In vivo biological safety investigation of Yb-CALGO femtosecond laser dental surgery.

While lasers have found their successful applications in various clinical specialties, in clinical dental practice, traditional mechanical drills are still predominantly utilized. Although erbium-doped lasers have been demonstrated for dental therapy, their clinical performance is still not satisfactory due to the long pulse width, low peak power, and small repetition rate. To attain a smaller thermal diffusion thus better biological safety and surgical precision, as well as more rapid ablation, the advancement of femtosecond laser techniques has opened another route of dental surgery; however, no biological safety investigation has been reported. Here, we present a systematic study of dental ablation by a Yb:CaAlGdO4 regenerative amplifier with a central wavelength of 1040 nm and pulse width of 160 fs. The in vivo experiment of dental surgery investigating the inflammatory response has been reported, for the first time to the best of our knowledge. It is demonstrated that dental surgery by Yb:CaAlGdO4 femtosecond laser ablation has better biological safety compared to the turbine drilling, thanks to its non-contact and ultrafast heat dissipation nature.

Photonic generation of dual-band triangular chirps utilizing a monolithic integrated mutual injection laser and application in radars.

We propose and demonstrate a dual-band microwave photonic radar scheme based on a monolithic integrated mutual injection laser. Based on the photon-photon resonance (PPR) and the gain switching effect of the integrated laser, the C-/X-band triangular chirp signals with high-quality and comparable power at 4.75-5.25 GHz and 9.5-10.5 GHz are generated. In the current proof-of-concept experiment, the range resolution of the dual-band chirp signals can reach 16.9 cm, compared with the single-band chirp signal that cannot distinguish the targets. Through the application of a single integrated device and a transceiver module sharing a set of antennas, the dual-band microwave photonic radar system scheme improves the system integration.

Understanding the effects of A-site Ag-doping on LaCoO3 perovskite for NO oxidation: Structural and magnetic properties.

The partial substitution of A-site in perovskites is a major strategy to enhance the catalytic oxidation activity. This study explores the use of silver (Ag) to partially replace the lanthanum (La) ion at the A-site in LaCoO3 perovskite, investigating the role of Ag in the ABO3 perovskite structure, elucidating the nitric oxide (NO) oxidation mechanism over La1-xAgxCoO3 (x = 0.1-0.5) perovskites. La0.7Ag0.3CoO3 with an Ag-doping amount of 0.3, exhibited the highest NO oxidation activity of 88.5% at 275 °C. Characterization results indicated that Ag substitution enhanced the perovskite, maintaining its original phase structure, existing in the form of a mixture of Ag0 and Ag+ in the La1-xAgxCoO3 (x = 0.1-0.5) perovskites. Notably, Ag substitution improved the specific surface area, reduction performance, Co3+, and surface adsorption oxygen content. Additionally, the study investigated the relationship between magnetism and NO oxidation from a magnetism perspective. Ag-doping strengthened the magnetism of La-Ag perovskite, resulting in stronger adsorption of paramagnetic NO. This study elucidated the NO oxidation mechanism over La-Ag perovskite, considering structural and magnetic properties, providing valuable insights for the subsequent development and industrial application of high oxidation ability perovskite catalysts.

Targeted Imaging of Endometriosis and Image-Guided Resection of Lesions Using Gonadotropin-Releasing Hormone Analogue-Modified Indocyanine Green.

Objective: In this study, we utilized gonadotropin-releasing hormone analogue-modified indocyanine green (GnRHa-ICG) to improve the accuracy of intraoperative recognition and resection of endometriotic lesions. Methods: Gonadotropin-releasing hormone receptor (GnRHR) expression was detected in endometriosis tissues and cell lines via immunohistochemistry and western blotting. The in vitro binding capacities of GnRHa, GnRHa-ICG, and ICG were determined using fluorescence microscopy and flow cytometry. In vivo imaging was performed in mouse models of endometriosis using a near-infrared fluorescence (NIRF) imaging system and fluorescence navigation system. The ex vivo binding capacity was determined using confocal fluorescence microscopy. Results: GnRHa-ICG exhibited a significantly stronger binding capacity to endometriotic cells and tissues than ICG. In mice with endometriosis, GnRHa-ICG specifically imaged endometriotic tissues (EMTs) after intraperitoneal administration, whereas ICG exhibited signals in the intestine. GnRHa-ICG showed the highest fluorescence signals in the EMTs at 2 h and a good signal-to-noise ratio at 48 h postadministration. Compared with traditional surgery under white light, targeted NIRF imaging-guided surgery completely resected endometriotic lesions with a sensitivity of 97.3% and specificity of 77.8%. No obvious toxicity was observed in routine blood tests, serum biochemicals, or histopathology in mice. Conclusions: GnRHa-ICG specifically recognized and localized endometriotic lesions and guided complete resection of lesions with high accuracy.

