Subpicosecond saturation of intersubband absorption in (CdS∕ZnSe)∕BeTe quantum-well waveguides at telecommunication wavelength

Abstract

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.

Estimation of effective mass and subbands in multi‐quantum wells using polarized light irradiation

“…In order to design a device consisting of multiple quantum wells, it is important to understand of nonparabolic nature of electron subbands of the MQWs structure [2,3]. We report that the optical interband transitions of In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As MQWs including 20-nm-wide well clearly appeared on photocurrent spectra with polarized light source.…”

Growth and properties of wide bandgap MgSe/ZnxCd1−xSe multiple quantum wells for intersubband devices operating at short wavelengths

“…However, the fundamental aspect of p-type doping is still in severe challenge because of strong self-compensation in II-VI wide bandgap semiconductors. The recent development of II-VI CdS/ZnSe [1], (CdS/ZnSe)/BeTe [2], and ZnCdSe/ZnCdMgSe [3] quantum wells (QWs) has opened up application in mid-and near-infrared (IR) region using the intersubband (ISB) transitions within the conduction band of the QW, i.e., unipolar devices such as IR photodetectors, quantum cascade lasers (QCL), as well as ultrafast all-optical switches (UOS). Previously, it has been proposed that the II-VI-based QWs are the promising candidates for UOS at near-IR wavelength region due to the enhanced electron-phonon interaction [2].…”

Photodetectors based on intersubband transitions using III-nitride superlattice structures

“…Material systems with large enough conduction-band offsets to accommodate intersubband transitions at these relatively short wavelengths include InGaAs/AlAsSb [11], (CdS/ZnSe)/BeTe [12], GaInNAs/AlAs [13], and GaN/Al(Ga, In)N QWs [14][15][16][17][18][19][20][21]. In the case of III-nitride heterostructures, their conduction-band offset-around 1.8 eV for the GaN/AlN system [17,20,[22][23][24] -is large enough to develop intersubband devices operating in the fiber-optics transmission windows at 1.3 and 1.55 μm.…”