Non-Linear Taper Spotsize Converter for Low-Loss Fiber-to-Chip Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spotsize converters for surface waveguides have limitations in controlling mode-field in one dimension, are difficult to control and reproduce, and are not well-suited for high-volume commercial use due to reliance on linear taper regions and complex etching techniques, which restricts their application in low-loss fiber-to-chip coupling and high-density planar lightwave circuits.
Innovation Solution
A surface waveguide-based spotsize converter with a non-linear thickness profile is achieved through a controllable tapering technique using an accelerator layer and etchant, allowing for adiabatic coupling of regions with different index contrasts, enabling efficient mode-transition and reducing fiber-to-chip coupling losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If linear taper regions and complex etching techniques are used, then spotsize converters can be fabricated, but manufacturing precision and ease of manufacture deteriorate due to difficulty in controlling and reproducing
Solution Approach 1:
The patent changes the geometric parameters of the taper region from linear to non-linear (parabolic or exponential profiles). This parameter change enables better mode-field control and adiabatic coupling while maintaining manufacturability through standard photolithography and etching processes, resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The patent introduces curved (non-linear) taper profiles instead of straight linear tapers. The parabolic or exponential curvature in the taper region provides superior mode transformation characteristics and adiabatic coupling performance, improving manufacturing precision while remaining compatible with conventional fabrication techniques
2Ease of manufacture
If linear taper regions are used, then fabrication is simpler, but coupling efficiency and mode-field control deteriorate
Solution Approach 1:
By changing the taper profile parameter from linear to non-linear (parabolic/exponential), the patent achieves both improved coupling efficiency through better adiabatic mode transformation and maintains relative fabrication simplicity using standard processing techniques
3Length of stationary object
If high-contrast waveguides are used, then bending radius can be reduced, but propagation loss increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform taper profile where the waveguide dimensions vary along the propagation direction. The non-linear taper provides different local confinement characteristics at different positions, enabling tight bends with reduced propagation loss by optimizing the mode transformation locally throughout the taper region
4Loss of energy
If low-contrast waveguides are used, then propagation loss is reduced, but bending radius must be increased
Solution Approach 1:
The non-linear taper profile dynamically changes the waveguide dimensions along the propagation direction, providing strong mode confinement at the input and gradual transition at the output. This parameter variation allows low-contrast waveguides to achieve smaller bending radii while maintaining low propagation loss, resolving the contradiction between these two parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables low-cost, commercially viable spotsize converters operable over a wide range of wavelengths, improving coupling efficiency and flexibility, and reducing the complexity and cost associated with high-density planar lightwave circuits.
Implementation Method 1
providing an accelerator layer disposed on the first layer, the accelerator layer comprising a second material, wherein the second material etches at a second etch rate in the first etchant; laterally etching the accelerator layer in the first etchant such that the shaped region is undercut; and etching the first layer in the first region in the first etchant
Implementation Method 2
the second material etches at a second etch rate in the first etchant; lateral etch front proceeds normally inward from each point on the sides, undercutting the mask layer in the shaped region. As the lateral etch front proceeds under the mask layer, an increasing amount of the surface of the first layer is exposed to the etchant
Data Source
AI summary
A method for forming a non-linear thickness-profile in a first layer of a first material is disclosed. The method comprises forming an accelerator layer of a second material on the first layer and forming a mask layer disposed on the accelerator layer, wherein the mask layer enables the accelerator layer to expose the first layer to a first etchant in a first region, where the exposure time for each point along a first axis varies non-linearly as a function of distance from a first point on the first axis. Since the time for which the first layer is exposed to the first etch in the first region is non-linear, the thickness of the first layer in the first region changes non-linearly along the first axis.