Semiconductor saturable absorber mirror structures with low saturation fluence

Spühler, G.J.; Weingarten, K. J.; Grange, Rachel; Krainer, L.; Haiml, M.; Liverini, V.; Golling, Matthias; Schön, S.; Keller, U.

doi:10.1007/s00340-005-1879-1

Cited by 127 publications

(69 citation statements)

References 26 publications

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“…For example, picosecond diode-pumped solid-state lasers have successfully been demonstrated up to 160 GHz at 1.06 µm [45] and up to 100 GHz at 1.5 µm [46,47]. The extension of these results to the femtosecond regime looks very promising considering for example the large progress on Yb-doped solid-state laser crystals that support sub-100 fs pulses [26,27,48] and the development of optimized SESAMs for gigahertz operation [49,50]. Furthermore, high average power ultrafast gigahertz lasers may become even more compact and cost-effective with the recent development of SESAM mode-locked optically-pumped semiconductor disk lasers (also referred to as optically-pumped vertical external cavity surface emitting lasers, OP-VECSELs) [51].…”

Section: Discussionmentioning

confidence: 99%

Self-referencable frequency comb from a 170-fs, 1.5-μm solid-state laser oscillator

et al. 2009

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We report measurement of the first carrier-envelope offset (CEO) frequency signal from a spectrally broadened ultrafast solid-state laser oscillator operating in the 1.5 µm spectral region. The f -to-2f CEO frequency beat signal is 49 dB above the noise floor (100-kHz resolution bandwidth) and the free-running linewidth of 3.6 kHz is significantly better than typically obtained by ultrafast fiber laser systems. We used a SESAM mode-locked Er:Yb:glass laser generating 170-fs pulses at a 75 MHz pulse repetition rate with 110-mW average power. It is pumped by one standard telecom-grade 980-nm diode consuming less than 1.5 W of electrical power. Without any further pulse compression and amplification, a coherent octave-spanning frequency comb is generated in a polarization-maintaining highly-nonlinear fiber (PM-HNLF). The fiber length was optimized to yield a strong CEO frequency beat signal between the outer Raman soliton and the spectral peak of the dispersive wave within the supercontinuum. The polarizationmaintaining property of the supercontinuum fiber was crucial; comparable octave-spanning supercontinua from two non-PM fibers showed higher intensity noise and poor coherence. A stable CEO-beat was observed even with pulse durations above 200 fs. Achieving a strong CEO frequency signal from relatively long pulses with moderate power levels substantially relaxes the demands on the driving laser,

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Section: Discussionmentioning

confidence: 99%

Self-referencable frequency comb from a 170-fs, 1.5-μm solid-state laser oscillator

et al. 2009

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“…Such a device exhibits higher reflectivity for higher pulse fluences and therefore favors pulsed over CW operation. The key advantage of the SESAM is its large flexibility to optimize the absorber parameters [33,34], which prevents mode locking instabilities such as Q-switched mode locking [35]. SESAM designs for high-power thin disk lasers often use a dielectric top coating for the reduction of two-photon absorption (Fig.…”

Section: Mode-locked Thin Disk Lasersmentioning

confidence: 99%

High-power ultrafast thin disk laser oscillators and their potential for sub-100-femtosecond pulse generation

et al. 2009

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Ultrafast thin disk laser oscillators achieve the highest average output powers and pulse energies of any mode-locked laser oscillator technology. The thin disk concept avoids thermal problems occurring in conventional high-power rod or slab lasers and enables high-power TEM 00 operation with broadband gain materials. Stable and self-starting passive pulse formation is achieved with semiconductor saturable absorber mirrors (SESAMs). The key components of ultrafast thin disk lasers, such as gain material, SESAM, and dispersive cavity mirrors, are all used in reflection. This is an advantage for the generation of ultrashort pulses with excellent temporal, spectral, and spatial properties because the pulses are not affected by large nonlinearities in the oscillator. Output powers close to 100 W and pulse energies above 10 µJ are directly obtained without any additional amplification, which makes these lasers interesting for a growing number of industrial and scientific applications such as material processing or driving experiments in high-field science. Ultrafast thin disk lasers are based on a power-scalable concept, and substantially higher power levels appear feasible. However, both the highest power levels and pulse energies are currently only achieved with Yb:YAG as the gain material, which limits the gain bandwidth and therefore the achievable pulse duration to 700 to 800 fs in It is important to evaluate their suitability for power scaling in the thin disk laser geometry. In this paper, we review the development of ultrafast thin disk lasers with shorter pulse durations. We discuss the requirements on the gain materials and compare different Yb-doped host materials. The recently developed sesquioxide materials are particularly promising as they enabled the highest optical-tooptical efficiency (43%) and shortest pulse duration (227 fs) ever achieved with a mode-locked thin disk laser.

