980-nm-pumped Er-doped LiNbO/sub 3/ waveguide amplifiers: a comparison with 1484-nm pumping

A Zn‐diffused Mach–Zehnder modulator on lithium niobate at 1.55‐μm wavelength

“…For highspeed and low-voltage operation, Ti indiffusion (TI) LiNbO 3 waveguide modulators are among the most favored candidates due to their low propagation loss and large electrooptic (EO) coefficient; commercially available Mach-Zehnder modulators used for optical communication at the 1.55-m wavelength have achieved switching rates of 40 GHz. Although the TI waveguide devices have remarkable properties for applications in optical integrated circuits, the annealing proton exchanged (APE) and Zn indiffusion (ZI) waveguides are still studied extensively due to less susceptible to photorefractive damage, particularly compared to those at wavelengths below 0.8 m [4,5].Recently, Er-doped waveguide amplifiers on LiNbO 3 with a 1.48-m or 0.98-m pumping wavelength have been demonstrated in order to realize waveguide lasers at around 1.55-m wavelength [6]. The active properties of the Er:LiNbO 3 can be further combined with the excellent electro-optic and acusto-optic properties of LiNbO 3 in order to make a more compact device, such as a mode-locked laser, Q-switch laser, or integrated transmitter [7,8].…”

Phonon‐assisted energy transfer in Er‐exchanged LiNbO 3

“…Such modification of fabrication technique was used to avoid surface damage, which otherwise degrades the optical properties of the crystals [8]. To clarify new probable specific features of fluorescence spectra of Er-exchanged LiNbO 3 originated from newly developed doping technique, we compared these spectra with the ones measured in Er:LiNbO 3 doped by Er-indiffusion technique, which is in a common use today [1,2]. To reach this aim, Z-and X-cut LiNbO 3 substrates were doped near the surface by indiffusion of a 12 nm thick evaporated Er layer at 1100 °C for 100 hours.…”

“…near 1550 nm [1,2]. However, Er doping is known to lead to upconversion in most host materials (including LiNbO 3 ) [2][3][4], which is widely recognized as a gain limiting factor in Er-doped amplifiers [2,3]. General feature of all the upconversion mechanisms consists of phononassisted processes, providing both a high efficiency of nonresonant excited-states absorption [5] and excited-states repopulation through its selective nonradiative decay within either isolated Er 3+ ions [3,5] or clustered ones [4,5].…”

“…near 1550 nm [1,2]. However, Er doping is known to lead to upconversion in most host materials (including LiNbO 3 ) [2][3][4], which is widely recognized as a gain limiting factor in Er-doped amplifiers [2,3].…”

“…Thus, the upconversion can be suppressed by a proper choice of doping technology [2,3] and/or postdoping processing [4,6], which may provide as sufficient decreasing the relative concentration of clustered ions [3,4,6] as well as a strong alteration of electron-phonon coupling via variation either a lattice site of Er 3+ ion [4,5] or a phonon spectrum of host [2,5]. In light of the wellestablished limitations [2,6] of Er indiffusion technique, Er exchange technique, inducing unusual chemical bonding rearrangement and evident crystal structure modification [7], appears to open the new possibilities for selective manipulation of phonon-assisted processes in Er:LiNbO 3 and, hence, for suppression of upconversion.…”