Experimentally observe waveguide mode pattern

[brianpile]

Hello:

I am passing 1 micron laser light through some semiconductor waveguide devices with my research group. We would like to observe the mode pattern on an infrared camera. The thinking is that if we observe a well defined pattern at the output of our devices, then it will be an indicator that we have coupled the light into the waveguide accurately. It's also interesting to see the mode pattern in itself.

The question is...what type of lens should we use to magnify the light output? Also, it seems to me that we need to get then lens quite close to the output of the device so that we are observing the actual mode pattern and not a diffracted version of it.

Any thoughts would be greatly appreciated!

-Brian (UCONN electrical engineering student)

 

[Valerie Park]

The best lens for a situation like this would be an infinity-corrected objective lens. Infinity-corrected objectives are designed to be used with a tube lens at a fixed distance from the image plane and provide excellent image quality and resolution. They also have low distortion and are ideal for imaging applications where high magnification is not required. Additionally, they can be placed right up against the output of the waveguide device, allowing you to observe the actual mode pattern and not a diffracted version of it.