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“…These losses have to be compensated by an active region with sufficient modal gain. To achieve maximum mode gain, the active QWs have to reside in standing wave antinodes, which corresponds to a high enhancement factor for the electric field distribution [37]. Usually, several QWs are placed into one antinode, but their number is limited by the width of the standing wave peak.…”

Section: 4mentioning

confidence: 99%

“…For stable mode-locking operation, the saturation energy of the absorber has to be lower than for the gain [4,10]. The ratio can be controlled by the field enhancement and the intrinsic absorber properties [37]. In the OP-MIXSEL [10], the saturable absorber has a higher field enhancement and QDs have been used to lower the modulation depth by adjusting the quantum-dot density ac-FIGURE 10 Sketch of the optimized EP-VECSEL design (not to scale) cordingly.…”

Section: 5mentioning

confidence: 99%

On the design of electrically pumped vertical-external-cavity surface-emitting lasers

et al. 2008

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Vertical-external-cavity surface-emitting lasers (VECSELs) yield an excellent beam quality in conjunction with a scalable output power. This paper presents a detailed numerical analysis of electrically pumped VECSEL (EP-VECSEL) structures. Electrical pumping is a key element for compact laser devices. We consider the optical loss, current confinement, and device resistance. The main focus of our investigation is on the achievement of an adequate radial carrier distribution for fundamental transverse mode operation. It will be shown that a trade off between the conflicting optical and electrical optimization has to be found and we derive an optimized design resulting in guidelines for the design of EP-VECSELs which are compatible with passive mode locking. Vertical-external-cavity surface-emitting lasers (VECSELs) [1] are of high scientific and industrial interest due to their large fundamental transverse mode output power, scaling with the device radius, the near diffraction limited output beam, and the suitability for intracavity frequency conversion [2] and passive mode locking [3,4]. Passive mode locking of an optically pumped VECSEL has been demonstrated with a semiconductor saturable absorber mirror (SESAM) [5] in a folded external cavity. After the first passively mode locked VECSEL was demonstrated in the year 2000 [6], the milestone of nearly 1 W average output power was achieved in 2002 with improved thermal management [7]. The pulses in the early experiments were often strongly chirped, but mode-locking dynamics in VECSELs revealed that a soliton-like pulse-shaping mechanism in the positive-dispersion regime can help to generate short pulses with low chirp. With the aid of intracavity dispersion control, it then became possible to obtain nearly transform limited picosecond pulses with record high output powers of 2.1 W at 4 GHz [4] and 1.4 W at 10 GHz [8]. The pulse width could be u Fax: +41-44-633-10-59, E-mail: keller@phys.ethz.ch significantly shortened to the sub-500-fs regime using faster SESAMs based on the ac Stark effect [9]. The vertical integration of the absorber into one monolithic structure with the gain quantum wells (QWs) is an important step towards higher pulse repetition rates with decreased cavity size and wafer-scale integration. This has been achieved for the first time and is referred to as the mode-locked integrated-externalcavity surface-emitting laser (MIXSEL) [10]. So far, all these devices have been optically pumped, which involves a more complex optical setup. Thus, an important step towards waferscale fabrication of compact ultrafast VECSELs is the design of electrically pumped VECSEL (EP-VECSEL) structures. This is challenging because of optical losses and Joule heating in the doped layers. Nevertheless, continuous-wave (cw) EP-VECSELs have been demonstrated [11,12] and output powers of up to 900 mW have been obtained with a 150-µm device diameter in multimode operation [13]. Also, mode locking with down to 15-ps FWHM pulse width [14] and a wafer-scale EP-VECSEL w...

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Semiconductor saturable absorber mirror structures with low saturation fluence

Cited by 127 publications

References 26 publications

Self-referencable frequency comb from a 170-fs, 1.5-μm solid-state laser oscillator

Self-referencable frequency comb from a 170-fs, 1.5-μm solid-state laser oscillator

High-power ultrafast thin disk laser oscillators and their potential for sub-100-femtosecond pulse generation

On the design of electrically pumped vertical-external-cavity surface-emitting lasers

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