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.

CMOS SPADs have appeared in 2003 and soon have risen to the status of image sensors with the creation of deep-submicron SPAD technology. The format of these image sensors has expanded from 8x4 pixels of our first LIDAR in 2004 to 512x512 pixels of recent time-resolved cameras, and the applications have literally exploded in the last three years, with the introduction of proximity sensing and portable telemeters. The current promise is that SPAD based sensors will be in every smartphone by 2018 and in every car by 2022. But SPAD technology was born for scientific applications and in scientific applications it will continue to innovate. For instance, super-resolution microscopy has already benefitted from SPAD imagers and this trend is expected to continue well in the next decade. In addition, other time-resolved techniques, such as time-of-flight PET, NIROT, FLIM, FRET, useful in many biomedical imaging modalities, will become more and more accurate and less and less expensive thanks to the scalability of CMOS technologies. With the introduction of SPADs in 3D CMOS IC technologies in 2014, SPAD based imagers will be more compact, while at the same time more advanced techniques and functionalities will be available. In the talk I will give a technical and economic perspective on SPADs and SPAD imagers, and a vision for the medium to long term.

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.

The generation of optical quantum states on an integrated platform will enable low-cost and accessible advances for quantum technologies such as secure communications and quantum computation. We demonstrate that integrated quantum frequency combs (based on high-Q microring resonators made from a CMOS-compatible, high refractive-index glass platform) can enable, among others, the generation of pure heralded single photons, cross-polarized photon pairs, as well as bi- and multi-photon entangled qubit and quDit states over a broad frequency comb covering the S, C, L telecommunications band, constituting an important cornerstone for future practical implementations of photonic  quantum information processing.

The transmission capacity of conventional single mode fiber has been exponentially increased in the past few decades by a variety of advanced technologies including the expansion of the optical bandwidth of transmission window and enhancement of the spectral efficiency. However, the capacity of existing standard single mode fiber may no longer satisfy the growing capacity demand and is approaching its fundamental limit around 100 Tb/s owing to the limitation of amplifier bandwidth, nonlinear noise, and fiber fuse phenomenon. To further increase the fiber capacity or spatial capacity, space division multiplexing (SDM) has attracted intensive research efforts as a solution to the problem of saturation of the capacity of conventional single mode fibers. In SDM transmission systems, several different signals are transmitted simultaneously by providing multiple spatial paths with cost effective ways. Multicore fibers (MCFs) are a kind of SDM fibers for transmitting several different signals simultaneously by providing multiple spatial paths in an optical fiber. MCFs for SDM transmission can be divided into two categories. The first type is a weakly-coupled MCF, in which each core is used as an individual waveguide with sufficiently low interference between neighboring cores. The second type is a strongly-coupled MCF, in which the crosstalk between cores is intentionally introduced by decreasing the core-to-core distance, resulting in the core density improvement.   In this talk, the state-of-the-art of MCFs as a future large capacity long-distance transmission media for SDM is presented. Advantages, technical challenges, and prospects of both the weakly-coupled MCFs and strongly-coupled MCFs are explained, and spatial density perspective of MCFs for SDM transmission is discussed.

I will review the configurations in which an optical system undergoes dynamical instabilities and how the resulting so-called dynamical complexity drives applications in e.g. secure optical communications, random number generation fro cryptography, brain-inspired optical computation, high-resolution imaging and sensing. Concepts such as deterministic chaos, entropy and fractal that originate from applied mathematics are of increasing interest in photonics. Harnessing these concepts has enabled significant improvement of laser properties including modulation bandwidth, multimode emission and beam quality. On the other hand, the availability and ease of operation of lasers in a wide range of configuration make them a convenient test bed for exploring basic concepts of nonlinear dynamics. The cross-fertilization of disciplines allows for identifying analogies with phenomena such as extreme events well known in economy and hydrodynamics or neuronal computation and regulatory networks in biology. In addition, nonlinear light-matter interaction yields interesting spatio-temporal instabilities arising from either modulation instability (leading to optical patterns) or from soliton interactions. In this field, the resurging interest in nonlinear propagation of exotic light beams such as accelerating waves and vortices has motivated analogies with dynamics in rotating or curved reference frames including gravitational effects.

Communications networks and systems are seeing extreme increase in network traffic which is growing at the tremendous rate of 30% per year. It is estimated that the energy and cost requirements will increase tenfold in coming ten years. But this progress is not sustainable from ecological and economic point of view. However, this information explosion can be dealt with, using integration of very small photonic components on very high density Photonic Integrated Circuits (PICs). The technological advancements in PICs have made them a popular choice for components of next generation networks. Silicon being the evident choice due to its high availability, mature fabrication technology, and low cost has attracted the researchers to explore the possibilities of integrating the fast photonics components on a chip. At the same time, the unique material properties and direct bandgap, group III-V materials have huge potential in applications like laser, amplifiers, modulators and detectors. Due to robustness, flexibility, reliability and performance of PICs, many commercial solutions are now available for a variety of applications.

The days of ultra high speed communication and immense internet network demand the most efficient system to be engaged for this purpose. The whole world especially the telecom and broadband sector is shedding their old technologies very fast and switching to the era of optical communication. But till date, the prominent barrier to be crossed is the O-E-O conversions. The data through optical cables are still limited to the frontier stage of data exchange where the data is fed to the circuitry in electrical domain and the switching takes place through traditional transistors and CMOS based circuits only. The research in this domain is recently most happening topic and has been adopted by all the large players from pioneer institutes round the globe. So the field in its nascent but highly classified state, demands contributions of all sorts. The basics and the principles are yet to be reconsidered to come up with brilliant ideas for a change in approach. Optimization of each and every aspect of the technology is welcomed by the global scientific society.

Research methodology, Concept & literatures, formulation of problems/solutions, Importance of professional networks/societies, Opportunities.

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).

The mid-infrared (mid-IR) spectral range (loosely defined as the wavelengths between 3-30µm) has become a burgeoning and dynamic field of research for a variety of technologically vital applications.  Nonetheless, the development of the mid-IR optical infrastructure still trails behind that of the shorter, more mature, telecom and visible wavelength ranges.  This can be viewed as a drawback of mid-IR photonics research (more expensive, limited efficiency components and materials), or alternatively, as an opportunity.  In particular, the mid-IR provides a design space where a wide range of engineered and intrinsic light matter interactions can be harnessed to develop a new generation of optical materials.  In this talk, I will discuss recent work developing novel optoelectronic, all-dielectric, plasmonic and phononic devices and structures for mid-IR wavelength applications.  In particular, I will discuss the range of phenomena which can be leveraged to demonstrate unique designer materials and mid-IR devices. I will cover work on new types of mid-IR sources, ENZ materials and waveguides, mid-IR filters, engineered thermal emitters, and designer plasmonic materials and structures for strong absorption and subwavelength confinement.  Ultimately, I will make an effort to demonstrate that the mid-IR provides a unique materials playground for the exploration, and implementation, of a range of light-matter interactions.

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.