Abstract
Transverse mode-locking in an end-pumped solid state laser by amplitude modulation with an acousto-optic modulator was investigated. Using the stochastic parallel gradient descent algorithm the modal power coefficients and the modal phases of the transverse mode-locked (TML) laser beam were reconstructed from the measured spatial and spatio-temporal intensity distributions, respectively. The distribution of the reconstructed modal power coefficients revealed that the average mode order of the transverse mode-locking process could be increased by a factor of about 8 compared to previous works, corresponding to an increase in the normalized oscillation amplitude by a factor of about 3. Furthermore, we found that besides a non-Poissonian modal power distribution, strong aberrations of the modal phases occurred in the experiment, resulting in a deformation of the oscillating spot. Additionally, we demonstrated the generation of up to four spots oscillating simultaneously on parallel traces by operating the TML laser on a higher mode order in the orthogonal direction to the transverse mode-locking process. TML lasers are of interest, e.g., for beam scanning purposes, as they have the potential to enable spot resolving rates in the multi-GHz regime.
Highlights
The idea of transverse mode-locking was already suggested [1] and demonstrated [2] by Auston in 1968, shortly after the first demonstration of locking longitudinal laser modes in 1964 [3, 4]
The results will be presented in four separate sections: In the first section (Sect. 3.1) the time-averaged intensity distribution of the transverse mode-locked (TML) laser beam measured by the CCD-camera will be discussed, and the reconstruction of the modal power coefficients for different TML states will be given
The pump power required for the different TML beams was in average 8 ± 1 W, while the combined output power of output A and B ranged from 26.3 ± 0.6 mW up to 71.1 ± 0.69mW
Summary
The idea of transverse mode-locking was already suggested [1] and demonstrated [2] by Auston in 1968, shortly after the first demonstration of locking longitudinal laser modes in 1964 [3, 4]. Auston showed that by locking the phases of multiple Hermite–Gaussian (HG) modes a fast scanning beam, oscillating in the transverse direction of the optical axis, could be generated Since this initial demonstration of transverse mode-locking in a He–Ne laser the successful locking of transverse modes was realized in semiconductor [5] and solid-state lasers [6, 7]. While in previous publications the spatio-temporal intensity distributions of TML lasers have been measured, no analysis of the modal power distribution or the modal phases have been performed [2, 5,6,7] In most cases it was estimated, that a number of 2–7 modes had contributed to the mode-locking process, while the highest average mode order claimed was n = 4 [2]. By operating the laser on a higher mode order in the direction orthogonal to the mode-locking process the generation of up to four spots oscillating simultaneously on parallel traces could be demonstrated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
