The 08-NLDM 785 nm ESP complements the Cobolt series of compact high-performance single frequency and narrow linewidth lasers covering a broad range of 405 nm – 1064 nm with a spectral purity of >60 dB as close as 0.3 nm away from the main peak.
Instead of using a partially transmissive Volume Bragg Grating element (VBG) as in the conventional frequency locked diode laser, a highly reflective VBG element is used as the wavelength selective component in the external cavity. An intra-cavity polarizing element and a polarizing beam splitter are used to control the level of feed-back from the VBG to the emitter and the output coupling out of the cavity. In this way, only the stimulated emission is coupled out of the cavity and the broad-band non-stimulated emission is leaking out of the VBG element. The resulting spectral purity is similar to what is achieved with an external VBG clean-up filter, but with the use of only one single VBG element making the system very cost effective.