High-purity linearly frequency-modulated signal generation based on the integrated semiconductor laser subject to the dynamical optoelectrical feedback.

A novel photonic method of linearly frequency-modulated (LFM) signal generation with high purity based on the monolithically integrated semiconductor laser (MISL) subject to the dynamical optoelectrical feedback is proposed and demonstrated in this paper. In this approach, the MISL is firstly operated in period-one state. By introducing the dynamical optoelectrical feedback to modulate the MISL, the generated LFM signals would be constantly optimized as long as the delay of the feedback loop is matched with the repetition period of the LFM signal. In this system, no additional high-speed external modulator, high-frequency electrical LFM oscillator are required, highly simplifying the framework and reducing the power consumption. In the current proof-of-concept experiment, one LFM signal with the bandwidth as large as 5.6 GHz is generated and the corresponding frequency comb contrast can be drastically improved by 51 dB. Furthermore, the effect of the delay mismatch is also discussed in this paper.

Broadband frequency modulation signal downconversion using a monolithic integrated mutual injection laser.

We propose a new, to the best of our knowledge, broadband signal downconversion scheme implemented by a monolithic integrated mutual injection laser. A mathematical derivation, simulation, and experimental verification are carried out. Because the period-one oscillation frequency can be selectively operated on a large scale by controlling the current on the integrated laser, the tuning downconversion range is realized without changing the experimental equipment. The experiment verifies that the downconversion of the linear frequency modulation signal with a bandwidth of 0.5 GHz from the center frequency of 18.75 to 0.85 GHz, and the spurious-free dynamic range (SFDR) has reached 71.7d B/H z 2/3. Compared with the scheme based on discrete components, the system has no electric local oscillator or external modulator, which provides a method for radar signal downconversion.

Four-channel all-optical wavelength conversion unit based on nonlinear effect of three-section monolithically integrated semiconductor lasers.

A simple and highly efficient four-channel all-optical wavelength conversion based on four-wave mixing effect of the directly modulated three-section monolithically integrated semiconductor laser is proposed and experimentally investigated. For this wavelength conversion unit, the spacing of the wavelength can be adjusted by tuning the bias current of the lasers and setting it to be 0.4 nm (50 GHz) as a demonstration is this work. A 50 Mbps 16-QAM signal centers at 4-8 GHz is experimentally switched to a targeted path. Up- or downconversion depends on a wavelength-selective switch, and the conversion efficiency can reach up to -2 to 0 dB. This work provides a new technology for photonic radio-frequency switching matrix and contributes to the integrated implementation of satellite transponders.

Simple multi-band linearly frequency-modulated signal generation with a multiplying bandwidth based on a gain-switching laser.

Multi-band linearly frequency-modulated (LFM) signal generation with a multiplying bandwidth is proposed and experimentally demonstrated. It is a simple photonics method based on the gain-switching state in a distributed feedback semiconductor laser without a complex external modulator and high-speed electrical amplifiers. With N comb lines, the carrier frequency and bandwidth of generated LFM signals are N times those of the reference signal. (N is the number of comb lines.) The number of bands and time-bandwidth products (TBWPs) of the generated signals could be easily adjusted by tuning the reference signal from an arbitrary waveform generator. Three-band LFM signals with carrier frequencies ranging from the X-band to K-band are given as an example, and the TBWP up to 20000. The results of auto-correlations of the generated waveforms are also given.

Experimental demonstration of the quantum noise randomized cipher based on cascaded phase shift keying without a high-level digital-to-analog converter.

