Solvent-free fluidic organic dye lasers

Abstract

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green- and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Förster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors.

Tunable and flexible solvent-free liquid organic distributed feedback lasers

“…The spectral width of the liquid DFB lasers optically pumped by a stripe (0.5 cm  0.08 cm) was typically between 2 and 3 nm, which is significantly smaller than the FWHM of the ASE peaks. As shown in a previous report, 13 the photoexcitation of the liquid organic light-emitting layer by a stripe is preferred to improve the device stability during the measurements. It should be noted however that these spectral linewidth values could be reduced down to 1 nm using smaller pump beam spot sizes, which is close to the resolution limit of our spectrometer.…”

“…9 In a lasing context, solventfree optofluidic organic lasers using 9-(2-ethylhexyl)carbazole (EHCz) doped with organic dyes were recently reported. 13 These devices were based on a Fabry-Perot microcavity structure and emitted in the green and red regions of the visible spectrum with lasing threshold in the nanosecond regime of about 20 and 500 lJ/cm 2 , respectively. Although their overall performances should be substantially improved for use in practical applications and blue lasing still needs to be demonstrated, this class of solvent-free optofluidic semiconducting lasers is expected to provide in the near future remarkable opportunities in optoelectronic and sensing applications.…”

“…In addition, cascade energy transfer from EHCz to green-and red-emitting laser dyes can be used to tune more efficiently the emission over a broad range of wavelengths. 13 The laser dyes were mixed with the liquid carbazole host in chloroform solution. After the full evaporation of the residual solvent, the liquid EHCz blends could be incorporated into the optofluidic devices by capillarity.…”

“…The gap between the PUA replica and the cover was then filled with the dye-doped EHCz by capillary action to complete the device structure. 9,13 Since DFB lasing occurs near the Bragg resonance wavelength according to the Bragg condition (i.e., mk Bragg ¼ 2n eff  K, where m is the order of the emission), the periods of grating structures must be carefully chosen for the second-order DFB operation (m ¼ 2). 14 One-dimensional grating structures with a period (height) of 280 nm (100 nm) for the blue-and green-emitting devices, and 400 nm (600 nm) for the red-emitting devices were individually employed as the corrugation patterns.…”

“…These decays of the emission are due to a bleaching of the light-emitting molecules. 13 To suppress this bleaching and obtain degradationfree laser characteristics, a microfluidic circuit should be integrated into the lasing devices in order to ensure a convectional circulation of the liquid semiconductor.…”