Uwe Bandelow, Markus Kantner, Hans Wenzel
01.01.2021 − 31.12.2021
Ultra-narrow linewidth lasers are key elements of high-precision metrology systems including optical atomic clocks, matter interferometers or gravitational wave detectors. The spectral width of the emitted optical power spectrum is essentially determined by the variance of the laser’s phase noise spectrum, that is influenced by numerous stochastic processes. The dominant process is quantum noise due to (incoherent) spontaneous emission of photons into the laser mode, which is well-described by Gaussian white noise. While this process is commonly included in (standard) stochastic laser theories, the description of real experiments requires an extension of the model by numerous further noise sources such as charge carrier recombination noise, pump current fluctuations as well as temperature fluctuations and even mechanical vibrations.
These processes are associated with non-Markovian effects (colored noise) and lead to significant low-frequency fluctuations and hence a broadening of the laser linewidth. As direct modeling by first principles methods (Heisenberg-Langevin equations) is hardly accessible, we pursue a data-driven modeling approach to reconstruct the noise covariance matrix and its dependency on control parameters from experimental data (provided by the Ferdinand-Braun Institute).
The goal of this project is the theory-based optimization of extended cavity diode lasers for space-based metrology systems. The limiting factor to achieve highly stable continuous-wave emission with very narrow spectral linewidth are noise-induced dynamical instabilities (especially hopping to coexisting attractors), which occur preferentially in designs with long (passive) resonator sections. The extended stochastic laser model (traveling wave model with Langevin noise sources), which will be developed within the scope of this project, will facilitate the understanding of performance bottlenecks and support the identification of an optimal laser design and suitable control schemes.
International workshops co-organized by the project-PIs with support by MATH+: