Master Thesis Defense: Nikolaos Andrianopoulos

On-Chip Frequency Conversion in Suspended GaAs Waveguides

Quantum frequency conversion is a well-documented effect of nonlinear optics, in which the nonlinear dielectric polarization of a material describes the response to an incident optical field. The result is the generation of new secondary fields of different frequencies, enabling a plethora of applications. Nowadays, this process has resurfaced to overcome the limitations that arose with the actualization of a fiber-based quantum network. Namely, the task is to convert the wavelength of the emitted single photons to the C-Band in order to avoid significant attenuation over long-distance communication. In this work, the first steps towards experimental realization of frequency conversion in suspended GaAs waveguides are presented. This included, creating and analyzing the design of second harmonic generation and difference frequency generation circuits using modal phase matching.

For the latter, a mechanically tunable version is examined. Apart from simulation efforts, a fiber coupling setup is established to direct mid-IR light to the chip. A sample with the acquired simulation parameters is fabricated and tested. In fact, transmission measurements are demonstrated for shallow-etched grating couplers targeted for λ = 1000nm TM, λ = 1550nm TE and λ = 2000nm TE modes at room and cryogenic temperatures. Finally, preliminary results of second harmonic generation are showcased at T = 297K, where conversion efficiency of η = 2.38% is achieved for an interaction length of L = 0.512mm.