Deciphering output coupling mechanisms in spiral microcavities with femtosecond light bullets.
A pump-probe two-photon-excited fluorescence technique deciphers in space and time the propagation of ballistic wave packets sustained by whispering-gallery modes (WGMs) in a spiral-shaped microcavity. Diffraction on the spiral discontinuity does not prevent the WGMs from closing. The resultant average Q of the resonator is 3 x 10(4) +/- 50%. Experimental results are compared with numerical simulations, providing evidence of a new contribution to output coupling: Part of the WGM evanescent wave is reflected at the spiral notch and leads to a propagating wave at an angle that matches the previously observed laser emission direction in 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran-doped poly(methyl methacrylate) and InGaN spiral lasers.
Courvoisier
F
F
Laboratoire de Spectrométrie Ionique et Moléculaire, Unité Mixte de Recherche Centre National de la Recherche Scientifique 5579, Université Claude Bernard Lyon 1, 43, Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
Boutou
V
V
Wolf
J P
JP
Chang
R K
RK
Zyss
J
J