GHz Figure‐9 Er‐Doped Optical Frequency Comb Based on Nested Fiber Ring Resonators

Abstract

The field of optical‐frequency‐combs (OFCs) has seen significant progress in recent years due to the advance of mode‐locked fiber lasers with low‐noise performance and long‐term reliability. With the emergence of applications, OFCs with repetition rates close to GHz have become highly sought after. However, generating GHz fiber‐based combs with low noise remains a significant challenge. In this study, a GHz figure‐9 Er‐doped OFC based on a nested fiber ring resonator is presented. By matching the free‐spectral range (FSR) of external and internal optical resonators, an 11‐fold increase in repetition rate from 82 MHz to 907 MHz is achieved. Notably, it is demonstrated that a single pulse operation with long‐term FSR matching can be achieved without any active feedback control. The comb offset frequency is detected using f‐to‐2f technique to ensure high coherence between pulses, which is distinguished from harmonic mode‐locking. The results show that the nested resonators are capable of generating GHz ultrafast OFC pulses with low phase noise via a more flexible cavity design than conventional short‐cavity solutions. This work provides a valuable contribution to the field of ultrafast laser and optical metrology, which demonstrates the potential of nested‐resonators for generating low noise OFCs with boosted repetition rate.

Recent Advances, Applications, and Perspectives in Erbium-Doped Fiber Combs

“…In 2023, Cao et al adopted a metho achieve a repetition rate of GHz in a laser cavity. An optical cavity was nested in an bium-doped fiber laser based on NALM to achieve a repetition rate of 907 MHz, and SNR of fceo was only about 30dB at a RBW of 10 kHz [92], as shown in Figure 5. However, compared with an NPR-based fiber laser [88,89] and a SESAM-based laser [44,90], the repetition rate of the NALM-based laser cavity has difficulty reaching above GHz due to the limitation of the mode-locking principle.…”

“…In 2023, Cao et al adopted a method to achieve a repetition rate of GHz in a laser cavity. An optical cavity was nested in an Erbium-doped fiber laser based on NALM to achieve a repetition rate of 907 MHz, and the SNR of f ceo was only about 30dB at a RBW of 10 kHz [92], as shown in Figure 5.…”

“…In 2023, Cao et al adopted a m achieve a repetition rate of GHz in a laser cavity. An optical cavity was nested i bium-doped fiber laser based on NALM to achieve a repetition rate of 907 MHz, SNR of fceo was only about 30dB at a RBW of 10 kHz [92], as shown in Figure 5. In addition, in order to apply optical frequency combs in space environments, researchers have conducted relevant studies on NALM fiber combs.…”

783 MHz fundamental repetition rate all-fiber ring laser mode-locked by carbon nanotubes

“…wing to the widespread applications in both scientific research and industries such as frequency combbased spectroscopy, [1][2][3] laser processing, 4,5) and bio-imaging, 6) high repetition rate fiber lasers have been developed intensively and many breakthroughs have been achieved. Techniques such as active mode-locking, 7) passively harmonic mode-locking, 8,9) dissipative four-wave mixing 10) and mode filtering 11) could achieve a very high repetition rate, however, they exhibit a higher instability in terms of output performance compared to fundamentally passive mode-locking. 12) Previous works have shown that ultrahigh repetition rates can be obtained by using short fiber Fabry-Perot resonators.…”