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Atom Optics Using an Optical Waveguide- Based Evanescent Field ATOM OPTICS USING AN OPTICAL WAVEGUIDE- BASED EVANESCENT FIELD DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Rajani Ayachitula Physics The Ohio State University 2010 Dissertation Committee: Professor Gregory P. Lafyatis, Advisor Professor Richard Furnstahl Professor Eric Herbst Professor Linn VanWoerkem Copyright by Rajani Ayachitula 2010 ABSTRACT The storage and manipulation of cold atoms near surfaces is of growing interest for applications like atom optics, the measurement of atom-surface interactions, and quantum information processing. In this work, we have constructed an apparatus to study cold atom physics above an optical waveguide. A two dimensional array of atoms trapped above our optical waveguide surface could serve as a quantum register, allowing for the individual addressing of single atoms from above or below using laser light. The first application of our system on the path to creating an addressable quantum register was to create a large area atom mirror. To realize our atom mirror, we had two main tasks: creating the cold atom source to drop onto the surface and creating the atom mirror out of our waveguide. We designed our apparatus to move magnetically trapped cold atoms from the Rb source to the region above the optical waveguide to conduct the dropping experiment. Several cooling and trapping steps are necessary to create our cold atom sample that will be dropped on our waveguide surface. We show that we have successfully created a 3mK cold atom sample of 3 ! 108 atoms to drop onto our surface to realize an atom mirror. Our atom mirror consists of an optical waveguide with gratings evaporated on top, which we use to couple ii light into the waveguide. By coupling light into a transverse electric mode of the optical waveguide, we create an evanescent wave above the waveguide surface. By coupling in tens of milliwatts of blue-detuned laser light, we create a sufficiently repulsive potential for a cold atom cloud. The strength of our repulsive potential is limited by scattering losses in our waveguide. Several processing steps that involve soaking the waveguide in a solution or heating the waveguide to high temperatures are required to manufacture our gratings on our waveguide surface. We show that we have created our optical waveguide with 20% coupling efficiency, while limiting our losses by maintaining a high quality waveguide surface. Combining our optical waveguide and our cold atom sample in an ultra-high vacuum environment, we have a system to demonstrate our atom mirror. The bouncing is detected using a weak quasi-resonant probe beam that is monitored by a photodetector. The atoms’ passage through the beam records the bouncing events. We have determined that our atoms must be at 10µK to properly resolve the bouncing. We have implemented the proper cooling mechanisms to cool our atoms in the ultra high vacuum environment to show this first bounce. iii For my mother, Nirmala and my father, Raj. iv ACKNOWLEDGMENTS First, I would like to thank my advisor, Professor Greg Lafyatis, for giving me novel ways to think about problems. When I was too lost in the trees to find the forest, he always helped me find my way to the back to the big picture. His insight has been valuable. I would also like to thank Professors Linn VanWoerkem, Eric Herbst and Richard Furnstahl for serving on my dissertation committee, reading the various general exams, annual reviews and this thesis in the process, and asking questions that helped me push this work along. When I first came into the lab, after finishing up coursework, I was greeted by an awesome group of people. Katharina Gillen was a great labmate and friend. I am sad I did not get to work with her longer, but regardless of where she is, she is an asset to physics. Andrei Modoran was always there to make a hilarious wisecrack or lift something really heavy, both of which I miss. James Keller, Rob Coridan, and Michael Chmutov as undergraduates made valuable contributions to the lab and have no doubt become successful. Without Justin McLaughlin, I may have not survived the times that the water lines broke, spraying water into our 500A power supply – I might owe him my life. Furthermore, his aptitude with both electronics and music has been quite an asset to the v lab. Jessica Roeder and Michael Eades are the newest additions to the lab and have already made useful contributions to the effort. Michael, with his extraordinary programming skills, has created LabView code we use regularly in the lab. And, he always kindly shares his donuts. Jessica is soon to take