Characterization and modeling of gain spectra of single-layer InAs/InP(100) quantum dot amplifiers

In this contribution we present the small signal net modal gain measurement results of single-layer InAs/InP(100) quantum dot amplifiers in 1.6 to 1.8 µm wavelength range. The material shows sufficient optical gain to be used in the long-wavelength optical coherence tomography. The modal gain has been observed as a function of current density and temperature. An improved rate equation model has been applied to analyse the measurements. A good fit of the theory to the measurements was obtained with a temperature dependent carrier injection efficiency which is below 2%

Characterisation of monolithically integrated dual wavelength AWG-lasers for mm-wave generation

In this paper we present characterisation results of monolithically integrated InP based quantum well dual wavelength lasers in which an Array Waveguide Grating (AWG) is used as intra-cavity filter to allow lasing on two wavelengths within a common optical amplifier of the device. The devices require accurate control of the optical loss of each wavelength which is achieved through the use of Michelson interferometers (MIs) in the cavity. The results show that reasonably stable dual wavelength operation is possible with a side mode suppression ratio better than 20dB for each of the two wavelengths without fast active feedback control

Fabrication of short GaAs wet-etched mirror lasers and their complex spectral behaviour

A versatile fabrication technique for GaAs-AlGaAs wet-etched mirror lasers is presented. This technique works independently of the Al concentration in the cladding layers up to a value of 70%, and it requires four photolithography steps. Ridge waveguide lasers have been successfully processed using a double heterostructure (DHS) as well as graded index separate confinement heterostructures (GRINSCH) having different quantum-well (QW) active layers. This technique is used to fabricate short-cavity lasers in GRINSCH structures having GaAs multiple-quantum-well (MQW) or bulk active layers. Laser operation was obtained in a 29-µm-long device using a 5-QW structure. Short lasers with QW active layers show a complex spectral behavior. These lasers operate at higher current densities (~20 kA/cm2) and emit light at more than one wavelength. This implies that higher order transitions are involved which is not the case when using a bulk GaAs active layer. Besides the two peaks corresponding to the n=1 and n=2 transitions, we found an intermediate peak which corresponds presumably to the forbidden transition E1-HH

Measurement and analysis of temperature-dependent optical modal gain in single-layer InAs/InP(100) quantum-dot amplifiers in the 1.6- to 1.8-µm wavelength range

In this paper, measurements and analysis of the small-signal net modal gain of single-layer InAs/InP(100) quantum-dot (QD) optical amplifiers are presented. The amplifiers use only a single layer of InAs QDs on top of a thin InAs quantum well. The devices have been fabricated using a layer stack that is compatible with active–passive integration scheme, which makes further integration possible. The measurement results show sufficient optical gain in the amplifiers and can thus be used in applications such as lasers for long-wavelength optical coherence tomography and gas detection. The temperature dependence of the modal gain is also characterized. An existing rate-equation model was adapted and has been applied to analyze the measured gain spectra. The current injection efficiency has been introduced in the model to obtain a good fit with the measurement. It is found that only a small portion ($sim$1.7%) of the injected carriers is actually captured by the QDs. The temperature dependence of several parameters describing the QDs is also discovered. The mechanisms causing the blue shift of peak gain as the current density increases and the temperature changes are analyzed and discussed in detail

Quantum dot twin stripe lasers as emitter and receiver in chaotic encrypted communication systems

The complex nonlinear and chaotic regimes observed in laterally coupled diode lasers – or twin stripe lasers– make this device a real contender for the emitter and receiver in chaotic encrypted communication systems, since the chaos is produced on chip and no other elements have to be added to the set-up. The main problem until now was to be able to synchronize two of those devices, due to the difficulty of fabricating a pair similar enough. Our approach is to use Quantum Dots for the active region of the twin stripes, which allows for the use of shallow etching to electrically isolate both stripes due to the zero dimensional confinement of the Quantum Dots. In this paper we present the first time that a pair of twin stripe lasers has been synchronized together with an observation of transitions to chaos such as those found in single-stripe lasers subject to external influences

Observation of Q-switching and mode-locking in two-section InAs-InP (100) quantum dot lasers at 1.53 µm

First observation of passive mode-locking in two-section quantum-dot lasers operating at wavelengths around 1.55 µm is reported. Pulse generation at 4.6 GHz from a 9 mm long device is verified by background-free autocorrelation, RF-spectra and real-time oscilloscope traces. The output pulses are stretched in time and heavily up-chirped with a value of 20 ps/nm, contrary to what is normally observed in passively mode-locked semiconductor lasers. The complete output spectrum is shown to be coherent over 10 nm. From a 7 mm long device Q-switching is observed over a large operating regime. The lasers have been realized using a fabrication technology that is compatible with further photonic integration. This makes the laser a promising candidate for e.g. a mode-comb generator in a complex photonic chip