To break the dependence on a high-speed and high-resolution digital-to-analog converter (DAC) in the traditional quantum noise randomized cipher (QNRC), a practical DAC-free modulation scheme based on cascaded phase-shift keying (PSK) is proposed and demonstrated by a proof-of-concept experiment. By employing seven cascaded phase modulators (PMs) driven by designed electrical voltage signals, a 128 PSK-QNRC system is achieved with a transmission rate of 10 Gbaud/s and a transmission distance more than 50 km, which eliminates the need for a DAC on the transmitter side. The bit error rate (BER) performance of the proposed scheme is compared to that of a traditional scheme based on an arbitrary waveform generator (AWG) with a sampling rate of 25 GSa/s. The results show that compared to a traditional scheme, the power penalties of the proposed scheme are -1.8d B, 0.9 dB, and 1 dB, respectively, at the rates of 10, 5, and 2.5 Gbps. In other words, the BER performance of the proposed scheme is close to the traditional scheme at a low transmission rate, but better than that of the traditional scheme at a high transmission rate, where the sampling rate of the DAC is not high enough to generate a complete waveform. This work greatly enhances the security of a QNRC system.

High-power Yb:CALGO regenerative amplifier and 30 fs output via multi-plate compression.

The pulse energy and average power are two long-sought parameters of femtosecond lasers. In the fields of nonlinear-optics and strong-field physics, they respectively play the role to unlock the various nonlinear processes and provide enough photon fluxes. In this paper, a high-energy and high-power Yb:CALGO regenerative amplifier with 120 fs pulse width is reported. This high-performance regenerative amplifier can work with high stability in a large tuning range of repetition rates. Varying the repetition rate from 3 to 180 kHz, the maximum output power of 36 W and the pulse energy up to 4.3 mJ, corresponding to a peak power of more than 20 GW are demonstrated. The output beam is near diffraction limited with M2 = 1.09 and 1.14 on the horizontal and vertical directions, respectively. In addition, multi-plate compression is employed to achieve 30 fs output with 23 W average power which is attractive for applications such as high-harmonic generation.

Low-power RF signal detection with wideband range based on an optically injected optoelectronic oscillator.

A novel method to detect a low-power radio-frequency (RF) signal with ultra-wide frequency range based on an optically injected optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The optical injection to a distributed feedback (DFB) laser has the advantages of amplifying one sideband of the modulated optical signal selectively and a wide tunable frequency range. The detection upper range that reaches up to 26 GHz and can be improved theoretically. To the best of the authors' knowledge, this is the widest detection range based on an OEO. At the same time, the detection characteristics are good. The sensitivity of the system is -92 dBm and the maximum gain is 12.18 dB at 15.047 GHz. Considering the real application of the detection system, the properties such as dynamic range and performance for detecting a modulated RF signal are also investigated.

Ultra simple low-power RF signal detection based on an optoelectronic feedback DFB laser.

An ultra simple and low cost method to detect low-power RF signal is proposed and experimentally demonstrated based on optoelectronic feedback DFB semiconductor laser. To our knowledge, according to public reports, this is the simplest photonics-assisted method which avoids using high sensitive optical modulators and narrow bandwidth optical filters. The RF signal, which matches the oscillation mode at the relaxation oscillation peak of the DFB laser, is amplified based on optoelectronic feedback. The RF signal from 1 to 4.5 GHz can be detected by adjusting the frequency of relaxation oscillation which is related to the laser bias current. The system provides a maximum gain of 15 dB for the low-power RF signal. The sensitivity of the system can reach up to as high as -97 dBm. Considering the real application of the detection system, the properties like dynamic range, resistance to large signals and performance for detecting modulated RF signal are also investigated.

All-optical gain optoelectronic oscillator based on a dual-frequency integrated semiconductor laser: potential to break the bandwidth limitation in the traditional OEO configuration.

A novel photonic method, to the best of our knowledge, to generate high-frequency micro/millimeter-wave signals based on the optoelectronic oscillator (OEO) with all-optical gain is proposed in this paper. The core device is the monolithically integrated dual-frequency semiconductor laser (MI-DFSL), in which the two DFB laser sections are simultaneously fabricated on one chip. Attributing to the combined impact of the photon-photon resonance effect and the sideband amplification injection locking effect, one widely tunable microwave photonic filter with a high Q value and narrow 3-dB bandwidth can be realized. In this case, the generated microwave signals would largely break the limitation in bandwidth once making full use of the optical amplifier to replace the narrow-band electrical amplifiers in traditional OEO configuration to provide the necessary gain. No additional high-speed external modulator, high-frequency electrical bandpass filters or multi-stage electrical amplifiers are required, highly simplifying the framework and reducing the power consumption. Moreover, this simple and compact structure has the potential to be developed for photonic integration. In the current proof-of-concept experiment, microwave signals with wide tuning ranges from 14.2 GHz to 25.2 GHz are realized. The SSB phase noises in all tuning range are below -103.77 dBc/Hz at 10 kHz and the best signal of the -106.363 dBc/Hz at 10 kHz is achieved at the frequency of 17.2 GHz.

