A new type of fiber Bragg grating is proposed, which is called sliced fiber Bragg grating. Unlike the regular fiber Bragg
grating which is a fiber based working device, the new sliced fiber Bragg grating can be used as a free space component.
For example, a sliced fiber Bragg grating can be used as a laser diode external cavity. A multimode fiber Bragg grating
written on a 100um core size is cut into small segments of 1 to 2mm. Each end surface of the fiber Bragg grating
segment is polished and then coated with an anti-reflection coating. The fiber Bragg grating segment, or sliced fiber
Bragg grating, is used to manufacture an external cavity laser diode. The sliced FBG external cavity laser diode
bandwidth is reduced from 0.19nm to 0.06nm.
The very narrow bandwidth laser system, which is generated by diode-pumped solid-state laser emitting at 1064nm
wavelength with a fiber Bragg grating external cavity, has up to 20nm spectral line width and up to 40dB side mode
suppression ratio. Due to the resolution limitation of measurement equipment the real spectral line width could be
smaller than 20nm.