In-situ 3D Refractive Index Characterization

For Scientific Research & Industry Modernisation.

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Customer Requirement

There is an increasing demand for high-throughput telecommunication today. With the continuous development of optical materials and optical fabrication technology, 3D photonic chips have become the best solution in optical communication systems due to low power consumption and high speed. Innofocus’s femtosecond laser direct-writing technology, which features low loss and the ability to produce complex and flexible optical waveguide structures, has enabled the intelligent and high-performance fabrication of 3D photonic chips. However, we are yet to find a method that can accurately characterize the 3D micro/nano structure written in the optical materials by femtosecond laser and its resulting refractive index distribution and surface morphology. Therefore, how to effectively characterize the index change becomes one of the major challenges for quality control in 3D photonic chips fabrication.

HoloViewTM, the 3D in-situ refractive index characterization system designed by Innofocus, has proved to enable characterize the 3D spatial refractive index distribution with our newly-developed optical imaging technology and image reconstruction algorithm. The system can precisely measure the refractive index distribution in material and effectively reconstruct the refractive index distribution, and form image of the 3D structure with an accuracy of 10-4. It is non-destructive and non-invasive, and it allows real-time monitoring the fabrication process, making it valuable for the applications in the disciplines of all-optical communications, sensors, biophotonic and micro/nano optical and photonic devices.

Product Performance

The key property of an optical component is refractive index distribution and surface morphology. High-performance optical components can only be successfully fabricated when meeting both requirements. Otherwise, distortion in electric field pattern, transmission loss and imperfection will occur, degrading the performance. On this other hand by understanding the refractive index variation and distribution, we can understand the properties of optical material and devices, which can be used to indicate whether the material or component is damaged.

For those optical components sensitive to variation of refractive index, such as optical waveguide and optical fiber gratings, there is no standard and quantitative method to characterize their 3D refractive index distribution. This issue become a bottleneck for accurately designing and fabricating optical components. To solve this bottleneck issue, Innofocus’s unique technology of 3D spatial characterization of refractive index is designed to accurately measure the modulation in refractive index with and without laser processing with an accuracy of 10-4. Furthermore, it can reconstruct the fabricated 3D structure. The main functions of the Innofocus HoloViewTM include:

1. In-situ measurement of the refractive index modulation,

3D distribution and surface smoothness of femtosecond laser processed optical waveguides, for optimizing parameters in the fabrication process.

2. Quantitative measurement of the refractive index distribution both on the surface and inside of the component,

and evaluation on whether the fabrication can meet the desired quality requirements of the component through comparison with original design (e.g., detection of any defects and decide consistency with design)

3. Determine whether the material is modified by measuring the refractive index variation.

Therefore, the method can be employed to determine the property change of optical components when they expose to extreme conditions such as high temperature, high humidity etc., and it can display whether the components are deformed, or damaged inside. Additionally, it can run a quantitative determination to find the damaged parts. Damage to the surface of the components can be easily identified, however, damage inside components caused by abrupt changes in working environment is challenging to detect. If a local refractive index variation occur inside an optical waveguide or FBG, it can be devastating to the performance of the components. At present, there is no other method that enables quantitative measurement and provides high-resolution 3D refractive index distribution profile. Our system is the only one available.

4. Quantitative design and measurement of refractive index distribution.

Based on the measurement, the system can enable scientific researchers to study laser-material interactions and display the results in 3D image in a convincing way. It is a perfect choice for scientists and engineers.

Customer Value

The world’s only available commercial equipment with high-resolution in-situ 3D refractive index distribution characterizing and imaging functionality.


Relative Solutions

Optimization For Production

Characterization of surface morphology of optical waveguide

Characterization of optical components

In-situ characterization of FBG