High-efficiency nonhomologous insertion of a foreign gene into the herpes simplex virus genome.

Efficient, accurate and convenient foreign-gene insertion strategies are crucial for the high-throughput and rapid construction of large DNA viral vectors, but relatively inefficient and labour-intensive methods have limited the application of recombinant viruses. In this study, we applied the nonhomologous insertion (NHI) strategy, which is based on the nonhomologous end joining (NHEJ) repair pathway. Compared to the currently used homologous recombination (HR) strategy, we obtained a higher efficiency of foreign-gene insertion into the herpes simplex virus (HSV) genome that reached 45 % after optimization. By using NHI, we rapidly constructed recombinant reporter viruses using a small amount of clinical viruses, and the recombinant virus was stable for at least ten consecutive passages. The fidelity of NHI ranged from 70-100% and was related to the sequence background of the insertion site according to the sequencing results. Finally, we depict the dynamic process by which the foreign-gene donor plasmid and viral genome are rapidly cleaved by Cas9, as revealed by quantitative pulse analysis. Furthermore, the NHI strategy exerted selection pressure on the wild-type and reverse-integrated viral genomes to efficiently integrate the foreign gene in a predetermined direction. Our results indicate that the use of a rationally designed NHI strategy can allow rapid and efficient foreign gene knock-in into the HSV genome and provide useful guidance for gene insertion into large DNA viral genomes using NHI.

Evaluate severe acute respiratory syndrome coronavirus 2 infectivity by pseudoviral particles.

Since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in humans in late 2019, it has rapidly spread worldwide. To identify the biological characteristics of SARS-CoV-2 in a normal laboratory environment (biosafety level 2 [BSL-2]), a lentiviral-based nucleocapsid was used to carry the spike protein of SARS-CoV-2 onto the surface of pseudoviral particles as a surrogate model to evaluate the infective characterization of SARS-CoV-2. This study indicated that SARS-CoV-2 has extensive tissue tropism for humans and may infect monkeys and tree shrews but not rodents. More importantly, the use of pseudoviral particles in this study allows rapid assessment of neutralizing antibodies in serum in a BSL-2 laboratory. This study will provide a quick and easy tool for evaluating neutralizing antibodies in the serum of recovering patients and assessing the potency of candidate vaccines.

Effect of l-thyroxine administration before breakfast vs at bedtime on hypothyroidism: A meta-analysis.

PURPOSE: To compare the effects of l-thyroxine (L-T4) administration before breakfast and administration at bedtime on hypothyroidism. METHODS: The PubMed, EMBASE, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI) and Wanfang databases were searched to identify relevant articles. All prospective or randomized controlled studies (RCTs) comparing L-T4 administration before breakfast to the administration at bedtime in patients with hypothyroidism were included in the analysis. RESULTS: Initially, 2884 articles were retrieved from the databases, and 10 articles were included in the quantitative analysis. The effect of L-T4 administration before breakfast compared with administration at bedtime had no statistically significant association with hormone thyrotropin (TSH) (Standardized mean differences [SMD] = 0.09, 95% confidence intervals (CI): -0.12, 0.30; P = .39), or free triiodothyronine (FT3) (SMD=-0.19, 95% CI: -0.53, 0.15; P = .28) in patients with hypothyroidism. However, the result of FT4 level was favourable for L-T4 bedtime administration group (SMD=-0.27, 95% CI: -0.52, -0.02; P = .03). CONCLUSION: Our meta-analysis revealed that L-T4 administration at bedtime is as effective as administration before breakfast for patients with hypothyroidism. Taking L-T4 at bedtime may be an attractive option for patients with hypothyroidism.

Seasonality of carbonaceous aerosol composition and light absorption properties in Karachi, Pakistan.

