Computer generated holograms design in null testing of optical freeform surfaces

Huang, Ya; Ma, Jun; Zhu, Rihong; Shen, Hua

doi:10.1117/12.2021053

Cited by 1 publication

(1 citation statement)

References 4 publications

(5 reference statements)

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“…The latter contains the measurement of the shape deviation in an optical manner while using a Computer Generated Hologram (CGH). A CGH is an optical null element, which generates a unique wavefront to enable the measurement of aspheres and freeforms, while using a phase shifting interferometer [17,18]. The individual surface errors of the considered mirror substrates M1/M3 and M2/M4 are measured using full aperture interferometry with specialized CGHs, each.…”

Section: Manufacturing Resultsmentioning

confidence: 99%

Design and manufacturing of a metallic telescope for ground-based quantum communication

Unger,

Heidler,

Peschel

et al. 2024

Optical Fabrication and Testing VIII

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Quantum communication is considered to be a key feature for secure communication e.g. between government organisations or other institutions with high security requirements. Therefore, the QuNET initiative was founded. It focuses on developing a quantum-secure German governmental agency network based on quantum key distribution (QKD). Freespace optical (FSO) links are a valuable part of infrastructure because they can be deployed temporarily, such as at summits or to bridge the last miles where there is no fiber infrastructure. In particular, high-throughput telescopes are of great importance as optical antennas for terrestrial networks or links between mobile nodes. The paper describes the development and manufacturing of an unobscured, afocal four-mirror metal telescope which is already tested for ground-based quantum communication. The off-axis system, operating with a full telescope aperture of 200 mm, a magnification of 20x, and a FOV (field of view) of 3.5 mrad and is designed to yield diffraction-limited performance for an operational wavelength of 810 nm and 1550 nm. The addressed wavefront error-target of the whole system amounts to 66 nm RMS (root mean square). The use case of the telescope implied an operational temperature range of -40 °C up to +50 °C. Therefore, an athermal system is realized using an aluminum-silicon alloy substrate material combined with a nickel-phosphorus polishing layer that allows to reach the required surface quality of the mirrors. To simplify the alignment of the telescope, its mechanical concept relies on a snap-together approach using two substrates with two optical mirrors on a common substrate, each. The manufacturing chain of these two so called mirror substrates is described in detail. That includes the CNC premanufacturing, ultra precision diamond turning and subsequent polishing steps. The resulting quality of the mirror substrates as well as of the telescope system is demonstrated by optical measurements using interferometric setups.

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Section: Manufacturing Resultsmentioning

confidence: 99%