Research JournalSpring 2014August 6th and 7th, 2014It has been a fun two days in the LTC. Dr. Noé invited me back to the LTC this week to talk at the final pizza lunch about my REU experience and to help mentor the high school students for a little. April 30th, 2014Today was URECA! The whole event went really well and was a lot of fun. Everyone loved our optics demonstrations and it was great seeing people enuthsiastic about optics. A copy of my poster can be found here. ![]() April 23rd, 2014I spent a good portion of today reading papers on the optics of twisted nematic SLMs. I've learned a lot and have come to realize how complicated liquid crystals are. This project is turning out to be very rewarding. April 22nd, 2014I talked to Marty today and realized that the set-up I used yesterday to characterize the polarization of the laser module was flawed. To fix the set-up, I removed the pinhole from the face of the photodetector and measured the current rather than the voltage. Below are the results of my measurement.
![]() The measurements show that the light from the laser module is elliptically polarized. Had the graph of intensity versus θ been a straight line, it would have indicated the light was circularly polarized; if the graph had been a sine wave moved up by half the maximum amplitude, it would have indicated that the light was linearly polarized. Marty and I also discussed how to test the phase range of our spatial light modulator. We came up with the idea of replacing one of the mirrors in a Michelson interferometer with the SLM and using MATLAB to vary the phase across the SLM, then using the resulting fringe shifts to measure the phase change.
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April 21st, 2014Today, I characterized the polarization of the laser module. I did so by shining the laser beam onto a photodetector with a 200 μm pinhole placed over its face. I then inserted a linear polarizer in front of the photodetector and rotated the polarizer in 5o increments, noting the intensity at each orientation using a multimeter. ![]() The intensity was flucuating greatly and I couldn't get any good readings for intensity. This reminds me of a PHY 300 lab, where we attempted to measure the intensity profile of a laser diode, but couldn't get good readings because of the prescence of competing modes. A similar situation could be occurring in the laser module. April 14th, 2014The SLM is up and running!!!! I was able to attach my laptop to the SLM using an XGA cable and my computer screen was automatically output on the SLM face. NOTE to future students: Make sure to connect the SLM to a power source before attaching the SLM to your laptop. ![]()
April 8th, 2014After looking at the code Dr. Herne sent me some more, I discovered the reason I was receiving an error when I attempted to run the code earlier was because I had forgotten to put quotation marks around the variable name, so MATLAB though it was a function. I am still getting an error that says the function cannot accept double type variables; I am going to ask Spencer about this to see if he knows how to fix it. Once I have that error fixed though, it should be easy to get the SLM up and running and to program it to mimic traditional optics such as a lens or mirror. April 7th, 2014Hui Cao gave the AMO seminar today. I wasn't able to attend because I had a midterm at the same time. I did however have lunch with Dr. Cao and some graduate students from Hal and Dr. Schneble's groups and talk to Dr. Cao when she toured the LTC. While I didn't have much of a chance to talk to her at lunch because the group was so big, I did get a chance to talk to her quite a bit at the LTC. Libby, Natalie, and Sam all came for Dr. Cao's tour and we took turns talking about our projects for this semester and Dr. Cao's research. It was very interesting. April 6th, 2014I had the pleasure of having dinner tonight with Hui Cao, Dr. Noé, and Hal Metcalf. Hui Cao is a professor of applied physics and physics at Yale University, as well as this week's AMO seminar speaker. Her interests include quantum optics, nano-particles, nonlinear optics, mesoscopic physics, and quantum chaos. The dinner was absolutely fantastic! Dr. Noé had run into Hui Cao on the ferry to the island earlier in the day and had told her about the LTC and its students, so she was already somewhat familiar with my work before dinner began, but I had the chance to talk to her more about our plans and goals for the SLM. Dr Cao's lab has 3 Hamatsu SLMs, but she still seemed very interested in hearing about our Cambridge Correlators SLM. Dr. Cao suggested a method for testing the phase range of our SLM where we set one half of the SLM to mimic a flat surface and slowly changed the phase ramp on the other half of the SLM and measure the fringe shifts. Dr. Cao was very knowledgeable, interesting, and inspiring. Her work has ranged from studying the colors of bird feathers to using random modulation to allow x-rays to probe further into the brain. The conversation at dinner was very lively and I am very thankful that I got to be a part of it. April 4th, 2014Natalie, Sam, Libby, and I had our weekly meeting with Dr. Noé today. The main focus of the meeting was our abstracts for URECA [They are due April 9th, Ekk!]. Going into the meeting Natalie, Libby, and Sam still had not chosen a project, so I talked to them for a while about possible projects and tried to narrow down their ideas into projects I felt were possible and simple enough that they could completely understand their project, but complicated enough that they would have to work hard and would really learn something. Once Dr. Noé came, we discussed their ideas and were able to find suitable projects for all three of them.
