Coherent Anti-Stokes Raman Scattering Microscopy
Coherent Anti-Stokes Raman Scattering (CARS) microscopy has been demonstrated to be a powerful tool for non-invasive, chemical imaging of biological systems. Our research thrust into CARS microscopy was initiated by our hypothesis that a single femtosecond laser source used in conjunction with nonlinear PCF can generate both Pump and Stokes beams - an elegant approach that would maintain high imaging resolution and eliminate the cost and complexity associated with aligning two independent signals. Unlike previous proof-of-principle implementations, a nonlinear PCF with two closely lying zero dispersion wavelengths is used to generate the Stokes pulse. This is critical for practical CARS microscopy as single ZDW PCFs strongly amplify noise in the pump laser source at frequencies which would significantly degrade image quality and makes it impossible to use for imaging. Our prototype CARS microscope not only satisfies requirements of high quality CARS imaging and multiplex CARS spectroscopy, but also has the advantage of being a very cost effective approach. In addition, biomedical laboratories that already have a Ti:sapphire laser, can readily extend their multimodal microscopy platform to include CARS microscopy, by using our PCF based approach.
Femtosecond Fiber Laser
Femtosecond lasers are particularly well suited to address the needs of the health care industry (dentistry, neurosurgery, otosurgery), due to its inherent ability to ablate with high power, precision, and directionality and minimum collateral damage. Our investigation into high-power femtosecond lasers was initiated by our hypothesis that the use of PCF technology would obviate the need for bulk optics and enable an exclusively fiber-based device – making femtosecond lasers compact, stable and thus more ubiquitous. The novelty of this project arises from the attempt to construct an exclusively fiber-based, high-power, ultra-short pulse (femtosecond) laser platform using Photonic Crystal Fiber (PCF) technology. This requires deep investigation of interplay between nonlinear and dispersion effects and other pulse reshaping mechanisms inside both the laser cavity and the subsequent amplifier. Such an understanding is critical in tailoring the dispersion characteristics of the photonic crystal fiber to achieve stable and short pulses. Another important aspect that is being addressed is the stability of desired mode-locked regimes under influence of the cavity dispersion and pump parameters. Short-pulse lasers are particularly well suited to address the needs of the health care industry, with specific applications in dentistry, ophthalmology, neurosurgery, and otosurgery.
Photonic Crystal Fiber Based Biosensors
Non-labeled optical biosensing has come to commercial fruition in various forms such as surface plasma resonance, resonating mirrors and grating couplers. These techniques all rely on sensing changes in the evanescent field. Consequently, those changes are small and a lot of care must be taken to improve the sensitivity and the signal to noise ratio of the biosensor. Our research focuses on the investigation of an integrated optical biosensor for label-free detection of biomolecules using hollow-core photonic crystal fibres (PCF). In hollow-core PCFs, the main mode, rather than the evanescent field, interacts with the biomolecules, and a more pronounced spectral variation is obtained. Our efforts to-date have focused on investigating a robust technique to fill hollow core photonic crystal fibers.
Metro Edge/Access Networks
We are currently witnessing resurgence in the telecommunications sector. The current growth is fueled by end-user demand for more bandwidth. For the first time, both consumer and business services are driving bandwidth demand with equal force, which augurs well for a sustained period of growth. With a popular bundle already offered by advanced service providers, including high-definition TV, video on demand etc., the required bandwidth per user can be up to 100Mb/s. Legacy SONET-based metro rings and copper-based access networks are incapable of supporting such bandwidth requirements. As such, current metro edge and access networks represent the last major bottleneck to deliver this bandwidth for residential and business users, and represent an impediment to the growth of a range of digital applications. The metro edge and access portion of the network requires new architectures that are capable of supporting multiple services over one integrated network which is scalable and fault tolerant. This research seeks to find a comprehensive scalable and adaptable solution that connects the end-user with the network core. The research centers on two key hypotheses: a) The foundation for adaptability in the metro edge networks of the future will be the Reconfigurable Optical Add/Drop Multiplexer (ROADM), which will allow for transported services to be switched optically, remotely and in real-time, and b) in the access portion of the network, fiber to the home will become the preferred technology for green-field deployments and passive optical networks (PONs), specifically Hybrid TDM/WDM(Time-Division Multiplexed & Wavelength-Division Multiplexed) PONs will emerge as the optimum architecture to ensure scalability.
