Dr. Vadym Zayets

It is very simple and fast-to-measure setup technology. From installing a sample to the first waveguide measurements takes 10-20 min. 30-50 waveguides can be measured per a day.

Merits of this setup are:

- short time for alignment (10-15 min is to align a new sample)

-reliability (after removal of sample, re installing, re alignment and re measure, the difference in measured fiber-waveguide-fiber transmission is better than 0.2-0.1 dB)

- simplicity (a student or technician can easily can do the alignment and measurements)

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Alignment steps:

1) alignment of input fiber with backside camera

2) alignment of output fiber.

 

 

 

 

 

 

 

 

 

 

 

 

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Step 1. Alignment of input fiber with backside camera

 

 

 

The cleaved edge

 

 

 

 

 

 

 

 

 

 

 

 

 

It is to align height of input fiber with camera

When the input fiber is below the waveguide, light propagates through the Si. There is no light in air.

 

When the input fiber is above the waveguide, a light of light can seen in air.

 

 

 

 

 

 

 

 

 

Sensitivity of the alignment to fiber position (video)

 

 

 

 

 

 

 

 

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Q. Width of Si nanowire waveguides is 450 nm, which is about or smaller that wavelength of visible light. How it is possible to see Si nanowire waveguide in a visible CCD camera?

A. Even the spot-size converter, which width is 100-150 nm, can see in a visible CCD camera very clearly. It is not waveguide itself we see in the camera, but the light reflection from sharp edge of the waveguide. Even in case of a very narrow waveguide the reflection is substantial.

To see the reflection from an edge of waveguide, it is necessary to adjust the angle of the top light illumination. Such adjustment should be done after each new sample installation.

 

 

 

 

 

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Step 2. Alignment of output fiber

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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How to adjust focus of each lens fiber

See demonstration video here adjustingFocus.mp4

When positions of both fibers are adjusted, move the fiber forward/backward toward the waveguide. At the same time , monitor the fiber-to-fiber coupling efficiency in real time.

You need to find the maximum of the fiber-to-fiber coupling efficiency.

In case when distance to film changes substantially, you need to re- scan the y- and z- positions of fiber again.

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Controlling software to download

 

Visual Basic 6 Control program (click to download)

 

LabView control program (click to download)

 

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