Temperature resistant fast InxGa1-xAs / GaAs quantum dot saturable absorber for the epitaxial integration into semiconductor surface emitting lasers.

T Finke,J P Reithmaier,U Keller,M Golling,V Sichkovskyi,J Nürnberg

doi:10.1364/oe.396198

T Finke, J P Reithmaier + Show 4 more

Open Access

https://doi.org/10.1364/oe.396198

Copy DOI

Journal: Optics Express	Publication Date: Jun 30, 2020
Citations: 6	License type: cc-by

Abstract

Quantum-dot-based semiconductor saturable absorber mirrors (SESAMs) with fast response times were developed by molecular beam epitaxy (MBE). Using quantum dots (QDs) in the absorber region of the SESAMs instead of quantum wells, enables additional degrees of freedom in the design, the control of saturation parameters and the recovery dynamics. However, if one wants to integrate such a SESAM element into semiconductor surface emitting lasers such as a mode-locked integrated external-cavity surface-emitting laser (MIXSEL), the saturable absorber layers have to withstand a longer high-temperature growth procedure for the epitaxial formation of distributed Bragg reflectors (DBR). Typically defect related SESAMs will be annealed at those growth temperatures and lose their high-speed performance. Here we present a systematic study on the growth parameters and post-growth annealing of SESAMs based on high-quality InxGa1-xAs/GaAs quantum dots (QDs) grown by MBE at growth temperatures of 450 °C or higher. The good quality enables the QDs to survive the long DBR overgrowth at 600 °C with only minimal shifts in the designed operation wavelength of 1030 nm required for growth of MIXSEL devices. The introduction of recombination centers with p-type modulation doping and additional post-growth annealing improves the absorption of the high-quality QDs. Hence, low saturation fluences < 10 µJ/cm2 and a reduction of the τ1/e recovery time to values < 2 ps can be achieved.

Highlights

Since its invention in 1992, semiconductor saturable absorber mirrors (SESAMs) [1] have been well established for passive mode-locking of different laser types from diode-pumped solid-state [2], fiber [3] and surface emitting semiconductor disk lasers [4,5]
We present a systematic study on the growth parameters and post-growth annealing of SESAMs based on high-quality InxGa1−xAs/GaAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) at growth temperatures of 450 °C or higher
It is a state-of-the-art MBE-grown fast quantum well (QW) SESAM [13,16], which consists of a single InGaAs QW absorber embedded in AlAs barriers and a comparable distributed Bragg reflectors (DBR) (Fig. 2(a))

Summary

Introduction

Since its invention in 1992, semiconductor saturable absorber mirrors (SESAMs) [1] have been well established for passive mode-locking of different laser types from diode-pumped solid-state [2], fiber [3] and surface emitting semiconductor disk lasers [4,5]. Due to its design flexibility, the SESAM enables operation over a wide range of pulse durations and repetition rates. The design of the DBR and the active region is adapted and optimized for the desired optical parameters, such as the operation wavelength λ, the modulation depth ∆R, the saturation fluence Fsat, the non-saturable losses ∆Rns, and the recovery time τ [6]. SESAMs for stable mode-locking of optically pumped semiconductor disk laser require low saturation fluences (< 10 μJ/cm2) [7] and can provide high repetition rates (> 10 GHz) [8] without Q-switching instabilities

Methods

Results

Conclusion