Room temperature passive mode-locked laser based on InAs/GaAs quantum-dot superlattice
- PDF / 298,811 Bytes
- 5 Pages / 595.28 x 793.7 pts Page_size
- 69 Downloads / 195 Views
NANO EXPRESS
Open Access
Room temperature passive mode-locked laser based on InAs/GaAs quantum-dot superlattice Mikhail Sobolev*, Mikhail Buyalo, Idris Gadzhiev, Ilya Bakshaev, Yurii Zadiranov and Efim Portnoi
Abstract Passive mode-locking is achieved in two sectional lasers with an active layer based on superlattice formed by ten layers of quantum dots. Tunnel coupling of ten layers changes the structural polarization properties: the ratio between the transverse electric and transverse magnetic polarization absorption coefficients is less by a factor of 1.8 in the entire electroluminescence spectrum range for the superlattice. Keywords: Mode-locking, Laser, Polarization, Quantum dots, Superlattice, In(Ga) As/GaAs
Background In recent years, intense efforts have been devoted to the studies of effects of tunneling coupling between electron states in semiconductor heterostructures with quantum dots (QDs), which offer much promise in the development of high-speed lasers [1], optical modulators [2], and amplifiers [3]. For optical amplifiers and modulators, it is desirable to have polarization-independent characteristics. Thus, dependencies of gain and absorption have been studied in quantum well structures [4] and QDs [5]. However, in standard uncoupled QD structures, the absorption coefficient at the lasing wavelength for transverse electric (TE)-polarized light differs by an order [2]. It is known that in structures with coupled QDs, the intensity of transverse magnetic (TM) polarization increases with the number of QD layers [2,5,6]. Direct current modulation of semiconductor lasers does not meet the needs of modern high-speed communication lines, so systems consisting of a laser and modulator are used. As more broadband alternative to the direct current modulation can be laser with integrated electro-optical modulator based on the Stark effect, high-speed performance of the Stark modulator is fundamentally limited by physical processes, namely, carrier escape from QDs and carrier removal from the p-n junction area. Because the same processes are crucial for the passive mode-locking (PML) regime, the modulation frequency ceiling can be determined by the largest feasible PML frequency in a laser * Correspondence: [email protected] Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg 194021, Russia
fabricated from the same structure. It should be noted that the implementation of two sectional PML lasers is technically easier than creating a high-speed modulator, because there is no need to eliminate parasitic capacitance and inductance. The modulation frequency ceiling can be determined by the largest feasible frequency of the of the PML regime in a laser fabricated from the same structure. In this communication, we report on a roomtemperature study a ten-layer system of tunnel-coupled In(Ga)As/GaAs QD. As shown in [7,8], the structure with ten tunnel-coupled layers of In(Ga)As/GaAs QDs exhibits the Wannier-Stark effect and is a quantum dot superlattice (QDSL). We have observed t
Data Loading...
