Silicon photonic crystal cavities at near band-edge wavelengths

Abstract

We demonstrate photonic crystal L3 cavities with resonant wavelength around 1.078 μm on undoped siliconon-insulator, designed to enhance spontaneous emission from phosphorus donor-bound excitons. We have optimised a fabrication recipe using readily available process materials such as polymethyl methacrylate (PMMA) as a soft electron-beam mask and a Chemical Vapour Deposition (CVD) grown oxide layer as a hard mask. Our bilayer resist technique efficiently produces photonic crystal cavities with a quality factor (Q) of ∼ 5, 000 at a wavelength of 1.078 μm, measured using cavity reflection measurements at room temperature. We observe a decrease of Q as the cavity resonance shifts to shorter wavelengths (Q 3, 000 at wavelengths < 1.070 μm), which is mostly due to the intrinsic absorption of silicon.Defect spins in solid state materials are attractive candidates for scalable implementation and integration of quantum information processing (QIP) 1,2 , metrology 3-5 and communication systems 6,7 . For example, coherent spins in diamond and their interactions with photons have been exploited for optically-mediated entanglement of matter-based systems 8,9 . While nitrogenvacancy (NV) centres in diamond possess many attractive features that have underpinned key quantum information/communication demonstrations, some of the optical properties are sub-optimal (broad phonon sideband and spectral broadening) while thin-film growth and fabrication processes still need to be perfected. For such reasons, other materials systems combining excellent optical and spin memory properties with mature fabrication techniques are being explored to develop effective spin-photon interfaces 2,10-12 . Amongst these have been vacancies in silicon carbide (SiC) and defects in silicon (Si). Silicon and SiC host defects and impurities with long spin coherence time 11,13 and narrow linewidth emission of photons 11,14-16 and permit coherent optical control of spins 17 . These features, combined with the mature industrial techniques in manufacturing and on-chip integration, make such spins attractive for efficient multiqubit coupling and realising large scale QIP systems. However, strong non-radiative processes in silicon-based host materials restrict fluorescence efficiency 15,18,19 and indistinguishable single photon generation 11,20 , thus limiting the potential of optical interfaces with most defects in silicon. This issue can, in principle, be addressed by engineering the local photonic environment in the host material: for example, incorporating photonic structures such as circular Bragg resonators (CBRs) 21 or photonic crystal cavities (PCCs) 22,23 can enhance photon emission and collection efficiency by several orders of magnitude, potentially allowing it to compete with non-radiative processes such as Auger recombination.Enhanced light-matter interaction in PCCs 22 has been demonstrated for various quantum emitters including NV centers in diamond 23 , rare-earth-doped crystals 12 and quantum dots in GaAs 24 , with observed improvements in the...

Hybrid Integrated Nanophotonic Silicon-based Structures

“…6(b) depicts the PL behavior of the fabricated s-SWNTs. It is seen that the obtained solution contains only semiconducting type with the chirality of (8,6) and (8,7) [44]. In addition, the PL emission happens around 1280 nm for the (8,7) chirality s-SWNTs which matches well with the resonance wavelength of the cavity.…”

“…Silicon photonics has now played a dominant role in photonic technology [3]. In group IV silicon photonics, photonic crystal (PhC) structures [4][5][6] have been widely exploited in order to take the benefit from slow-light mode in such a periodic modulation geometry of the refractive index [7]. With the band gaps from dielectric lattices, PhCs are of great interest for applications in optical sensors [8], multi/demultiplexers [9], quantum information processing [10].…”

Photon-mediated entanglement scheme between a ZnO semiconductor defect and a trapped Yb ion

“…Due to intrinsic bandedge absorption, the high quality factor region in Fig. 3 may not be achievable at D 0 X-D 0 transition 24 , thus low mode volume cavities with moderate quality factors should be targeted. While nanophotonic fabrication in ZnO is relatively immature compared to other quantum defect host crystals, small mode volume ZnO nanowire cavities have enabled UV lasers 25 and ZnO cavities fabricated by focused ion beam milling 26 , a method that has been used to achieve high cooperativity in rare-earth doped systems 27 , exhibit quality factors up to 1000.…”

Advancements and Perspectives in Optical Biosensors

“…Whispering gallery mode (WGM) reprinted from ref ( 53 ) under a Creative Commons Attribution 4.0 International License, 2015. 2D photonic crystal array reprinted with permission from ref ( 54 ). Copyright 2019 AIP Publishing.…”