Erbium-doped Radiation-hard Frequency Comb

The primary objective of the proposed activity is to evaluate the performance of a fiber laser based Optical Frequency Comb (OFC) system, under well-defined ionizing radiation conditions.The target OFC performance shall assume the performance requirements of a defined future application of ESA. This OFC performance (specification) be established at the start of the project and will be the reference value for the final system. The final OFC performance, following well-defined radiation exposure parameters, shall meet the same performance of the un-radiated system. In order to meet the OFC performance after radiation, a specially developed radiation-hard doped fiber shall be developed as an integral element of the project. 

The advent of Optical Frequency Combs (OFC) has provided an enabling system for high-resolution spectroscopy, timing, ranging, metrology, clocks and the generation of ultra-pure frequencies in both the visible and rf spectral regions while being simultaneously phase coherent in both domains, enabling a direct rf-optical link.Many variations of the OFC exist broadly ranging from those based on (a) Rare Earth (RE) doped solid-state lasers, to (b) RE doped fiber lasers and finally to (c) Ultra-high Q micro systems. Most of the development efforts for commercial applications were based on the second category as they are more efficient than those in (a) and can be optically miniaturised. Accompanying the reduction in size and the efforts to establish a ?turn-key? system, which have been quite successful, the fiber laser based OFC system is subject to known fiber darkening effects that lead to a reduction in performance. As these OFC systems are, effectively, a high precision (and high resolution) ruler in frequency (and length) space, any alteration in this core aspect will have a negative performance on the final system. The purpose of this activity is to explore the limits of the space radiation environment, where these systems are likely to operate, and take design steps to mitigate the deleterious aspects of the radiation. A specially designed optical fiber meeting the desired, and pre-defined, parameters of the OFC system will play a central role in the successful conclusion of this activity. A successful conclusion of the project would open up mission possibilities with mission durations of 1 year and longer.