Quantum Dot Distributed Feedback Lasers Research Articles

Frequency-Dependent Linewidth Enhancement Factor of Quantum-Dot Lasers

We present detailed measurements of the linewidth enhancement factor (LEF) of a quantum-dot distributed-feedback laser emitting around 1.3 mum above and below threshold. The above threshold method is based on the measurement of the frequency modulation and amplitude modulation response of the laser and shows significant dependence on modulation frequency. Drive current dependent measurements with both methods yield LEF values between 1 well below and 3 well above threshold, converging around 2 close to threshold.

1.55 $\mu$m InAs/InAlGaAs Quantum Dot DFB Lasers

For the fabrication of quantum dot (QD) distributed feedback (DFB) lasers, self-assembled InAs/InAlGaAs QDs were grown on the InP/InGaAs grating structures by a molecular beam epitaxy. Ridge-waveguide QD DFB lasers with a stripe width of 3 mum were fabricated. Single-mode lasing operation around the wavelength of 1.56 mum was successfully achieved under the pulsed and continuous-wave (CW) modes at room temperature. The lasing operation was also observed up to 70 degC under pulsed mode, which is the first observation on the single-mode lasing around 1.55 mum. The characteristic temperatures calculated from the temperature dependence of the threshold current density were 121.8 K from room temperature to 45 degC, which was reduced to 74.2 K from 45 degC to 70 degC.

Bandwidth enhancement of injection-locked 1.3 [micro sign]m quantum-dot DFB laser

Optical injection locking of a quantum-dot distributed-feedback laser at 1.3 µm is reported. Using an injection ratio of 5.3 dB, an optical detuning of −40 pm, and a slave laser biased at 20 mA, the modulation bandwidth of the injection-locked laser was 16.3 GHz. This is over four times higher than the modulation bandwidth of the free-running quantum-dot laser. At a slave laser bias of 5.0 mA, injection locking resulted in a resonance frequency of 21.9 GHz, over eleven times higher than the relaxation frequency of the free-running slave laser.

InAs-InAlGaAs quantum dot DFB lasers based on InP [001

The InAs-InAlGaAs quantum dot (QD) lasers with the InAlGaAs-InAlAs material system were fabricated on distributed feedback (DFB) grating structures on InP (001). The single-mode operation of InAs-InAlGaAs QD DFB lasers in continuous-wave mode was successfully achieved at the emission wavelength of 1.564 mum at room temperature. This is the first observation on the InP-based QD lasers operating around the emission wavelength window of 1.55 mum. The threshold current density of the InAs-InAlGaAs QD DFB laser with a cavity length of 1 mm and a ridge width of 3 mum, in which one of the cleaved facets was coated with 95% high-reflection, was 1.23 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (176 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sup> for single QD layer). The sidemode suppression ratio value of the QD DFB laser was as high as 42 dB at the driving current of 100 mA

Room temperature continuous-wave operation of InAsSb quantum-dot distributed feedback lasers

InAsSb self-assembled quantum-dot (QD) distributed feedback (DFB) lasers based on (001) InP substrate have been grown by metalorganic vapor-phase epitaxy. A highly tensile-strained InGaAs was used as the barrier layer for InAsSb QDs. Single-mode emissions near 1.87μm have been demonstrated from narrow ridge waveguide DFB lasers in continuous-wave operation at temperatures up to 320K (47°C), with a characteristics temperature of 55K up to temperature of 310K.

Nondegenerate four-wave mixing in quantum dot distributed feedback lasers

We present wavelength conversion using nondegenerate four-wave mixing in loss-coupled distributed feedback lasers based on InAs quantum dots (QDs) grown on a GaAs substrate. The conversion efficiency is measured to be -15 to -30 dB for a signal-pump detuning range from 0.33 to 8 nm. The third-order optical susceptibility (/spl chi//sup (3)/) normalized to the optical linear gain in the QDs is estimated to be 3/spl times/10/sup -20/ m/sup 3//V/sup 2/ to 9/spl times/10/sup -20/ m/sup 3//V/sup 2/ for the signal-pump detuning range.

Dynamic properties of quantum dot distributed feedback lasers: high speed, linewidth and chirp

The dynamic properties of distributed feedback lasers (DFBs) based on InAs/InGaAs quantum dots (QDs) are studied. The response function of QD DFBs under external modulation is measured, and the gain compression with photon density is identified to be the limiting factor of the modulation bandwidth. The enhancement of the gain compression by the gain saturation with the carrier density in QDs is also analysed for the first time. The linewidth of the QD DFBs is found to be more than one order of magnitude narrower than that of conventional quantum well (QW) DFBs at comparable output powers. The figure of merit for the narrow linewidth is compared between different semiconductor materials, including bulk, QWs and QDs. Linewidth re-broadening and the effects of gain offset are also investigated. Finally, the chirp of QD DFBs is studied by time-resolved-chirp measurements. The wavelength chirping of the QD DFBs under 2.5 Gbps modulation is characterized. The strong dependence of the linewidth enhancement factor on the photon density is explained by the enhancement of gain compression by the gain saturation with the carrier density, which is related to the inhomogeneous broadening and spectral hole burning in QDs.

High frequency characteristics of InAs/GaInAs quantum dot distributed feedback lasers emitting at 1.3 [micro sign

The high frequency properties of InAs/GaInAs quantum dot distributed feedback (DFB) lasers emitting at 1.3 /spl mu/m have been examined. The lasers display a small static linewidth of 1.3 MHz and a chirp as low as 83 MHz/mA. More than 5 GHz small-signal modulation bandwidth was observed in the first devices indicating the potential for high-speed operation of quantum dot lasers.