University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations 2015 Optomechanical Devices and Sensors Based on Plasmonic Metamaterial Absorbers Hai Zhu University of Pennsylvania, [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Mechanics of Materials Commons, and the Optics Commons Recommended Citation Zhu, Hai, "Optomechanical Devices and Sensors Based on Plasmonic Metamaterial Absorbers" (2015). Publicly Accessible Penn Dissertations. 2129. https://repository.upenn.edu/edissertations/2129 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/2129 For more information, please contact [email protected]. Optomechanical Devices and Sensors Based on Plasmonic Metamaterial Absorbers Abstract Surface plasmon resonance is the resonant oscillations of the free electrons at the interface between two media with different signs in real permittivities, e.g. a metal and a dielectric, stimulated by light. Plasmonics is a promising field of study, because electron oscillations inside a subwavelength space at optical frequencies simultaneously overcome the limit of diffraction in conventional photonics and carrier mobilities in semiconductor electronics. Due to the subwavelength confinement, plasmonic esonancesr can strongly enhance local fields and, hence, magnify light-matter interactions. Optical absorbers based on plasmonic metamaterials can absorb light resonantly at the operating wavelengths with up to 100% efficiency. We have explored plasmonic absorbers at infrared wavelengths for thermal detectors, e.g. a gold nanostrip antenna absorber that can absorb 10-times light using only 2% of material consumption comparing to a uniform gold film. In an optomechanical device, the optical mode and mechanical mode are mutually influenced, through the optical forces exerted on the mechanical oscillator and the detuning of optical resonance by the mechanical oscillator, so that the mechanical oscillations are either amplified or suppressed by light. We designed an optomechanical device integrated with plasmonic metamaterial absorber on a membrane mechanical oscillator, wherein a tunable Fano-resonant absorption in the absorber arises from the coupling between the plasmonic and Fabry-Perot reonsances. The absorber traps the incident light and heat up the membrane, causing an increase in thermal stress and a normal plasmomechanical force on it. This is a light-absorption-dependent elastic force arising from the opto-thermo-mechanical interactions. Due to the finite thermal esponser time in the membrane, the elastic plasmomechanical force is delayed and, consequently, generates a viscous component modifying the damping rate of the mechanical oscillator. We have observed optomechanical amplification and cooling in the device at designed detuning conditions. In particular, on the condition that the optomechanical gain beats the intrinsic mechanical damping, the oscillation becomes coherent, i.e. phonon lasing. We successfully demonstrated phonon lasing with a threshold power of 19 μW. This device is promising as an integration- ready coherent phonon source and may set the stage for applications in fundamental studies and ultrasonic imaging modalities. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Materials Science & Engineering First Advisor Ertugrul Cubukcu Keywords Absorber, Metamaterial, Nanophotonics, Optomechanics, Phonon laser, Plasmonics Subject Categories Mechanics of Materials | Optics | Physics This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/2129 OPTOMECHANICAL DEVICES AND SENSORS BASED ON PLASMONIC METAMATERIAL ABSORBERS Hai Zhu A DISSERTATION in Materials Science and Engineering Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2015 Supervisor of Dissertation __________________ Ertugrul Cubukcu Assistant Professor, Materials Science and Engineering Graduate Group Chairperson __________________ Shu Yang Professor, Professor, Materials Science and Engineering Dissertation Committee Ritesh Agarwal, Professor, Materials Science and Engineering Lee C. Bassett, Assistant Professor, Electrical and Systems Engineering Cherie R. Kagan, Stephen J. Angello Professor, Electrical and Systems Engineering OPTOMECHANICAL DEVICES AND SENSORS BASED ON PLASMONIC METAMATERIAL ABSORBERS © 2015 Hai Zhu To My Family iii ACKNOWLEDGMENT This thesis summarizes my Ph.D. work in the past half-decade at Penn MSE department. During the time, I have tasted sweetness of success as well as bitterness of failure. I would not be sitting here and writing this without the support from many awesome people, to whom I am going to express my sincere appreciation in this acknowledgment. First and