arXiv subjects

Dennis C. Kirsch

Publications and source records attributed to Dennis C. Kirsch.

3 recordsLinked to original sources

arXiv2026

Self-starting Dynamics in All-fibre All-Normal-Dispersion Thulium Mamyshev oscillator

Ultrashort pulse formation from noise represents a fundamental self-organisation process in nonlinear dissipative systems and remains central to ultrafast photonics. Mamyshev oscillators offer a particularly valuable platform for investigating this phenomenon because they do not rely on conventional saturable absorbers. Instead, pulse formation is governed by self-phase modulation in normal-dispersion fibres combined with periodic offset spectral filtering. Achieving self-starting pulse formation in these systems is challenging, particularly at longer wavelengths, due to limited normal-dispersion components and the complex gain dynamics. This work reports, to the best of current knowledge, the first self-starting, all-fibre, all-normal-dispersion Thulium-doped Mamyshev oscillator operating near 1.9um. The cavity employs a compact Fabry-Perot design incorporating a dispersion-engineered Thulium-doped gain fibre, a highly nonlinear passive normal-dispersion fibre, and a pair of chirp-free broadband fibre Bragg gratings. The oscillator self-starts without external seeding or active modulation and stabilises noise-like pulse generation regime at a fundamental cavity repetition rate. Real-time measurements and numerical simulations reveal the build-up pathway from noise through transient multi-pulsing and pulse competition to a stationary noise-like envelope. Our results show that both tailored laser components and gain-medium-specific dynamics are essential for enabling self-starting ultrashort pulse generation in Mamyshev oscillators and for extending these laser concepts beyond the near-infrared, thereby facilitating the development of compact and robust shortwave infrared (SWIR) sources and new regimes of ultrafast self-organisation.

physics.optics↗

arXiv2022

Unravelling Saturable Absorption of Thulium-doped Fibres for New Level of Integrated Femtosecond Pulse Generation

The ultrashort pulse laser operation is crucially defined by engaging explicit modulators. Conventionally, they are laborious to incorporate into an all-fibre design or involve the design of sophisticated cavities. We exploit Thulium-doped fibre as the gain and simple, highly integrated saturable absorber with a modulation depth of 23% and a high thermal damage threshold. Hence, pulses as short as 350fs carrying 1nJ energy at a repetition rate of 45MHz have been demonstrated. The laser average output power showed long-term stability with ~1%. The utilised concept of all-fibre saturable absorber provides technological grounds for a down-scaled, highly integrated laser architecture.

physics.optics↗

arXiv2021

Gain-controlled Broadband Tuneability in Mode-locked Thulium-doped Fibre Laser through Variable Feedback

Broadband wavelength tuneability can ensure a new level of versatility for laser systems and extend areas of their applications. Principle limitations of achieving wide tuning wavelength ranges are generally defined by the spectral bandwidth of the gain and traditional tuneability techniques, relying on electrically controlled or bulk filters, reducing laser efficiency and generation stability. In this work, we present nearly 90 nm tuneability in ultrafast Tm-doped fibre laser within the span from 1873 to 1962 nm by implementing variable feedback for efficient control of the excitation level of the active medium and, hence, the gain spectrum. The highest laser efficiency is observed with 20% feedback, generating 580-fs soliton pulses at 1877 nm central wavelength with 1.5 nJ output pulse energy. By combining the nonlinear Shrodinger equation and population inversion rate equations for the gain medium, the developed numerical model helps to unveil nonlinear pulse evolution under the influence of dynamically varying gain spectrum. The resulting laser system presents a compact and straightforward approach to achieve laser generation with a broad range tuneability of wavelength and operation regimes, which is not impaired by the limitations on laser stability or power performance and can be translated to other wavelength ranges.

physics.optics↗