Characteristics of carbonaceous aerosol (CA) and its light absorption properties are limited in Karachi, which is one of the most polluted metropolitan cities in South Asia. This study presents a comprehensive measurement of seasonality of CA compositions and mass absorption cross-section (MAC) of elemental carbon (EC) and water-soluble organic carbon (WSOC) in total suspended particles (TSP) collected from February 2015 to March 2017 in the southwest part of Karachi. The average TSP, organic carbon (OC), and EC concentrations were extremely high with values as 391.0 ± 217.0, 37.2 ± 28.0, and 8.53 ± 6.97 µg/m3, respectively. These components showed clear seasonal variations with high concentrations occurring during fall and winter followed by spring and summer. SO42-, NO3-, K+, and NH4+ showed similar variations with CA, implying the significant influence on atmospheric pollutants from anthropogenic activities. Relatively lower OC/EC ratio (4.20 ± 2.50) compared with remote regions further indicates fossil fuel combustion as a primary source of CA. Meanwhile, sea salt and soil dust are important contribution sources for TSP. The average MAC of EC (632 nm) and WSOC (365 nm) were 6.56 ± 2.70 and 0.97 ± 0.37 m2/g, respectively. MACEC is comparable to that in urban areas but lower than that in remote regions, indicating the significant influence of local emissions. MACWSOC showed opposite distribution with EC, further suggesting that OC was significantly affected by local fossil fuel combustion. In addition, dust might be an important factor increasing MACWSOC particularly during spring and summer.

Simple frequency-tunable optoelectronic oscillator using integrated multi-section distributed feedback semiconductor laser.

A novel approach to realizing an optoelectronic oscillator (OEO) based on an integrated multi-section (IMS) distributed feedback (DFB) laser is proposed and experimentally demonstrated. Our scheme adopts the method of direct modulation and a built-in microwave photonic filter (MPF), making the structure simpler and more flexible than an external modulator and electrical bandpass filter (EBPF). The IMS-DFB laser, which can overcome the drawbacks of using discrete lasers, is the key device in the scheme. Further, the two DFB sections, which are fabricated by Reconstruction Equivalent Chirp (REC) technique, are injected mutually. The SSB phase noise of the generated signal at the frequency of 20.3 GHz is -115.3 dBc/Hz@10kHz and -92.9 dBc/Hz@1kHz. The sidemode suppression ratio (SMSR) is 60.94 dB, which is a 40 dB improvement over a single loop. Furthermore, we demonstrate that the phase noise improves about 8 dB at the frequency offset of 1 kHz, when employing 13 km and 5.4 km fibers as the dual loop. The simple and compact structure, which consists of an IMS-DFB laser with high wavelength controlling accuracy and low process requirement, is a promising development for OEO integration.

Semi-quantum noise randomized data encryption based on an amplified spontaneous emission light source.

The first semi-quantum noise randomized cipher based on amplified spontaneous emission (ASE) light source employing Y-00 protocol is proposed and demonstrated by a proof-of-principle experiment. As the signal carrier, ASE light can provide another fundamental uncertainty, namely, self-beating noise of ASE signal, which is much bigger than quantum shot noise of mesoscopic coherent state and also inevitable. By incorporating both the shot noise and beat noise of ASE signals, the security will be improved with a larger number of masked signals (NMS) under intrinsic noise. After formulating NMS and Q-factor in theory, we investigate the impacts of key system parameters on the security and transmission performances, respectively, in order to optimize the system design. To evidence the theoretical results, an experimental setup with balanced photodetector (BPD) as decoder is constructed. The local light modulated by M/2-ary running key is applied as optical threshold signal, which is fed into BPD together with the M-ary ASE signal, outputting the binary signal. Eventually, a 128-level Y-00 realization based on ASE source is realized at 2.5Gb/s over 100-km fiber. The experimental results agree with the theory in the trend, which indicate the validity and feasibility of the proposed scheme.

Photonic generation of linearly chirped microwave waveforms using a monolithic integrated three-section laser.

Photonic generation of linearly chirped microwave waveforms (LCMWs) using a monolithic integrated three-section laser is experimentally demonstrated in this work. All three sections of the laser cavity, including the front DFB section, phase section and rear DFB section, have the same active layer, which can avoid the butt-joint re-growth process. The gratings in both DFB sections are fabricated by the Reconstruction Equivalent Chirp technique, which can significantly decrease the difficulties in realizing precise grating structure. By adjusting the integrated three-section semiconductor laser to work in the period-one (P1) state and applying a sweeping signal to the front DFB section, the beating signal, i.e., an LCMW with a large time bandwidth product (TBWP), can be generated. In the current proof-of-concept experiment, an LCMW with a large TBWP up to 5.159 × 105 is generated, of which the bandwidth and the duration time are 6.7 GHz and 77 us respectively. The compressed pulse width is 150 ps. In addition, by adjusting the bias currents of the rear DFB section and front DFB section as well as the amplitude of the sweeping signals, LCMWs with tunable center frequency and tunable bandwidth can be achieved.