Abstract

Efficient amplified spontaneous emission (ASE) from terfluorene (T3, the molecular structure as shown in figure 1) has been report by Lin et al. [1], We have report on the fabrication of low-threshold distributed feedback (DFB) organic solid-state lasers based on the terfluorene. The silicon wafer with 2μm silicon dioxide was used as the substrate. A second-order DFB grating with the period of 280mn or 300nm had been realized by the electron-beam lithography of the e-beam resist. The gratings had a duty ratio of 70:30 (hill: valley) to lower the laser threshold. Then the 80-mn thick organic thin film (T3) was deposited on the grating by the vacuum deposition. The organic DFB lasers was pumped by pulsed Nd-YAG laser (λ=355nm. 10Hz). Lasing action was observed near the Bragg wavelength: mλ_Bragg= n_effA, m is the order of the emission, A is the grating period, n^ is the effective refractive index of the waveguide. The lasing was surface emitting; the laser emission wavelength and the Bragg wavelength can be tuned by varying the grating period and .the effective refractive index of the waveguide (e.g. varying the film thickness). Figure 2 shows the surface-emission spectra of the organic DFB laser compared with photoluminescence (PL) and ASE spectra of the T3 material. The lasing action occurred at 423mn (A=280mn) and 448mn (A=300nm) above the threshold. The emission wavelength is in the deep blue region. The full width at half maxima of the laser was measured to be about O.llmn, limited by the resolution of the spectrometer. Figure 3 shows the output intensity of the organic laser versus the pump intensity for thickness of 280mn. A low threshold of 0.53KW/cm² was observed.

© 2007 IEEE