9:00 AM - MQ02.03.04
Aluminum Gallium Arsenide Photonic Waveguides for 780 nm Optical Delivery for Quantum Sensors Based on Ultra-Cold Atoms of Rubidium
Jessica Maclean1,Mark Greenaway2,Richard Campion1,Mark Fromhold1,Chris Mellor1
University of Nottingham1,Loughborough University2
An on-chip approach to optical delivery for portable quantum sensors is described. The optical design, epitaxy, nanofabrication and measurement of polarisation-maintaining, deep-etched aluminium gallium arsenide (AlxGa(1-x)As) waveguides for near-infra-red 780 nm light was achieved, in an analogous approach to earlier work at (1300-1550) nm wavelengths . Material characterisation techniques were developed to infer improved optical quality and reduced optical loss intrinsic to the material, grown by Molecular Beam Epitaxy (MBE). High, continuous-wave optical power densities were guided with low polarisation noise and photonic waveguide performance was stable over time. The optical loss was measured to be below 4.3(±0.4) dB cm-1 corresponding to an attenuation coefficient, α, of 1.0 (±0.08) cm-1 for single mode waveguides and demonstrating improved performance data . The polarisation extinction ratio was better than −19 (±1) dB for orthogonal polarisations.
These novel components illustrate the feasibility of passive photonic integrated circuits for the 780 nm wavelength. Future work will investigate the optical switching properties of these structures. The ultimate aim of the work is the creation of waveguide-based photonic circuits for compact cold atom sensors based on the D2 hyperfine transition of 87Rb at 780.24 nm . Further applications include free-space short-wave communications, hybrid quantum systems  and epitaxial structures transparent to shorter wavelengths for other cold atom species and trapped ions. To this end, recent experiments examined device functionality as a function of wavelength.
 Heaton, J.M., Bourke, M.M., Jones, S.B., Smith, B.H., Hilton, K.P., Smith, G.W., Birbeck, J.C.H., Berry, G., Dewar, S.V. and Wight, D.R., “Optimization of Deep-etched, Single-mode GaAs / AlGaAs Optical Waveguides using Controlled Leakage into the Substrate”, Journal of Lightwave Technology, 17(2), 267-281 (1999).
 Maclean, J.O., Greenaway, M.T., Campion, R.P., Pyragius, T., Fromhold, T.M., Kent, A.J., Mellor, C.J., “III-V semiconductor waveguides for photonic functionality at 780 nm” Proc. SPIE 8988, Integrated Optics: Devices, Materials, and Technologies XVIII, 898805 (2014)
 Bongs, K., Malcolm, J., Ramelloo, C., Zhu, L., Boyer, V., Valenzuela, T., Maclean, J., Piccardo-Selg, A., Mellor, C., Fernholz, T., Fromhold et al., “iSense: A Technology Platform for Cold Atom Based Quantum Technologies” Optics InfoBase Conference Papers [1-55752-995-7] (2014)
 Gleyzes, S., El Amili, A., Cornelussen, R.A., Lalanne, P., Westbrook, C.I., Aspect, A., Esteve, J., Moreau, G., Martinez, A., Lafosse, X., Ferlazzo, L., Harmand, J. C., Mailly, D. and Ramdane, A., "Towards a monolithic optical cavity for atom detection and manipulation," European Physical Journal D, 53(1), 107-111 (2009).
Acknowledgements: We should like to thank Dr M.C. Rosamond and Prof. E.H. Linfield for expertise in Electron Beam Lithography at the School of Electronic and Electrical Engineering, University of Leeds, UK. This work was supported by the Engineering and Physical Sciences Research Council [grant number SM-30535 EP/M013294/1] through the EPSRC UK Quantum Technologies Hub for Sensors and Metrology.