High gain and double phase conjugation with strongly doped Co:BaTiO₃ in reflection grating configurations

A study of highly doped photorefractive Co:BaTiO₃ reveals its usefulness for wave mixing through reflection grating interactions. Gain and noise figures are characterized for a counter-propagating pump-signal amplifier. Gain as high as 3 × 10⁷, extraction efficiency as high as 40% and noise equivalent power as low as 0.15 pW were demonstrated. To the best of our knowledge this is the highest photorefractive gain reported to date. In addition the double phase conjugate mirror (DPCM) is operated in a reflection grating geometry. High absorption limits the DPCM reflectivity to about 1%.