Abstract
An on-chip tunable photonic delay line is a key building block for applications including sensing, imaging, and optical communication. However, achieving long and tunable delay lines within a small footprint remains challenging. Here, we demonstrate an on-chip tunable photonic delay line using ultralow loss high confinement Si3N4 waveguides with integrated microheaters. As an example of potential application, we embed a 0.4 m delay line within an optical coherence tomography (OCT) system. We show that the delay line can extend the OCT imaging range by 0.6 mm while maintaining a high signal to noise ratio. Our tunable photonic delay line is achieved without any moving parts which could provide high stability, critical for interference based applications.
Highlights
On-chip tunable photonic delay lines are one of the key building blocks for realizing optical systems-on-chip.1–3 achieving tunable long delay lines that are broad bandwidth within a small footprint remains challenging
In order to achieve such a tight bending radius, we choose the width to be 780 nm and show that despite the much stronger overlap with the waveguide surfaces than the ones typically experienced in individual micrometer-size devices,20 we achieve tens of millimeters long delay lines with low propagation losses (0.17 dB/cm ± 0.01 dB/cm)
We show that the propagation loss has a linear dependence with the waveguide length, which indicates that the additional loss due to the misalignment is negligible
Summary
On-chip tunable photonic delay lines are one of the key building blocks for realizing optical systems-on-chip.1–3 achieving tunable long delay lines that are broad bandwidth within a small footprint remains challenging. In order to achieve low optical losses for delay lines of tens of centimeters over several millimeters square area, we design the waveguides to be fundamentally robust to misalignments between different lithography fields.
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