Mode locking in a tapered two-section quantum dot laser: design and experiment.

In this Letter, the pulse generation and pulse train stability of a tapered two-section InAs/InGaAs quantum dot laser emitting at 1250 nm are numerically predicted and experimentally verified. Simulations based on a multi-section delayed differential equation model are used to properly design a laser source able to generate stable mode-locked pulses at a 15 GHz repetition rate with picosecond width and output power larger than 1 W, and to identify the device stability regions depending on the bias conditions. Possible instabilities are associated with the existence of a leading or trailing edge net gain window outside the optical pulse. Experimentally, we confirm the existence of different stability regions where instabilities manifest in broadband or multi-periodic pulse train amplitude modulations. Our results confirm the correctness to the design and may be helpful in achieving high-power pulses while avoiding detrimental pulse train instabilities, both being important for time-critical applications.

Orange-to-red tunable picosecond pulses by frequency doubling in a diode-pumped PPKTP waveguide.

A compact picosecond all-room-temperature orange-to-red tunable laser source in the spectral region between 600 and 627 nm is demonstrated. The tunable radiation is obtained by second-harmonic generation in a periodically poled potassium titanyl phosphate (PPKTP) multimode waveguide using a tunable quantum-dot external-cavity mode-locked laser. The maximum second-harmonic output peak power of 3.91 mW at 613 nm is achieved for 85.94 mW of launched pump peak power at 1226 nm, resulting in conversion efficiency of 4.55%.

High peak-power picosecond pulse generation at 1.26 µm using a quantum-dot-based external-cavity mode-locked laser and tapered optical amplifier.

In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 µm spectral band from a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser (QD-ECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peak-power pulsed light source for nonlinear bio-imaging applications across the 1.0 µm - 1.3 µm spectral range.

1.3 microm quantum dot laser in coupled-cavity-injection-grating design with bandwidth of 20 GHz under direct modulation.

Using a multi section laser in coupled cavity injection grating design based on 1.3 microm InGaAs/GaAs quantum dot (QD) active region we were able to enhance the 3 dB modulation bandwidth well beyond the inherent material modulation bandwidth. The material bandwidth was determined by measurements on distributed feedback (DFB) devices to approximately 8 GHz. The special multisectional design allows interaction between the lasing mode and a second mode used as catalyst and enables a high resonance frequency of the device. Based on active QD material this approach allowed us to reach a cut off frequency of 20 GHz in the small signal response of the device.

High-power quantum-dot-based semiconductor disk laser.

We demonstrate multiwatt cw output power from an optically pumped quantum-dot semiconductor disk laser. Continuous-wave output power of 4.35 W with 22% slope efficiency was demonstrated at a center wavelength of 1,032 nm. This represents an increase in power of 15 times and an increase in slope efficiency of 10 times from the previously published results using Stranski-Krastanow grown quantum dots. An intracavity diamond heat spreader was used for thermal management. The maximum output power was limited by the available pump power, and no sign of thermal rollover was observed.

Quantum dot laser with 75 nm broad spectrum of emission.

We report on a quantum dot laser having an emission spectrum as broad as 74.9 nm at 25 degrees C in the 1.2-1.28 wavelength interval with a total pulsed output power of 750 mW in single lateral mode regime and the average spectral power density of >10 mW/nm. A significant overlap and approximate equalization of the ground-state and the excited-state emission bands in the laser's spectrum is achieved by means of intentional inhomogeneous broadening of the quantum dot energy levels.