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Thermal Effects and Small Signal Modulation of 1.3- μ m InAs/GaAs Self-Assembled Quantum-Dot Lasers

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ABSTRACT

We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

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The schematic diagram of the InAs/GaAs ten-layer QD laser structure.
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Figure 1: The schematic diagram of the InAs/GaAs ten-layer QD laser structure.

Mentions: The ten-layer self-assembled InAs/GaAs QD laser structure, as shown in Figure 1, was grown on GaAs (100) substrate by molecular beam epitaxy (MBE). The structure consists of QD active region sandwiched between two 1.5-μm C- and Si-doped Al0.35Ga0.65As cladding layers. The active layer comprises 2.3 monolayer (ML) of InAs QDs capped by a 5-nm In0.15Ga0.85As layer. A 33-nm GaAs layer is used to separate the two QD layers [13]. The wafer was processed into 4-μm-wide ridge waveguide (RWG) lasers by standard photolithography process and wet chemical etching at room temperature (RT) [14]. Ridge height of approximately 1.3 μm was obtained before the pulsed anodic oxidation (PAO) process. A 200 ± 5 nm-thick oxide layer was formed by PAO method, whose experimental setup can be found in [15]. Subsequently, p-contact layers (Ti/Au, 50/300 nm) were deposited by electron beam evaporation, while n-contact layers (Ni/Ge/Au/Ni/Au, 5/20/100/25/300 nm) were deposited on the backside of the substrate following lapping down to ~100 μm. Finally, the wafer was cleaved into laser bars and the cleaved facets were left uncoated. The devices were mounted p-side down on a heat sink for measuring the small signal modulation characteristics. The small signal modulation response of the QD lasers was measured under continuous wave (CW) biasing condition using a vector network analyzer (VNA), a high-speed photoreceiver and laser diode current source. A thermoelectric temperature controller was used to regulate and monitor the device temperature during measurements.


Thermal Effects and Small Signal Modulation of 1.3- μ m InAs/GaAs Self-Assembled Quantum-Dot Lasers
The schematic diagram of the InAs/GaAs ten-layer QD laser structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211460&req=5

Figure 1: The schematic diagram of the InAs/GaAs ten-layer QD laser structure.
Mentions: The ten-layer self-assembled InAs/GaAs QD laser structure, as shown in Figure 1, was grown on GaAs (100) substrate by molecular beam epitaxy (MBE). The structure consists of QD active region sandwiched between two 1.5-μm C- and Si-doped Al0.35Ga0.65As cladding layers. The active layer comprises 2.3 monolayer (ML) of InAs QDs capped by a 5-nm In0.15Ga0.85As layer. A 33-nm GaAs layer is used to separate the two QD layers [13]. The wafer was processed into 4-μm-wide ridge waveguide (RWG) lasers by standard photolithography process and wet chemical etching at room temperature (RT) [14]. Ridge height of approximately 1.3 μm was obtained before the pulsed anodic oxidation (PAO) process. A 200 ± 5 nm-thick oxide layer was formed by PAO method, whose experimental setup can be found in [15]. Subsequently, p-contact layers (Ti/Au, 50/300 nm) were deposited by electron beam evaporation, while n-contact layers (Ni/Ge/Au/Ni/Au, 5/20/100/25/300 nm) were deposited on the backside of the substrate following lapping down to ~100 μm. Finally, the wafer was cleaved into laser bars and the cleaved facets were left uncoated. The devices were mounted p-side down on a heat sink for measuring the small signal modulation characteristics. The small signal modulation response of the QD lasers was measured under continuous wave (CW) biasing condition using a vector network analyzer (VNA), a high-speed photoreceiver and laser diode current source. A thermoelectric temperature controller was used to regulate and monitor the device temperature during measurements.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

No MeSH data available.


Related in: MedlinePlus