Mantas Butkus

High-power quantum-dot-based semiconductor disk laser

Semiconductor disk lasers (SDLs), also referred to as vertical external cavity surface emitting lasers (VECSELs), offer an effective solution for combining high output power with high beam quality, from a power scalable semiconductor laser [1]. The first SDLs based on InAs/GaAs sub monolayer (SML) and InGaAs Stranski-Krastanow (SK) grown quantum dot (QD) gain material were recently demonstrated, with output power of 1.4 W and 0.3 W respectively [2,3]. Here, we report the first multi-Watt cw output from a QD SDL.

Quantum Dot Based Semiconductor Disk Lasers for 1–1.3 μm

Optically pumped quantum dot (QD)-based semiconductor disk lasers (SDLs) have been under intense research after their first demonstration and important enhancements of their parameters have been achieved since then. In this paper, we present recent developments in QD-based SDLs emitting in the 1-1.3 μm spectral region. Three different wavelength ranges of 1040, 1180, and 1260 nm were explored. Power scaling up to 6 W was achieved for 1040 and 1180 nm devices and up to 1.6 W for 1260 nm device. New spectral regions were covered by direct emission and frequency doubling was used to demonstrate spectral conversion into visible region with green, orange, and red light. Also, the broad gain bandwidth of QD materials was explored and wavelength tuneability up to 60 nm around 1040 nm, 69 nm around 1180 nm, and 25 nm around 1260 nm was demonstrated. The efficiency of excited and ground state emission in QDs was also compared. All these improvements allow new possibilities in applications of QD SDLs, reveal their potential, and suggest the aims for future research in the field.

Optically pumped semiconductor quantum dot disk laser operating at 1180 nm

We demonstrate an optically pumped semiconductor disk laser using 39 layers of Stranski-Krastanov InGaAs quantum dots self-assembled during epitaxial growth on a monolithic GaAs/AlAs distributed Bragg reflector. The gain structure bonded to an intracavity diamond crystal heat spreader allows 1.75 W single-transverse-mode output (M(2)<1.2) with circular beam shape operating at 1180 nm in a disk laser geometry.

85.7 MHz repetition rate mode-locked semiconductor disk laser: fundamental and soliton bound states.

Mode-locked optically pumped semiconductor disk lasers (SDLs) are in strong demand for applications in bio-medical photonics, chemistry, space communications and non-linear optics. However, the wider spread of SDLs was constrained as they are operated in high repetition rates above 200 MHz due to short carrier lifetimes in the semiconductors. Here we demonstrate experimentally and theoretically that it is possible to overcome the limitation of fast carrier relaxation and show significant reduction of repetition rate down to 85.7 MHz by exploiting phase-amplitude coupling effect. In addition, a low repetition rate SDL serves as a test-bed for bound soliton state previously unknown for semiconductor devices. The breakthrough to sub-100 MHz repetition rate will open a whole new window of development opportunities.

Subpicosecond quantum dot saturable absorber mode-locked semiconductor disk laser

We report the generation of subpicosecond pulses from a passively mode locked, optically pumped quantum well semiconductor disk laser using a quantum dot semiconductor saturable absorber mirror (SESAM). We obtained 870 fs pulses at a repetition rate of 895 MHz with average output power of 45 mW at 1027.5 nm. The mode locking operation was insensitive to SESAM temperature over the range of −10 to 85 °C, with the pulse duration variation thought to be dominated by the temperature dependence of the group delay dispersion.

High-Power Quantum-Dot Vertical-External-Cavity Surface-Emitting Laser Exceeding 8 W

We report on a record-high output power from an optically pumped quantum-dot vertical-external-cavity surface-emitting laser, optimized for high-power emission at 1040 nm. A maximum continuous-wave output power of 8.41 W is obtained at a heat sink temperature of 1.5°C. By inserting a birefringent filter inside the laser cavity, a wavelength tuning over a range of 45 nm is achieved.

Flip Chip Quantum-Dot Semiconductor Disk Laser at 1200 nm

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.

High Repetition Rate Ti:Sapphire Laser Mode-Locked by InP Quantum-Dot Saturable Absorber

We report the first demonstration of a Ti:sapphire laser mode-locked with a quantum-dot mode-locker (QDM) at repetition rates up to 1.77 GHz with 8-ps pulse duration and 400-mW average output power. So far, with quantum-well-based mode-lockers, a repetition rate of only up to 300 MHz has been achievable in our experiments. We show that QDM can support mode-locking in a wide range of repetition rates from 100 MHz to 1.8 GHz.

P-i-n junction quantum dot saturable absorber mirror: electrical control of ultrafast dynamics.

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.

Non-diffracting beams from surface-emitting lasers

We present an overview of recent advances in generation of non-diffracting (Bessel) beams from surface-emitting lasers, such as electrically and optically pumped VECSELs, and discuss their applications in optical trapping/tweezing and manipulation of micromachines. Our experiments on VECSEL-generated watt power level Bessel beams with central lobe diameters of a few to tens micrometers suggest that the semiconductor surface-emitting lasers are the best candidates for replacement of gas and solid-state counterparts for power-demanding applications in optical manipulation.