In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power.
We describe the development of hybrid quantum well (QW)/quantum dot (QD) active elements to achieve broad spectral bandwidth spontaneous emission and gain. We have previously reported that the placement of the QW within the active element is a critical factor in obtaining broad spectral bandwidth emission. We now present new designs to further broaden the spontaneous emission from hybrid structures by increasing the number of QD layers and dot density, and by using QDs with wider state-separation. Introducing chirped QD layers reduced the modulation in the spontaneous emission spectra, and by utilising self-heating effects and state-filling, a spontaneous emission with 3dB line-width of 350nm is obtained.
In this paper we report a hybrid quantum well (QW) and quantum dot (QD) structure to achieve a broad spontaneous
emission and gain spectra. A single quantum well is introduced into a multi-layer stack of quantum dots, spectrally
positioned to cancel the losses due to the second excited state of the dots. Attributed to the combined effect of QW and
QDs, we show room temperature spontaneous emission with a 3dB bandwidth of ~250 nm and modal gain spanning over
~300 nm. We describe how this is achieved by careful design of the structure, balancing thermal emission from the QW
and transport/capture processes in the QDs. We will also compare results from a QD-only epitaxial structure to describe
how broadband gain/emission can be achieved in this new type of structure.
We report on spectrally resolved differential carrier lifetime measurements of un-doped and modulation p-doped 1300nm
quantum dot laser. We find that the differential carrier lifetime is significantly reduced for p-doped samples compared to
essentially identical un-doped samples in line with enhanced Auger recombination. With increasing temperature the
results from the un-doped sample are unchanged, whilst an increase in differential carrier lifetime is observed for the pdoped
sample. This is in agreement with the Auger rate reducing with increasing temperature. The effect of modulation
p-doping on inter-level scattering times and the recombination rate of the excited state are discussed.