Selective grating obtained by dye microstructuration based on local photobleaching using a laser writer

Abstract

We propose a method to pattern organic optically active materials based on local photo-bleaching for making wavelength selective grating. Usually, photo-bleaching is considered as a limitation for organic emitter. Here, this property is exploited to locally suppress dye emission and absorption at the microscale with abrupt interface and no changes in layer thickness. Periodic patterns were fabricated and exhibit diffraction only at 590nm wavelength with spectral selectivity of 11nm. Based on laser writer flexibility and efficiency, this study shows the potential of local photo-bleaching for several applications like wavelength selective grating fabrication.

Raman investigation of local photo‐bleaching in TDBC dye layer for photonics applications

“…For bleached TDBC, no significant emission was detected. For active TDBC, we clearly see that the maximum of the emission is obtained at around 590 nm, as expected, [ 10 ] only under UV or between ~500 and 600 nm of pumping. Therefore, we expect that fluorescence will potentially disturb the Raman spectra only for green pumping because no signal for the excitation spectra is found at 405 and 633 nm and that the fundamental emission (i.e., 590 nm) is far from the UV pump.…”

“…This assumption was finally confirmed by X-ray Photoelectron Spectroscopy (XPS) measurements indicating similar stoichiometry and small change in the nature of an N atomic bonds after bleaching. Therefore, this work indicates that TDBC molecule is only slightly affected by the photo-bleaching mechanism even if optical properties are radically changed at around 590 nm wavelength [10] . These observations can now explain the fact that the refractive index is not changed by the photo-bleaching out of the fundamental energy at ~590 nm wavelength [6,10,14] .…”

“…The concentration of the TDBC aqueous solution is 8.39×10 -3 M. The spin coated layer has a 17 nm thickness evaluated by plasmon fitting [6,17] . For the insolation (Figure 1-b) laser writer [10] or Nikon optical microscope was then used to locally insolate the layer. After insolation, regions which have been exposed to the light are locally photo-bleached (Figure 1-c).…”

“…Advantage can also be taken from photobleaching like for mobility measurement in biology [4] or for Tetrachloro Diethyl Benzimidazolo Carbocyanine (TDBC) dye. For TDBC J-aggregated layers, photo-bleaching is widely used for strong coupling studies [5][6][7][8][9] and more recently for wavelength selective grating fabrication [10] . Indeed, TDBC dye layers have very interesting optical properties since they have a high oscillator strength at around 590 nm wavelength [11][12][13] which can be suppressed under illumination [6] .…”

“…Indeed, TDBC dye layers have very interesting optical properties since they have a high oscillator strength at around 590 nm wavelength [11][12][13] which can be suppressed under illumination [6] . Therefore, using local insolation, photo-bleaching can thus both spectrally and spatially change the refractive index with very high contrast at the micro-scale [10] . This property could be also exploited for other applications like light concentration [11] or integrated optics since the refractive index contrast is even higher [14] than usual materials [15] .…”