Er-doped fiber frequency comb with mHz relative linewidth

Abstract

A low-noise fiber frequency comb is demonstrated to improve the frequency accuracy and linewidth by suppressing the phase noise caused by the nonlinear self-phase modulation as well as the amplified spontaneous emission within the Er-doped fiber amplifier. The linewidth of the carrier-envelop- offset signal measures less than 1.9 mHz and the frequency stability well follows the reference Rb clock. This achievement will facilitate the use of the fiber frequency comb for industrial applications to precision near-infrared spectroscopy, frequency calibration, optical clocks and length metrology.

Comb-referenced laser distance interferometer for industrial nanotechnology

“…The comb used as the wavelength ruler is stabilized to the Rb atomic clock by phase-locked loop (PLL) control of the repetition rate ( f r ) precisely to 100 MHz and also the carrier-envelop-offset frequency ( f ceo ) to 30 MHz. The f ceo is extracted using a fiber-type f - 2f interferometer3536. The four DFB laser output beams, each having an optical power of 10 mW, are combined into a single-mode fiber so that they propagate along the same optical path together all the way within the interferometer.…”

Optical Frequency Comb Generation based on Erbium Fiber Lasers

“…The amplifier is used to increase both the pulse energy and spectral width of the oscillator output and thus producing shorter, more intense pulses. There is significant flexibility in the design of an ultrafast erbium amplifier, which can employ temporal compression methods via self-similar amplification propagation [138], soliton self-compression [139][140][141], or a combination of both. These methods have the significant advantage of being constructed from fiber components fusion spliced together and are thus truly alignment-free.…”

“…More commonly, the amplifier is designed with sufficient normal GVD so that the pulses have a positive chirp. This dispersion can be removed by adding anomalous GVD, either by the use of a grating compressor [138] or by simply passing the light through standard single-mode fiber [22,25,70,106] or large mode-area optical fiber [139,142]. For amplifiers employing solitonic compression methods, positively chirped pulses from the erbium-doped fiber with an energy greater than that of a fundamental soliton are injected into a length of anomalous GVD fiber.…”

Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber

“…Typically, optically referenced frequency combs require a stable cw laser locked to an optical cavity and/or an atomic or molecular reference. However, direct comb spectroscopy eliminates the need for a cw laser, which is advantageous for portable, practical systems, for which fiber-laser-based combs are well-suited [2,3]. Hu et al [4] have directly optically referenced an Er fiber laser-based frequency comb to a Rb cell by generating its second harmonic and stabilizing to the two-photon transition in Rb.…”