The slag in a molten state formed at a step of refining stainless steel is adjusted such that the slag has a basicity in the range of 1. The receiving communication device determines the timing error by processing a synchronization signal via a first stage filtering and interpolation process that includes predetermined coefficients and a second stage interpolation process that includes a minimal number of dynamically determined coefficients. Thus, an acoustooptic device can be obtained in which no laser damage nor optical damage is caused, and an ultraviolet acoustooptic device and an optical imaging apparatus using the same can be provided that do not necessarily require to be water-cooled. The second disk has B1\u02dcBm blocks for storing B1\u02dcBm data respectively.