Hannover 2016 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 45: Ultrashort Laser Pulses I
Q 45.6: Talk
Thursday, March 3, 2016, 12:15–12:30, a310
Resolving the evolution of femtosecond modelocking via real-time spectroscopy at 90 MHz — •Georg Herink1,2, Bahram Jalali2, Claus Ropers1, and Daniel S. Solli1,2 — 1IV. Physik, Friedrich Hund Platz 1, 37077 Göttingen — 2Department of Electrical Engineering, University of California, Los Angeles
Kerr-lens mode-locking (KLM) arises from noise and each starting event is highly stochastic and non-repetitive [1]. Conventional forms of time-resolved spectroscopy are incapable to trace the process with single-shot resolution over long record intervals. Here, we present real-time spectroscopy of the mode-locking transition in a KLM oscillator over 900,000 consecutive pulses. This is enabled by the Time-Stretch Dispersive Fourier Transformation (TS-DFT) and real-time electronic sampling [2,3]. We resolve the dynamics over the entire buildup with features on various timescales, i.e., the noisy onset of mode-locking milliseconds before the establishment of a femtosecond pulse, rapid spectral broadening and wavelengths shifts within few hundred roundtrips. In addition, we identify a previously unreported beating process via the Kerr nonlinearity which governs the spectral broadening. This process can be employed as a time-resolved probe of the intracavity nonlinearity. We expect that the results stimulate further theoretical analysis of mode-locking and establish real-time spectroscopy as a diagnostic tool for novel ultrashort sources and nonlinear systems.
[1] U. Keller, Nature 424, 831 (2003). [2] A. Bhushan, F. Coppinger, B. Jalali, Electronics Letters 34, 839 (1998). [3] D. Solli, G. Herink, B. Jalali, C. Ropers, Nature Photonics 6, 463 (2012).