The great thing about all three projects is that they lend themselves well to demonstrations, which should attract people to the LTC's table during URECA. Dr. Noé also had some ideas for my project. He thought, and I agreed, that the two goals of my project should be to get the SLM working and to demonstrate optics concepts using the SLM. It would be nice to mimic some traditional optics, such as lens, mirrors, and diffraction gratings using the SLM. I would also like to produce fractal diffraction patterns and optical vortices if time permits. Some possible titles we came up with were "Shaping the Wavefronts of Light Using a Spatial Light Modulator" and "Creating Designer Wavefronts Using a Spatial Light Modulator". April 2nd, 2014I annotated the codes that Dr. Herne sent me today and I also downloaded and annotated some programs that were necessary to run the code, but were not mentioned in the email, such as RenderText.m, which writes text onto an image. I was happy to see that the diffraction fork code is fairly simple and I could easily understand all of it. I received an error when I tried to run the code today, but I think it may be because I set up one of the variables wrong. It should be an easy fix and I am sure Stefan or Spencer could help me. March 30th, 2014I started writing my abstract today for URECA. It's nice to look at the big picture, but also very stressful. The abstract still needs a lot of work. March 28th, 2014Dr. Noé called Catherine Herne today from Colgate University. Dr. Herne has been using a Cambridge Correlator's SLM for optical tweezer applications and has ties to Kiko Galvez, a professor at Colgate University and a longtime friend of the LTC. Dr. Noé wasn't able to reach Dr. Herne by phone, but she did email us back later in the afternoon. Dr. Herne's email was extremely helpful. She laid out the steps for getting our SLM functional and sent me one of her codes for producing an optical vortex and referred me to a MATLAB code which would display the output on an external display [the SLM].
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March 24th, 2014Over the summer, I came across an OPN article which discussed a technique for identifying bacterial colonies based on their forward scattering pattern which was being developed at the Applied Optics Lab at Purdue. The article really interested me because it combined both microbiology and optics, the former of which I had a significant amount of experience in and the later which I hoped to gain a lot of experience in over the summer. Originally I wanted to do a project that mimicked what they were doing at Purdue, but I soon realized that this was too ambitious and advanced to accomplish over the summer. My initial interest did lead me to complete a very rewarding project related to diffraction and optical vortices. Anyways though, the reason behind this foray into the past is Dr. Noé found an article in OPN about the Purdue Applied Optics Lab. I will have to draft an email to them about their work because I would really love to learn more.
![]() March 6th, 2014Dr. Noé lent two books last week, A Jewel in the Crown and Quantum Physics for Poets, to help prepare me for working at the University of Rochester in Prof. Boyd's lab this upcoming summer. A Jewel in the Crown is about the history of the Institute of Optics at the University of Rochester, while Quantum Physics for Poets is about the theories of quantum physics without all of the math. I've started reading A Jewel in the Crown and it is fantastic. The book is comprised of 75 essays by those associated with the Institute and spans the time period from the 1910's to 2003. I love learning about the early days of optics in the US and A Jewel in the Crown is helping me grow a greater appreciation for optics and the early scientists who worked in the field. Fun fact: Prior to WWI, most scientists in the field of optics and optics industry was located in Germany. When WWI broke out, it was immediately apparent that Ally reliance on the German optics scientists and industry was unsatisfactory, so in 1917, institutes of optics were founded in London and Paris. The US followed suit by founding the Institute of Applied Optics [now the Institute of Optics] at the University of Rochester in 1929. March 4th, 2014Today I attended a lecture by Nobel laureate, Frank Wilczek, at the Simons Center. The lecture was entitled "Expanding the Doors of Perception" and was about how our senses only allow us to sample and experience a very small portion of physical reality. The talk was very interesting and provided me with a lot of food for thought. I was particularly intrigued by a question posed by one of the graduate students in Eden Figueroa's lab which asked in so many words if Dr. Wilzcek thought that the history of physics would be different if humans had developed different senses than the ones we currently have and would this change in senses affect the 'final outcome' of physics. ![]() February 28th, 2014I had my first tutor training of the semester for Stony Brook's Academic Success and Tutoring Center today. I have been tutoring students in PHY131/132 since December of last year and have found the whole experience to be very rewarding. It feels amazing when a student has been struggling with something and all of the sudden the switch flips and everything makes sense to them. I know from experience physics isn't always easy, so it feels good helping the kids who are willing to put in the extra work in their classes. After my training finished, I returned to the LTC just in time to see Sam and Natalie's presentations. Sam presented on the Doppler effect, while Natalie discussed the optics of color. Dr. Noé then showed us the Michelson interferometer in which Doppler shifts occur when the mirror is moved. Curious about the relationship between Michelson interferometers and the Doppler effect, I found a paper which describes a method for measuring optical Doppler shifts using a rotating mirror. Doppler shifts are usually demonstrated using sound in classrooms because it is hard to move a light source smooth enough so that the signal is larger than the noise. Demonstrating optical Doppler shifts may be a good project for Libby and Natalie. February 27th, 2014After speaking to a graduate student and an