Principal Investigator  |  Postdocs  |  Graduate Students  |  Undergraduate Students  |  Collaborators  |  Alumni

Principal Investigator

I am an Assistant Professor in the Department of Electrical, Computer and Energy Engineering (ECEE) at the University of Colorado, Boulder, and Principal Investigator of the Nanophotonic Systems Lab. In the Fall 2013 term, I taught ECEN 5156, Physical Optics.

Previously, I have been a Postdoctoral Associate and independent investigator in the Optics and Quantum Electronics Group at MIT's Research Laboratory of Electronics. There, I directed as Principal Investigator projects in nano-optomechanics and in energy-efficient nanophotonic circuits, and pursued related interests in nanoscale device design and photonic circuit theory. During my graduate research, I led the design aspect of a collaborative research effort that demonstrated a number of firsts in nanophotonic circuits for telecom applications - including telecom-grade filters, polarization transparency, and true-hitless switching. My Ph.D. advisors at MIT were Prof. Hermann A. Haus (2000-03), and then Profs. Erich P. Ippen and Franz X. Kärtner (2003-07).

Areas of Interest

  • Nano-optomechanics, light forces, strong coupling, self-adaptive nanophotonics
  • Energy-efficient nanophotonics for on-chip microprocessor interconnects
  • High-fidelity integrated photonic circuits for signal processing
  • Fundamental limitations of devices based on the physics of light
  • Novel device physics for photonic device design and control


Our lab currently has new postdoc openings. See Openings for more information.

Fabio Pavanello

Dr. Fabio Pavanello received his Ph.D degree in Electrical engineering from the Institute of Electronics, Microelectronics and Nanotechnologies (IEMN) - CNRS (University of Lille I) in France for work performed on uni-travelling carrier photodiodes (UTC-PDs) for THz frequencies generation.

During his Ph.D he developed a contact based on plasmonic gratings to enhance the response of vertically illuminated photodiodes and to reduce thermal heat dissipation which is one of the key factors limiting their maximal output power. His work included design, clean-room fabrication and characterization of UTC-PDs.

This work was conducted in the framework of the European project MIcrowave and TErahertz PHOtonics (MITEPHO) for which Dr. Fabio Pavanello was awarded a Marie Curie Fellowship by the European Union.

His current research interests involve the design and the characterization of a wide range of photonic devices (modulators, gratings, filters...) fabricated on un-modified CMOS platforms for CPU-to-DRAM optical links to overcome the bandwidth and energy efficiency limitation of electrical links.

Yossef (Yossi) Ehrlichman

I am a postdoctoral research associate at the Nanophotonic Systems Lab. I am working on Silicon RF photonics. I am investigating photonic devices to be incorporated in electronic systems in order to improve overall system performance and to reduce power consumption. My research interests include devices for optical communication, signal processing electronic/photonic integration, and data converters (A/D, D/A).

I received my Ph.D. and M.Sc. EE from Tel-Aviv University. I received a MBA and B.Sc. EE from the Technion. During my Ph.D. I worked on photonic integrated mixed-signal circuits. I developed an electronic/photonic integration method called Direct Digital Drive (DDD). DDD allows applying digital signals directly on analog photonic devices, without any mediating electronic circuits. I demonstrated this method for a small electro-optical D/A converter and a compact QAM modulator for coherent optical communication.

At Tel-Aviv University I taught “Digital Electronic Circuits” for undergraduates at the School of Electrical Engineering. I was a teaching assistant in several circuits’ related courses.

I worked at SemiConductor Devices (SCD) as and electro-optical engineer at the R&D division. SCD develops and manufactures cooled and uncooled IR detectors.

Graduate Students

Xiaoge (Savvy) Zeng

My main interest is in nanooptomechanical system design. By confining light in nanoscale, optical field is greatly enhanced. Strong optical force is thus produced to move nanomechanical movable parts, which in turn changes the optical properties of the system. Based on the interplay between optical field and mechanical motion, various devices could be designed, such as all-optical self-tuning resonators. I am also interested in general active and passive nanophotonic devices, and application of integrated optics in nonlinear optics and quantum optics.

Yangyang (Yang2) Liu

I am currently interested in optical structures in which optical forces play an active role in determining device performance.

Cale Gentry

Cale received his B.S. in Engineering Physics at the University of Oklahoma with a design sequence in solid state electronics.

During his PhD, Cale has developed a numerical simulation tool implementing a film matching method for designing efficient fiber-to-chip grating couplers. His current research interests include the design and characterization of nonlinear and quantum integrated sources. This has led to the proposal of a novel 'dark state laser' resonator geometry utilizing imaginary coupling (Q-splitting) enabling ultra-wide tunable single-frequency laser sources using a Vernier-like tuning mechanism. He has also demonstrated wide-band seeded four-wave mixing via dispersion compensation based on a coupled cavity resonator geometry. Currently he is working on the design and fabrication of integrated quantum photonic sources and circuits in collaboration with researchers at NIST. You can email him at Cale(dot)Gentry(at)Colorado(dot)edu.

