Research Terms
Researchers at the University of Central Florida have developed a process using nonlinear optical procedures to exactly reverse the propagation direction and phase variation of a beam of light. Until now, purely optical techniques have been used to realize optical phase conjugation (OPC), which is used for many applications, ranging from laser medicine to imaging to communications. However, the classical approach is limited by its inability to adapt the phase conjugation quickly and precisely. Now, using the UCF electronic optical phase modulation (E-OPC) process, optical transmission through complex media such as biological tissue, traditionally limited by multiple light scattering, can now be realized.
In laser medicine, this technique can fluorescently label a cell (such as a cancer cell) and use the advantages of OPC to selectively interact with these cells without effect to surrounding tissues. These actions can be thermal, mechanical or chemical, all mediated by the back propagated optical beam. This process can also be applied to defense applications where the light/electromagnetic waves come from objects of interest. Using this method, it is possible to use OPC to illuminate, interfere or destroy the object that was illuminated.
Technical Details
The UCF invention combines electronic and optical phase conjugation. Typically, there is an efficiency limitation due to phase conjugation relying on nonlinear optical processes. However, the invention resolves this issue by introducing electronic phase conjugation (E-OPC) as a complementary method. OPC defines a special relationship between two coherent optical beams propagating in opposite directions with reversed wavefronts and identical transverse amplitude distributions. The two-step process of E-OPC begins by measuring the wavefront of the signal wave (fluorescence) using a reference beam and charge-coupled device (CCD) arrays so that both quadratures of the wavefront are measured. The measured wavefront is then conjugated in the electrical domain and applied to a spatial modulator array that generates the phase modulated beam to back propagate to the sample. E-OPC removes the wavelength and efficiency limitation as CCDs respond over a broad spectrum and provides the unique ability to remove aberrations due to a turbid medium.
Researchers at the University of Central Florida have invented a technique for capturing and reconstructing images of phase objects with greater accuracy and quality than conventional optical diffraction tomography (ODT) inversion methods. Example objects include transparent samples such as biological cells, tissues and optical fibers with high contrast, complicated structure, or sizeable optical path difference (OPD).
With such targets, most non-iterative tomographic reconstruction methods adopt the weakly-scattering assumption, which degrades the imaging quality. In contrast, the UCF Iterative Optical Diffraction Tomography (iODT) method, with its algorithmic process, reconstructs such objects and those with complex permittivity with better accuracy, fast convergence, and sub-wavelength resolution.
Technical Details: The UCF iODT approach improves the reconstruction quality of multiply scattering two-dimensional and three-dimensional phase objects by iteratively reducing the error between the fields diffracted by the reconstructed object and the true fields measured experimentally or obtained through simulations of phantoms for all illumination angles.
In one example application, the first iteration of iODT provides an estimate of the unknown refractive index (RI) profile using the standard linearized ODT inversion algorithm. Subsequent iterations improve the estimate by applying a perturbative correction based on differences between the fields diffracted by the imperfectly reconstructed object and the measured fields diffracted by the true object. The process includes translating this error into an error in the associated complex phase and then computing a correction to the reconstructed object function. The method uses the Rytov approximation in every iteration as it is more applicable to the perturbative function, as opposed to the original function. Since the magnitude (distribution) of the perturbative function becomes smaller (smoother) at higher iterations, the Rytov approximation improves. Further, as expected, the number of phase vortices in the perturbative complex phase is gradually reduced in a self-healing process as the iterations converge. In essence, the embodied iterative algorithm is a nonlinear reconstruction based on perturbative expansion, much like a higher-order Born or Rytov expansion for forward propagation.
Partnering Opportunity: The research team is looking for partners to develop the technology further for commercialization.
Stage of Development: Prototype available.
Optical Fiber Refractive Index Profiling by Iterative Optical Diffraction Tomography, Journal of Lightwave Technology, Vol. 36, No. 24, December 15, 2018
The University of Central Florida invention is a quantum key distribution (QKD) system that overcomes a general class of security attacks adopting faked-state photons, as in the detector-control and, more broadly, the intercept-resend attacks. The unconditional security offered by quantum key distribution (QKD) relies on the laws of quantum physics. The laws dictate that any attempt by an adversary to know about the secret key would inevitably introduce disturbance that alerts the legitimate parties. This ultimate information-theoretic security has been proved for idealized devices. In practice, however, real-life components of QKD systems may deviate from these idealized models or encounter new scenarios offering vulnerabilities that the adversary might use. This invention uses commercial single-photon detectors (SPDs) in a user's receiver. Thus, it is impossible for an intruder to avoid triggering the alert detectors, no matter what faked state of light the intruder uses.
Partnering Opportunity
The research team is seeking partners for licensing and/or research collaboration.
