J. Warga

Enhanced light emission in photonic crystal nanocavities with Erbium-doped silicon nanocrystals

Photonic crystal nanocavities are fabricated in silicon membranes covered by thermally annealed silicon-rich nitride films with Erbium-doped silicon nanocrystals. Silicon nitride films were deposited by sputtering on top of silicon on insulator wafers. The nanocavities were carefully designed in order to enhance emission from the nanocrystal sensitized Erbium at the 1540nm wavelength. Experimentally measured quality factors of ∼6000 were found to be consistent theoretical predictions. The Purcell factor of 1.4 was estimated from the observed 20-fold enhancement of Erbium luminescence.

Electroluminescence from silicon-rich nitride/silicon superlattice structures

Luminescent silicon-rich nitride/silicon superlattice structures (SRN/Si-SLs) with different silicon concentrations were fabricated by direct magnetron cosputtering deposition. Rapid thermal annealing at 700 °C resulted in the nucleation of small amorphous Si clusters that emit at 800 nm under both optical and electrical excitations. The electrical transport mechanism and the electroluminescence (EL) of SRN/Si-SLs have been investigated. Devices with low turn-on voltage (6 V) have been demonstrated and the EL mechanism has been attributed to bipolar recombination of electron-hole pairs at Si nanoclusters. Our results demonstrate that amorphous Si clusters in SRN/Si-SLs provide a promising route for the fabrication of Si-compatible optical devices.

Sensitized erbium emission from silicon-rich nitride/silicon superlattice structures

Erbium-doped silicon-rich nitride/silicon superlattice structures were fabricated by direct magnetron cosputtering deposition on Si substrates. Rapid thermal annealing resulted in the nucleation of small amorphous Si clusters, which efficiently sensitize 1.54μm emission via a nanosecond-fast nonresonant energy transfer process, providing an alternative route toward the fabrication of Si-compatible devices based on Er sensitization.

Carrier dynamics and erbium sensitization in silicon-rich nitride nanocrystals

Ultrafast two-color pump-probe measurements, time-resolved photoluminescence (TRPL), and photoluminescence excitation measurements were performed on Si-rich nitride (SRN) and Er doped SRN (Er:SRN) nanocrystals samples. Transient absorption data were compared with picosecond TRPL and excited state absorption cross (ESA) sections σ were measured at different wavelengths. Our data show that σ in Er:SRN, which is approximately 10−19cm2 at 1.54μm, does not scale with the ∼λ2 behavior predicted by simple free carrier absorption models. Finally, our data demonstrate that in Er:SRN efficient energy transfer to Er ions occurs on the nanosecond time scale with reduced ESA compared to Er-doped oxide-based systems.

Enhanced stimulated Raman scattering in silicon nanocrystals embedded in silicon-rich nitride/silicon superlattice structures

In the last few years several strategies have been developed to engineer efficient light sources and amplifiers in Si-based materials, with the aim to demonstrate a convenient path to monolithic integration of optical and electronic devices within the mainstream Si technology In particular, light amplification by Stimulated Raman Scattering (SRS) in silicon waveguides has been recently demonstrated despite intrinsic limitations related to the nature of the bulk Si materials have been pointed out . The narrow-band (105 GHz) of stimulated Raman gain in Si limits its applicability in the context of Si photonics, and makes it unsuitable for its use in broad band division multiplexing (WDM) applications, unless expensive multi-pump schemes are implemented. Additionally, Raman amplification in Si is a small effect. Therefore, in order to build a laser based on stimulated Raman effects in Si, very high power intensity and very low absorption losses are required. Finally, Raman gain in Si is further reduced by the competing nonlinear effect of two-photon absorption. This effect generates electron-hole pairs, which remain excited in the sample for a long time (micro to milliseconds) and lead to strong absorption at both the pump and signal frequencies.

Enhanced Stimulated Raman Scattering in silicon nanocrystals embedded in silicon-rich nitride/silicon superlattice structures

In the last few years several strategies have been developed to engineer efficient light sources and amplifiers in Si-based materials, with the aim to demonstrate a convenient path to monolithic integration of optical and electronic devices within the mainstream Si technology In particular, light amplification by Stimulated Raman Scattering (SRS) in silicon waveguides has been recently demonstrated despite intrinsic limitations related to the nature of the bulk Si materials have been pointed out . The narrow-band (105 GHz) of stimulated Raman gain in Si limits its applicability in the context of Si photonics, and makes it unsuitable for its use in broad band division multiplexing (WDM) applications, unless expensive multi-pump schemes are implemented. Additionally, Raman amplification in Si is a small effect. Therefore, in order to build a laser based on stimulated Raman effects in Si, very high power intensity and very low absorption losses are required. Finally, Raman gain in Si is further reduced by the competing nonlinear effect of two-photon absorption. This effect generates electron-hole pairs, which remain excited in the sample for a long time (micro to milliseconds) and lead to strong absorption at both the pump and signal frequencies.

Silicon nanocrystals in silicon nitride structures: Towards efficient light emission under optical and electrical pumping

In this paper, we will discuss light emission, Er sensitization and electroluminescence from small (2 nm-diameter) Si nanoclusters embedded in silicon nitride/Si superlattice structures fabricated by direct co-sputtering on Si substrates. In particular, we will show efficient Er emission sensitization via controllable non-radiative energy transfer and we will demonstrate enhanced electroluminescence from superlattice-based electrical devices. Our results demonstrate that small Si clusters embedded in silicon nitride-based matrices provide alternative routes towards the fabrication of Si-compatible optical devices based on Er sensitization.

Enhanced erbium emission in photonic crystal nanocavities

We fabricated photonic crystal nanocavities to enhance erbium (Er) emission in silicon rich nitride nanocrystals. We observed experimental quality factors of ~6000 and 20-fold enhancement, in agreement with numerical calculations of the Purcell effect.