Comparison of dynamic properties of InP/InAs quantum-dot and quantum-dash lasers

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 109, 161104 (2016) and may be found at https://doi.org/10.1063/1.4965846.The dynamic properties of MOVPE grown InP/InAs quantum-dot and quantum-dash lasers, showing identical structural design, emitting in the C-band are investigated and compared to each other. Based on the small-signal measurements, we show the impact of the density of states function on the cut-off frequency, being larger for quantum dots at low currents, and reaching similar values for quantum dashes only at higher currents. The large-signal measurements show error-free data transmission at 22.5 and 17.5 Gbit/s for the quantum-dot and quantum-dash lasers.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP7/EU/264687/Postgraduate Research on Photonics as an Enabling Technology/PROPHE

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 106, 031114 (2015) and may be found at https://doi.org/10.1063/1.4906451.Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP7/EU/264687/Postgraduate Research on Photonics as an Enabling Technology/PROPHE

Highly efficient non-degenerate four-wave mixing under dual-mode injection in InP/InAs quantum-dash and quantum-dot lasers at 1.55 μm

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 107, 191111 (2015) and may be found at https://doi.org/10.1063/1.4935796.This work reports on non-degenerate four-wave mixing under dual-mode injection in metalorganic vapor phase epitaxy grown InP/InAs quantum-dash and quantum dot Fabry-Perot laser operating at 1550 nm. High values of normalized conversion efficiency of −18.6 dB, optical signal-to-noise ratio of 37 dB, and third order optical susceptibility normalized to material gain χ(3)/g0 of ∼4 × 10−19 m3/V3 are measured for 1490 μm long quantum-dash lasers. These values are similar to those obtained with distributed-feedback lasers and semiconductor optical amplifiers, which are much more complicated to fabricate. On the other hand, due to the faster gain saturation and enhanced modulation of carrier populations, quantum-dot lasers demonstrate 12 dB lower conversion efficiency and 4 times lower χ(3)/g0 compared to quantum dash lasers.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP7/EU/264687/Postgraduate Research on Photonics as an Enabling Technology/PROPHE

InAs/GaAs excited state quantum-dot transmitters operating under long-delayed optical feedback

© Copyright 2016 Society of Photo‑Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, and modification of the contents of the publication are prohibited.In this work, the sensitivity to external optical feedback of two different InAs/GaAs QD Fabry-Perot (FP) lasers is investigated under long cavity regime. The first, which has a 1.5 mm-long cavity, emits on the GS while the second one, which is 1 mm long, radiates solely on the ES transition. The results indicate that for the same bias level, the ES laser presents a larger sensitivity to external feedback, the critical level being under 1% versus above 9% for the GS laser. In particular, the ES laser exhibits a route to chaos such that the first destabilization occurs for a lower feedback strength than for the GS laser.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Modekopplung, dynamische und nichtlineare Eigenschaften der MOVPE-gewachsenen Quantenpunkt- und Quantenfaden-Halbleiterlasern

