Thin-film lithium niobate circulator-free dispersion compensator in a time-lens system for femtosecond-pulse generation.

We demonstrate a circulator-free thin-film lithium niobate (TFLN) dispersion compensator based on the cascading 2 × 2 multimode interferometer (MMI) and two identical chirped Bragg gratings (CBGs). The cascaded MMI-CBG structure provides a dispersion value of 920 ps/nm/m over a 20 nm bandwidth covering 1537 to 1557 nm, featuring a compact footprint of 1 mm × 0.7 mm. Utilizing this device within a TFLN electro-optic time-lens system, we successfully generate 863-fs pulses at a 37 GHz repetition rate. Our compact, scalable, low-loss, and circulator-free dispersion compensator is the building block for the efficient generation of high-peak-power femtosecond laser pulses.

Arbitrary-ratio 1 × 2 optical power splitter based on thin-film lithium niobate.

Optical power splitters (OPSs) have been widely used in photonic integrated circuits, but an OPS with a large fabrication tolerance and free choice of power splitting ratio (PSR) is still highly desired for thin-film lithium niobate (TFLN) platform. Here, we propose and experimentally demonstrate several 1 × 2 OPSs with PSRs from 50:50 to 5:95 using TFLN platform. The proposed devices are built by multimode interference structure to achieve a broad bandwidth and large fabrication tolerance. Various PSRs can be obtained by adjusting the geometry structure of the multimode interference region. All of our fabricated devices feature an insertion loss lower than 0.3 dB at the wavelength of 1550 nm, and a PSR variation less than 3% in the range of 1520 nm to 1590 nm.

Effect of the Pulsed Electromagnetic Field Treatment in a Rat Model of Senile Osteoporosis In Vivo.

This study assessed the effects of pulsed electromagnetic fields (PEMF) in a rat model of senile osteoporosis and the underlying molecular events. 24-month-old male Sprague-Dawley (SD) rats were randomly divided into control and PEMF groups (n = 8 per group) using a random digit table, while 3-month-old male SD rats were set as the young-age control group. Rats in the PEMF group were treated by PEMF for 40 min/day for 5 days/week. Bone mineral density/microarchitecture, level of serum bone-specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase 5b (TRACP5b), and Wnt/ß-catenin signaling genes in rat bone marrow cells were then analyzed. The 12-week PEMF intervention showed a significant effect on inhibition of age-induced bone density loss and deterioration of trabecular bone structures in the PEMF group rats versus control rats, that is, the treatment enhanced bone mineral density of the proximal femoral metaphysis and the fifth lumbar (L5) vertebral body and improved the proximal tibia and L4 vertebral body parameters using bone histomorphometry analysis. Furthermore, the BALP level in the bones was significantly increased, but the TRACP5b level was reduced in the PEMF group of rats versus control rats. PEMF also dramatically upregulated expression of Wnt3a, LRP5, ß-catenin, and Runx2 but downregulated PPAR-γ expression in the aged rats. The results demonstrated that PEMF could prevent bone loss and architectural deterioration due to the improvement of bone marrow mesenchymal stromal cell differentiation and proliferation abilities and activating the Wnt signaling pathway. Future clinical studies are needed to validate these findings. © 2022 Bioelectromagnetics Society.

Electrically pumped widely tunable O-band hybrid lithium niobite/III-V laser.

Significant improvements in the lithium niobate on insulator (LNOI) platform are pushing LNOI-based laser sources to the forefront of integrated photonics. Here, we report the first, to the best of our knowledge, electrically pumped hybrid lithium niobate/III-V laser by butt coupling an InP-based optical gain chip with a LNOI photonic integrated circuit (PIC). In the PIC, a Vernier filter consisting of two LNOI microring resonators is employed to select the lasing wavelength. A wavelength tuning range of more than 36 nm is achieved in the O band. The hybrid laser has a maximum on-chip optical power of 2.5 mW and threshold current density of 2.5kA/cm2. A side mode suppression ratio better than 60 dB is achieved.

Enhanced catalytic performance of a PdO catalyst prepared via a two-step method of in situ reduction-oxidation.

A supported PdO nanocatalyst prepared by a facile in situ reduction process followed by an oxidation step showed significantly enhanced activity for the removal of pollutants from natural gas vehicles. The excellent catalytic performance is mainly due to high dispersion of the uniform PdO nanoparticles generated during the novel two-step method.