Mode-locking Instabilities for High-Gain Semiconductor Disk Lasers Based on Active Submonolayer Quantum Dots

Abstract

Submonolayer quantum dots (SML QDs) combine the large gain cross section of quantum wells (QWs) with the potential benefits of a stronger confinement. We demonstrate here an optically pumped vertical external-cavity surface emitting laser (VECSEL) based on active SML QDs. The ultrafast SML QD VEC-SEL is optimized for passive modelocking with an intracavity semiconductor saturable absorber mirror (SESAM) around 1030 nm. We have achieved the highest cw output power of 11.2 W from a QD-based VECSEL to date. With a birefringent filter inside the VECSEL cavity, we obtain a tuning range of 47 nm centered at 1028 nm. Any attempt to passively modelock the VECSEL with a QW SESAM reveals fundamental limitations. The intrinsically higher linewidth enhancement factor of SML QDs compared to QWs or self-assembled Stranski-Krastanov QDs is further increased at higher pump powers. Our experiments confirm prior theoretical predictions that a strong amplitude-phase coupling can destabilize cw modelocking and introduce chaotic multiple pulse fluctuations.

Advances in wide-tuning and narrow-linewidth external-cavity diode lasers

“…The basic structure is shown in Figure 5. Commonly used optical filter components include the Fabry-Perot (FP) cavity etalon [28], acoustooptic tunable filter (AOTF) [29,30], electro-optic tunable filter [31], birefringent filter (BRF) [32,33], interference filter (IF) [34,35], micro-electro-mechanical systems (MEMS) tunable optic filter [36], alldielectric thin film Fabry-Perot filter (AFPF) [37], guided-mode resonator filter (GMRF) [38], and liquid crystal film [39]. By choosing different optical filters, the wavelength-tuning and linewidth-narrowing laser mechanisms also change accordingly.…”

Spatio-Temporal Modeling and Device Optimization of Passively Mode-Locked Semiconductor Lasers

“…Semiconductor quantum wells are an ubiquitous choice for semiconductor gain chips due to their mature fabrication technology, which provides great flexibility and has lead to excellent results [KEL06, TIL15, GAA16, LAU18]. Nonetheless, semiconductor gain chips have also been realized with Stranski-Krastanov quantum dots [HOF08a, HOF11a, NEC19, FIN20] and submonolayer quantum dots [ALF18]. If the active region is further more grown into a p-i-n scheme and contacted, the gain chip can also be electrically pumped [JIA93a, MUL05a, CHI20].…”

Submonolayer Quantum-Dot Based Saturable Absorber for Femtosecond Pulse Generation

“…In recent years, submonolayer (SML) QDs have emerged as an alternative to SK QDs and have been shown to outperform SK QDs in both lasers and detectors. [7][8][9] With regard to their use as a saturable absorber, SML QDs have several advantages over SK QDs including higher confinement, higher absorption and a faster gain recovery. 9,10 Moreover, tuning the emission wavelength of SK QDs or QWs in the range of 950-1300 nm involves using highly strained QWs 11 or complex changes to the QD active region including adding strain reducing layers, 12 growing on metamorphic buffers 13 or embedding QDs in different QW layers.…”