GeSb-Based Thin Films for Optical Storage Applications

Abstract

There are several applications of information technologies that can benefit from the large advances achieved in the field of ultrashort pulse generation. These include, among others, optical switching, routing or storage. The need for mass storage media compatible with all-optical information processing schemes using ultrashort laser pulses has lead us to investigate the feasibility of performing reversible phase change optical recording with ultrashort laser pulses. This work reports on the investigation of the optical writing/erasing (W/E) characteristics of Sb-rich GeSb based films with ps laser pulses. The optical contrast, W/E thresholds, amorphizability, amorphous phase stability and transformation time of these phase change media have been determined as a function of several parameters including pulse energy, film composition and thickness, and substrate properties. The write and erase operations are performed in static conditions using 10 ps laser pulses at 583 nm. The laser beam is spatially filtered and focused on the sample surface while the evolution of the reflectivity of the irradiated surface is measured in real time with a resolution of about 1 ns by means of a HeNe probe laser (633 nm). The films are initially either in crystalline or amorphous phase and are irradiated with a single pulse or with two pulses in order to reverse (erasing) the phase transformation induced by the initial (writing) pulse. In some cases, multiple laser pulses were accumulated in order to perform repetitive cycling among the amorphous and crystalline phases.