BCMU-PDA

Channel waveguides of PTS-PDA single crystal on a Si/Si02 substrate have been fabricated by a photolithography technique [26]. The value of M2 in the PTS-PDA chain axis direction is found to be 3 X 10 cm /W at 1.06 pm. There will be a considerable contribution from two-photon resonance in this system. 

---

Fig. 7.34 The narrow energy range UPS spectra of 4-BCMU PDA, for the light polarization vector, E, parallel or perpendicular to the direction of the n-system.

The optical absorption maxima are revealed to be at 520, 500 and 420 nm for PTV, MOPPV and PPV films, respectively. X-ray diffraction patterns indicate that the PAV films have low crystallinity. The values of these PAV films evaluated by third-harmonic generation (THG) measurement at 1.85 pm are found to be 5.85 x 10 " esu, 3.2 X 10 esu, and 7.8 x 10 esu for PTV, MOPPV and PPV films, respectively. These values are non resonant values and are almost the same as that reported for a processible polydiacetylene (n-butoxycarbonylmethyl urethane) (n-BCMU-PDA, n = 4,3) thin film [18]. 

Near resonant z-scan studies provide both nonlinear refractive coefficients, ni, and two photon absorption coefficients, p. Results for a selection of PDAs in solution at 532 nm are given in Table 1. Diethylamino-PDA (lid) and the related quatemized polymer (15a) show comparable magnitudes of nonlinear absorption and refraction to those of poly-4-BCMU, with figures of merit, T, which satisfy the requirement for nonlinear optical switching devices. The metal-containing PDAs... 

The use of soluble PDAs in device-like structures is possible because they can be cast to form waveguides or quasi-waveguides. The films have various degrees of order, and this is manifested as a difference in colour the red phase is less ordered than the blue phase. The time-resolved intensity-dependent refractive index n2 for 4-BCMU has been measured by plasmon techniques [110] and found it to be 10" m W" Measurement of interferometric bistability in the same compound [110] has given an appreciably higher figure (5 X 10 m W at 653 and 700 nm). The reason for this discrepancy is not clear, and more work is needed in this area. THG studies on other soluble PDAs also give values around 10 esu, which corresponds to = 10 m [111]. 

---