Photonics

Research Description

Group: Hornak (CSEE), Timperman (Chem.), Gannett (Pharmacy), Myers (Physics), Wu (MAE WVU).

Research Experiences: Students will use existing software to design biolayers for surface coverage and optimum physical coupling to device. They will also characterize the biolayer surfaces using atomic force microscopy. Students will also be trained to functionalize waveguide detection devices and perform optical measurements.

Evanescent Wave-Based Transduction – Integrated optical techniques exploiting the interaction of evanescent waves in waveguides with biolayers have received considerable attention as a means for molecular recognition. For example, we have recently demonstrated that a vertical stack of resonantly coupled slab waveguides can detect surface loadings of 0.2 nanograms/mm2 with an optimized limit of detection expected to exceed 0.1 picograms/mm. The integrated Stacked Planar Affinity Regulated Resonant Optical Waveguide (SPARROW) architecture shown in Figure 1 reduces fabrication and optical alignment complexity and our results achieved with ion assisted e-beam deposited alumina waveguides (Figure 2) indicate the potential for high operational stability and sensitivity necessary for field applications. The microfluidically addressed SPARROW testbed device will serve as a platform for exploration of the stated recognition applications and we anticipate leveraging its enabling components (waveguides, biolayers) in other building blocks and testbeds. The REU student participants will learn to fabricate and analyze data from our next target, a mixture of contaminant simulant (standard proteins and cell lysates of E. Coli) and anthrax simulant (Bacillus atrophaeus), that will be used to test the functionality of the device and evaluate performance of a single channel system. We will then use the testbed for exploration of the use of P450’s for detection of explosives and large molecule toxins. The participants will become acquainted with several microfluidic fabrication techniques, attachment of antibodies via surface functionalization, and will analyze data.

Photonic Crystal Mediated Transduction – The sensitivity of photonic crystal (PC) band structure and defect transmission states to refractive index changes either at planar boundaries of a 2-D crystal or at individual lattice sites, make these structures potentially attractive for integrated point detection biosensor devices. We have analyzed the optical transmission properties of Si and GaN semiconductor PCs as a function of defect cluster size and refractive index to identify design windows with viable fabrication dimensions and measurable spectral shifts for ranges of induced refractive index change of interest. We are in the process of fabricating PCs in these materials using e-beam lithography and enhanced lateral overgrowth techniques. The REU participants will learn to grow the GaN structures via MOCVD or MBE techniques and will help with their electrical and structural characterization. They will also learn to characterize the PC’s and analyze their spectral properties.

Integrated Spectroscopy – Using selective area growth (SAG) and the Metal Organic Chemical Vapor Deposition (MOCVD) method, 3-dimensional structures have been fabricated that can form microchannels (Figure 3) and attachment studies of molecules to the exposed crystallographic planes have begun. UV-Visible emitters and detectors have been fabricated from GaN, AlN and InN and their alloys. The REU participants will help measure the spectral response of the emitters and aid with the surface functionalization.