Go to USC Nanostructure Materials
Devices Laboratory
Home >>

Welcome to NMDL!

     We are a multi-disciplinary group driven by curiosity and testable ideas that draw upon multiple traditional disciplines ranging from physics, chemistry, materials science, biochemistry, biology (cell and molecular), applied math, scientific computation / simulations, and biomedical, chemical, and electrical engineering to investigate some of the most challenging inter-disciplinary issues involving semiconductor materials and devices.

     Currently, our focus is on realizing on-chip scalable integrated quantum nanophotonic systems. As evident, "quantum" nanophotonic systems exploit the rules of quantum mechanics for information sensing, imaging, communication, and processing beyond what laws of classical physics allow. Targeted areas of applications range from quantum imaging (i.e. spatial resolution determined by the Heisenberg uncertainty principle), metrology, quantum repeaters for long-distance secure communication, and quantum computing.

     Check our latest news. [Click Link]

Current Focus: A paradigm for quantum optical circuits

     The long-sought goal of on-chip integrated solid-state quantum photonic systems for information processing continues to be elusive owing to the lack of a platform comprising spatially-ordered arrays of on-demand single photon sources of adequate photon emission characteristics buried in a matrix with planar surface. To this end, we have taken a major step forward by exploiting an approach to spatially-selective synthesis of semiconductor single quantum dots (SQD, Fig. 1(a), red region is the QD on mesa top) that holds considerable promise in spectral uniformity and single photon emission purity for addressing the challenge as captured in the different panels of Figure 1 (b)-(d). Such single quantum dot single photon source array has been planarized in GaAs (translucent layer in Fig. 1(e)) which enables the deterministic integration of such single photon source with light manipulating units in its surroundings to create interconnection and hence circuits.

Figure 1 (a) SEM of arrays of single mesas containing the SQD on mesa top (schematic indicates location of SQD marked in red on mesa along with a magnified SEM image of single mesa bearing QD). (b) color-coded image of emission wavelength of the SQDs in the 5X8 array with like-color circles the ones emitting within 0.2nm (c) Histogram of the spectral emission wavelength of SQDs in the 5X8 array indicating uniformity < 1.8nm. (d) Two photon coincidence count versus time between the count for pulsed excitation showing a value < 0.01 for zero time delay, revealing a single photon purity of > 99.5%. Such source arrays offer high potential for realizing on-chip integrated quantum optical circuits.(e) Schematic of the demonstrated SQDs array in planarized GaAs matrix ready for on-chip integration with light control units.

Getting the single photon to do something useful:

     Check our current focus. [Click Link]

Scope of Efforts:

     We utilize (lab facility) a unique suite of material / quantum nanostructure synthesis techniques (ranging from cutting-edge vapor phase to solution chemistry based) with in-situ and real-time growth monitoring and control at the atomic layer scale, structural examination [high-resolution transmission electron microscopy, ex-situ and in-situ atomic force and scanning tunneling microscopy], Quantum optical examination [high-resolution photoluminescence(HRPL), time-resolved HRPL, time-corrected photon studies in Hanbury Brown and Twiss (HBT), unbalanced Mach–Zehnder interferometer and Hong-Ou-Mandel (HOM) interferometer], and electrical and opto-electronic (photocurrent) characterization. We utilize custom-designed state-of-the-art quantum optical instrumentation to probing the quantum optical behavior at the single photon level establishing single photon emission statistics (sub Poissonian) and purity, determining photon indistinguishability, and two-photon interference-the basic phenomena that underlie quantum information.


    We are constantly on the look-out for "a few good students". If you have a strong undergraduate degree in science or engineering are self-driven, curious, communicative, committed to PhD, and your passion to learn greater than fear of walking unknown territory, then contact Professor Madhukar: Email, and Professor Zhang: Email. We are the place for you!

Back to top

Home| Major Projects| Members| Research| Lab & Facilities| Publications| Location| Links| Gallery
Copyright © 2007 Nanostructure Materials and Devices Laboratory, USC Viterbi School of Engineering