Measurement of photon echoes at 1.5 μm in Er³⁺:Y₂SiO₅ using a diode laser and amplifier

Photon echo measurements in the 1.5-μm region on Er3+ were conducted in Y2SiO5 crystals. A critical parameter, the optical dephasing time, was observed to be due to nuclear spin fluctuations and mutual Er-Er spin flips. A 1.5-μm laser diode and an Er-doped fiber amplifier were used in the measurements. Time evolution of linewidth measured with three pulse stimulated echoes showed 89Y spin flip distribution had a slower component contributing to spectral diffusion. In a magnetic field of 8 kG, the homogenous linewidth increased from 20 KHz at a 50 μs delay to 120 KHz to a 700 μs delay.