*4.1.2 LD's directional emission*

The directional emission beam with a small divergent angle of LD can be easily collected and focused on phosphor film compared to the LED's Lambertian emission, as shown in **Figure 2(b)**. LD's etendue is very small and can achieve high-luminance lighting; hence, LD can be used in automotive lighting. Bayerische Motoren Werke (BMW) proposed a headlamp by exciting blue LD on remote phosphor film. It was reported that the efficiency and brightness of LD-based headlamp are higher than LED-based headlamp [17]. LD-based headlamp can project the high luminescent, low divergent white beam to half-mile from the vehicles. The laser beam's visual range is 600 m, while that of the LED is 300 m [18]. In the case of LD-based SSL, a small phosphor area and small lens are required; thus, generated light can be more efficiently coupled into an optical fiber and used for micro luminaires.
