We present the first self-mode-locked optically pumped quantum-dot semiconductor disk laser. Our mode-locked device emits sub-picosecond pulses at a wavelength of 1040 nm and features a record peak power of 460 W at a repetition rate of 1.5 GHz. In this work, we also investigate the temperature dependence of the pulse duration as well as the time-bandwidth product for stable mode locking.

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to their architecture, VECSELs can combine advantages of solid-state and semiconductor lasers, such as high output powers, beam quality and being accessible for a wide spectral range [3][4][5]. Moreover, recent reports such as the achievement of passive mode-locking operation with 400-fs pulses at 4.35-kW peak powers [6] as well as employment in the field of intra-cavity frequencymixing applications demonstrate the versatility of such a laser system [7]. It is worth to note that the way to highpower pulsed VECSELs was further paved very recently with the use of self-mode-locking techniques in saturable absorber free systems, which can even run at higher harmonics [8]. Quantum-well (QW)-VECSELs have been even shown to generate a record-high continuous-wave (CW) output power of 106 W at an emission wavelength of 1028 nm [9], while for quantum-dot (QD) VECSELs, a record-high CW output power of 8.4 W was obtained at an emission wavelength of 1040 nm [10]. Furthermore, an optimum output power of nearly 23 W was demonstrated very recently for a single-frequency VECSEL, at 1013 nm [11]. However, for further improvement in such VECSELs' performances, an understanding and quantification of the power loss channels in such devices is essential. Overheating generally limits the VECSEL output efficiency [12]-an effect that reduces gain until complete shutdown of the laser. The onset of this effect is marked by the so-called thermal roll-over power. Thus, heat management is generally very important for such systems [13][14][15][16][17], and methods for a precise determination of a VECSEL's thermal impedance were seeked in recent years [12,18]. But besides heating losses, also non-heating power losses are expected, in particular optical losses [12,18,19], i.e., intra-cavity scattering and spontaneous emission in the chip. In this work, we illuminate optical surface-scattering of intra-cavity light at the semiconductor chip in an Abstract We report on an analysis of optical surfacescattering losses in vertical-external-cavity surface-emitting lasers. In this study, a laser chip with enhanced surface roughness compared with a high-quality chip is employed in order to allow for investigation of a scattering loss component described in theoretical considerations. A simple model for the extraction of the laser chip's thermal resistance from experimental input-output characteristics based on thermal roll-over is expanded with respect to a non-thermal component of losses. Thereby, we demonstrate good agreement of experimental data with theoretical modeling when taking into account a power loss component proportional to an optical surface-scattering-loss coefficient in relation to photon out-coupling rates.

In this letter, we report on a high-power operation of an optically pumped quantum-dot semiconductor disk laser designed for emission at 1180 nm. As a consequence of the optimization of the operation conditions, a record-high continuouswave output power exceeding 7 W is obtained for this wavelength at a heat-sink temperature of 2 • C. A wavelength tuning over a range of 37 nm is achieved using a birefringent filter inside the cavity.

Vertical-external-cavity surface-emitting lasers (VECSELs) have proved to be versatile lasers which allow for various emission schemes which on the one hand include remarkably high-power multi-mode or single-frequency continuouswave operation, and on the other hand two-color as well as mode-locked emission. Particularly, the combination of semiconductor gain medium and external cavity provides a unique access to high-brightness output, a high beam quality and wavelength flexibility. Moreover, the exploitation of intra-cavity frequency conversion further extends the achievable radiation wavelength, spanning a spectral range from the UV to the THz. In this work, recent advances in the field of VECSELs are summarized and the demonstration of self-mode-locking (SML) VECSELs with sub-ps pulses is highlighted. Thereby, we present studies which were not only performed for a quantum-well-based VECSEL, but also for a quantum-dot VECSEL.