Distinguished Lecturer Program

The continuing growth in demand for bandwidth (from residential and business users), necessitates significant research into new advanced technologies that will be employed in future broadband communication systems. Two specific technologies which are becoming increasingly important for future photonic systems are wavelength tunable lasers and optical frequency combs. Although these topics have been studied for over two decades their significance for the development of future ultra-high capacity photonic systems has only recently been fully understood. Wavelength tunable lasers are currently becoming the norm in optical communication systems because of their flexibility and ability to work on any wavelength. However, as their operating principles are different to standard single mode lasers they can effect how future systems will operate. For example as optical transmission systems move towards more coherent transmission (where the data is carried using both the intensity and phase of the optical carrier), the phase noise in these tunable lasers will become increasingly important. Optical frequency combs also have many applications for future photonics systems, and for telecommunications they can be used to obtain the highest spectral efficiency in optical transmission systems by employing the technology of optical frequency division multiplexing (OFDM) that has been widely employed to increase spectral efficiency in wireless systems. Wavelength tunable lasers and optical frequency combs are thus topics at the leading edge of current photonics systems research, and their detailed understanding promises new applications in all-optical signal processing, optical sensing and metrology, and specifically telecommunications. This talk will focus on the development and characterization of various wavelength tunable lasers and optical frequency combs, and then outline how these sources can be employed for developing optical transmission systems and networks which make the best use of available optical spectrum.

The most demanding challenges in diagnostics require detection of low concentrations of virus, proteins, or nucleic acids within test samples comprised of only a few droplets of test sample.  The idea of a “liquid biopsy” in which biomarkers for disease can be detected in a single droplet of blood from a fingerstick will enable diagnostic tests to be performed with much less pain, inconvenience, and invasiveness compared to tissue biopsy or a blood draw performed by a phlebotomist.   The potential to perform routine (daily) ultrasensitive diagnostic tests using simple assay protocols and inexpensive detection instruments is the driving force behind “personalized” cancer treatment that is directed towards specific mutations as they evolve, the ability to adjust antiviral therapy in response to viral load, and the ability to detect/identify deadly pathogens.
This presentation will summarize recent efforts in the Cunningham group to develop point-of-care, digital-resolution technologies for sensing pathogens and molecular disease biomarkers in bodily fluids.  Utilizing the unique properties of photonic crystal nanostructured surfaces, we have developed approaches for enhancing the output of photon emitters, such as semiconductor quantum dots (QD), by >100x, enabling individual emitters to be detected with high contrast.  We are applying photonic crystal enhanced fluorescence (PCEF) of QD tags towards detection of circulating mRNA and miRNA that are correlated with specific mutations involved in prostate cancer.  In parallel, we have developed a new form of biosensor microscopy, called NanoParticle Photonic Resonator Absorption Microscopy (NP-PRAM) in which plasmonic gold nanoparticles serve as resonant-matched nanoantennas that, when attached to a photonic crystal surface, enabling single nanoparticles to be visualized with high contrast.  We are developing novel assay methods and detection instruments that enable NP-PRAM to quantify femtomolar concentrations of miRNA biomarkers, with a simple, rapid test that does not require chemical amplification.  We are also applying NP-PRAM to detection intact HIV particles as a direct approach to viral load monitoring.  While PCEF and NP-PRAM detection systems are intended for the laboratory bench, we are also developing mobile sensing platforms that utilize a smartphone’s internal camera as the detection instrument, in conjunction with a handheld special-purpose cradle.  We are developing microfluidic chips that perform nucleic acid amplification assays, in which the amplification process can be dynamically imaged to enable counting of pathogenic DNA.

Two-dimensional (2D) Van der Waals materials have emerged as a very attractive class of optoelectronic material due to the unprecedented strength in its interaction with light. In this talk I will discuss approaches to realize quantum photonic devices by integrating these 2D materials with microcavities, and metamaterials. I will first discuss the formation of strongly coupled half-light half-matter quasiparticles (microcavity polaritons) [1] and their spin-optic control [2] in the 2D transition metal dichacogenide (TMD) systems. Prospects of realizing condensation and few photon nonlinear switches using Rydberg states in TMDs will also be discussed. Following this, I will discuss the broadband enhancement of light-matter interaction in these 2D materials using photonic hypercrystals [3, 4] and chiral metasurfaces. Finally, I will talk about room temperature single photon emission from hexagonal boron nitride [5] and the prospects of developing deterministic quantum emitters using them through strain engineering [6]. The realization of room temperature single photon emitters and few photon nonlinear switches using 2D materials presents an attractive direction for robust next generation quantum photonic technologies.

As various systems and networks in our society grow larger and more complex, analysis and optimization of such systems are becoming increasingly important. Such tasks are classified as combinatorial optimization problems, which are generally difficult to solve with current digital computers. It is well known that combinatorial optimization problems can be converted to ground-state-search problems of the Ising model, a theoretical model for the interacting spins. Recently, several approaches to find solutions to the Ising model using artificial spin systems have been studied intensively. A coherent Ising machine (CIM) is one of such systems in which degenerate optical parametric oscillators (DOPO) are used as artificial spins. By using a long-distance (typically 1 km) fiber cavity that contains a phase sensitive amplifier based on a periodically poled lithium niobate waveguide, we can generate thousands of DOPO pulses multiplexed in time domain. Since a DOPO phase only takes either 0 or  at above threshold, we can stably express an Ising spin with a DOPO by allocating phase 0 () as spin up (down). The “spin-spin interaction” can be implemented by using a measurement-feedback scheme, with which we can effectively realize mutual injection of lights among thousands of DOPO pulses. The networked DOPOs are most likely to oscillate at a phase configuration that best stabilize the whole network, which gives the solution to the given Ising problem. Based on this scheme, we realized a CIM with fully-coupled 2000 DOPO pulses, by which we could find good solutions to 2000-node combinatorial optimization problems in less than 100 microseconds. In the talk, I will detail the basic principle and the experimental details of the CIM, as well as our effort for finding its applications.   

