Final Presentation Day!

It was the final presentation day of my 30-day summer internship!

Surprisingly, Joe had already copied my slides into the computer so I didn't need to copy again using a USB drive. Personally, I feel I did okay on my presentation, and it was nice that everyone went through their presentations well. I felt I really learned a lot this summer, and more importantly, I was able to work on the things I enjoy. 

After the presentation, we got our certificates and recommendation letters. Gerry and I introduced our labs to Ms. LaBarr.

In the afternoon, I worked on my final task: write a document to record all the things I've done. Dr. Qiao also told me that the results I got might be continuously used by other lab members. So I needed to write every detail down. It was during this process that I realized I did so many things in these short thirty days.

Finally, Thanks to everyone in the AOFIM lab who supported me all the time! It was indeed a wonderful summer!

The day before final presentation

The day before the final presentation!

In the afternoon we had a presentation dry run with Dr. Qiao and Lauren, and I got many suggestions. So I worked on the presentation all night and fortunately, I finished editing and was able to practice a couple times. I changed the .gif image to three separate photos so it doesn't look too distracting. I also made my control model clearer so it looks like a complete cycle.

Day 29

Today is our practice presentation day!

I really enjoyed knowing other interns' projects and I learned a lot through their presentations. As I predicted, my presentation was still too long: it took more than twelve minutes. (supposed to be within ten minutes). I also received some very helpful suggestions for my presentation. For example,  with Titus's suggestion, I changed my probe beam's color to yellow so it's easier for viewers to differentiate the different types of beams. Also, Matt suggested me to change my delay line into real images, so I used a gif file maker suggested by Henry to make a gif image. 

In order to take a small video of the delay line, I turned on the delay line again. Surprisingly, I realized that I deleted by mistake a command to pre-set the "jog" mode last time, so I looked up the method book again to reset the single-step jog mode. 

The APT motor control method book with hundreds of methods:

The delay line jogs from zero point delay point to a certain distance away:

Day 28

I worked on my powerpoint slides all day. Dr. Qiao gave me many suggestions on my slides and I was editing them. Finally, I finished my slides before I left.

In the night, I practiced several times and did a powerpoint recording. I also presented it to my Mom and my brother. It was 15minutes long (the presentation is supposed to be 10min); however, I realized I really couldn't remove anything more from my slides.

Day 27

This morning all the lab members were preparing our short presentation to Dean Sophia. I made three slides for this presentation and I talked about the principle of Pump-Probe imaging system and the system I want to build. It was also a very good chance for me to learn what Ph.D.s are working on.

We need to finish our slides by next Monday and I felt that I still need to update lots of things. Currently, I have 18 slides, and I'm trying to shrink them down to 8-10 slides.

Day 26

It's getting closer to our final presentation.

With Lauren's help, we inserted the GPIB expansion card into the PC. The PC is too old and many drivers need to be updated. The whole afternoon I was updating software and drivers, from NI updating service itself to Labview. Besides that, I worked on slides to make them look better. In the slides, I added what I'm working on now and what I'm trying to do. Building a correct set-up is such a challenging and time-consuming task -- I was looking for a single connector during the day but still haven't found the correct one.

My plan for the whole system:

Day 25

This morning when I was reading the delay line software manual I realized that the software itself can set triggering to the delay line stage. One thought was to set "perfect" delay time both on CCD and on delay line software to make them work automatically. Considering this "perfect" would never be possible due to the uncertainty of CCD exposure time and delay time, I still needed to find a way to sync all the things together. Fortunately, I found another way to solve the problem. I downloaded Thorlabs' APT controller, which supported Labview, C++,  and Matlab editing. I wrote the Matlab code to control the APT, which was connected to the delay line. APT works like a server, while Matlab scripts work as a client.

I tested my stage moving and the "jog" worked pretty well:

Day 24

Today I worked more on the code I wrote -- the Probe beam path code and CCD camera code. I made a start button for the CCD camera code so users can just click the button to gather images. I was still checking my spot size code. They looked right. I also found an extension in Matlab which can easily change my script into an application.

I added the right-most extension ("CCD camera triggering"):

Day 23

Today was a work day! I worked all day on my presentation slides, and I updated almost every slide. As Dr. Qiao suggested, I added more diagrams and explanations to make my presentation more clear to listeners from different knowledge backgrounds. It was a tough process to find relevant images for each slide. Sometimes I had to draw a whole diagram myself. Since I changed some diagrams, I had to rewrite my equations on Latex. I also made more specific about what I had done this summer.

It's pouring rain outside ...

Day 22

Dr. Qiao came to the lab this morning and I showed her my CCD camera software and script on Matlab. Dr. Qiao said that we should sync the delay line and CCD camera, so a computer can control the both the delay line and CCD camera at the same time. Since we didn't have any code to control the delay line, I sent an email to Thorlabs to see if they have any good idea. I also added a simple slide to explain the basic principle of my project.