Nathan Dostart

Nathan's main interests lie in discovering and harnessing interesting physical phenomena in the fields of optomechanics, nonlinear optics, and quantum optics to create novel photonic devices on-chip and improve upon existing technologies. During his undergraduate career, Nathan conducted research in optics, material dynamics, and photovoltaics. His introduction to optics research was through working with Prof. Gaurav Bahl to theoretically and numerically understand photon-phonon interactions in silica microresonators to enhance gain in Stimulated Brillouin Scattering. His senior design project investigated nonlinearities in embedded granular media for shock-mitigating materials. Nathan has also designed a solar simulator and gained experience with high-vacuum technology while working with solar panels on a CubeSat style satellite.

After joining the Nanophotonic Systems Lab under Prof. Milos Popovic, Nathan has continued to work on optomechanics while additionally beginning work in integrated photonics. By taking advantage of the close integration of electronics and optics in advanced CMOS processes, he has designed novel optical filters and other devices on-chip.

Nathan received his B.S. in Mechanical Engineering from the University of Illinois, Urbana-Champaign in 2014. He is a National Science Foundation Graduate Research Fellow.

Imbert Wang

Imbert is interested in the design, fabrication, and testing of integrated nonlinear and quantum photonics.

Undergraduate Students

Josep Maria Fargas Cabanillas

Josep is pursuing a double degree in Engineering Physics and Industrial Engineering at the Universitat Politècnica de Catalunya in the CFIS program. In the summer of 2014 he collaborated with the research group led by ICREA Professor at ICFO Morgan Mitchell on the project titled “Active magnetic field control for a Bose Condensate”. He is interested in quantum control, quantum optics, and quantum computation. Currently he is working on the design of compact tunable waveguide couplers that can be used in linear optics quantum computation.


We are always interested in discussion and welcome any feedback on our and our colleagues' research efforts. Feel free to contact us.

Current and previous collaborators include:

  • Dr. Peter T. Rakich  -  Sandia National Labs (Albuquerque, NM)
  • Prof. Vladimir Stojanovic  -  MIT
  • Prof. Franz X. Kärtner  -  MIT
  • Prof. Erich P. Ippen - MIT
  • Prof. Rajeev J. Ram  -  MIT
  • Dr. Tymon Barwicz  -  IBM Watson Research Center (Yorktown Heights, NJ)
  • Anatoly Khilo, Charles Holzwarth, Marcus Dahlem  -  MIT
  • Dr. David O. Caplan  -  MIT Lincoln Laboratory (Lexington, MA)
  • Prof. Hank Smith  -  MIT
  • Dr. Michael R. Watts  -  Sandia National Labs
  • Dr. Marco Romagnoli  -  Pirelli Labs S.p.A. (now PGT Photonics)
  • Luciano Socci  -  Pirelli Labs S.p.A.
  • Prof. Lionel Kimerling  -  MIT
  • Dr. Shoji Akiyama - formerly MIT
  • Prof. Kazumi Wada - University of Tokyo, Japan (and MIT)


Jeff Shainline (Aug. 2010 - Feb. 2013)

Jeff was a postdoctoral research associate in our lab whose work focused primarily on chip-based integrated silicon photonics. He contributed to projects in optical interconnects for many-processor-to-DRAM communication (a collaborative effort with MIT, Berkeley, IBM, and Micron); superconducting transition-edge sensors on a chip in collaboration with NIST researchers; and correlated photon pair generation, also a collaboration with NIST. Jeff is now a physicist at NIST in Boulder, Colorado.

Mark Wade (Jun. 2011 - Dec. 2015)

During his PhD, Mark has mainly worked on electronic/photonic integration in advanced CMOS microelectronics processes. He has designed many integrated optical components including microring filters, modulators, detectors, and vertical grating couplers. These devices were challenging to design within the constraints of modern CMOS nodes, in particular IBM's 45nm and 32nm nodes. He was part of the team that demonstrated the world's first monolithically integrated chip-to-chip optical link, and his devices have been used to demonstrate ultra-energy efficient transmitters in IBM's 45nm process. His interests include novel devices based on microring resonators, Photonic Design Automation tools, and finding practical problems where integrated photonics can make a large impact.

Mark received his B.S. degrees in electrical engineering and physics from Louisiana Tech University in 2010. He received his M.S. in electrical engineering with a focus in optics in 2013. He is a NIST Measurement Science and Engineering Fellow and a National Science Foundation Graduate Research Fellow.

PhD Thesis [PDF]

Gil Triginer Garces (May 2014 - Apr. 2015)

Gil was a visitor from Catalonia researching applications of resonator-based four-wave mixing for his master's thesis at Escola Tecnica d'Enginyeria de Telecomunicacio de Barcelona, Universitat Politecnica de Catalunya. Gil explored the design of SiN microresonators for four-wave mixing-based two-mode squeezing. He also researched the applications of arbitrary linewidths in optical parametric oscillators. He will be pursuing a Ph.D. at the University of Oxford.
Master's Thesis [PDF]

Rajesh Kumar (Sep. 2013 - Dec. 2014)

Rajesh was a postdoctoral research associate in our lab. His work focused on implementing efficient grating couplers in a native CMOS platform.

