Extreme Refractive-, Diffractive- and Hybrid-Hyperchromats: Minimizing the Equivalent Abbe Number of a Two-Lens System

Werner, Lukas; Förster, Erik; Kraus, Matthias H.; Hillmer, Hartmut; Brunner, Róbert

doi:10.3390/photonics10050556

Cited by 3 publications

(1 citation statement)

References 19 publications

(24 reference statements)

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“…This means that, for such a single imaging DOE, an achromatic effect can be achieved for at least two wavelengths. Conversely, if shorter wavelengths and 1st order, as well as longer wavelength range with higher order are combined, a strong spreading of the focal positions occurs, which can be interpreted as a hyperchromatic effect [18,19].…”

Section: Basic Application Concepts For Wavelength-selective Doesmentioning

confidence: 99%

Tailoring Wavelength-Selective Diffraction Efficiency Using Triple-Layer Double-Relief Blazed Gratings Incorporating Materials with Intersecting Dispersion Curves

Schmidt,

Hillmer,

Brunner

2023

Photonics

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Diffractive optical elements (DOEs) fundamentally provide the possibility to simultaneously utilize multiple orders for different imaging functions within a system. However, to take advantage of this property, it is necessary to tailor the assignment of specific wavelengths or wavelength ranges with high diffraction efficiency to specific diffraction orders. To achieve this wavelength-selective assignment to different orders, simple diffractive profile shapes are not suitable; instead, multilayer DOEs are required. In this study, we conducted theoretical, scalar investigations on the diffraction efficiency of triple-layer double-relief DOEs for the purpose of tailored wavelength selectivity. Specific materials such as nanocomposites, layer materials, and high-refractive-index liquids with strong dispersion were included, in addition to inorganic glasses, to enable wide design freedom for wavelength selectivity across multiple orders. To simultaneously account for both positive and negative orders, specific material combinations featuring intersecting or touching dispersion curves were utilized. For various material combinations, we calculated significantly different efficiency profiles for multiple orders by varying the relief depths. Further, we discuss the possibility of fine-tuning the efficiency profiles by using high-index liquids as an intermediate layer between two solid profiles, whose dispersion properties can be varied continuously or at least in small steps.

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Section: Basic Application Concepts For Wavelength-selective Doesmentioning

confidence: 99%

Tailoring Wavelength-Selective Diffraction Efficiency Using Triple-Layer Double-Relief Blazed Gratings Incorporating Materials with Intersecting Dispersion Curves

Schmidt,

Hillmer,

Brunner

2023

Photonics

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Unlocking the potential of extreme hyperchromats: pushing the limits of axial color splitting

Werner,

Förster,

Hillmer

et al. 2024

Fiber Lasers and Glass Photonics: Materials Through Applications IV

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In contrast to conventional optical systems, which are optimized for wavelength-independent imaging, hyperchromats aim for strongly wavelength-dependent focal lengths. In this contribution, the design parameters of hyperchromatic two-lens optical systems were derived that provide strong axial color splitting expressed by extremely low equivalent Abbe numbers. These systems have been investigated for compositions of either pure refractive or all diffractive lenses, as well as hybrid configurations thereof. First, lens doublets made of cemented elements are considered and the variables affecting the equivalent Abbe number of the system are investigated. In particular, the influence of the focal lengths of the individual lenses and the Abbe numbers of the selected lens materials are taken into account. The best parameter-sets were determined by paraxial numerical simulations for different cemented configurations. To ensure a simple implementation, especially to avoid exotic or potentially harmful materials, only readily available inorganic standard glasses were considered. In the next phase of this investigation an air gap was inserted between the two lenses, which is an additional influence parameter on the equivalent Abbe number. Following the paraxial considerations, selected two-lens configurations were transferred to the non-paraxial domain and refined using optical design software, also taking aberrations into account. To further reduce achievable equivalent Abbe numbers, an aspherical surface was introduced to compensate for spherical aberrations. Finally, for the refractive doublets an equivalent Abbe number of 2.4 was achieved, which corresponds to only 12% of the smallest Abbe number of the selected materials. This result was even surpassed by the hybrid hyperchromat, resulting in an extraordinary minimum equivalent Abbe number of -0.6 that is more than five times smaller than the Abbe number of diffractive lenses.

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Advanced linear axial wavelength spreading through cascaded double hyperchromats

Werner,

Hillmer,

Brunner

2024

J. Opt. Soc. Am. A

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This study explores the design and optimization of cascaded double-hyperchromatic optical systems (i.e., 2×2 lenses), focusing on achieving an extremely linear axial spectral decomposition characterized by an exceptionally low equivalent Abbe number. The investigation involves two double hyperchromats, considering both purely refractive systems and hybrid configurations that combine refractive and diffractive elements. For purely refractive systems, alternating focal length signs of divergent and collective lenses are crucial to achieve significant axial chromatic dispersion. In hybrid systems, the position of the diffractive optical element (DOE) and the selection of focal lengths play key roles in obtaining extremely low equivalent Abbe numbers. The optimized systems demonstrate absolute equivalent Abbe numbers of 0.983 for purely refractive and 0.65 for hybrid systems—more than four times lower than the absolute Abbe number of a single diffractive element. Notably, even systems using standard materials exhibit significantly low equivalent Abbe numbers of 2.5 and 1.4 for pure refractive and hybrid configurations, respectively. These results offer promising opportunities for improving optical applications based on axial spectral decomposition, overcoming previous limitations of axial chromatic spreading.

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Extreme Refractive-, Diffractive- and Hybrid-Hyperchromats: Minimizing the Equivalent Abbe Number of a Two-Lens System

Cited by 3 publications

References 19 publications

Tailoring Wavelength-Selective Diffraction Efficiency Using Triple-Layer Double-Relief Blazed Gratings Incorporating Materials with Intersecting Dispersion Curves

Tailoring Wavelength-Selective Diffraction Efficiency Using Triple-Layer Double-Relief Blazed Gratings Incorporating Materials with Intersecting Dispersion Curves

Unlocking the potential of extreme hyperchromats: pushing the limits of axial color splitting

Advanced linear axial wavelength spreading through cascaded double hyperchromats

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