Abstract

Optical frequency combs have been revolutionizing many research areas and are finding a growing number of real-world applications. While initially dominated by Ti:Sapphire and fiber lasers, optical frequency combs from modelocked diode-pumped solid-state lasers (DPSSLs) have become an attractive alternative with state-of-the-art performance. In this article, we review the main achievements in ultrafast DPSSLs for frequency combs. We present the current status of carrier-envelope offset (CEO) frequency-stabilized DPSSLs based on various approaches and operating in different wavelength regimes. Feedback to the pump current provides a reliable scheme for frequency comb CEO stabilization, but also other methods with faster feedback not limited by the lifetime of the gain material have been applied. Pumping DPSSLs with high power multi-transverse-mode diodes enabled a new class of high power oscillators and gigahertz repetition rate lasers, which were initially not believed to be suitable for CEO stabilization due to the pump noise. However, this challenge has been overcome, and recently both high power and gigahertz DPSSL combs have been demonstrated. Thin disk lasers have demonstrated the highest pulse energy and average power emitted from any ultrafast oscillator and present a high potential for the future generation of stabilized frequency combs with hundreds of watts average output power.

Highlights

  • Optical frequency combs produced by modelocked lasers have revolutionized many research areas over the last decade in the fields of optical metrology, spectroscopy or attosecond science, to name a few

  • The residual integrated phase noise of only 339 mrad is the lowest value obtained from a gigahertz diode-pumped solid-state lasers (DPSSLs). These results clearly showed the benefit of a wavelength-stabilized pump source, and demonstrate that a tight carrier-envelope offset (CEO) lock can be achieved in DPSSLs with repetition rates in the gigahertz range using cost-efficient commercial multi-transverse-mode pump diodes

  • Two similar DPSSLs were successfully applied for ultra-low-noise microwave generation using five-stage pulse interleavers to multiply the repetition rate of the detected pulse trains to 3.2 GHz [75] and for dual-comb spectroscopy in a range between 1.55 and 2.25 μm after spectral broadening in an highly nonlinear fiber (HNLF) [76]

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Summary

Introduction

Optical frequency combs produced by modelocked lasers have revolutionized many research areas over the last decade in the fields of optical metrology, spectroscopy or attosecond science, to name a few. The first frequency combs were demonstrated from solid-state Ti:Sapphire lasers [11,12,13] as a result of their high peak power that is necessary to generate the coherent octave-spanning spectrum required for CEO detection in a nonlinear optical fiber. Pump diodes can be directly modulated via their injection current with a high bandwidth, which enables simple control or stabilization of fCEO via the pump current This is the most common method to CEO-stabilize fiber laser frequency combs using the self-referencing f-to-2f interferometry method [24]. Beside DPSSLs based on bulk gain media and TDLs, ultrafast dielectric waveguide lasers constitute another promising technology for future compact frequency comb generation with laser diodes pumping These lasers combine advantages of ion-doped solid-state and semiconductor lasers, with the potential to achieve high output powers with excellent beam quality and wafer-scale production capability with a high level of integration.

Optical Frequency Comb Self-Referencing
Nonlinear Interferometry for fCEO Detection
Coherent Supercontinuum Spectrum Generation
CEO Stabilization Loop
Self-Referenced DPSSLs with Bulk Gain Material
Chromium-Doped Lasers
One-Micrometer Ytterbium-Doped Lasers
Self-Referenced DPSSLs in Thin Disk Geometry
Findings
Conclusions and Outlook
Full Text
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