[Show abstract][Hide abstract] ABSTRACT: We experimentally study the generation and amplification of stable picosecond-short optical pulses by a master oscillator power-amplifier configuration consisting of a monolithic quantum-dot-based gain-guided tapered laser and amplifier emitting at 1.26 µm without pulse compression, external cavity, gain- or Q-switched operation. We report a peak power of 42 W and a figure-of-merit for second-order nonlinear imaging of 38.5 W2 at a repetition rate of 16 GHz and an associated pulse width of 1.37 ps.
[Show abstract][Hide abstract] ABSTRACT: We exploit the coupled emission-states of a single-chip semiconductor InAs/GaAs quantum-dot laser emitting simultaneously on ground-state (λGS = 1245 nm) and excited-state (λES = 1175 nm) to demonstrate coupled-two-state self-mixing velocimetry for a moving diffuse reflector. A 13 Hz-narrow Doppler beat frequency signal at 317 Hz is obtained for a reflector velocity of 3 mm/s, which exemplifies a 66-fold improvement in width as compared to single-wavelength self-mixing velocimetry. Simulation results reveal the physical origin of this signal, the coupling of excited-state and ground-state photons via the carriers, which is unique for quantum-dot lasers and reproduce the experimental results with excellent agreement.
[Show abstract][Hide abstract] ABSTRACT: 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%.
[Show abstract][Hide abstract] ABSTRACT: In this Letter, a design for a tapered InAs/InGaAs quantum dot semiconductor optical amplifier is proposed and experimentally evaluated. The amplifier's geometry was optimized in order to reduce gain saturation effects and improve gain efficiency and beam quality. The experimental measurements confirm that the proposed amplifier allows for an elevated optical gain in the saturation regime, whereas a five-fold increase in the coupling efficiency to a standard single mode optical fiber is observed, due to the improvement in the beam quality factor M<sup>2</sup> of the emitted beam.
[Show abstract][Hide abstract] ABSTRACT: Compact CW lasers in the visible spectral region are of great importance for vast number of applications including biophotonics, photomedicine, spectroscopy and confocal microscopy. Currently, commercially available lasers of this spectral region are bulky, expensive and inconvenient in use. Also, there is a lack of diode lasers emitting in the visible spectral range, particularly in the yellow region, where a range of important fluorescent probes are optimally excited. An attractive way to realize a compact yellow laser source is second harmonic generation (SHG) in a periodically poled nonlinear crystal containing a waveguide  which allows high-efficient frequency conversion even at moderate power level. In this respect, periodically poled lithium niobate (PPLN) waveguided crystal is one of the best candidates for efficient SHG. In recent years, the progress made with the fabrication of good quality waveguides in PPLN crystals in combination with availability of low-cost, good quality semiconductor diode lasers, offering the coverage of a broad spectral range between 1 μπι and 1.3 um , allows compact CW laser sources in the visible spectral region to be realized.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate all-room-temperature CW second harmonic generation with 174 nm tunability from blue to red (between 478 nm and 652 nm) in a single PPKTP waveguide pumped by broadly-tunable semiconductor laser diodes.
[Show abstract][Hide abstract] ABSTRACT: Fundamental mode-locking is achieved in a 1.036 GHz cavity using a semiconductor quantum dot saturable absorber mirror with a fast relaxation time component of down to 550 fs. The dispersive cavity delivers 1.7 ps wide pulses with spectra supporting sub-picosecond pulse durations and an M² of 1.3. An average output power of up to 339 mW at wavelengths around 1,032 nm is achieved and the saturable absorber’s damage threshold is identified as a limitation for further power scaling.
No preview · Article · Mar 2013 · Applied Physics B
[Show abstract][Hide abstract] ABSTRACT: A broadly tunable quantum-dot based ultra-short pulse master oscillator power amplifier with different diffraction grating orders as an external-cavity resonance feedback is studied. A broader tuning range, narrower optical spectra as well as higher peak power spectal density (maximun of 1.37 W/nm) from the second-order diffraction beam are achieved compared to those from the first-order diffraction beam in spite of slightly broader pulse duration from the secondorder diffraction.
No preview · Article · Feb 2013 · Electronics Letters
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Jan 2013 · IEEE Journal of Selected Topics in Quantum Electronics
[Show abstract][Hide abstract] ABSTRACT: DBR stabilized InAs/GaAs quantum dot comb laser diode is demonstrated. It generates 4+ low-noise comb lines within the temperature range 25-65°C. The DBR section improves comb spectrum stability in the changing operating conditions.
