Charlton J. Chen

Temperature-Tuning of Near-Infrared Monodisperse Quantum Dot Solids at 1.5 µm for Controllable Förster Energy Transfer

We present the first time-resolved cryogenic observations of Forster energy transfer in large, monodisperse lead sulfide quantum dots with ground-state transitions near 1.5 microm (0.8 eV), in environments from 160 K to room temperature. The observed temperature-dependent dipole-dipole transfer rate occurs in the range of (30-50 ns) (-1), measured with our confocal single-photon counting setup at 1.5 microm wavelengths. By temperature-tuning the dots, 94% efficiency of resonant energy transfer can be achieved for donor dots. The resonant transfer rates match well with proposed theoretical models.

Digital resonance tuning of high-Q∕Vm silicon photonic crystal nanocavities by atomic layer deposition

We propose and demonstrate the digital resonance tuning of high-Q/Vm silicon photonic crystal nanocavities using self-limiting atomic layer deposition. Control of resonances of 122 plusmn 18 pm per hafnium oxide atomic layer is achieved.

Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation

We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

Deterministic tuning of slow-light in photonic-crystal waveguides through the C and L bands by atomic layer deposition

We demonstrate digital tuning of the slow-light regime in silicon photonic-crystal waveguides by performing atomic layer deposition of hafnium oxide. The high group-index regime was deterministically controlled (redshift of 140±10 pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110±30 pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive postfabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

Observations of interior whispering gallery modes in asymmetric optical resonators with rational caustics

We propose asymmetric resonant cavities with rational caustics and experimentally demonstrate interior whispering gallery modes in monolithic silicon mesoscopic microcavities. These microcavities demonstrate unique robustness of cavity quality factor against roughness Rayleigh scattering. Distinct resonant families and directional radiation from interior whispering gallery modes are observed experimentally using angle-resolved tapered fiber measurements and near-field images, which can be used for microcavity laser and cavity quantum electrodynamics applications.

Digital resonance tuning of high-Q/V m silicon photonic crystal nanocavities by atomic layer deposition

We propose and demonstrate the digital resonance tuning of high-Q/Vm silicon photonic crystal nanocavities using self-limiting atomic layer deposition. Control of resonances of 122 plusmn 18 pm per hafnium oxide atomic layer is achieved.

Selective tuning of silicon photonic crystal cavities via laser-assisted local oxidation

Ultra-high-Q nanocavity resonance tuning by laser-assisted thermal oxidation of silicon is demonstrated by using a 532 nm continuous wave laser. The resonance is blue-shifted by >;2nm. The quality factor remains >;200,000.

Negative refraction and nonlinearities in photonic bandgap nanostructures

Recent important advances in subwavelength nanostructures offer extraordinary control over the properties of light. We can now manipulate the propagation, storage, and generation of light, as well as practically prescribe light-matter interaction based on first-principles. Photonic crystals, in particular, offer the unique ability for arbitrary control of dispersion as well as ultrahigh quality factor (Q) and modal volume (Vm) nanocavities. In this talk, we will present, to our knowledge, the first near-field experimental observations of near-infrared subwavelength imaging in negative refraction photonic crystals, as well as discuss our efforts in enhanced nonlinearities in photonic crystal nanocavities.

Weak coupling of monolayer lead sulfide quantum dots to silicon photonic crystal cavities at near-infrared wavelengths

We present experimental analysis of weak coupling for monolayer lead sulfide quantum dots coupled to silicon photonic crystal cavities between 4K and room temperature, as well as power-saturation measurements of dots at 4K.

Observation of efficient Förster energy transfer at 1.5 μm through temperature-tuning of monodisperse quantum dot solids

We present time-resolved cryogenic observations of Forster energy transfer in large, monodisperse lead sulphide quantum dots with ground state transitions near 1.5 mum (0.8 eV), in environments from 160 K to room temperature.