Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

Abstract

Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources.

Electro-optic comb based real time ultra-high sensitivity phase noise measurement system for high frequency microwaves

“…Figure 1 shows schematics of the working principle (a) and experimental setup (b) of our method. It is using a “two wavelength delayed self-heterodyne interferometer” 18 , 19 . The two wavelength delayed self-heterodyne interferometer has been originally developed to measure the timing jitter of mode-locked lasers.…”

Ultrasensitive, high-dynamic-range and broadband strain sensing by time-of-flight detection with femtosecond-laser frequency combs

“…By using such tightly synchronized microwave phase as the strain sensing ruler, both high resolution and large dynamic range in TOF 6 detection are possible. Due to the ultralow timing jitter property of typical free-running femtosecond Er-fibre MLLs 23,30 , high-quality synchronization and high-resolution TOF detection over broad bandwidth is possible, which is useful for high-resolution dynamic sensing over broad bandwidth. Note that, however, for high-resolution static sensing, such low-jitter property is not necessarily required since the residual phase noise/timing jitter is fully suppressed by the laser-microwave synchronization.…”

Ultra-precise timing and synchronization for large-scale scientific instruments

“…A jitter noise floor of 2.8 × 10 −13 fs 2 ∕Hz (with 80 mW input power) and 2 × 10 −9 fs 2 ∕Hz (with 400 μW input power) was achieved in Ref. [42] and [43], respectively. In comparison with the BOC, this linear detection scheme can reach a smaller noise floor at low input power levels, while the noise floor will decrease more slowly with increasing input power (e.g., in the shot-noiselimited region, the BOC noise floor decreases 20 dB/decade, while in the case of linear detection, it drops only 10 dB/decade).…”

“…As an alternative to the BOC, the timing jitter of mode-locked lasers can also be measured by a linear optical timing detection method based on optical heterodyning [41][42][43]. The concept is shown in Fig.…”

“…In Ref. [43], a similar optical heterodyne technique is realized with the help of fiber delay lines. The long and short wavelength tails of a mode-locked laser are interfering with their delayed copies, and the common carrier frequency offset components are rejected by mixing the two heterodyne beat notes after PDs.…”