A mode-locked all-fiber laser based on the nonlinear multimode interference (NL-MMI) effect of graded-index fiber (GIMF) is proposed and demonstrated. The saturable absorber (SA) used in consists a step-index (SIMF) connected by GIMF. Compared with theoretically SMF-GIMF-SMF structure, introduction SIMF eliminates restriction length GIMF provides more flexible method making an SA NL-MMI. Through bending device to certain state, modulation depth was measured be 3.16%. output pulses have...

A novel mode-locking method based on the nonlinear multimode interference in stretched graded-index optical fiber (GIMF) is proposed this Letter. The simple device geometry, where light coupled and out of GIMF via single-mode fibers, demonstrated to exhibit temporal intensity discrimination required for mode locking. saturable absorber (SA) characteristics are controllable by simply adjusting strength stretching applied. modulation depth device, which consists ∼23.5 cm GIMF, tuned from...

An Er-doped mode-locked fiber laser with a saturable absorber based on single mode - graded index multimode (SMF-GIMF-SMF) inner micro-cavity is demonstrated. The modulation depth of the was measured to be 1.9% when SMF-GIMF-SMF structure bent certain state. Such simple enables mode-locking operation in ring and ultrafast pulses pulse energy 0.026 nJ width 528 fs at fundamental repetition rate 14.34 MHz can generated. In addition, harmonic also achieved.

An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) China. The systematic frequency shifts the are evaluated with a total uncertainty 2.3×10−16. To measure its absolute respect to NIM's cesium fountain NIM5, flywheel H-maser NIM5 transferred Sr laboratory through 50-km-long fiber. A fiber comb, phase-locked reference this H-maser, used for measurement. measured be 429228004229873.7(1.4)Hz.

We present a robust, transportable ${\mathrm{Ca}}^{+}$ optical clock, with systematic uncertainty of $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ limited by the black-body radiation (BBR) field evaluation and an uptime rate $>75%$ over 20-day period. The clock is then installed in air-conditioned car trailer, making it more convenient for applications. Referenced to stationary laboratory geopotential measurements are made total 0.33 m (statistically 0.25 systematically 0.22...

Abstract Two 87 Sr optical lattice clocks (OLCs) are being developed and operated at the National Institute of Metrology (NIM), located on different campuses that 40 km apart. In order to compare frequencies these two OLCs, a 58-km noise canceled fiber link is built transfer both 1542-nm laser microwave reference from Changping campus Hepingli campus. commercial frequency combs (OFCs) with adapted single-branch 698/1542 nm outputs coherently unite 698-nm clock lasers laser. The fractional...

A challenge in industrial non-contact surface mapping applications is to resolve the competing requirements of high measurement precision and sufficient large working distance. In this letter, we introduce a three-dimensional (3D) profilometry system with micrometer-level at 100-mm distance for non-cooperative targets by employing an electro-optic dual-comb conjunction time-domain coherent averaging. The detection capability weak diffuse reflective signals enhanced 15 dB via averaging 1000...

A new absolute distance measurement system is demonstrated in this paper, which based on a dual-wavelength passive mode-locked fiber laser. By controlling the intracavity loss and spectral filtering, cavity by single-wall carbon nanotube saturable absorber able to generate two pulse trains at slightly different repetition rates simultaneously with high mutual coherence. Comparisons commercial interferometers located 80-m large-scale dimensional standard show combined uncertainty of 6 μ m + 1...

A mode-locked high pulse energy fiber laser with a linear cavity by using an all-fiber structured graded index multimode (GIMF) based saturable absorber (SA) is presented. The absorption effect of the SA on nonlinear interference (NL-MMI). This first time GIMF-based has been used in cavity. stable fundamental mode-locking operation can still be maintained at maximum pump power. output solitons have center wavelength, spectral width, duration, and repetition rate 1571 nm, 4 675 fs, 11.69 MHz,...

A passively mode-locked fiber laser with controllable pulse width is demonstrated by use of an all-fiber saturable absorber based on a hybrid no-core (NCF)-graded index multimode (GIMF) structure incorporated into Er-doped ring cavity. Such NCF-GIMF has tunable intracavity filtering effect. As result, the mode-locking operation achieved and spectral bandwidth in normal dispersion regime only stretching device. Soliton pulses 7.7-23 ps are generated, bound solitons variable widths also...

Abstract We report the 87 Sr optical lattice clock at NIM with a laser referenced to 30 cm ULE cavity. Several improvements, such as atomic temperature and density, frequency stabilization, fiber noise cancellation, etc, have been made since its first evaluation in 2015. Its systematic shifts are carefully evaluated total relative uncertainty of 2.9 × 10 −17 . The measured absolute is 429 228 004 229 873.07(0.13) Hz 3.1 −16 , reference ensemble primary secondary standards published Circular...

We report a robust, compact, and transportable optical clock (TOC-729-2) based on trapped single 40Ca+ ion with systematic uncertainty of 1.1×10−17, which is limited by the black-body radiation shift at room temperature. By comparing it previous (TOC-729-1) similar but completely independent, instability was measured to be better than 1.2×10−14/τ. Benefiting from modular integrated design, this TOC constructed in volume ∼0.33 m3 excluding controlling electronics 19-in. racks. After being...