Chris Poulton (May 2012 - May. 2014)

Chris was an undergraduate researcher in our group. His research involved implementing high-Q photon crystals in a 45nm CMOS process. He is currently pursuing his Ph.D. at MIT.

Jelena Notaros (May 2013 - June 2015)

Jelena was an undergraduate researcher in our group. Her research involved helping develop a numerical tool to solve for complex-wavevector photonic Bloch modes in integrated devices. Jelena will be pursuing a Ph.D. at MIT.

Andy Kee (Nov. 2013 - Aug. 2014)

Andy was an undergraduate researcher in our group.

Jeff Jennings (Sep. 2013 - May. 2014)

Jeff was an undergraduate working as a web designer and administrator for the group.

Derek Gann (May 2013 - Aug. 2013)

Derek was an undergraduate research assistant in our lab. His primary work was in automating data collection systems around the lab. He built software that allowed the user to control a tuneable IR laser in conjunction with a source-meter from a labVIEW GUI on a desktop. This was designed for rapid data collection when taking optical spectra of voltage modulated devices, i.e. many spectra at a series of voltages, or when taking IV characteristics of photo-responsive circuits, i.e. a series of IV curves at various laser powers and/ or wavelengths. He also built a labVIEW GUI to control both a gigahertz pattern generator and a digital sampling oscilloscope. This was designed to help accelerate data collection on bit error characteristics of fully functional optical modulators. Derek is currently aiding in research with pump-probe and plasmon resonance-enhanced imaging techniques in liquid crystal systems in Prof. Ivan Smalyukh's lab with an anticipated graudation in spring 2014.

Emily Donahue (June 2013 - Aug. 2013)

Emily visited our group from Cornell University for 9 weeks as an NSF NNIN REU intern.  Emily did nanofabrication in the CNL, and used e-beam lithography to write waveguide and microring resonator circuits on a silicon-on-insulator chip.

Miljan Dasic (June 2012 - Oct. 2012)

Miljan was a visiting undergraduate research assistant in our group.  Miljan worked on the design of low loss optical filters and power splitters, as well as computational grid index averaging techniques for efficient simulation of optical resonators.  Miljan presented papers at the IEEE Telfor 2013, and at IEEE Student Projects Conference in Nis, Serbia (2013) winning a Best Paper award.

Juan Llinas (Summer 2012)

Juan visited our group from the University of Illinois at Urbana-Champaign (UIUC) for 9 weeks as an NSF NNIN REU intern.  Juan studied electromigration limitations in metals and did microfabrication of chromium and titanium microheaters on chip for thermo-optic tuning of silicon photonic devices.  He successfully demonstrated thermal tuning of microring resonators as part of his project. He is currently pursuing his Ph.D. at the University of California, Berkeley.

Dan Klemme (Summer 2012)

Dan visited our group from Bethel University for 9 weeks as an NSF NNIN REU intern.  Dan did nanofabrication in the CNL, and used e-beam lithography to write waveguide and microring resonator circuits on a silicon-on-insulator chip.  Dan is now pursuing his PhD degree at the University of Minnesota in the group of Prof. Sang Hyun Oh.

Kareem Nammari (May 2012-Aug 2013)

Kareem started in our lab as an undergraduate research assistant and continued his Master's work with us on on-chip CPU-memory photonic interconnects funded by the DARPA POEM program.

Ian Franklin

Ian was an undergraduate research assistant in our lab funded by the DLA program [link].  He was funded by our NSF grant on "Molding Optical Field Patterns for Highly Efficient Design of Strong-Confinement Photonic Devices" (2011-2014) to develop a Matlab graphical user interface for optical mode solvers for use in outreach activities.  He subsequently did optical measurements and loss analysis of deep-UV fabricated passive microring resonators.

Fletcher Richman

Fletcher was an undergraduate research assistant in our lab funded by the DLA program. He built a microheater PID controller to thermooptically tune resonances of on-chip photonic devices. He is currently a growth engineer at PivotDesk and a managing director at Spark Boulder.

Stevan Urosevic (Jan. 2010 - Aug. 2010)

Stevan was an undergraduate research assistant in our lab.  He studied the design of grating-based optical fiber-to-chip couplers for advanced CMOS electronics-photonics integration and built optimization codes.  Stevan subsequently pursued a Master's degree at MIT.

Katrina Bossert (Spring 2010)

Katrina was an undergraduate research assistant and did an independent study project in our lab.  She carried out finite-difference time domain (FDTD) simulation studies of adiabatic photonic structures.  Katrina is a PhD student in Aerospace Engineering at CU Boulder, doing remote sensing/LIDAR based atmospheric studies.