Stimulated emission and optical properties of pyranyliden fragment containing compounds in PVK matrix

Abstract

Organic solid state lasers are thoughtfully investigated due to their potential applications in communication, sensors, biomedicine, etc. Low amplified spontaneous emission (ASE) excitation threshold value is essential for further use of the material in devices. Intramolecular interaction limits high molecule density load in the matrix. It is the case of the wellknown red light emitting laser dye-4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). The lowest ASE threshold value of the mentioned laser dye could be obtained within the concentration range between 2 and 4 wt%. At higher concentration threshold energy drastically increases. In this work optical and ASE properties of three original DCM derivatives in poly(N-vinylcarbazole) (PVK) at various concentrations will be discussed. One of the derivatives is modified DCM dye in which the methyl substituents in the electron donor part have been replaced with bulky trityloxyethyl groups (DWK-1). These sterically significant functional groups do not influence electron transitions in the dye but prevent aggregation of the molecules. The chemical structure of the second investigated compound is similar to DWK-1 where the methyl group is replaced with the tert-butyl substituent (DWK-1TB). The third derivative (DWK-2) consists of two N,N-di(trityloxyethyl)amino electron donor groups. All results were compared with DCM:PVK system. Photoluminescence quantum yield (PLQY) is up to ten times larger for DWK-1TB with respect to DCM systems. Bulky trytiloxyethyl groups prevent aggregation of the molecules thus decreasing interaction between dyes and amount of non-radiative decays. The red shift of the photoluminescence and amplified spontaneous emission at higher concentrations were observed due to the solid state solvation effect. The increase of the investigated dye density in the matrix with a smaller reduction in PLQY resulted in low ASE threshold energy. The lowest threshold value was obtained around 21 J/cm 2 (2.1 kW/cm 2) in DWK-1TB:PVK films.

Deep‐Red Lasing and Amplified Spontaneous Emission from Nature Inspired Bay‐Annulated Indigo Derivatives

“…Comparison to reported materials showing ASE and lasing with red and deep‐red emission wavelengths were summarized in paper by Mamada et al, Figure shows the best ASE performance obtained for Cibalackrots A and B. Thickness dependent ASE threshold can be attributed to the strength of waveguide formed in the organic layer, similar thickness dependence has previously been reported for other organic materials . The ASE thresholds reported here are comparable to the best‐reported ASE thresholds for red and deep‐red emitting materials . Photostability of 230 nm thick films of 2 wt% doped Cibalackrot B in mixed host were also investigated at pump intensity of 2 × E th (≈20 µJ cm −2 ) as shown in Figure .…”

“…The spectral narrowing effect was clearly seen in all samples with FWHM dropping down to 10 nm at higher pumping intensities. These threshold values are comparable to other red and deep‐red laser dyes at doping concentrations of 5 wt% or higher.…”

Glass-forming nonsymmetric DWK-dyes with 5,5,5-triphenylpentyl and piparazine moieties for light-amplification studies

“…1, [5][6][7] To maintain a high transparency and optical clarity of such systems, those are usually obtained by expensive and technologically complicated thermal evaporation in vacuum on the glass/indium tin oxide (ITO) substrates. [6][7] Recently, we have demonstrated DCM-type dyes [= (2-(2-(4-(bis(2-(trityloxy)ethyl)amino) styryl)-6-methyl-4H-pyran-4ylidene)malononitrile derivatives (DWK)-type dyes] with additional incorporated bulky triphenyl moieties, [8][9][10][11] which provide the ability to form thin-solid films by non-expensive solution processing. Spin-coated neat films based on mono-styryl-and symmetric 2,6-bis-styryl-DWK-type dyes showed significantly increased photoluminescence quantum yields (PLQY) and notably lower amplified spontaneous emission (ASE) threshold energies in comparison with the conventional DCM dye.…”

“…Spin-coated neat films based on mono-styryl-and symmetric 2,6-bis-styryl-DWK-type dyes showed significantly increased photoluminescence quantum yields (PLQY) and notably lower amplified spontaneous emission (ASE) threshold energies in comparison with the conventional DCM dye. [8][9][10][11] However, the linking type of the bulky moieties via ether bonds is chemically unstable as de-trytilation may take place in slightly acidic conditions. It results in crystallization of the amorphous neat films, which leads to the decrease in the PLQY and increase in the ASE threshold values of the light-amplification medium.…”

Material gain concentration quenching in organic dye-doped polymer thin films

“…Additionally, DCM is quite sensitive to intermolecular interaction, such that typical dye concentrations do not exceed 2.0 wt.%. To overcome this limitation, Vembris et al added bulky trityloxyethyl groups to the molecule and successfully impeded quenching for these DCM derivatives [41].…”