The past decade has seen accelerated progress in III-V semiconductor infrared photodetector technology. The advent of the unipolar barrier infrared detector device architecture has in many instances greatly alleviated generation-recombination (G-R) and surface-leakage dark current issues that had been problematic for many III-V photodiodes.   Meanwhile advances in a variety type-II superlattices (T2SLs) such as InGaAs/GaAsSb, InAs/GaSb, and InAs/InAsSb, as well as in bulk III-V material such as InGaAsSb and metamorphic InAsSb, have provided continuously adjustable cutoff wavelength coverage from the short wavelength infrared (SWIR) to the very long wavelength infrared (VLWIR).   The confluence of these developments has led to a new generation of versatile, cost-effective, high-performance infrared detectors and focal plane arrays based on robust III-V semiconductors, providing a viable alternative to HgCdTe (MCT).

During the last 20 years, different nanomaterials have been applied in healthcare applications such as cancer imaging, lymph node mapping and brain diseases therapy. These nanomaterials can be engineered to serve as a platform for challenges in highly sensitive optical diagnostic tools, biosensors, and guided imaging and therapy. Nanomaterials surface can be decorated with functional biomolecules to selectively target specific sites in vitro and in vivo.  Importantly, they possess unique tunable spectral and optoelectronic properties, which have significant advantages for various biological applications such as tumor growth monitoring, single biomolecule detection, targeted drug delivery therapy, and control release of gene silencing materials. The flexibility and versatility of nanomaterials may provide the keys to answer important biological questions and ultimately improve diagnostics and therapy of human diseases. A synergistic combination of nanomaterials with biophotonics provides unprecedented opportunities to address many current challenges in disease diagnosis and therapy. For example, quantum dots, gold nanoparticles, gold nanorods, gold nanoshells, upconversion nanocrystals, iron oxide nanoparticles, carbon nanotubes, carbon dots, silica nanoparticles, aggregation-induced emission (AIE)-based nanoparticles, etc. are among the commonly investigated nanomaterials in biophotonics. The flexibility in optical and electronic tuning allows these nanomaterials to emit or scatter from visible to near-infrared (NIR) region, an essential characteristic for tailoring specific needs in biophotonic applications. In this talk, we will highlight the use of nanomaterials with different sizes, compositions, and shapes for biophotonic and nanomedicine applications (e.g. guided bioimaging, multimodal imaging, sensing, in vivo surgery, gene delivery, etc). Also, we will discuss important factors on designing bioconjugated nanomaterials for biophotonic applications as well as the future trend of using nanomaterials in the biophotonic and nanomedicine field. Certainly, the in vitro and in vivo nanotoxicity of nanomaterials will be one of the main challenges to be overcome if we would like/want to pursue in vivo biophotonic or nanomedicine technologies with nanomaterials. The toxicity assessment of nanomaterials in cell culture and animal models will be presented. This talk is intended to promote the awareness of past and present developments of nanomaterials in biomedical fields, the potential toxicity of nanomaterials, and the approaches to engineer new types of safe nanomaterials, whereby encouraging researchers to think about exciting and promising biophotonic and nanomedicine applications with nanomaterials in the near future.

Biophotonics is a multidisciplinary research frontier that employs light for medical diagnostics, bioimaging, biosensing, laser tissue engineering, and light activated therapy. It involves the study of light activated processes, from molecular, cellular to tissue levels. This talk, intended for multidisciplinary education, will include the following two major topics: biophotonic imaging techniques (e.g. imaging techniques, fluorescent markers, cellular imaging, multi-spectral imaging, imaging of soft and hard tissues, in vivo imaging), and engineering of optical biosensors for healthcare applications. For biophotonic imaging, the discussion will focus on fluorescence and optical coherence tomographic techniques. For example, confocal fluorescence microscopy and two-photon laser scanning microscopy are widely employed techniques for cellular, in vivo and ex vivo tissue imaging. The use of exogenous fluorophores as labeling agents will also be covered. This lecture will discuss the fluorophore characteristics as well as developments of new fluorophores for biophotonic imaging. Some cellular imaging examples will be presented where optical imaging is used to probe structures and functions of viruses, bacteria, and eukaryotic cells. Then imaging at the tissue level and in vivo imaging will be presented. The field of optical biosensors has become a topic of great interest due to the strong demand in rapid healthcare diagnostics and the worldwide concern of chemical and bioterrorism threats. These optical biosensors provide unique advantages, such as the ability to principally remote sensing with high selectivity and specificity and the ability to use unique biorecognition schemes. In this lecture, we will cover selected basic optical principles and various techniques utilized in biophotonic sensing. The discussion is intended to stimulate the interest of students or young researchers who want to expand their research career in this field. This lecture will conclude with some discussions of future directions of biophotonic imaging and sensing.