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The linewidth enhancement factor (LEF) of an InAs/InGaAs quantum dot Fabry-Perot laser in a wide wavelength range from 1110 to 1300 nm, including ground state (GS) and exited state (ES) bands, is studied. LEF spectra were derived from amplified spontaneous emission spectra measured below the threshold in the pulse regime. The ES optical transition is characterised by significantly lower values of the LEF (≤0.54) as compared to the GS (≥1.21). Moreover, a zero LEF is observed within the ES spectral band. At sufficiently high currents, a near-zero LEF (|α| ≤ 0.1) is achieved in a wide spectral interval from 1146 to 1175 nm, in which the optical gain is not less than 9 cm−1.

A 31 µm in diameter microdisk laser with an InAs/InGaAs quantum dot active region has been tested in the continuous-wave regime at elevated temperatures. Lasing is achieved up to 100°C with a threshold current of 13.8 mA. The emission spectrum demonstrates single-mode lasing at 1304 nm with a side mode suppression ratio of 24 dB and a dominant mode linewidth of 35 pm.

In this paper, we study experimentally the generation of picosecond short optical pulses with an improved peak power of 42 W at a repetition rate of 16 GHz and an associated pulse width of 1.4 ps. Pulses from a tapered quantum dot laser emitting at 1250 nm are amplified using a tapered quantum dot optical amplifier without any pulse post-compression. We specifically investigate the amplification behavior of this master-oscillator power-amplifier configuration with a focus on the pulse peak power, pulse width, average power and amplified spontaneous emission towards improving the figure of merit for two photon excitation microscopy.

We propose a model for operation of mode-locked (ML) quantum-well semiconductor laser consisting of a reverse biased saturable absorber and a forward biased amplifying section. To describe the dynamics of this laser we use the traveling wave model. Numerical simulations performed for the InGaAs/InGaAlAs laser structure emitting at 1,55 um.

A broadly tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source is demonstrated, consisting of an external cavity passively mode-locked laser diode with a tapered semiconductor amplifier. By employing chirped quantum-dot structures on both the oscillator's gain chip and amplifier, a wide tunability range between 1187 and 1283 nm is achieved. Under mode-locked operation, the highest output peak power of 4.39 W is achieved from the MOPA, corresponding to a peak power spectral density of 31.4 dBm/nm.

We present λ=1.26 μm all quantum-dot (QD) master-oscillator-power-amplifier (MOPA) system with a pulse energy of 321 pJ, and peak power of 30.3 W at a repetition rate of 648 MHz for nonlinear bio-imaging applications.

Passively modelocked VECSELs continue to improve their performance in terms of output power, repetition rate and pulse duration. Recently, up to 6.4 W of average power in 28-ps pulses have been achieved from a modelocked VECSEL with an integrated saturable absorber (MIXSEL, [1]). The shortest pulse duration generated by a VECSEL was 60 fs and below 35 mW of average output power in harmonic modelocking [2]. To date, femtosecond VECSELs were based on quantum well (QW) gain structures and the average output power has been limited to

In recent years, quantum-dot (QD) mode-locked semiconductors lasers have shown great potential as ultrashort pulse laser sources [1]. For instance, the generation of ultrashort transform-limited pulses with pulse durations of 360 fs has been previously demonstrated in tapered index-guided mode-locked quantum-dot lasers without any dispersion compensation - however, peak power reached only 2.25 W, for a typical average power of 15.6 mW [2]. In our recent work, we have shown that output average/peak power and pulse energy can be greatly increased using a tapered (or flared) gain-guided structure [3]. In [3], two-section devices incorporating 5 or 10 QD layers with a total length of ∼2.78mm were used, resulting in pulse repetition rates of the order of 14.6 GHz. With an absorber-to-gain lengths ratio of 1∶7, the highest peak power achieved was 3.6W from both QD structures. On the other hand, a maximum average power of 209 mW corresponding to 14.2 pJ pulse energy with 6-ps pulse duration was achieved for the 5-layer QD laser. The generation of high-peak-power pulses is vital for a variety of applications such as biomedical nonlinear microscopy and imaging, where a combination of high peak power and average power (up to the limit tolerable by the bio-sample) are most effective in enhancing the nonlinear effects required. In this paper, we report the highest peak power (to our knowledge) of 15 W directly from a monolithic quantum-dot tapered laser, with sub-picosecond pulse width.

