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

Mario Mangold,Matthias Golling,Bauke W Tilma,Ursula Keller,Christian A Zaugg,Sandro M Link

doi:10.1364/oe.22.006099

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.

Highlights

High power ultrafast laser sources with high gigahertz pulse repetition rates can be used in a broad field of applications, such as high-resolution optical sampling [1], frequency metrology [2] and ultra high-speed and high-bandwidth communication systems [3]
Coherent optical communication requires low-noise sources such as diode-pumped solid-state lasers (DPSSLs) modelocked with a semiconductor saturable absorber mirror (SESAM [4]), which have quantum noise limited performance [5]
The AR section reduces pump light reflection at the surface of the modelocked integrated external-cavity surface emitting laser (MIXSEL) chip and provides a flat and slightly positive group delay dispersion (GDD) within ± 15 nm bandwidth centered around the design wavelength of 960 nm

Summary

Introduction

High power ultrafast laser sources with high gigahertz pulse repetition rates can be used in a broad field of applications, such as high-resolution optical sampling [1], frequency metrology [2] and ultra high-speed and high-bandwidth communication systems [3]. Optically pumped SESAM-modelocked semiconductor disk lasers (SDLs) or vertical-external-cavity surface-emitting lasers (VECSELs [10, 11]) can be fabricated using inexpensive wafer scale mass production at considerably lower costs, making this technology the most prominent candidate for widespread industrial applications Those lasers are excellent candidates for such applications as they deliver femtosecond pulses with multi-watt average output power and excellent beam quality [12,13,14]. The modelocked integrated external-cavity surface emitting laser (MIXSEL [19]) combines the gain of VECSELs with the saturable absorber of a SESAM in a single integrated semiconductor layer stack This concept enables high-power ultrafast semiconductor lasers with reduced complexity, packaging, and manufacturing cost. To the best of our knowledge, in the pulse repetition rate range from 15 GHz to 101.2 GHz we obtained the highest average output power and highest peak power of any fundamentally modelocked laser (see Fig. 2)

MIXSEL concept and design

Experimental results

Conclusion and outlook