Ultra‐Short‐Pulse QD Edge‐Emitting Lasers

Abstract

IntroductionHigh-power, electrically pumped edge-emitting monolithic semiconductor lasers based on InAs/GaAs quantum dots (QDs) offer significant advantages including ultra-short pulse generation due to ultrafast gain and absorption recovery [1, 2] and emission energies in the near-infrared spectral range [3]. Owing to their inherent inhomogeneous QD size distribution, a broadening of gain and absorption profile is realized, leading to broadband wavelengths emission. This inhomogeneous broadening together with ultrafast carrier dynamics is particularly advantageous for ultrafast applications including the generation, propagation, and amplification of subpicosecond optical pulses with high pulse peak power [4] and the generation of spectrally tunable emission [5,6]. The reduced density of states allows for the exploitation of QD materials in harnessing spectral versatility in novel dual-state emission. The spectral coverage of these QD lasers perfectly matches a wide range of relevant biophotonic applications including nonlinear excitation imaging techniques. The unique combination of efficient light generation, ultrafast carrier dynamics, and broadband gain bandwidth can deliver exclusive advantages in ultrafast microelectronic scale components, thereby stimulating major advances in ultrafast science and technology.In order to enable initial device design and optimization of novel pulse generating QD lasers and amplifiers, a new and efficient theoretical framework is presented as briefly introduced in Section 2.2. This framework takes into account specifically fundamental aspects associated with QD gain materials and allows for modeling of both continuous-wave (CW) emission and ultra-short pulse generation via passive mode-locking (PML) and subsequent amplification. The obtained understanding is applied to technologically realize and optimize QD laser and amplifier structures with particularly broad gain bandwidth enabling spectral versatility through broadband tunability of CW-emission generated in the visible wavelength range by second-harmonic-generation (SHG). This broad wavelength range is accessible only by the QD features as presented in Section 2.3. Novel functionalities based on the broad gain bandwidth and sophisticated QD laser design are explored inThe Physics and Engineering of Compact Quantum Dot-based Lasers for Biophotonics, First Edition. Edited by Edik U. Rafailov.

Dynamics of temporally localized states in passively mode-locked semiconductor lasers

“…Hence, we obtain the following PDE system The Eqs. (14)(15)(16) can be understood as a generalization of the Haus master equation to large gain and absorption per pass. Indeed, one of the main advantages of the model of [36] is the consideration of large gain and absorption per round-trip, a feature that is still preserved by the exponential terms in Eqs.…”

“…Indeed, one of the main advantages of the model of [36] is the consideration of large gain and absorption per round-trip, a feature that is still preserved by the exponential terms in Eqs. (14)(15)(16). The longitudinal variable (z) identifies as a fast time variable and represents the longitudinal evolution of the field within the round-trip.…”

“…We recall that the steady states of Eqs. (14)(15)(16) are actually the periodic solutions of Eqs. (1)(2)(3).…”

“…Notice that in the case where the domain is sufficiently large so that if the field intensity is zero, the proper conditions for G and Q are of the Robin type and are simply Eqs. (15)(16) setting E = 0…”

“…Note that in the case of Eqs. (14)(15)(16), the solution appears upon increasing g as a saddle-node bifurcation (SN) and not a saddle-node of limit cycle (SNL) as for Eqs. (1-3).…”