undergraduate alum from Dr. Boyd's lab, I have accepted the offer from the University of Rochester to work in Prof. Boyd's group! I am very excited to be a part of the University of Rochester's REU program and I can't thank Dr. Noé enough for all of his help. The Univerity of Rochester has a very impressive graduate optics program and I am going to use this summer as an opportunity to learn more about the school as I am very interested in the University as a possible choice for graduate school. February 26th, 2014With Dr. Noé's assistance, I was lucky enough to receive three summer research opportunity offers. Listed below are the three labs who made me offers: Dr. Grover Swartzlander's Optical Vortex Applications Laboratory- working on optical lift Dr. Nick Bigelow's CAT (Cooling and Trapping) group- working on BECs with LTC alum Azure Hansen Dr. Robert Boyd's quantum photonics research group- working on most likely OAM Much of my time recently has been devoted to deciding which lab I would like to work in over the summer. It's been really fun and informative reading up on the three labs and I would be honored to work in any of them. February 21st, 2014Today for about the fifth time this month, I reconfigured my website which reminds me that I need to ask Dr. Noé to back up the website in case of a mishap. I take pride in my research website and I derive joy from making sure it is as user-friendly as possible. I updated my main page, so that it now has a different headshot and also includes a Guides section. Besides that, I editted my Matlab, Linux, and Latex guide. February 19th, 2014I decided to switch it up today and research Matlab. I learned some Matlab basics this past fall in PHY277 and started my research by looking over the lecture notes from class. I also decided to create a Matlab Guide and link to it from my SLM guide. February 11th, 2014I spent my time in the lab today researching spatial light modulators and now have copious notes on them in my research notebook . I started to add some more information to my Spatial Light Modulator User Guide, but I want to understand spatial light modulators better before I write too much. I am going to continue to update the user guide throughout this semester and I hope that future LTC students can use the guide to gain an understanding of spatial light modulators.
February 9th, 2014I updated my webpage today to make the layout more aesthetically pleasing and functional. I now have my work from each semester in a separate directory, so that it is easier to keep track of everything. I also created a Spatial Light Modulator User Guide, which I hope to fill with lots of useful information on the operations and applications of our spatial light modulator. January 29th, 2014
I set up Stefan's spatial filtering set-up today, but I didn't see any improvement in the quality of the mode. I will have to talk to Stefan to figure out what exactly his setup was. I also found a paper about optical vortices which mentioned spatial filtering. Hopefully, this technique will improve the beam's mode. January 28th, 2014Back to school means back to the lab for me. I'm excited to be back and I am hoping to continue and tie up the loose ends related to my summer research. My two main goals at this point are to test out Stefan's spatial filtering method for creating better LG modes and modelling the Fresnel diffraction pattern going through the spiral phase plate. Over the past semester, I figured out how to use ImageJ to get averaged line outs, which does a lot to eliminate the irregularities in the images of the beam, and will allow us to compare the ideal LG modes to the experimental beams. This should be relatively fast and will give us a lot of quanitative data. I plan on spending today studying Stefan's spatial filtering and trying to implement it in my set up. September 4th, 2013Optical vortices evolving from helicodial integer and fractional phase steps In this paper, Michael Berry explores the mathematics behind optical vortices arising from helicodial integer and fractional phase steps, modeling both the formation and propagation of optical vortices. The paper is pretty dense and I'm going to have to read it at least 10 more times before I can fully follow, but here is some of general information I picked up on my first read-throughs. Spiral phase plates are reflective or refractive surfaces shaped into one turn of a helicoid with a pitch of the helicoid that produces a desired phase step. They are commonly used in creating screw-dislocation waves. Obviously, it is desirable to have an accurate model of optical vortices formed after the spiral phase plate; in this paper, Berry presents a model that is sufficiently realistic, but simple enough to easily control analytically. [His model is for that of an infinite plane wave incident on a spiral phase plate, not a finite Gaussian beam, and does not capture some of the diffraction phenomena produced by spiral phase plates, such as scattering at the edge of the step.] Efficient conversion of a Gaussian beam to a high purity helical beam
August 28th, 2013Stefan and I started modelling pure Laguerre-Gaussian modes ℓ=1-8 and the impure Laguerre-Gaussian modes that result from passing a Gaussian beam through a spiral phase plate. The LG beams produced by the spiral phase plate did not match the profiles of the LG beams produced by a spiral phase plate in the Israeli paper and so we have some problem solving to do. I was thinking of plotting the beams in GNU plot. I will have to talk to Dr. Noe about this. August 27th, 2013I'm excited to be back on campus, so that I can continue my research. I had a chance to speak with Dr. Noé briefly yesterday about my research and it sounds like there is a lot of work to be done. We also finished and submitted our abstract for OSA's Annual Frontiers in Optics Meeting. Stefan also agreed to join the project to help out with the MatLab programming. To sum up my project in a single sentence, we are trying to find a technique which improves the efficiency of spiral phase plates when converting Gaussian beams to pure LG modes. Below is a tentative list of things we hope to accomplish in the upcoming month:
I plan to start by testing the affect of ingoing Gaussian beam radius on the quality of the LG mode for modes ℓ=1-8. |