The orientation of the transition dipole moment for S1-S4 excitation in rhodamine 6G is measured by excited state absorption with a picosecond pump and probe technique. An orientation parallel to the longitudinal direction of the molecule is found. The result is discussed in terms of molecular symmetry.

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1.5-µm-wavelength distributed feedback lasers with a deeply etched first order vertical grating were realized for the first time. It was shown that we can obtain an effective coupling by reducing the stripe width. The sample with the cavity length of 430 µm, 1.8 µm stripe width and 0.2 µm grating depth on each lateral side exhibited a 12.5 mA threshold current, 37% total differential quantum efficiency and 35 dB submode suppression ratio at a bias current of two times the threshold.

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