PATTERN DYNAMICS IN A LARGE FRESNEL NUMBER LASER CLOSE TO THRESHOLD

A high Fresnel number laser close to threshold can be set at a detunin g value where it displays only the first transverse pattern with zero intensity in its center. However, the availability of a large phase sp ace gives rise to a new type of dynamics. Precisely, for this highly s ymmetric situation, the intensity pattern undergoes a transition betwe en stable and oscillating superpositions of traveling and standing wav es. Such a transition corresponds to the so-called Takens-Bogdanov bif urcation. We report experimental evidence of such a behavior.