Ablation, Photobleaching, and Photodegradation

An azocopolymer was employed by Hattori et to produce SRGs with pulsed lasers as well as with a cw laser. In the first experiment, s-polarized beams of a 532 nm line of the mode-locked Nd YAG laser were made to impinge on the polymer surface. The average beam power was 0.4W, with a pulse duration of 100 ps and repetition rate of 82 MHz. In the second experiment, an SRG with 25 nm modulation amphtude was formed by exposing the film to an interference pattern of two s-polarized lights with 2.8 W/cm intensity, for 40 minutes. Infrared (IR) absorption spectroscopy indicated 

10 Temporal profiles of QCM resonant frer uencies when the laser beam is switched on and off. From reference 59. 

It has been demonstrated that photobleaching and photodegradation can play an important role on the SRG formation on ELBL films. These results will be discussed separately when the influence of film architecture is analyzed in Section 14.4.9, 

In order to produce surface-relief electro-optic gratings, Munakata et 

The films can be reused after the gratings had been completely erased by keeping the sample at 80 C for one minute. 

---