High temperature cavity polaritons in epitaxial Er2O3 on silicon

Abstract

Cavity polaritons around two Er 3+ optical transitions are observed in microdisk resonators fabricated from epitaxial Er 2 O 3 on Si͑111͒. Using a pump-probe method, spectral anticrossings and linewidth averaging of the polariton modes are measured in the cavity transmission and luminescence at temperatures above 361 K. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3109791͔On-chip optical interconnects with wavelength division multiplexing are being pursued as a low-power low-latency high-bandwidth alternative to metal interconnects.1 Significant research has focused on integrating optical gain material into the Si platform, with III-V wafer bonding to Si being the most successful candidate to date.2 In addition there is a long history of efforts to incorporate Er 3+ into Si material systems for light emission and optical gain. Erbium-doped fibers are the dominant amplifiers for telecommunications because of their high quantum efficiency and because the shielded Er 3+ 4f transition wavelengths are largely insensitive to temperature and the host matrix.3 However, the small gain coefficient of Er 3+ -doped materials is insufficient for dense microphotonic applications. 4 To compensate for erbium's small emission cross section, stoichiometric erbium compounds are potential alternatives that achieve Er 3+ densities 100 times greater than erbium's solubility limit in doped materials.5-8 The high density and weak inhomogeneous broadening of stoichiometric erbium crystals can intrinsically produce large dispersive resonances in the refractive index and vacuum-Rabi splitting of optical cavity modes. 9Rabi splitting and the associated cavity-polariton modes can be described as a consequence of linear dispersion or as nonperturbative coupling between the dipole͑s͒ and an optical cavity, while perturbative coupling to a single ion produces Purcell-enhanced emission.10 For rare-earth emitters, cavity polaritons have been observed around a single Er 3+ transition in an oxidized polycrystalline erbium layer, 11 but the effect was quenched at T տ 40 K. 12 We have previously shown that atomic layer epitaxy produces high quality single-crystal Er 2 O 3 films on silicon and offers the prospect of electrical injection through precisely controlled heterostructures.8 In this letter, we describe the spectroscopy of small mode-volume Er 2 O 3 microdisk resonators formed from this material, and we analyze the properties of high temperature ͑T Ͼ 361 K͒ cavity polaritons formed between the cavity's whispering-gallery modes ͑WGMs͒ and two Er 3+ transitions in the 1500 nm band.Analyzing the polariton response involves continuously tuning a cavity mode across the Er 3+ transitions. As a mode is shifted through an optical transition, the resonances anticross ͑i.e., the vacuum-Rabi splitting͒ and produce symmetric hybrid modes ͑i.e., the cavity polaritons͒, which appear in both the cavity transmission and photoluminescence ͑PL͒. In terms of cavity quantum electrodynamics ͑cQED͒, the fundamental quantity for cavity polaritons is the Ra...

Atomic layer deposition of Er2O3 thin films from Er tris-guanidinate and water: process optimization, film analysis and electrical properties

“…11,12 In addition, the lattice constant of Er 2 O 3 is twice as large as that of Si, 13 thus the growth of epitaxial Er 2 O 3 on Si substrates should be possible. 14,15 Physical vapor deposition (PVD) techniques that include among others, evaporation, molecular beam epitaxy (MBE), sputtering, etc. 16,17 and chemical coating techniques namely, chemical vapor deposition (CVD), 18 atomic layer deposition (ALD), 19 sol-gel deposition 20 and spin coating, 21 are the two major thin lm fabrication processes.…”

Energy Transfers between Er3+ Ions Located at the Two Crystalographic Sites of Er2O3 Grown on Si(111)

“…Erbium oxide (Er 2 O 3 ) has great potential as a light amplifier material in silicon photonics at telecommunications wavelengths. [1][2][3][4][5][6][7] This is because Er 2 O 3 contains a huge number of Er 3þ ions that emit light at 1.5-m wavelength and because of the lattice matching between Er 2 O 3 and Si substrate, which means defect-free Er 2 O 3 film can be grown on Si substrate. 2,3) A unit cell of Er 2 O 3 has symmetry T 7 h and contains 32 erbium ions, 24 at sites with C 2 symmetry and eight at sites with C 3i symmetry (Fig.…”

Energy levels and interaction between Er³⁺-ions located at the two crystalographic sites of Er₂O₃ grown on Si(111)

“…Erbium oxide (Er 2 O 3 ) has great potential as a light amplifier material in silicon photonics [1][2][3]. The unit cell of erbium oxide has symmetry T h 7 and contains 32 erbium ions, 24 at sites with C 2 symmetry and 8 at sites with C 3i symmetry (see Fig.…”

“…Recently, Gruber et al precisely determined the energy levels of Er 3+ -ions, including Stark-splittings due to the crystal field, located at the C 2 and C 3i sites from calculations, and assigned the origin of photoluminescence (PL) peaks on the basis of the site-dependent energy levels [2]. On the other hand, Michael et al have succeeded in creating cavity polaritons using a micro-disk cavity of Er 2 O 3 on Si(111) at a high temperature (T > 361 K) and suggested the existence of asymmetric energy transfer or diffusion between the two sites on the basis of the Gruber's PL peak assignments, They also pointed out some issues with respect to enhancing the intensity of cavity polaritons in the Er 2 O 3 cavity; for example, understanding the carrier dynamics at the C 2 and C 3i sites and interactions between the sites and suppression of non-radiative transfer between them [3].…”