We demonstrate a double-layer Si 3 N 4 multi-ring resonator system, where an S-bend waveguide is cross-coupled with a ring cavity loaded with two sub-ring resonators. The device performance is ...analyzed by using the transfer matrix method. The alignment-error-induced device performance variations are also discussed. The measured spectra coincide well with the simulated results. The device has high tuning flexibility and more design freedom with two sub-rings placed above the ring cavity. The spectrum profile can also be tuned by changing the cross-coupling coefficient. A heater placed above the resonator can shift the resonant wavelength effectively.
The authors report their latest results on II-VI intersubband all-optical switches in which the 10 dB absorption saturation energy is lowered to ~2.0-2.2 pJ for 1.55-1.58 mum by decreasing the ...thickness of the active layer and increasing the refractive index difference between the core layer and the cladding layers in waveguides. Such low saturation energies greatly improve the switching performance. <7 pJ pump energy at 1520 nm is sufficient for realizing 10 dB switching operation at 1566 nm (switching energy: ~0.7 pJ/dB). To the best of our knowledge, these switching energy and saturation energy values are the lowest reported ones for such ultrafast intersubband all-optical switches at telecommunication wavelengths.
Ultrafast all-optical cross phase modulation (XPM) was enhanced in the InGaAs/AlAsSb coupled quantum wells using new InAlAs coupling barrier. Furthermore, a high XPM efficiency of 0.15 rad/pJ, which ...is approximately three times as large as that of a previous sample with the AlAs coupling barrier, was obtained by realizing the strong optical confinement in a narrower waveguide. From the analysis of the quantum levels and the measurement of the absorption spectra, the enhanced XPM efficiency was suggested to be contributed by the refractive index dispersion of the interband transition that was modulated by the intersubband transitions (ISBTs). This large XPM efficiency is expected to give a higher performance in Mach-Zehnder interferometer-type ultrafast all-optical switch.
We have detected a cyclotron resonance signal of the electrons induced by an external photoexcitation in an undoped ZnSe/BeTe type-II quantum well. The experimental spectra have also been well ...reproduced by the dielectric function (Drude) model. The photo-induced electron density is estimated at 1 × 1012 cm−2.
CdS/ZnSe multiple quantum wells (MQWs) shows very strong photoluminescence at low temperatures. The strong photoluminescence (PL) arises from the interface localization of the type-II excitons. A ...systematic study was attempted on the exciton density dependence of magneto-PL behavior up to 53 T by using a pulse magnet. We obtained a strong excitation density dependence of the type-II exciton Bohr radius trapped in interface roughness potentials.
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