Compact Femtosecond Lasers for Multiphoton Imaging

  • Shamil Mirkhanov

Student thesis: Doctoral ThesisDoctor of Philosophy


Multiphoton imaging currently is one of the main development directions in Laser Scanning Microscopy. A simplified way to assess suitability of a given laser for MPI applications is a figure of merit (FOM) approach based on peak power and average power of the particular excitation laser used. The first systematic studies of FOM for two-photon imaging within 336fs – 3.5 ps pulse duration range and repetition rate from 2.85 MHz to 90 MHz at 1 micron using a Yb fiber laser have been done in the first part of this thesis. Vertical External Cavity Surface Emitting Lasers (VECSELs), also called Semiconductor Disc Lasers (SDL) are nowadays capable of producing sub-100-fs pulses, multi-kW peak powers, and mode-locking has been demonstrated for wavelength range from 675nm to >2 microns. These flexible, low cost lasers have the potential to allow multi-source multiphoton microscopy system design. One of the most challenging aspects of VECSELs is the deposition of heat into the active region, leading to strong temperature – dependent performance. In contrast, recently introduced Distributed Bragg Reflector (DBR) free technology helps to address these challenges. The second part of this thesis describes the development of 1µm DBR free VECSEL - Membrane External Cavity Surface Emitting Laser (MECSEL), that demonstrated the record CW output power for these lasers reported so far. Finally, a new concept of DBR-free semiconductor saturable absorber based on the membrane technology was suggested. For the first time a membrane saturable absorber structure grown using MOVPE and processed via lateral etching is realized. This membrane saturable absorber was used to mode-lock a 1µm VECSEL for the first time.
Date of Award2018
Original languageEnglish
SupervisorKeith Wilcox (Supervisor) & Kees Weijer (Supervisor)

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