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

Abstract

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.

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

“…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].…”

“…Self-starting and reliable femtosecond pulse formation is achieved by passive modelocking with a semiconductor saturable absorber mirror (SESAM, [23,24]). In terms of cost-efficiency and reliability, their performance is similar or better than of femtosecond fiber oscillators, and furthermore, they can access higher average power levels [25,26]. In addition, femtosecond DPSSLs also have low intrinsic noise which makes them well-suited for optical frequency comb applications.…”

Sub-100 femtosecond pulses from a SESAM modelocked thin disk laser

“…To date, sub-100-fs pulses directly from a TDL have not been achieved [8]. Therefore, external pulse compression of TDLs was applied based on different techniques such as passive spectral broadening using self-phase modulation (SPM) [9], active spectral broadening in fiber amplifiers [10], and compression in gas-filled hollow core fibers [11].…”

Perfect Precision in Industrial Micro Machining

“…It was followed by many experiments that successfully scaled the average output power [4], increased the pulse energy and intensity [5], or reduced the pulse duration [6], partly by employing other laser materials than Yb:YAG that offer a broader gain bandwidth. The straightforward approach to generate higher laser pulse energies has always been to reduce the pulse repetition rate, leading to a concentration of more power in fewer pulses.…”