Figure 1

Synthesis and nonlinear optical measurements of silica–benzil (BZL:pSiO\(_2\)) nanocomposites. Mesoporous silica (pSiO\(_2\)) membranes (a), obtained by oxidation of electrochemically etched mesoporous silicon, constitute the host scaffold in the composite technology, while crystalline benzil (BZL) (b) represents the guest material ensuring non-linear optical functionality of the resulting composite material. (c) SEM image of top side of pSiO\(_2\) membrane. (d) BZL molecular structure. pSiO\(_2\) membranes were completely filled with BZL melt via capillary imbibition at about 105 \(^{\circ }\)C (e). A further slow cooling through the crystallization point (\(T_{cr}\) = 96 \(^{\circ }\)C ) leads to the formation of BZL nanocrystals inside the silica channels (f). (h) Sketch of the nonlinear optical setup (SHG experiment): Nd:YAG laser (\(\lambda =\) 1064 nm, \(E_p=\) 100 \(\upmu\)J, \(\tau =\) 30 ps); \(\lambda /2\), half-wave plate, GP Glan polarizer, \(L_1\) and L\(_2\) lenses, Sp measured sample, F interference filter (532 nm), PD photodiode, PM photomultiplier. The rotating half-wave plate serves to set a light polarization direction, (g) shows four fixed light polarization directions (s, sp, p or ps) used in angular (\(\alpha\)-scans) SHG measurements.