Parallel Microcavity Trimming for Picometer Wavelength Uniformity
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Solution Overview
Problem
Existing microfabrication processes for resonant spatial light modulators (SLMs) result in significant variations in the resonant wavelengths of photonic crystal cavities, exceeding nanometer levels, which degrade the SLM's performance by causing unwanted variations in optical modulation.
Innovation Solution
A parallel trimming process using laser-assisted thermal oxidation in a high-pressure chamber with in-situ characterization and holographic fanout of the trimming laser is employed to adjust the resonant wavelengths of photonic crystal cavities in an SLM to picometer precision, aligning them uniformly across the array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional microfabrication processes are used to manufacture resonant spatial light modulators, then manufacturing complexity is reduced and ease of manufacture is improved, but manufacturing precision deteriorates with nanometer-level variations in resonant wavelengths
Solution Approach 1:
The patent applies preliminary action by performing laser trimming on selected microcavities based on initial wavelength measurements. The system identifies which cavities require trimming before final assembly, allowing precise adjustment of resonant wavelengths to within a few picometers of the target value. This preliminary characterization and selective trimming approach achieves high manufacturing precision without requiring complete redesign of the fabrication process.
2Productivity
If parallel trimming of multiple microcavities is performed, then productivity is improved by adjusting multiple devices simultaneously, but device complexity increases due to the need for arrayed beam generation
Solution Approach 1:
The patent employs copying by using a spatial light modulator to generate an array of beamlets from a single input laser beam. The SLM creates holographic copies of the beam at multiple locations corresponding to different microcavities in the array. This allows parallel trimming of multiple cavities simultaneously while using a single laser source, achieving high productivity without requiring multiple independent laser systems.
Solution Approach 2:
The patent replaces mechanical beam steering systems with optical field manipulation. Instead of using mechanical mirrors or moving parts to direct beams to different cavities, the system uses a spatial light modulator to programmatically shape and direct the optical field. This substitution of mechanical systems with optical field control enables parallel trimming while reducing mechanical complexity and increasing flexibility.
3Reliability
If resonant wavelength variations exceeding nanometer levels are present, then device complexity remains low with simple fabrication, but reliability deteriorates due to degraded optical modulation performance
Solution Approach 1:
The patent implements feedback by measuring the resonant wavelength of each microcavity, comparing it to the target wavelength, and using this information to determine which cavities require trimming and by how much. The system iteratively adjusts the trimming parameters based on measured wavelengths, ensuring that each cavity is brought within a few picometers of the target value. This feedback loop guarantees reliable optical modulation performance by eliminating wavelength variations that would otherwise degrade performance.
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 process achieves resonant wavelength uniformity within a few picometers, enhancing the SLM's performance by improving pixel-to-pixel controllability and reducing non-uniformity, thereby improving optical modulation efficiency.
Implementation Method 1
The process to adjust or trim the optical cavities involves carefully-controlled oxidation of semiconductor material forming the optical cavity
Implementation Method 2
directing a plurality of optical beams onto the two or more microfabricated devices to thereby adjust in parallel the characteristics
Implementation Method 3
The optical cavities can be designed to transmit or reflect incident light at the resonant wavelength. The resonant wavelength of the optical cavity can be modulated
Data Source
AI summary
Methods and systems are described for precisely adjusting characteristics of microfabricated devices after device fabrication. The adjustments can be carried out in parallel on a plurality of the microfabricated devices. By carrying out the adjustment process, uniformity of feature sizes to a few picometers (one standard deviation) and corresponding uniformity of operating characteristics for a plurality of microfabricated devices are possible.