A collaboration between Eidgenössische Technische Hochschule Zürich (Zürich, Switzerland) and the Optoelectronics Research Centre (Southampton, England) has resulted in a very compact, synchronously pumped optical parametric oscillator (OPO) that contains an optical fiber to provide feed-back of the oscillating signal wave. The OPO is based on periodically poled lithium tantalate pumped by a recently developed high-power modelocked Yb:YAG thin disk laser. The first device, based on nonoptimized components, generates 900-fs pulses at 1.43 to 1.47 mm with up to 2.7 W of average signal output power when pumped with 8 W. The repetition rate is 35 MHz.
Notable is the extreme insensitivity of the OPO to intracavity losses, a result of its very high parametric gain. A deliberate insertion of 10 dB of loss into the cavity had only a small effect on the efficiency. Other advantages of the fiber-feedback OPO are its compactness and the greatly reduced sensitivity to resonator-length changes compared to other synchronously-pumped OPOs. Future prospects include soliton formation and pulse compression via nonlinearity in the feedback fiber. The fiber-feedback OPO appears to be very suitable as a key element in a red-green-blue display system. Contact Rüdiger Paschotta at [email protected].