Die eingereichte Arbeit untersucht die Eigenschaften von auf InP basierenden optischen Quantenpunkt- (quantum dot, QDot) und Quantenfaden (QDash)- Halbleiterlasern. Der erste Teil der Arbeit widmet sich den Grundlagen und Vorteilen der QDot/QDash Laser. Im zweiten Teil der Arbeit wird die Herstellung und Entwicklung der QDot/QDash Laser gezeigt. Der dritte Teil der Arbeit widmet sich den systematischen Experimenten der QDot/QDash Einsektions- und Zweisektions- (modegekoppelter-) Lasern. Erstmalig wird demonstriert, dass die MOVPE-gewachsenen passiv modegekoppelter QDot Laser Ex-Facette optische Pulse mit Halbertsbreiten im ps Bereich und Pulsewiederholfrequenz von ~33 GHz emitieren. Die Modenkopplungsfrequenz der passiven modegekoppelten Laser kann in 300-400 MHz Bereich angepasst werden, wobei in Einsektions modegekoppelten Lasern die Modenkopplungsfrequenz 10-fach weniger abstimmbar ist. Die Einsektions modegekoppelten QDot/Qdash Laser zeigen ein erheblich geringeres Zeit-Bandbreiten-Produkt und ein auf Autokorrelations-Messung basierendes Lorentzprofil des Pulses. Die Einsektions modegekoppelten Laser zeigen keine Ex-Facette Pulseemission und somit ist eine externe Komprimierung des Pulses erforderlich. Die Messung der Pulsform und Pulsphase der Einsektions modegekoppelten QDot/Qdash Laser mittels eines FROG Aufbaus (Frequenzaufgelösten Autokorrelation) zeigt einen nonlinearen Chirp und Intensiäts-Oszillationen. Zusammengefast, Qdot aund Qdash basierte passiv Zweisektionsslaser weisen gleiche Modekopplungs- und dynamische Eigenschaften auf. Im Gegensatz dazu, zeigen Einsektionsmodegekoppelte QDot/Qdash Laser zeigen unterschiedliche dynamische Eigenschaften; Grund dafür ist die Konkurenz zwischen sog. Supermode. Im vierten Teil der Arbeit wird Vierwellenmischung basierte Wellenlängenkonversion in der Kavität der Qdot und Qdash Laser untersucht. 1490-µm lange Qdash Laser demonstrieren eine normalisierte Konversionseffizienz von -18.6 dB mit einem Signal-zu-Rausch-Verhältnis von 37 dB und 3 THz Frequenzverstimmung, wobei 1250-µm lange Qdot laser 12 dB und 14.7 dB niedrigere Konversionseffizienz und Signal-zu-Rausch-Verhältnis aufweisen. Der Grund dafür ist, dass Vierwellenmischung in Qdash Laser von Zwei-Photonen-Absorption, einer schnellen Sättigung des Gewinns und erhöhter Ladungsträgermodulation profitieren kann. Im Vergleich mit Qdot Laser, eignen Qdash basierte Laser sich daher besonders für effiziente Vierwellenmischung. Im fünften Teil der Arbeit wurden dynamische Eigenschaften von Qdot/Qdash Lasern mit kurzen Kavitätslängen unter Klein-/Grosssignal Modulation untersucht. Qdot Laser stellen höheren D-faktor bei niedrigerem Strom dar, was bedeutet, dass Qdot Laser eine höhere Resonanzfrequenz und Sätigung der -3 dB Modulationsbandbreite bei niedrigem Strom bieten. Das Merkmal kann in Konzepte für energieeffiziente Laserquellen nützlich sein. Im Vergleich mit Qdash Laser, demonstrieren Qdot Laser stärkere Dämpfung der Resonanzoszillationen aufgrund starker Verstärkungskompression. Qdot Laser besitzen eine -3 dB Bandbreite von 8.1 GHz und ermöglichen eine fehlerfreie Übertragung und Detektion von intensitätsmodulierten Signalen (OOK) mit einer Rate bis zu 22.5 Gbit/s. Qdash Laser bieten gleiche -3 dB Bandbreite aber bei mind. zweimal grösserem Strom, und OOK fehlerfreie Übertragung mit einer Rate bis zu 17.5 Gbit/s mit Potenzial bis zu 20 Gbit/s. Wärmeableitung-zu-Bitraten-Verhältnis ist 8 bzw. 11 pJ/bit für Qdot bzw. Qdash Laser. Ein optimierter Laser Chip Aufbau reduziert Parasitäreffekte und Aufwärmung des Lasers, dadurch können Energieeffizienz bzw. dynamische Eigenschaften verbessert werden.This thesis focuses on the study of novel InAs quantum dot (QDot) and quantum dash (QDash) structures based lasers grown on InP substrates. It firstly covers device fabrication and processing, as well as the static characterization. Systematic investigation of passively mode-locked two-section lasers and single-section mode-locked lasers based on QDot and QDash active material is presented. For the first time to our knowledge, we demonstrate ps range ex-facet pulse emission from MOVPE-grown InP/InAs QDot passively mode-locked two-section laser at ~33 GHz repetition frequency. The mode-locking frequency of QDot and QDash passively mode-locked two-section lasers can be tuned in a range of 300–400 MHz, whereas single-section mode-locked lasers allow a factor of 10 lower frequency tunability. Regarding pulse characteristics, we observe significantly lower time-bandwidth product for single-section mode-locked lasers and Lorentzian shaped pulse emission, nevertheless single-section mode-locked lasers do not exhibit ex-facet pulse emission and thus are subject to external compression. FROG-measurements reveal the presence of the non-linear chirp component and intensity oscillations on the leading edge of the optical pulses both in QDot and in QDash single-section mode-locked lasers. To summarize, QDot and QDash passively mode-locked two-section lasers demonstrate close mode-locking properties and dynamics, while some difference between mode-locking dynamics is observed between their single-section mode-locked counterparts mainly related to the artifacts of supermodes competition. Discussing intracavity based four-wave mixing frequency conversion, we report on the large normalized conversion efficiency of -18.6 dB, OSNR of 37 dB, and a frequency detunings up to 3 THz 1490 µm-long InP/InAs quantum-dash lasers operating at 1550 nm under dual-mode optical injection. We observe a larger conversion efficiency for 1490 µm-long QDash devices in comparison to 1250 µm-long QDot lasers, fabricated by the same growth and processing techniques. QDot devices with delta-function DOS show a four times lower third-order optical susceptibility, a 12 dB-lower normalized conversion efficiency and 14.7 dB-lower optical signal-to-noise ratio. The analysis confirms that such a difference is not only due to the cavity length but also to additive contributions to the gain such as TPA, faster gain saturation, and enhanced modulation of carrier populations. Our results unveil which structural approach must be followed in realization of lasers for efficient nondegenerate four-wave mixing based wavelength conversion. Finally, we have compared dynamic properties of short-cavity quantum-dot and quantum-dash lasers under small-and large-signal operation. We observed a larger D–factor for quantum-dot lasers, which implies a larger resonance frequency at lower bias current, and a saturation of the modulation bandwidth at lower bias levels. This feature can be useful in concepts for energy efficient laser sources. Larger gain compression is the reason for the overdamped resonance frequency peak in quantum-dot lasers, whereas moderate damping is observed in quantum-dash devices. We have shown 8.1 GHz modulation and error-free 22.5 Gbit/s large signal modulation for InP/InAs quantum-dot lasers. Quantum-dash show similar small signal modulation bandwidths, though at significantly higher injection currents and a bit rate of 17.5 Gbit/s (error-free) with potential for 20 Gbit/s. Dissipated heat-to-bit rate ratios are as low as 8 and 11 pJ/bit for quantum-dot and quantum-dash lasers, respectively. It is important to note that parasitics and heating effects can be strongly reduced for the present devices in the future by means of optimized laser chip and mounting leading to further improved dynamic properties of the lasers.EC/FP7/264687/EU/Postgraduate Research on Photonics as an Enabling Technology/PROPHE

Feedback sensitivity of InAs/GaAs Fabry-Perot quantum-dot lasers operating on the excited state transition

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Optical Nonlinearities in Injection-Locked Nanostructure Light-based Emitters

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Non-linear and dynamic properties of MOVPE-grown InAs/InP quantum-dot and quantum-dash Fabry-Perot lasers

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