over the experiment and has really picked up things in a very short amount of time. I have no doubt that she will, in time, be leading a team of her own. I appreciate the effort that all three of these guys have put in the past year trying to get things up and running. By the end, as the only graduate student working on laser cooling at Ohio State, I was lucky enough to be part of a network of great people to talk to about research. Of those individuals, Dr. Charles Sukenik , Dr. Jamil Abo-Shaeer, and Dr. Martin Zweirlein have been an important part of the end of this process for me. They deserve an award for patience for dealing with my discussions, texts, and emails. I also must give a proper thesis shout out to “The Physics Boys.” Rakesh Tiwari, Mike Fellinger, Rob Guidry, Jim Davis, and Kevin Driver have helped me in many ways, especially in the past year – for which I am grateful. For an only child, it is kind of nice to have so many little brothers in such close proximity. I am lucky to have spent a good portion of my graduate school experience with astronomers, Juna Kollmeier, Rik Williams, and Amy Stutz. They shared my early- morning to late-night schedule, celebrated with me when I got the MOT and magnetic traps up and running, and were always up for 3 am visits to Kroger for various potato products – for which, I am quite thankful. Their current success is a testament to how great they are as people and scientists. vi Another successful astronomer who deserves mention is Louis Strigari. We spent most of the first few years of graduate school fighting over problem sets and whose solution was “garbage” and whose solution was right. Although we were often frustrated with each other, I appreciate his passion for physics and the healthy debates we were somehow capable of having on no sleep at 4 am with teaching duties looming in a mere 3 hours. I cannot forget to mention Maria Gonzalez-Sanchez, Lorena Galan-Platas, Maria- Jose Roa-Garcia, and Agus Munoz-Garcia, who stayed wonderful friends despite my terrible Spanish vocabulary and inability to keep from becoming an abuela at 10pm. Gracias a cada uno de vosotros por todo en esos anos. - la chica adentro de mi os da gracias tambien. Other friends and colleagues without whom this thesis could not have been written and deserve thanks include: Aimee Bross, from whom I learned many of my processing skills and how to “take it out on the last hill” with running and with trying to finish this – which was so important; Jenn Holt, for having an amazing solution to any problem, big or small, as well as her appreciation for Bauhaus; Rita Rokhlin, who taught me to use the atomic force microscope and kept me in line; Tom Kelch, who always had a creative solution for how to build any part; The main machine shop guys, John Spalding, John Shover, Pete Gosser and Josh Gueth, who would get my precision parts done quickly and perfectly and who were quick with a good “zipperhead” joke when I was injured, got staples and needed to lighten up; JD Wear, Brian Keller, Brian Dunlap, and Terry Bradley for dealing with all of my computer problems and questions; Kent vii Ludwig for letting me borrow (on super-extended loan) several parts that I hope he sees again some day and for the constant reminders that there is a life outside of the lab; Dr. Robert Davis, who was always willing to talk to me about noise problems; Mark Reed, who dealt promptly with any building issues I had; Harold Whitt and Chris Healy for making sure that my labs were always set up and for helping me get the demos together for my outreach presentations; Brenda Mellett, who answered any question I had regarding some obscure graduate school rule or regulation; Bob Wells and Mark Studer, who besides working on my surface mount electronics and packing all of my books, were quick with some hilariously inappropriate joke to get my day started. John Spalding, Mark Reed, and John Shover deserve further mention for the actual moving of the evacuated apparatus to the new building (which was not easy). They also skillfully brought down the heavy 500A power supply safely from above the evacuated apparatus so I could fix it, and then put it safely back up. The typed words do no justice to the care and skill with which they did either. They made a difficult process so seamless – for that, many thanks. I also have to thank Katie Comer, Nicole Gibbs, Joelle Fenger, Glene Mynhardt, Elizabeth Bentley, Joann Strunk, Alana Kumbier, Kristine Koehler, Jessica Kohlschmidt, Carolyn Burke, Amanda Campbell, Judith Cusin, Siri Hoogan, and Richard Mitsak for helping me remember that I am not just the sum of my parts.
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