foremost, I must thank my dear advisor, Prof. Ertugrul Cubukcu, for all his great support, including inspiring guidance, patient encouragement, and kind concerns, from beginning to end. I am very fortunate to have met him. He possesses immense knowledge in physics, optics, and electrical engineering. I have been introduced to the field of nanophotonics and optomechanics and kept motivated all by his mentorship. He is enthusiastic about scientific research and full of ideals, and as a result I have got opportunities to engage in multiple interesting projects and enriched my experience and skills. He asked to always consider the major factor before the minor ones. That advice deeply influenced me and will benefit me forever. I will never forget his strong support during my hard time at school and in life. He has devoted tremendous time and effort to the entire course of my Ph.D. work and made my success. I want to acknowledge my thesis committee members, Prof. Ritesh Agarwal, Prof. Lee C. Bassett, Prof. Nader Engheta, and Prof. Cherie R. Kagan, for their valuable time and effort on my research proposal, annual thesis progress reports, and dissertation defense. Their insightful comments and suggestions made this thesis better-looking. I feel lucky that Prof. Agarwal can attend my dissertation defense though he was recently burdened with his newborn angel. I am grateful to Prof. Bassett for graciously joining my committee on short notice. Prof. Engheta provided the courses of Electromagnetic and Optical Theory I & II, which benefited me profoundly. His excellent research work on metamaterials was important references for my Ph.D projects. Although he is unable to attend the dissertation defense, I want to express my appreciation towards Prof. Engheta. Prof. Kagan is my first known faculty among the committee. Her lectures on semiconductors and nanotechnologies sparked my interest towards nano research. I want to express my gratitude towards Prof. Kagan. iv I also want to thank my awesome labmates, Prof. Fei Yi, Mr. Jason Reed, Mr. Qiushi Guo, Dr. Jiechang Hou, Prof. Feng Liu, Mr. Euijae Shim, Mr. Alexander Zhu, Mr. Guanqing Hao, Ms. Stephanie Malek, and Mr. Yichen Lu, for all kinds of help. It is a precious experience for us from all over the world to meet and work together at Penn. Prof. Yi and Mr. Reed are almost everywhere in my memories associated with LRSM Rm 400. We had many productive collaborations, wherein they gave so much help and support. I want to give special thanks to Prof. Yi and Mr. Reed (Dr. Reed by the time of my thesis deposition). I also want to specially thank Mr. Guo and Dr. Hou for the pleasant collaboration experiences. I am grateful to faculties and staff that have assisted me on my work and life at Penn. I have invested a lot of time doing research at the Quattrone Nanofabrication Facility (QNF), Wolf Nanofabrication Facility (WNF), Nanoscale Characterization Facility (NCF, the formerly PRNF), and Nano/Bio Interface Center (NBIC). I must acknowledge these facilities and thank the associated staff for providing trainings and consultation. I thank Prof. Robert Carpick for granting me access to the Optical Profilometer in his lab. I thank Prof. Dawn Bonnell for sharing the precious PVD materials. I thank Prof. Christopher Murray and Dr. Xingchen Ye for helping with the FTIR tool in their lab. I thank Prof. Daniel Gianola and Prof. Christopher Murray for giving me the opportunities for teaching assistant practice in MSE/MEAM 505 and MSE 360. I thank the lovely administrative staff of the MSE department, including Ms. Vicky Lee, Ms. Pat Overend, and Ms. Irene Clements, for all the care and assistance they provided during my years spent at the LRSM Building. Last but not least, I want to express my deepest love and appreciation to my family. My grandmother Ailian Tan nurtured me since I was born and has influenced my character. My grandfather Quan Zhu is my idol and has always been motivating me to fight my way. My father Shujun Zhu and mother Chiping Huang raised me up healthy and happy with their selfless and unconditional love. They have been trusting and supporting me, so I could reach here on the scientific career path. To them, I am indebted forever. Finally, I want to express my special gratitude to the love of my life, Fei Li, for her non-stop accompany since 2011. She made my Ph.D. life not dull at all. I lost my wedding band after an experiment ran overtime, but Fei comforted me saying v “working hard should be rewarded” and encouraged me to get over the guilt. It is her constant support and encouragement that allows me to pursue what I like to do with no