Blu-ray recordable disc. The laser wavelength is only 405nm, numerical aperture is 0.85, the color of the laser is blue, so it is called Blu-ray disc, is a once written disc. It Can be used to play high-definition movies and be large capacity data storage, etc. BD-R according to the number of layers can be classified to single layer and double layer. Single layer's capacity is 25GB, double layer's capacity is 50GB. BD-R according to production process can be classified as HTL and LTH. HTL's recording medium is inorganic phase change materials, reflectivity of recording medium after it is burned by laser will be lower, and LTH's recording medium is organic dye, reflectivity of recording medium after it is burned by laser will become higher. BD-R's 1X speed is 4.92 m/s, according to the recording speed BD-R can be divided into 4X, 6X and 8X disc. By forming pit and land of light and shade to record data. Single layer HTL BD-R disc manufacturing technology: on the 1.1mm thickness of the substrate, first sputtering reflecting layer, then filling the recording medium, finally coating and curing glue layer. BD-R is also the same as the DVD+R, which uses the high frequency wobble groove. BD-R is addressed by the phase change of the wobble groove.