A multi-branch, fiber-based frequency comb with millihertz-level relative linewidths using an intra-cavity electro-optic modulator

Abstract

We demonstrate that fiber-based frequency combs with multi-branch configurations can transfer both linewidth and frequency stability to another wavelength at the millihertz level. An intra-cavity electro-optic modulator is employed to obtain a broad servo bandwidth for repetition rate control. We investigate the relative linewidths between two combs using a stable continuous-wave laser as a common reference to stabilize the repetition rate frequencies in both combs. The achieved energy concentration to the carrier of the out-of-loop beat between the two combs was 99% and 30% at a bandwidth of 1 kHz and 7.6 mHz, respectively. The frequency instability of the comb was 3.7x10(-16) for a 1 s averaging time, improving to 5-8x10(-19) for 10000 s. We show that the frequency noise in the out-of-loop beat originates mainly from phase noise in branched optical fibers.

Optical Frequency Comb Generation based on Erbium Fiber Lasers

“…Widely employed in fiber communications, lithiumniobate, electro-optic phase modulators (EOM) offer an obvious and extremely high bandwidth means of modulating an erbium comb [44,68,81,96,97,124,153]. The refractive index of the EOM crystal changes proportionally to an applied voltage by a few parts in 10 6 , which represents a change in cavity length and, therefore, in the repetition rate.…”

“…Moreover, the flexibility of the fiber-based platform and the ubiquity of low cost, high quality components in the erbium gain window has spurred research into different oscillator designs (see Sec. 3), multi-branch frequency combs [42][43][44][45], difference frequency generation to other wavelength bands [46][47][48][49][50][51][52], variable repetition-rate systems [53][54][55][56], synthesis of arbitrary optical frequencies [57][58][59][60][61][62][63][64], and robust fieldable systems [65][66][67][68][69][70][71]. In fact, one could argue that a significant majority of the demonstrations of comb applications have been done with erbium fiber lasers, driven largely by the rapidly maturing erbium comb technology.…”

Dynamics of a Dispersion-Managed Passively Mode-Locked Er-Doped Fiber Laser Using Single Wall Carbon Nanotubes

“…Especially, the performance of an optical frequency comb depends on the characteristics of the laser [25][26][27]. Therefore, analysis of SWNT fiber lasers is important for optical frequency combs.…”

Intracavity polarization control in mode-locked Er-doped fibre lasers using liquid crystals

“…In some examples two full polarization con− trollers are used (one before and one after polarization beam splitter) [18], in some setups proper position of the fibre guarantees that mode−locking will be obtained with only one PC (placed before PBS) [19]. Other examples include two [20], three [21] or four [22] wave plates. However, the biggest challenge is not the number of wave plates but the mechanism of their adjustment.…”