. It provides a five-fold reduction in the system length compared to a 4fsystem with identical effective focal length. Measurements of phase plates with this system are compared to measurements performed with a commercial low-coherence interferometer. The telephoto-lens-based system can measure wavefronts with accuracy better thanλ/10 Root Mean Squared (RMS) atλ=633 nm. Experimental investigation shows that the system has a high tolerance to components alignment errors.
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- Award ID(s):
- 1711669
- PAR ID:
- 10306586
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 29
- Issue:
- 23
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 38395
- Size(s):
- Article No. 38395
- Sponsoring Org:
- National Science Foundation
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