Characterize the refractive-index dispersion of p-DCB at the DBT emission wavelength

Characterize the refractive-index dispersion of para-dichlorobenzene from the reported wavelength of 589 nm to the dibenzoterrylene emission wavelength of approximately 744 nm, in order to determine the refractive-index contrast relevant to cryogenic metallo-dielectric antenna design.

Background

The antenna performance depends critically on the refractive index of the organic host layer. The paper uses a refractive index of 1.9 for para-dichlorobenzene, but that value was measured at 589 nm rather than at the approximately 744-nm emission wavelength of dibenzoterrylene. Since the effective mode index of the organic layer determines whether emission remains within the collection lens’s numerical aperture, measuring the wavelength-dependent refractive index would improve the reliability of the antenna design and optimization.

References

This value, however, was measured at $\lambda=589\,\mathrm{nm}$ , and the dispersion of the refractive index toward the DBT's emission wavelength has, to our knowledge, not been characterized.

— Designing metallo-dielectric antennas for cryogenic applications  (2609.11809 - Luo et al., 10 Sep 2026) in Section 2, “Antenna design”

Since the way in which DBT incorporates into the p-DCB lattice is not known, the resulting effective index cannot be predicted a priori; however, whenever the transition dipole projects predominantly onto the lower-index axes, the effective index approaches $1.45$--$1.64$, corresponding to the favorable regime spanned by the lower part of the efficiency maps in Fig.~\ref{collection_efficiency_colormaps}, where high collection efficiencies are obtained even for the thicker organic layer.

— Designing metallo-dielectric antennas for cryogenic applications  (2609.11809 - Luo et al., 10 Sep 2026) in Section 2, “Antenna design”