Iterative reconstruction of thermally induced phase distortion in a Nd 3+ :YVO 4 laser

Ludovic Grossard (1) , Agnès Desfarges-Berthelemot (1) , Bernard Colombeau (1) , Claude Froehly (1)

1 XLIM-PHOT - Photonique Fibre et Sources Cohérentes

The thermal distortions in a continuous-wave end-pumped Nd:YVO 4 laser are experimentally investigated by use of an external TEM 00 probe beam (TEM standing for transverse electric magnetic). After a round-trip of this probe through the active medium, three irradiance profiles are recorded along its propagation axis. The distorted phase pattern of this probe beam is then reconstructed from these profiles by means of a Gerchberg-Saxton-like iterative algorithm. To identify the contribution of each kind of aberration in the phase profile, we have computed a Zernike polynomial expansion, and have shown that the main terms constituting the aberration are (in order) defocusing (optical path difference (OPD) 0.7 λ FWHM (full width at half-maximum)), spherical aberration (OPD 0.3 λ FWHM), and first-order astigmatism (OPD of ±0.14 λ p FWHM). Moreover, all higher-order terms result in a significant phase peak (λ/4 FWHM over 400 µm).

Mots clés: Solid-state laser; thermal distortions; diode-pumping; phase retrieval algorithm

Domaines: Optique / photonique

Ludovic Grossard, Agnès Desfarges-Berthelemot, Bernard Colombeau, Claude Froehly. Iterative reconstruction of thermally induced phase distortion in a Nd 3+ :YVO 4 laser. Journal of Optics A: Pure and Applied Optics, 2002, 4 (1), pp.1-7. ⟨10.1088/1464-4258/4/1/301⟩. ⟨hal-02112343⟩