We demonstrate an instantaneous all-optical manipulation of optical absorption in InGaAs/GaAsquantum dots (QDs) via an electro-absorption effect induced by the electric field of an incidentfree-space terahertz signal. A terahertz signal with the full bandwidth of 3 THz was directly encodedonto an optical signal probing the absorption in QDs, resulting in the encoded temporal features asfast as 460 fs. The instantaneous nature of this effect enables femtosecond all-optical switching atvery high repetition rates, suggesting applications in terahertz-range wireless communicationsystems with data rates of at least 0.5 Tbit/s.

Wavelength bistability and tunability are demonstrated in a two-sectional quantum-dot mode-locked laser with a nonidentical capping layer structure. The continuous wave output power of 30 mW (25 mW) and mode-locked average power of 27 mW (20 mW) are achieved for 1245 nm (1295 nm) wavelengths, respectively, under the injection current of 300 mA. The largest switching range of more than 50 nm and wavelength tuning range with picosecond pulses and stable lasing wavelengths between 1245 and 1295 nm are demonstrated for gain current of 300 and 330 mA.

Broadband wavelength tunability over 136 nm (between 1182.5 nm and 1319 nm) of picosecond pulses in passive mode-locked regime is demonstrated in a multi-section quantum-dot laser in external cavity configuration at room temperature. The maximum peak power of 870 mW with 15 ps pulse duration was achieved at 1226 nm wavelength.

The performance of a self-biased saturable absorber mirror operating via the Franz-Keldysh effect is studied experimentally. Very low saturation fluences, less than 1 J/cm 2 , are obtained. Results agree well with theoretical predictions.

980 nm VCSELs show under 20 Gbit/s large signal modulation clearly open eyes without adjustment of the driving conditions between 0 and 120degC.

High-power operation of monolithic modelocked lasers based on 1.26 µm self-organised quantum dots has been achieved in the 30–60°C range for the first time. A 60°C peak power reaches 1.7 W with a pulse width of 3.2 ps at a repetition frequency of 5 GHz.

Ridge-waveguide lasers with an InAs/InGaAs quantum dot active region have been subjected to accelerated ageing at 65 and 85 °C. No sudden failure was found during the 2070 h test. Activation energy of 0.79 eV was estimated, suggesting the 40 °C-lifetime > 10 6 h.

High-power narrow ridge waveguide lasers emitting with wavelength around 1.3 µm were realised with a single In0.36GaAsN0.022 quantum well with GaAs barriers. Narrow vertical far-field angle of 35° was obtained. Single lateral mode continuous-wave operation with slope efficiency of 0.57 W/A, series resistance of 2.6 Ω, and kink-free output power of 210 mW was achieved.

Multiple layers (up to 10) of InAs/InGaAs/GaAs quantum dots considerably enhance the optical gain of quantum dot lasers emitting around 1.3 µm. A differential efficiency as high as 88% has been achieved in these lasers. An emission wavelength of 1.28 µm, threshold current density of 147 A/cm2, differential efficiency of 80%, and characteristic temperature of 150 K have been realised simultaneously in one device.

AlGaAs-GaAs diode lasers with the active region based on a dense array of self-organised InAlAs-InAs quantum dots have been fabricated with 3.5 W output power for both facets with a peak conversion efficiency of 45% in a 100 /spl mu/m-wide stripe with uncoated facets were obtained.

Diode lasers emitting at 947 nm with sub-monolayer deposited InAs/GaAs quantum dots in the active region have been fabricated. The 3.9 W output power limited by catastrophic optical damage and the peak conversion efficiency of 50.5% were achieved at 10°C in 100 µm wide stripes with uncoated facets.

Room temperature, continuous-wave operation at 1.3 /spl mu/m is reported for InGaAsN triple quantum well lasers. The layers were grown by MBE using an RF-coupled plasma source for nitrogen. Large broad area lasers exhibit very low threshold current density down to 680 A/cm/sup 2/ and a slope efficiency of 0.59 W/A (output per two facets). Maximum output powers of 2.4 and 4 W are reached at 10/spl deg/C under CW and pulsed operation, respectively. These values are a significant improvement over those previously published for lasers in the InGaAsN material system.