Ultrafast InGaAs/InGaAlAs multiple-quantum-well electro-absorption modulator for wavelength conversion at high bit rates

Abstract

A series of GaAsSb / GaAs/ AlGaAs samples with varying GaAs spacer width are studied by electric-field modulated absorption EA and reflectance spectroscopy and modeled using a microscopic theory. The analysis of the Franz-Keldysh oscillations of GaAs capping layer and of the quantum-confined Stark shift of the lowest quantum well QW transitions shows the strong inhomogeneity of the built-in electric field indicating that the field modulation due to an external bias voltage differs significantly for the various regions of the structures. The calculations demonstrate that the line shape of the EA spectra of these samples is extremely sensitive to the value of the small conduction band offset between GaAs and GaAsSb as well as to the magnitude of the internal electric field changes caused by the external voltage modulation in the QW region. The EA spectra of the entire series of samples are modeled by the microscopic theory. The good agreement between experiment and theory allows us to extract the strength of the modulation of the built-in electric field in the QW region and to show that the band alignment between GaAs and GaAsSb is of type II with a conduction band offset of approximately 40 meV.

All-optical devices and signal processing for all photonic network

“…Both XAM and XPM induced in an EAM can be utilized for wavelength conversion. There are several previous reports concerning to pure XAM type EAM-based wavelength converter [12][13][14][15][16][17][18][19]. In this paper, an advanced type EAM-based wavelength converter, in which XPM is utilized by delayedinterferometer (DI), is investigated.…”

“…Unlike electrical 3R transponders (Optical-Electrical-Optical conversion), all-optical regenerators (OpticalOptical conversion) are likely to be less complex and require fewer high-speed opto-electronic and electronic components since they use optical signal processing, which leads to a small footprint and low power consumption, even if they operate at high bit rate. So far, various types of all optical switching devices utilizing optical nonlinearity of fibers [1][2][3][4][5], semiconductor optical amplifiers (SOAs) [6][7][8][9][10][11], and electro-absorption modulators (EAMs) [12][13][14][15][16][17][18][19]. Alloptical regeneration performance depends on the physics of each optical nonlinearity, which has a respective trade-off between the switching speed and the required optical power for switching.…”

Optimising negative chirp of an electroabsorption modulator for use in high‐speed optical networks

“…In this respect Figure 1(c) illustrates a negative chirped pulse which leads to pulse compression and therefore when such pulses travel through a singlemode fiber the pulse-width broadening can be compensated due to this negative chirp. Blue-shifted structures have been proposed for such modulators [22,23] since these remain stable at optimum operating conditions [24].…”

Spatially nonlocal effects on optical absorption properties in coupled quantum wells with an applied electric field

“…In the past few years, linear and nonlinear optical properties of low-dimensional quantum systems, such as quantum wells (QWs), quantum dots (QDs), and other nanostructures, have attracted much interest from theoretical and applied aspects. [1][2][3][4][5][6][7][8][9][10] Most of the previous studies on the optical properties of the low-dimensional systems, however, are based on the local optical response theory, in which optical fields inside nanostructures are considered as invariant, and consequently optical susceptibility tensors ← → χ (ω) are used to characterize optical properties of nanostructures. For example, in 2008, Chen et al studied the second-order nonlinear optical susceptibility in asymmetric coupled quantum wells (CQWs), and showed a very large second-order optical susceptibility by optimizing the structural parameters.…”