DenseLight DL-CLS Series is a cooled ultra narrow linewidth laser in BTF/DIL package with a single frequency emission. This laser is based on proprietary external cavity laser design utilizing a built-in fiber Bragg grating, offering very stable performance of lasing wavelength, narrow spectral linewidth and excellent SMSR. The as-built lasing wavelength can be specified precisely to 1nm, and further precision (down to picometer range) can be achieved through minor tuning in the internal cooler temperature or drive current. The device can be intensity modulated up to 622Mbps. High speed frequency modulation can be achieved by directly modulating its drive current. Typical output power is up to 20mW CW, with pulsed power up to 50mW. Higher output power are available on custom models.