Parameter Investigations of Waveguide-Integrated Lithium Niobate Photonic Crystal Microcavity
Despite significant progress, fabricating two-dimensional (2D) lithium niobate (LN)-based photonic crystal (PhC) cavities integrated with tapered and PhC waveguides remains challenging, due to structural imperfections. Notable, especially, are variations in hole radius (<i>r</i>) and inc...
Saved in:
| Main Authors: | , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
|
| Series: | Photonics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2304-6732/12/5/475 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Despite significant progress, fabricating two-dimensional (2D) lithium niobate (LN)-based photonic crystal (PhC) cavities integrated with tapered and PhC waveguides remains challenging, due to structural imperfections. Notable, especially, are variations in hole radius (<i>r</i>) and inclination angle (°), which induce bandgap shifts and degrade quality factors (Q-factor). These fabrication errors underscore the critical need to address nanoscale tolerances. Here, we systematically investigate the impacts of key geometric parameters on optical performance and optimize a 2D LN-based cavity integrated with taper and PhC waveguide system. Using a 3D Finite-Difference Time-Domain (FDTD) and varFDTD simulations, we identify stringent fabrication thresholds. The <i>a</i> must exceed 0.72 µm to sustain Q > <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mrow><mn>7</mn></mrow></msup></mrow></semantics></math></inline-formula>; reducing <i>a</i> to 0.69 µm collapses Q-factors below <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></semantics></math></inline-formula>, due to under-coupled modes and bandgap misalignment, which necessitates ±0.005 µm precision. When an <i>r</i> < 0.22 µm weakens confinement, Q plummets to 2 × <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></semantics></math></inline-formula> at <i>r</i> = 0.20 µm (±0.01 µm etching tolerance). Inclination angles < 70° induce 100× Q-factor losses, requiring ±2° alignment for symmetric modes. Air slot width (<i>s</i>) variations shift resonant wavelengths and require optimization in coordination with the inclination angle. By optimizing <i>s</i> and the inclination angle (at 70°), we achieve a record Q-factor of 6.21 ×<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><msup><mrow><mn>10</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></semantics></math></inline-formula>, with, in addition, C-band compatibility (1502–1581 nm). This work establishes rigorous design–fabrication guidelines, demonstrating the potential for LN-based photonic devices with high nano-fabrication robustness. |
|---|---|
| ISSN: | 2304-6732 |