Er:fiber-based femtosecond frequency comb stabilized to an Yb⁺ single-ion optical frequency standard

Abstract

An erbium fiber-based femtosecond optical frequency comb stabilized to an Yb+ single-ion optical frequency standard was created. For the first time, a combination of an extra-cavity acousto-optic frequency modulator with fiber outputs and an intracavity electro-optic phase modulator based on a KTP crystal were used to stabilize offset frequency and one of the optical components of the Er:fiber femtosecond comb. As a result a locking bandwidth of 30 kHz for the optical comb offset frequency has been obtained. It is shown that the relative instability introduced by the stabilization and measurement systems into the output radio frequencies (in addition to the instability of the reference optical signal) is no worse than 5 × 10−14 for averaging times of 1 s and 2 × 10−16 for averaging times of 400 s.

Investigation of the fiber femtosecond comb temperature changes

“…The frequency of each component is described by the formula: fN=f0+N*frep [2]. Due to the stabilisation of f0 and one component of the optical comb by an external optical reference standard, the intermode radio frequency frep of the FC is stabilised [3]. These systems are widely used for metrological tasks, including the positioning of terrestrial and space objects.…”

“…When operating the Er:fiber-based FC [3] in free regime during the working day, a change in the RF signal level f0 (10-15 dB) and in its frequency (20-30 MHz) was observed. This change in frequency and RF signal level of f0 negatively affects the operation of the FC phase lock systems in the full stabilisation regime.…”

Fiber femtosecond frequency combs and their applications

“…This standard has large dimensions (compared to the Nd:YAG/I2 standard), however, its predicted relative long-term instability reaches the level of ~10 -18 . It was shown that the fiber FC introduces into the output microwave frequencies a relative instability of no more than 5•10 −14 (for an averaging time of 1 s) and 2•10 −16 (for an averaging time of 400 s) in addition to the instability of the reference optical standard [7].…”

Волоконные Фемтосекундные Синтезаторы Частот И Их Применения

“…Данный стандарт обладает большими габаритами (по сравнению с Nd:YAG/I2 стандартом), однако, его прогнозируемая относительная долговременная нестабильность достигает уровня ~10 -18 . При этом показано, что волоконный ФСЧ вносит в выходные СВЧ частоты относительную нестабильность не более 5•10 −14 (для времени усреднения 1 с) и 2•10 −16 (для времени усреднения 400 с) [7].…”