Subwavelength High-Contrast Grating Planar Lenses for Semiconductor Integration
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Solution Overview
Problem
Conventional optical lenses and reflectors face challenges in integration within semiconductor devices due to their bulky thickness, limited numerical aperture, and difficulties in microfabrication, particularly in achieving high contrast and low loss for applications requiring precise optical properties.
Innovation Solution
The use of subwavelength High-Contrast Gratings (HCG) configured as planar lenses and reflectors, which utilize a high-index material grating surrounded by a low-index material to control reflection and transmission, allowing for high resolving power, engineered phase, and low loss, enabling integration within semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional lenses are used to achieve high numerical aperture, then focusing power is improved, but device thickness and weight increase
Solution Approach 1:
The patent changes the fundamental parameter of lens design from conventional refractive optics to subwavelength grating structures. By operating in the subwavelength regime where the grating period is smaller than the wavelength of light, the patent achieves high numerical aperture (NA > 0.8) while maintaining an ultrathin profile (thickness < λ/4), resolving the contradiction between focusing power and device thickness.
Solution Approach 2:
The patent employs composite high-contrast grating structures consisting of high-index dielectric materials (such as silicon, GaAs, or TiO2) with refractive indices greater than 2.0, surrounded by low-index materials. This composite approach enables simultaneous achievement of high numerical aperture, low loss, and ultrathin thickness, overcoming the limitations of conventional single-material lenses.
2Measurement precision
If conventional reflectors are used to achieve high numerical aperture, then focusing power is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the reflector surface into subwavelength grating elements with periodic structures. This segmentation transforms the complex aspherical surface requirement into a planar array of simple periodic gratings, which can be fabricated using standard photolithography and etching techniques, thereby reducing manufacturing complexity while maintaining high numerical aperture.
Solution Approach 2:
The patent transitions from three-dimensional aspherical mirror surfaces to two-dimensional planar grating structures. By encoding the focusing function in the lateral periodic pattern rather than surface curvature, the patent simplifies fabrication to planar processes while achieving comparable or superior optical performance.
3Volume of moving object
If zone plates are used to achieve planar structure, then device thickness is reduced, but energy loss increases
Solution Approach 1:
The patent changes the material parameter from opaque or absorbing materials used in conventional zone plates to high-index dielectric materials with low optical loss. By operating in the dielectric regime rather than metallic or absorbing regime, the patent achieves both planar ultrathin structure and low energy loss simultaneously.
Solution Approach 2:
The patent uses composite dielectric-grating structures with high-index materials (silicon, GaAs, TiO2) that provide both the phase modulation necessary for focusing and low optical absorption. This composite approach eliminates the energy loss problem of conventional zone plates while maintaining the planar geometry advantage.
4Measurement precision
If conventional lenses are used to achieve high numerical aperture, then focusing power is improved, but integration difficulty with semiconductor devices increases
Solution Approach 1:
The patent merges the optical lens function directly with the semiconductor device substrate by fabricating subwavelength gratings on or near the semiconductor chip. This integration eliminates the need for separate bulky optical components and their alignment mechanisms, reducing overall device complexity while achieving high numerical aperture through the grating structure itself.
Solution Approach 2:
The patent integrates optical functionality into the planar two-dimensional semiconductor fabrication domain rather than requiring three-dimensional assembly of separate optical components. By encoding optical function in lateral grating patterns that can be fabricated using standard semiconductor photolithography, the patent simplifies integration while achieving high numerical aperture.
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
HCG-based lens-reflectors provide high numerical aperture and low loss, facilitating integration in semiconductor devices, enhancing imaging and other applications with improved focusing capabilities and reduced size and weight.
Implementation Method 1
an incident wave which excites multiple modes within the high-contrast grating and is focused for reflection and/or transmission
Implementation Method 2
a high-contrast grating (HCG) having grating elements spaced apart from one another, in which the high-contras grating elements having subwavelength dimensions
Data Source
AI summary
Planar lenses and reflectors are described comprising subwavelength high-contrast gratings (HCG) having high index of refraction grating elements spaced apart from one another in straight and/or curved segments and surrounded by low index material. The high-contrast grating is configured to receive an incident wave which excites multiple modes within the high-contrast grating and is focused for reflection and/or transmission by said high contrast grating. The width of the high contrast grating bars vary along a distribution direction of the grating bars which is perpendicular to the length of the grating bars and/or varies along the length of one or more grating bars to focus said reflection and/or transmission. The HCG is configured to provide double focusing, whose use is exemplified within a vertical cavity surface emitting laser (VCSEL) structure using focusing HCG structures for both the top and bottom mirrors.