Pulse repetition rate scaling from 5 to 100 GHz with a high-power semiconductor disk laser

Abstract

The high-power semiconductor laser studied here is a modelocked integrated external-cavity surface emitting laser (MIXSEL), which combines the gain of vertical-external-cavity surface-emitting lasers (VECSELs) with the saturable absorber of a semiconductor saturable absorber mirror (SESAM) in a single semiconductor layer stack. The MIXSEL concept allows for stable and self-starting fundamental passive modelocking in a simple straight cavity and the average power scaling is based on the semiconductor disk laser concept. Previously record-high average output power from an optically pumped MIXSEL was demonstrated, however the long pulse duration of 17 ps prevented higher pulse repetition rates and many interesting applications such as supercontinuum generation and broadband frequency comb generation. With a novel MIXSEL structure, the first femtosecond operation was then demonstrated just recently. Here we show that such a MIXSEL can also support pulse repetition rate scaling from ≈5 GHz to >100 GHz with excellent beam quality and high average output power, by mechanically changing the cavity length of the linear straight cavity and the output coupler. Up to a pulse repetition rate of 15 GHz we obtained average output power >1 W and pulse durations <4 ps. Furthermore we have been able to demonstrate the highest pulse repetition rate from any fundamentally modelocked semiconductor disk laser with 101.2 GHz at an average output power of 127 mW and a pulse duration of 570 fs.

Tantalum pentoxide waveguides and microresonators for VECSEL based frequency combs

“…This can be coupled with intra-or extra-cavity heat-spreaders, which are becoming a standard feature of high performance results. The most noteworthy variant of thermally managed VECSELs is the Membrane External Cavity Surface Emitting Laser (MECSEL) [34][35][36] where the periodic gain structure is acid-etched completely from (On a log-log scale) Peak power results for sub-ps VECSELs (blue) and MIXSELs (red) [28][29][30][31][32][33] . Results are distinguished by direct output (circle) external pulse compression (upward-triangle) and repetition-rate tunable (downwardtriangle).…”

High power sub-200fs pulse generation from a colliding pulse modelocked VECSEL

“…4 Secondly, the semiconductor gain medium of the VECSEL is advantageous for applications requiring high repetition rates (>1GHz), as the relatively short carrier lifetime largely suppresses spontaneous Q-switching instabilities, often observed with dielectric gain media. 5 The passive modelocking of VECSELs has been demonstrated with semiconductor saturable absorber mirror (SESAM) at repetition rates ranging from 85MHz to 100GHz, 6,7 and at operating wavelength ranging from 665nm 8 to 1960nm. 9 To date, the best performance in terms of power and pulse duration has been demonstrated between 960 and 1080nm, 10,11 where the semiconductor media benefit from the maturity and advantages of GaAs-based materials.…”

Recent advances in ultrafast semiconductor disk lasers

“…Nevertheless, repetition rates up to 50 GHz have been obtained with a fundamentally mode-locked VECSEL 35 . Recently, the maximum repetition rate has been increased up to 100 GHz with the MIXSEL 51 , which was possible due to the simple linear cavity. The cavity length was only 1.5 mm in this case.…”

“…A repetition rate-tuning range of several GHz has been demonstrated with an SESAM-mode-locked VECSEL in the 1-10 GHz repetition rate range without changing any cavity components 86,118,119 . With the MIXSEL, a scaling range from 5 to 100 GHz has been achieved using the same MIXSEL semiconductor chip but different OC 51 . The transmission and ROC of the OC had to be adapted to ensure a stable cavity configuration.…”

“…Therefore, we target ultrafast VECSELs, which provide 100-150-fs pulses with average output powers of several hundreds of mW directly from the oscillator. The rapid progress in the field of SESAM-mode-locked VECSELs 27,28,45 and MIXSELs 50,51 indicates that the desired performance is within reach.…”