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Aug 2012 · IEEE Photonics Technology Letters
[Show abstract][Hide abstract] ABSTRACT: In this letter, we present the first 2-W flip chip quantum-dot (QD) semiconductor disk laser operating at 1200 nm. Compared to other techniques used for thermal management, e.g., intracavity heat spreader approach, the flip chip design preserves undisturbed optical spectrum and exhibits low intracavity losses. The latter is particularly essential for power scaling of lasers with QD gain media.
No preview · Article · Aug 2012 · IEEE Photonics Technology Letters
[Show abstract][Hide abstract] ABSTRACT: We demonstrate compact all-room-temperature laser sources broadly tunable in the visible spectral region in CW (between 567 nm and 629 nm) and picosecond regimes (between 600 nm and 627 nm) by frequency-doubling in a periodically-poled KTP waveguide using a tunable quantum-dot external-cavity diode lasers.
[Show abstract][Hide abstract] ABSTRACT: A tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source using all chirped quantum dot (QD) structures is demonstrated (60nm tunability). Under fundamental mode-locked operation, the highest peak power of 4.39 W is achieved.
[Show abstract][Hide abstract] ABSTRACT: In this paper we present experimental results related to the dynamic switching of the emission wavelength of a passively mode-locked InAs/InGaAs quantum dot laser. The wavelength switching is achieved through application of varying optical feedback, as opposed to varying electrical biasing conditions, whereas the different regimes of operations include pulse operation either from the ground or the excited state and dual mode locking. Furthermore, through the same technique, Q -switching elimination was achieved, allowing stable pulse amplitude, which is a highly desired feature in many applications.
No preview · Article · May 2012 · Journal of the Optical Society of America B
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a CW tunable compact all-room-temperature laser system in the visible spectral region from 567.7nm to 629.1nm, by frequency doubling in a periodically-poled KTP waveguide crystal using a tunable quantum-dot external-cavity diode laser.
[Show abstract][Hide abstract] ABSTRACT: We present γ=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
[Show abstract][Hide abstract] ABSTRACT: We report on nonlinear optical properties of a p-i-n junction quantum dot saturable absorber based on InGaAs/GaAs. Absorption recovery dynamics and nonlinear reflectivity are investigated for different reverse bias and pump power conditions. A decrease in absorption recovery time of nearly two orders of magnitude is demonstrated by applying a voltage between 0 and -20 V. The saturable absorber modulation depth and saturation fluence are found to be independent from the applied reverse bias. (C)2012 Optical Society of America
[Show abstract][Hide abstract] ABSTRACT: We present the first full gain characterization of two vertical external cavity surface emitting laser (VECSEL) gain chips with similar designs operating in the 960-nm wavelength regime. We optically pump the structures with continuous-wave (cw) 808-nm radiation and measure the nonlinear reflectivity for 130-fs and 1.4-ps probe pulses as function of probe pulse fluence, pump power, and heat sink temperature. With this technique we are able to measure the saturation behavior for VECSEL gain chips for the first time. The characterization with 1.4-ps pulses resulted in saturation fluences of 40-80 μJ/cm2, while probing with 130-fs pulses yields reduced saturation fluences of 30-50 μJ/cm2 for both structures. For both pulse durations this is lower than previously assumed. A small-signal gain of up to 5% is obtained with this technique. Furthermore, in a second measurement setup, we characterize the spectral dependence of the gain using a tunable cw probe beam. We measure a gain bandwidth of over 26 nm for both structures, full width at half maximum.
[Show abstract][Hide abstract] ABSTRACT: We present high average power femtosecond VECSELs based on both quantum dot (QD) and quantum well (QW) gainwith extremely low dispersion. 1.05 W in 784-fs pulses could be achieved from a QD-VECSEL modelocked by a QD-SESAM with fast recovery dynamics. A similar QW-gain structure modelocked by the same SESAM enabled stable 480-fs with an average output power of 300 mW at a repetition rate of 7 GHz. Furthermore, we investigated repetition rate scaling by changing the cavity length. We demonstrated fundamentally modelocked pulses over a tuning range from 6.5 GHz to 11.3 GHz. Without any realignment of the cavity over the whole tuning range, the pulse duration remained nearly constant around 625 fs (+/- 3.5%) while the output power was 169 mW (+/- 6%). The center wavelength changed only about +/- 0.2 nm around 963.8 nm. A tunable repetition rate can be of interest for various metrology application such as optical sampling by laser cavity tuning.