A low phase noise high power Er-fiber frequency comb synchronized to the hydrogen maser clock by harmonic phase locking

We demonstrate a low phase noise all polarization-maintaining (PM) Er-fiber optical frequency comb (OFC) with low phase noise, which is synchronized to the hydrogen maser clock (HMC) using the 18th harmonic of the repetition rate for tight phase locking. The instability of the locked carrier envelope offset frequency is 1.24 × 10−18@1 s, the phase noise of the OFC is −96 dBc/Hz at 1 Hz offset, and the corresponding RMS timing jitter of the repetition rate is 62 fs (1 Hz–1 MHz). The residual frequency instability of the repetition rate (200 MHz) is 1.46 × 10−14@1 s, and the residual phase noise of the OFC normalized to 10 MHz is −138 dBc/Hz at 1 Hz offset and declines to about −160 dBc/Hz at the far-end, much lower than that of the HMC (−122 dBc/Hz at 1 Hz and −156 dBc/Hz at the far-end)

Polarization-multiplexed dual-comb fiber laser based on an all-polarization-maintaining cavity configuration

In this study, we present a polarization-multiplexed, erbium-doped dual-comb fiber laser based on an all-polarization-maintaining cavity configuration. We observed that the dual-comb fiber laser easily realized the self-starting mode-locking operation due to the non-linear amplifying loop mirror (NALM) with a non-reciprocal phase shifter. Furthermore, owing to the sharing of the NALM part, the two outputs from this laser configuration had similar center wavelengths, with small different repetition rates (∆frep). In the free-running operation, the standard deviation of relative stability for Δfrep of 2.09 kHz was measured to be 1.59 Hz, and the full width at half-maximum of the relative beat note between the two frequency combs in the optical frequency domain was approximately 1 kHz. These results show that the two frequency combs from this laser configuration have high relative stability and mutual coherence

Visualization 2: Non-diffracting optical Bloch oscillations in hexagonal photonic lattices

visualization 2 Originally published in Optics Express on 03 April 2017 (oe-25-7-7475

Visualization 1: Non-diffracting optical Bloch oscillations in hexagonal photonic lattices

visualization 1 Originally published in Optics Express on 03 April 2017 (oe-25-7-7475

Phylogenetic analysis and virulence characteristics of methicillin-resistant Staphylococcus aureus ST764-SCCmec II: an emerging hypervirulent clone ST764-t1084 in China

ABSTRACTPrevious studies have shown that the increased prevalent ST764 clone in China, Japan, and other Asian areas. However, the knowledge of the genetic features and virulence characteristics of methicillin-resistant Staphylococcus aureus (MRSA) ST764 in China is still limited. In this study, we identified 52 ST764-SCCmec type II isolates collected from five cities in China between 2014 and 2021. Whole genome sequencing showed that the most common staphylococcal protein A (spa) types of ST764 in China were t002 (55.78%) and t1084 (40.38%). Virulence assays showed that ST764-t1084 isolates had high haemolytic activity and α-toxin levels. Of the critical regulatory factors affecting α-toxin production, only the SaeRS was highly expressed in ST764-t1084 isolates. Mouse abscess model indicated that the virulence of ST764-t1084 isolates was comparable to that of S. aureus USA300-LAC famous for its hypervirulence. Interestingly, ST764-t002 isolates exhibited stronger biofilm formation and cell adhesion capacities than ST764-t1084 isolates. This seems to explain why ST764-t002 subclone has become more prevalent in China in recent years. Phylogenetic analysis suggested that all ST764 isolates from China in Clade III were closely related to KUN1163 (an isolate from Japan). Notably, genomic analysis revealed that the 52 ST764 isolates did not carry arginine catabolic mobile element (ACME), which differed from ST764 isolates in Japan. Additionally, most ST764 isolates (69.23%) harboured an obvious deletion of approximately 5 kb in the SCCmec II cassette region compared to KUN1163. Our findings shed light on the potential global transmission and genotypic as well as phenotypic characteristics of ST764 lineage