Nanophotonics Research Group at Koç University focuses on experimental and theoretical photonics. On the experimental side, we work on the nanofabrication of waveguide based plasmonic structures primarily for use in optical communications applications. To that end, we utilize the electron beam lithography system at Sabancı University Nanofabrication Center (SUNUM), Koç University Clean Room and Koç University Surface Science and Technology Center (KUYTAM).

We have an opto-electronics characterization lab at the engineering department. In this lab, we build optical setups to measure the properties of the samples that we fabricate. Our setups are built on low vibration optical tables, and we utilize wavelength tunable lasers.

In order to design these photonic structures, we model and numerically simulate the devices. The high performance computer cluster at Koç University helps us run large simulations within a reasonable amount of time. The main simulation techniques we use are FDTD and FEM.

There are two main research directions at the moment.

# Plasmonics

Through the use of the optical properties of metals at visible and infrared wavelength ranges, it becomes possible to design waveguides that are deep subwavelength in cross section. As a result, one can concentrate light into volumes far smaller than the wavelength (i.e. \( \lambda^3 \)). In the microwave regime—in your cell phones for instance—microwave signals with wavelengths on the order of centimeters are routinely focused to deep subwavelength circuits. There are strong parallels between the techniques used in microwave and optics applications.

# Quantum Optics

For communications based on quantum states of matter, where quantum mechanical properties such entanglement lead to new and exciting possibilities, waveguides and transmission lines are needed to carry the quantum states, \( \lvert\psi\rangle \), from one point in the circuit to the other. Therefore, the interaction of quantum states of matter in the form of qubits, embedded in a waveguide geometry, and the light pulses used to control the state of the qubit is worthwhile studying. We analyze the scattering of light pulses from qubits embedded in waveguides to come up with new effects and designs with potential uses in quantum communications.

## Funding Sources

Our research is funded by TUBİTAK and Koç University.