Strained superlattice with and without DBR From Wikipedia, the free encyclopedia A distributed Bragg reflector (DBR) is a reflector used in waveguides, such as optical fibers. It is a structure formed from multiple layers of alternating materials with varying refractive index, or by periodic variation of some characteristic (such as height) of a dielectric waveguide, resulting in periodic variation in the effective refractive index in the guide.reflectorwaveguidesoptical fibersrefractive index Each layer boundary causes a partial reflection of an optical wave. For waves whose wavelength is close to four times the optical thickness of the layers, the many reflections combine with constructive interference, and the layers act as a high-quality reflector.wavelengthoptical thicknessconstructive interference Hope to enhance QE in SSL photocathodes, while maintaining high polarization

DBR photocathode results

DBR QE: micro-Mott vs. H1 chamber

Effect of heating on polarization

Analyzing power

Standard SSL formula

Conclusions QE in micro-Mott slightly lower than in H1 chamber (load-locked system makes changing cathodes much easier though) DBR polarization excellent – comparable to best cathodes we’ve seen DBR enhancement is at wavelength where polarization isn’t maximum. Standard cathode has thus far yielded poor QE – our fault or the cathode? (working to resolve)

Full pile data sets, DBR