Charlton J. Chen

Learn More
Self-starting of passively mode-locked lasers with fast saturable absorption is studied. Our basic assumption is that the lasers will self-start when cw operation is unstable and mode-locked operation is stable. We start with a standard model, closely related to the Ginzburg – Landau equation, that is valid when the change in the time variation of the laser(More)
We propose and demonstrate the digital resonance tuning of high-Q / V m silicon photonic crystal nanocavities using a self-limiting atomic layer deposition technique. Control of resonances in discrete steps of 122± 18 pm/hafnium oxide atomic layer is achieved through this postfabrication process, nearly linear over a full 17 nm tuning range. The cavity Q is(More)
The crystal structure of the photoprotein obelin (22.2 kDa) from Obelia longissima has been determined and refined to 1.7 A resolution. Contrary to the prediction of a peroxide, the noncovalently bound substrate, coelenterazine, has only a single oxygen atom bound at the C2-position. The protein-coelenterazine 2-oxy complex observed in the crystals is(More)
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 140Ϯ 10 pm per atomic layer͒ without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential(More)
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(More)
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(More)
We present the first time-resolved cryogenic observations of Fö rster energy transfer in large, monodisperse lead sulfide quantum dots with ground-state transitions near 1.5 µm (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(More)
In this letter, we propose the use of the newly developed corrugated quantum well infrared photodetectors ͑C-QWIPs͒ for polarization detection. The corrugated structure, which serves as an optical coupler as well as the polarization-sensitive component, is in this case directly created into the active region of the QWIP, therefore dispensed with the need of(More)
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(More)
  • 1