We report hertz level relative linewidth distributed feedback diode lasers with external optical from a high finesse F-P cavity, and demonstrate the efficient phase noise suppression laser reduction of technique. The is dramatically suppressed throughout measurement frequency range. Especially at Fourier 17 kHz, approximately reference significantly by more than 92 dB. Above this frequency, maintains white plateau as low -124.4 dBc/Hz. laser's FWHM reduced 7 MHz to 4.4 Hz, its instantaneous...

We present a narrow-linewidth diode laser with optical feedback from high-finesse two-mirror nonconfocal cavity. The laser's full-width-at-half-maximum linewidth is reduced to 100 Hz, and its instantaneous 30 Hz in the Lorentzian fitting. To best of our knowledge, it narrowest ever achieved method. phase noise has been significantly by more than 50 dB frequency range 10 kHz. Our experiment demonstrates efficient reduction suppression technique.

We experimentally demonstrate a monolithic single-frequency nonplanar ring oscillator (NPRO) laser pumped by diode lasers from thermally excited ground level directly into metastable of Nd3+:YAG gain medium. Continuous-wave output power 4.54 W is obtained at 1064 nm with 7.6 input 885 nm, and the slope efficiency 76.9% incident above 2 W. Compared 50.7% using 808 pumping for same NPRO, this direct shows potential advantage in improving energy efficiency. The observation consistent an...

NIM-Sr2 optical lattice clock has been developed on the Changping campus of National Institute Metrology (NIM). Considering limitations in NIM-Sr1, several improved parts have designed including a differential pumping stage vacuum system, permanent magnet Zeeman slower, water-cooled anti-Helmholtz coils, an extended viewport for etc. A laser with short-time stability better than 3 × 10 −16 is realized based self-designed 30-cm-long ultra-low expansion cavity. The systematic frequency shift...

Abstract A local time scale can be generated by steering flywheel clocks with state-of-the-art optical lattice clocks. This paper presents our simulations about the influence of clock’s operational strategies and noise characteristics on performance scale. By post-processing measured frequency difference between clock Sr1 hydrogen maser HM50 at National Institute Metrology (NIM), during modified Julian date (MJD) 59029–59059, a 0.68 ns variation referencing to TT(BIPM20) is demonstrated.

We present a extended-cavity diode laser (ECDL) with kilohertz linewidth by optical feedback from monolithic folded Fabry–Perot cavity (MFC). In our experiments, an MFC replaces the retroreflecting mirror in traditional ECDL configuration. Beat-note measurements between this MFC-ECDL and narrow-linewidth reference are performed demonstrate that of is about 6.8 kHz. Phase locking to achieved unity gain as small 10.2

An ultranarrow bandwidth Faraday atomic filter is realized based on cold Rb87 atoms. The operates at 780 nm the 52S1/2, F=2 to 52P3/2, F′=3 transition with a of 7.1(8) MHz, which approaching natural linewidth transition. peak transmission achieves 2.6(3)% by multi-pass probe method. This atoms may find potential applications in self-stabilizing lasers future.

An optical frequency comb based on Yb:ring fiber laser was demonstrated. This is the first time, to our knowledge, f(ceo) has been generated directly from oscillator without further amplifications above 500 MHz repetition rate. The signal-to-noise ratio of offset 40 dB at 300 kHz resolution bandwidth, which supports easy stabilization. stabilized for more than 6 h in an open air environment temperature control. rate in-loop tracking stability 4.46×10(-13)/τ(1/2).

We report the experimental realization of a 88Sr magneto-optical trap (MOT) operating at wavelength 461 nm. The MOT is loaded via 32 cm long spin-flip type Zeeman slower which enhances population by factor 22. total laser power available in our experiment about 300 mW. have trapped 1.6 × 108 atoms with 679nm and 707 nm repumping laser. two lasers enhance lifetime factors 11 7, respectively. cloud has temperature 2.3 mK, measured recording time evolution absorption signal.

We demonstrate coherent beam combination between independent femtosecond Yb-fiber lasers by using the active phase locking of relative pulse timing and carrier envelope based on a balanced optical cross-correlator extracavity acoustic frequency shifter, respectively. The broadband quantum noise fiber is suppressed via precise cavity dispersion control, instead complicated high-bandwidth phase-locked loop design. Because reduced simplified loop, stable that lasts for 1 hour has been obtained,...

We present the characterization of carrier envelope offset frequency 490 MHz femtosecond Yb-fiber ring laser. After amplification and compression, 1.7 W 90 fs pulses were produced for octave-span-spectrum generation from 600 nm to 1300 nm. More than 30 dB S/N ratio signal was measured through a quasi-common-path interferometer.

An optical frequency comb is built by using a commercial femtosecond laser and signal-noise (S/N) ratio of the fceo signal obtained to be about 30 dB. Its repetition rate offset are highly stable tracking stability verified. absolute measurement 1064 nm Nd: YAG realized this stabilized comb. The superior 3.710-14 at 100 s 281630111757362 Hz. experimental result in accordance with recommended value International Committee Weights Measures(CIPM).