Objectives and approaches The objective of this research is to design and demonstrate efficient, ultrasmall III-V semiconductor light sources based on nonlinear frequency conversion. The approach is to use high quality factor photonic crystal resonators to (1) provide phase matching, which is impossible in unprocessed III-V semiconductors, and to (2) greatly reduce the device footprint.
Intellectual merit The specific goals of this research are to demonstrate: Highly efficient second harmonic generation in photonic crystal structures; Photonic-crystal based devices for sum frequency and difference frequency generation; Enhanced spontaneous parametric down conversion and two photon emission. The proposed devices could serve as ultrasmall, ultralow power, on-chip light sources for wavelengths from visible through mid-infrared. The proposed research could also enhance the extremely low efficiency processes of spontaneous parametric down conversion and two photon emission, which can serve as sources of entangled photons for quantum information experiments.
Broader impacts The proposed experiments open a new approach to study nonlinear optical effects using semiconductor nanostructures and would have a significant impact on the nanophotonics and nonlinear optics communities. Moreover, the same platform could be employed for sensing and spectroscopy of biological and chemical molecules, as well as for quantum information experiments with entangled photons. The project will include educational and outreach activities integrated with research, which the PI has already initiated, including active recruitment of minorities and women for science and engineering careers, development of new classes and textbook, undergraduate research and advising, and participation in outreach programs for high-school students and teachers.
In nonlinear optical devices, one color (wavelength) of light can be converted to another via a variety of processes. In our work, we are focusing on nonlinear optical devices based on III-V semiconductors such as GaAs, GaP and InP, as these materials have a very high second order nonlinearity, they can be processed using standard microfabrication techniques, and they also allow integration of active gain media such as quantum dots or quantum wells, as well as potential on-chip integration with detectors, switches and modulators. In particular, we focus on building small mode-volume, high quality (Q) factor optical microcavities in such materials, as they have the potential to reach similar conversion efficiencies to traditional, bulkier devices, but in significantly more compact architecture. Our microcavity of choice is a photonic crystal cavity produced by periodic patterning of semiconductor membranes. Application wise, such nanophotonic structures can serve as ultrasmall, ultralow power, on-chip light sources for wavelengths from visible through mid-infrared, and can enhance the extremely low efficiency processes of spontaneous parametric down conversion and two photon emission, which can be employed in sources of entangled photons for quantum communication. Moreover, the same platform can be employed for sensing and spectroscopy of biological and chemical molecules. Some of our most important results include the design and demonstration of multiply resonant photonic crystal cavities for nonlinear frequency conversion [Optics Express 19, pp. 22198-22207 (2011)], and integration of visible quantum emitters with an on-chip nanophotonic frequency conversion interface [Applied Physics Letters 101, 161116 (2012)]. In addition to the significant research results described above, the project has also made significant contributions to education and human resources, as well as resources for science and technology. A number of students from our group and outside have been trained to perform these experiments (we have even introduced a similar experiment in the photonics laboratory class taught at Stanford). In addition to the PI, all three of the graduate students involved with this project have been women.