In the afternoon, I went to RIT Undergraduate Symposium with my brother and Zihao. We listened to all the presentations in the Mathematical science section. Staffs like stress-concentration coupling, spiral waves, and critically packed spherocylinders were really intriguing. After all the four presentations, we finished all the posters. One interesting project was to investigate the use of arrows in mathematics and science. I also went to posters about Quantum Turing Machine (Qubit).

Finally, I worked on making CCD routine more automatically. In addition, I updated my code so it became more user-friendly.

Day 21

I had a meeting with Dr. Qiao today, and Dr. Qiao gave me some great suggestions on my presentation slides.

I finished my ABCD law Matlab code today. Finally, I got a spot size that was very close to the result got from the previous method (5.244824842569mm compare to  5.171716695698mm).  Since I found the beam size was too large to reach the objective diameter, I calculated the original beam size which could fit the objective. In order to find the incident radius, I wrote a very very long equation. Surprisingly, Matlab actually solved it. The answer was a little bit impossible; it was even smaller than the beam size when the beam emitted from the laser box.  However, we can actually change the answer by decreasing the distance between the objective and the sample. 

Day 20

I learned ABCD law today and I was trying to write code for probe beam's path in Matlab; I think this is a good way to double check my calculations. Although I knew how to do matrixes multiplications, I'm not sure how to get spot size.

I was checking camera's exposure again today. I could see the light integrated during a certain exposure time on the images collected. But I couldn't tell the shape of the object. I think there exists a transition time between the light on and off, which caused the decreasing of resolution.

In dark:

Short moment with the light on during exposure time:

 A good news is that Dr. Qiao came back and I'll have a meeting with her tomorrow.

Day 19

I invited Zihao last night, and Zihao actually came this morning. Gerry and I introduced our projects to Zihao, and he seemed very interested in what we are working on this summer ... ...

I asked Lauren my confusion left yesterday and I found that I forgot to consider the diameters of the lenses. After recalculation, I got very close resolutions for the two lenses. Cayla helped to check my calculations today and we didn't find any obvious mistakes in my code. I also looked up convolution and edited my presentation slides a little bit. 

I looked back to Fourier Transform today, and I think I'll work more on Pump-Probe tomorrow.

Day 18

Almost forgot tomorrow I can bring a friend. I've contacted a past year intern -- not sure whether he would like to come.

It's Monday today so I felt hard getting up this morning (even forgot to set the alarm). I majorly worked on double lens system today. I did some researches on the double lens system. Basically, I needed to solve equations for each lens separately. I put another convex lens between objective and camera to display the whole object in the small CCD sensor.

Lauren left me two different convex lenses. She said I could pick one and she gave me a hint related to the resolution of the image. So I looked up resolution limitation of the lenses. It looks like according to two equations, the longer the focal length, the smaller the NA,  and higher the resolution. I will ask Lauren whether this is correct tomorrow. Even though I thought I should use the longer focal length one, I still used the small one with lower f, since it was much easier to adjust the height and position. 

Pump-Probe Imaging Project Outline Draft

Pump-Probe Imaging project Outline     

Yizuo Chen

1. (Title)Pump-Probe imaging for analyzing femtosecond laser-induced structure changes

Two images: surface before hitting by laser; surface after hitting by laser(final state).

2. (Summary)

·         Femtosecond laser has been widely used for optical and photonics fabrication

·         The pump-probe imaging system was constructed to investigate silicon ablation process.

·         (*)The images of surface structures at different delay times were collected and analyzed.

·         (*)The patterns of surface structure changes reflected effects of femtosecond laser on the silicon ablation.

3. Femtosecond laser has been used on material removal in various ways.

Several images of femtosecond laser cutting glasses, nanostructure, etc.

4. The pump-probe imaging system was constructed.

Left: Combine the real system and the model image

Right: the model diagram with specific lengths and measurements.

5.  Dynamic change of optic substrates was investigated  by changing the delay time

6.  Zero time delay point: Intensity autocorrelation and Second Harmonic Generation

Show the equal distances of pump beam and probe beam generates SHG

Image: zero-time delay setup diagram

7. The laser intensity was determined through calculations.

Show the calculations of the Gaussian beam energy by using propagation formula and focus equation

8. A real image capture camera was built by using a CCD camera and an objective.

Show the inverse Focus equation used for putting the objective.

Show images of investigating principles of camera imaging.  

9.Time delay line was controlled through software; CCD camera and delay box.

Show how to control the time delay line through software, CCD camera, and delay box through Labview or Matlab

10. The delay box was tested by connecting to an oscilloscope box.

Image: connect the delay box and oscilloscope box

Front panel programming to set up the triggering and delay time.

An attempt to send CCD and laser box signals using delay box.

11. CCD camera was connected to a laptop by using Matlab scripts.

Frame rate and exposure time were set and the trigger method was tested. All the images will be sent to a folder and be analyzed automatically.

Image: plotted graph of the pixel sums of testing in a dark room with light.

