Erbium-doped Lithium Niobate waveguide lasers: recent progress

Erbium diffusion doping of LiNbO3 (e.g. 30 nm / 1130 °C / 150 hrs) is the preferred method to fabricate an excellent laser material for integrated optics. After Er-doping single mode channel waveguides are defined by the standard indiffusion technique of Ti-stripes. By optical pumping at λ = 1480 nm a wavelenth dependent gain of up to 2 dB/cm is achieved (1530 nm < λ < 1610 nm). Different types of narrow linewidth Distributed Bragg Reflector (DBR-) and Distributed FeedBack (DFB-) lasers will be presented. They are based on photorefractive gratings holographically defined in Ti/Feand in Ti/Fe/Er-codoped waveguide sections. Single frequency emission at several wavelengths within the Er-gain band around λ ~ 1550 nm and an output power of up to 8 mW have been achieved. The range for continuous tuning of acoustooptically tunable lasers could be extended to 47 nm (1530 nm < λ < 1577 nm). The emission linewidth has been reduced to 12 pm. Moreover, a tunable frequency shifted feedback laser with a variety of remarkable properties has been developed. As one application optical frequency domain ranging will be presented with a resolution better than 1 mm. The concept of ring lasers in Er:LiNbO3 is introduced with their potential to be used as optical gyro. First experimental results are reported; by pumping the ring of 60 mm diameter with a laser diode (λ = 1480 nm) clockwise and counter-clockwise lasing at λ = 1603 nm has been achieved with an output power up to 150 μW.