Spectrally aligned integration of miniaturized substrate-free thin-film filters for fiber optical networks

Abstract

This paper presents the active alignment of miniaturized, substrate-free optical thin-film filters (TFFs) according to the filters’ spectral transfer properties for integration into fiber optical networks. Optical TFFs are often designed for a specific narrow angle of incidence (AOI) range. Hence, a sufficient manufacturing precision of the angled photonic components connected to the optical filter is needed. These components then can no longer be used for different scenarios where i.e. the incident angle is changed. Conversely, the individual miniaturized optical filter chips can also vary in specification due to slight inhomogeneities during the production on a largescale wafer. Therefore, not all filter chips on the wafer meet the demanded specifications at the designed AOI, resulting in a reduced yield. Moreover, it requires a time-consuming separation into different quality classes by measuring single filter chips on the wafer. To maximize the amount of usable chips, a procedure was developed to actively align the chips inside a precision optics assembly system by measuring the transmitted power at different wavelengths while tilting them towards the optical axis. When the optimal angle is found, the chip is glued into the optical network platform. Next to maximizing the yield, the production steps can be reduced because the prior separation into quality classes becomes redundant. Manufacturing tolerances during the thinfilm deposition are equalized due to the active spectral alignment on a universal optical platform. With this technique, a more versatile process for TFF integration compared to passively aligned assemblies on fixed angle components is demonstrated.

Integrable thin-film Fabry-Pérot type electro-optic modulator

“…Electro-optic polymers can be spin coated and no crystal growth process is needed. The miniaturization yields thousands of substrate-free elements from a single coating run, which can be used without collimating lenses [12] and are capable to be aligned to achieve the needed spectral transfer properties [13]. The addressable wavelength range for the developed electro-optic polymer is in the near infrared wavelength range.…”