12. Labview system was built to connect the CCD camera with a computer.

Image: diagram from Labview.

An attempt to connect all the systems together.

13. (*) The pump-probe images reveal the femtosecond laser material interaction mechanism. Show the sample images captured by CCD camera in different delay time.

14. (*) Comparison algorithm was used to show the periods of the sample surface structure evolution.

Diagrams to show the comparison algorithm

15. (*) Show the patterns found by using the algorithm

Images to show the diagrams or data.

16. Conclusion.

·         Femtosecond laser has been widely used for optical and photonics fabrication

·         The pump-probe imaging system was constructed to investigate silicon ablation process.

·         (*)The images of surface structures at different delay times were collected and analyzed.

·         (*)The patterns of surface structure changes reflected effects of femtosecond laser on the silicon ablation.

17. My Contributions.

                  ·         Controlled Delay line software to find the zero time delay point.

·         Determined the laser intensity by writing Matlab Code for pump beam spreading and focusing.

·         Wrote CCD camera routine in Matlab to set CCD camera’s triggering and to save all the images to a computer automatically.

·      Worked on Delay Box Front Panel Programming and Tested it with an oscilloscope box to generate time delay between signals.

·         Worked on camera imaging principles in order to develop CCD camera to a real camera.

·         Wrote Probe beam propagation code in Matlab to calculate the change of probe beam’s spot size as well as the position of the objective

·         Worked on constructing the system on Labview; (stopped by the lack of visual acquisition software).

     

*: not sure whether can be done on time

Day 17

It was a surprise it was Joe's son who held camera yesterday during the interview!

After calculating the spot size during the beam propagation, I found the spot size in the sample would be around 9mm, which was much larger than the aperture of the objective. The position of the objective was on the way before the beam even reached the sample.  If my calculations were correct, we might have to change the beam expanding process to decrease the original radius of the laser beam.

We found the exposure time was actually 2 ^ n sec (n is the scale on Matlab); thus we can just set a relatively long exposure time and capture the laser beam in a very dark room. So we can see the final integrated light on camera.

Next week I will work on decreasing the spot size and testing more on the exposure time.

Day 16

Today we were supposed only work in the afternoon and have a field trip to Mees Observatory at night. However, my mom sent me here early so I was able to look at Dr. Qiao's comments on my outline. I also started putting my presentation slides together. After I drew all the paths and put names of optic instruments on a photo, I realized the objective was not in the photo --. I also asked Lauren some math notations on a textbook so I was able to understand the formulas better.

We continued working on building the camera again. After attempting trying different light intensities as well as different filters, I used my phone as the object and it worked pretty well. By the way, when we were testing our camera, we were being interviewed. I have no idea what I talked about; I just know I was so nervous when I was facing two enormous cameras.

I felt so happy that the camera actually worked.

A picture captured by the camera:

Half Way!

We are half way done with our internship!

This morning Lauren gave Henry and me a really intriguing challenge: to make a real camera by using CCD. CCD camera is only able to gather the intensity of the light, functioning similarly to a sensor in the real image capturing camera. The whole morning we were basically trying to figure out how the objective worked and camera imaging worked. After that, I used Focus Equation again and used inverse propagation formula to predict the position of the CCD. Later Lauren told me that what she wanted me to do was actually to make the camera work for natural light first. So classic "1 / d0 + 1 / di = 1 / f " equation appeared again and Henry and I started solving system equations. I was solving it manually which made things way more complicated comparing to what Henry did by solving in Matlab.

Finally, we actually tested our calculations by constructing a small experiment. We changed the distance between light source and a convex lens, and compared the result with the answers we got by using calculations. We found that short distances worked pretty well, but long distances didn't. We would continue working on it tomorrow.

Some images were taken during the experiment (with Henry):

Day 14

This morning I was working on the outline. Since I haven't got any results yet, I majorly wrote about what I had done so far in my outline. When I was writing the outline I realized I still didn't quite understand Second Harmonic Generation (SHG). For example, I was not sure why the frequency doubled after the light beam goes through the nonlinear crystal. So I was reading an optic textbook about the SHG. I saw frequency in polarization density doubled but still didn't know how polarization connected to the laser beam. Maybe I will ask Lauren about this tomorrow.

I was also learning some basic Differential Equations. Some values looked so familiar to me since they were very similar to the characteristic roots of recursive sequences. Maybe they are the same in some aspect... I'll learn more about this tomorrow.

Day 13

Labview still didn't work without a proper visual acquisition software, so I was testing the CCD camera using Matlab. Before I started, I set camera's exposure time and frame rate. The Matlab codes I wrote were able to make CCD camera capture 200 pictures and save them in a certain folder and analyze these pictures automatically.

I made a dark room and asked Henry to turn on the light after I started camera capturing the pictures. The sums of all the pixel values in each picture were printed into a .txt file. Obviously, the brighter the room is, the larger the sum will be. we could tell when the light was turned on after plotting all the sums on a graph.