Ultrafast all-optical switching at an optical communication wavelength has been investigated by utilizing an intersubband transition (ISBT) of II–VI-based multiple quantum wells (MQWs) fabricated in high-mesa waveguide devices. The waveguide structure consists of a CdS∕ZnSe∕BeTe MQW core layer and two top and bottom ZnMgBeSe quaternary cladding layers grown by molecular beam epitaxy on a (001) GaAs substrate. A marked increase in waveguide transmittance was observed only for transverse-magnetic-polarized subpicosecond pulse with increasing incident pulse energy at λ=1.57μm, indicative of the ISBT absorption saturation. The pulse energy necessary for a 10dB transmittance increase is as low as 13.3pJ for a waveguide device with 2.7μm mesa, and the saturation pulse energy can be even further reduced by employing a narrower mesa structure. Ultrafast gate switching within a time window of 0.56ps was also demonstrated with pump pulse at λ=1.57μm and probe pulse at λ=1.63μm in this waveguide device.
PACS 42.65. Pc, 78.67.De Ultrafast all-optical switching at optical communication wavelength has been investigated by utilizing an intersubband transition (ISBT) of II -VI-based multiple quantum wells (MQWs) fabricated in high-mesa waveguide devices. At first, we have achieved λ ~ 1.55 µm ISBT absorption in (CdS/ZnSe)/BeTe QWs. The QWs consists of Cl-doped CdS/ZnSe well and BeTe barrier. The ISBT optical nonlinearity in the wafer sample exhibits sub-ps relaxation time and sub-pJ/µm 2 saturation energy, indicating a promising characteristic for high-speed switching. The waveguide device fabricated consists of a CdS/ZnSe/BeTe MQWs core layer and two top and bottom ZnMgBeSe quaternary cladding layers. Ultrafast gate switching within a time window of 0.56 ps was demonstrated with pump pulse at λ = 1.57 µm and probe pulse at λ = 1.63 µm in this waveguide device.
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