Optics In Paris

 

Dark Field Image Example:  Bright Field Image Example:  

  If I can’t have dragon gutters when I end up buying a house, what’s the point? I found these at Château de Pierrefonds after a couple hours of biking through the forests around Compiègne. I found a random advertisement for math and physics teachers while I was wandering around the city. I especially love that somebody goes around with a “quantum” sticker just in case. Iconic. Paris celebrates the summer solstice with a huge music festival called Fête de la Musique. The genre changed every block and the music was incredible!

 I did some alignment at the beginning of my internship to make sure that the lenses, camera, and other optical components I was working with were in the right place. Meanwhile, another intern has been working on getting a Spatial Light Modulator Set Up. This week, they brought it upstairs to integrate it into our system. That means doing the alignment all over again to make sure each mirror, lens, filter, and the spatial light modulator itself are in the right place. Once we roughly position the mirrors we work with, we pick two mirrors and "walk the beam" by making small adjustments to center the laser with one mirror, and then correcting its position with to other.  

The position of objects in the s and p image is easily messed up by little angles, or by the crystals changing position. I've done lots of tests to figure out the best way to position them to keep the stable and I've learned to do image registration, taking two images and getting them to overlap correctly. It was a lot harder than I thought it would be, and I ended up learning how to do it both in Fiji Image and in MATLAB.  In this first image, I realized I hadn't taken into account that the s and p images mirrored each other. So even when they "overlapped" the computer had a difficult time lining everything up.  This is just before I implemented my image registration into the other code I am using. Gray represents overlapping pixels and green and pink represent image 1 and image 2 when they don't overlap well. The registration code is finished and I wanted to see how accurately I could position the crystals in the same place over and over again. Since they mo

This week we saw the large hadron collider, every nerds dream trip. I mean, it’s all underground, but we stood by it and talked about science. Close enough, right? Geneva has some of the bluest water I’ve ever seen! Bonus last photo - we found a neighborhood slide and I way underestimated how fast I could go..

We are using birefringent crystals to split our beam of light into s and p polarized states. S and P come from German words for parallel and perpendicular. The light passes through one crystal, which transmits only one polarization state on towards the camera and sends the other one through a second crystal, which then reflects the polarized light onto the other half of the camera. The result are mirrored images, like this!  These aren't nanorods at all. Its just dust and marker on a glass slide. But it is easier to see how these images line up than the nanorods, which just look like little speckles. The crystals are held in place with a 3D printed frame. If they aren't aligned correctly, the two images can overlap instead of having a nice clear divide down the middle. That would compromise our measurements, so I'll work on checking out consistent those crystals are later. 

 Here are some calibration measurements I've done! I rotate a polarizer through 360 degrees with a small step and take a picture at each point. Really, its an s polarization picture and a p polarization picture in one! Then, I choose a region of interest (a small number of pixels that could represent a single nanorod) and plot the intensity of s light and p light together.  Teflon diffuses the polarization of light, but we can still see that the "red" s light is consistently brighter than the "blue" p light. That was part of my calibrations from last week.   If a sample doesn't have an orientation, say if its round like a latex bead, we get something like this:  And if we aren't looking at a real object at all and see only background, it looks like this:  A nanorod may look very similar to the Teflon calibration sample, but the width of the "peanut" shape and the relative intensity between s and p can change. That ratio is one way I want to try

Paris is beautiful! These first two pictures are my friend Sophie’s. Somehow we got lucky enough to be in Paris on internships at the same time and it has been amazing! The last picture is hers too … but don’t hold it against her. I was just being difficult haha Pan de queijo is incredible and if you haven’t had some, that should be one of your top priorities this week. For real. Look it up right now. I went to an incredible Jazz club! Bad news, I still can’t dance The ravens here will play games with you! I met one in the park that loved to drop and catch water bottle lids. I visited Shakespeare and Company and visited lots of little parks that pop up all over the city. It was a good nature week

 The professor I am working with already had code set up to control the motors rotating polarizers and quarter wave plates in MATLAB, so I've been working on developing data collection code. Since our camera for now is go-pro (we are waiting for a real scientific camera to come in the mail, but that isn't getting in the way of getting work done now!), I built a MATLAB function that detects new saved images, moves the motors, and processes data. It was a lot of work and I don't have a lot to show for it, but it will make data collection much easier later! 

 

My Navigo pass started working! Now I can go anywhere muahaha … The public transportation here is amazing. Every once in a while it gets super crowded and it becomes the worlds most intense game of jello that nobody acknowledges. Most of my lab work this week was getting a camera up and running with the equipment we already had in the lab. Then I started collecting some basic measurements. Tuesday was rough because nothing was working, but it got better from there. Today after I visited l’arc de triomphe, I was wandering around this city and came across this old church. It seemed empty, but I went inside and discovered a free concert. The music was incredible and it was so fun to find by accident and talk to the other people there. I think I was the only tourist haha and it felt a little magical. Even though my French isn’t great, so many people said hello as they left and were very kind. Sophie and I had some AMAZING crepes, but my favorite part was drinking juice out of these little