Ultra-broadband Optical Gain Engineering in Solution-processed QD-SOA Based on Superimposed Quantum Structure

Abstract

In this work, the optical gain engineering of an ultra-broadband InGaAs/AlAs solution-processed quantum dot (QD) semiconductor optical amplifier using superimposed quantum structure is investigated. The basic unit in the proposed structure (QDs) is designed and fabricated using solution-processed methods with considerable cost-effectiveness, fabrication ease, and QDs size tunability up to various limits (0.1 nm up to the desired values), considering suitable synthesis methods. Increasing the number of QDs, the device can span more than 1.02 μm (O, C, S, and L bands) using only one type of material for all QDs, and is not restricted to this limit in case of using more QD groups. Also, it can manipulate the optical gain peak value, spectral coverage, and resonant energy for customized optical windows, among which 1.31 μm and 1.55 μm are simulated as widely-applicable cases for model validation. This makes the device a prominent candidate for ultra-wide-bandwidth and also customized-gain applications in general. Variation impact of homogeneous and inhomogeneous broadenings, injection current and number of QD groups on optical gain are explained in detail. Besides proposing a design procedure for implementation of an ultra-broadband optical gain using superimposed QDs in solution-processed technology, the proposed gain engineering idea using this technology provides practically infinite bandwidth and an easy way to realize. By introducing this idea, one more step is actually taken to approach the effectiveness of solution process technology.

High-speed and high-contrast two-channel all-optical modulator based on solution-processed CdSe/ZnS quantum dots

“…Therefore, the size of each QD group related to the desired wavelengths can digress from the central value of the radius resulting in the distribution of energy levels called IHB. Considering these effects of QDs size non-uniformity on the absorption spectra of the MD, the IHB of energy levels is modeled by the Gaussian function in which the QDs ensemble is divided into 2 M + 1 groups of identical dots with an energy interval of Δ E =1 meV 38 – 41 . …”

“…Here, is the interband or intersubband transition energy of the most probable size of QDs ( M + 1 -th QD group), n is the index related to the number of active modes, the index of i is equal to 1 for channel-1 and 2 for channel-2, and ξ 0 is QD coverage in which the Full-wave Half Maximum (FWHM) is equal to 34 , 38 . On the other hand, intrinsic effects such as pressure or temperature on all QDs lead to the HB of energy levels which homogeneously impact all groups.…”

“…It is well known that such interaction leads to a temperature-dependent linewidth. The HB is modeled by a Lorentzian function with as its FWHM which is considered as 20 meV at room temperature 38 , 42 . …”

Superimposed Quantum Dots: Emerging Optoelectronics

“…Using solutionprocessed technology different groups of these materials are synthesized and mixed and using spin coating sprayed on the surface. Considering precise optical and electrical analysis, it is shown that the proposed structure has more than 2.5eV bandwidth [3].…”

“…If we use the superimposition of QDs, we can realize multi wavelength lasers in a single cavity [1,2]. The ultra-broadband semiconductor optical amplifiers can be implemented by this idea [3]. Multi wavelength photodetector with multi-electrical output is another most important application that can be realized using this idea [4].…”