All-optical polarization scrambler based on polarization beam splitting with an amplified fiber ring.

Optical-fiber-based polarization scramblers can reduce the impact of polarization sensitive performance of various optical fiber systems. Here, we propose a simple and efficient polarization scrambler based on an all-optical Mach-Zehnder structure by combining a polarization beam splitter and an amplified fiber ring. To totally decoherence one polarization split beam, a fiber ring together with an amplifier is incorporated. The ratio of two orthogonal beams can be controlled by varying the amplification factor, and we observe different evolution trajectories of the output state of polarizations on the Poincaré sphere. When the amplification factor exceeds a certain threshold, the scrambler system exhibits nearly ideal polarization scrambling behavior. A commercial single wavelength laser with a linewidth of 3 MHz is utilized to characterize the scrambling performance. We found that when the sampling rate is 1.6 MSa/s, a scrambling speed up to 2000krad/s can be obtained for the average degree of polarization being less than 0.1. We also exploit these random polarization fluctuations to generate random binary numbers, indicating that the proposed technique is a good candidate for a random bit generator.

White matter hyperintensity, parent artery steno-occlusion, and neurological deterioration in anterior circulation single subcortical infarction patients.

BACKGROUND: The evidence for the association between white matter hyperintensity (WMH) severity and neurological deterioration (ND) in patients with single subcortical infarction (SSI) remains unclear and whether the association between them is modified by anterior circulation parent artery steno-occlusion (PAS) is unknown. Herein, we aimed to prospectively investigate the internal relevance. METHODS: In this prospective study, the severity of WMH and PAS were assessed in 288 consecutive patients with anterior circulation SSI arriving at our hospital, a tertiary teaching hospital affiliated with Fudan University, 24 h after onset from January 2017 to December 2018. The multivariable logistic regression model was used to estimate the association between WMH severity and the risk of ND within 7 days after stroke onset as well as the interactive effect between WMH severity and PAS on ND among patients with SSI. RESULTS: PAS modified the association between WMH severity and ND among patients with SSI (pinteraction = .029). After multivariate adjustment, the odds ratios of moderate-severe WMH associated with ND were 1.61 (95% CI, 0.50-5.19; ptrend = .428) for patients with PAS, and 0.37 (95% CI, 0.14-0.97; ptrend = .043) for those without PAS. Adding WMH severity to conventional risk factors improved risk prediction for ND in patients without PAS (net reclassification improvement: 48.2%, p = .005; integrated discrimination index: 2.5%, p = .004) but not in those with PAS. CONCLUSION: There was a modified effect of PAS on the association between WMH severity and ND within 7 days after stroke onset among patients with anterior circulation SSI, which deserves more research attention. WMH was negatively associated with ND in anterior circulation SSI patients without PAS.

Subacromial osteolysis following hook plate fixation for acromioclavicular dislocation: a systematic review and meta-analysis.

BACKGROUND: Clavicular hook plates are extensively used in the treatment of acromioclavicular (AC) dislocation. Subacromial osteolysis is a typical complication following hook plate fixation. We performed a systematic review and meta-analysis to determine the incidence of subacromial osteolysis and analyzed the associated characteristics of subacromial osteolysis to guide surgeons. METHODS: PubMed, EMBASE, and Cochrane Library databases were comprehensively searched for relevant literature. We screened the literature based on the eligibility criteria, extracted relevant data and assessed the quality of the included studies. Pooled odds ratios (ORs) or mean differences (MDs) with 95% confidence intervals were calculated by a fixed-effects or random-effects model. Heterogeneity was evaluated by the chi-squared test and I2 statistics. A meta-regression analysis was performed to explore the potential source of heterogeneity. RESULTS: Thirty-two studies met the inclusion criteria. The total pooled incidence of subacromial osteolysis was 29%, and the only covariate that could influence the incidence of subacromial osteolysis was the radiological measurement method (P=0.017). Patients in the hook plate fixation with coracoclavicular (CC) ligament reconstruction group had lower odds of subacromial osteolysis (OR, 2.54, 95% CI 1.54 to 4.18; P < 0.001). There were no significant differences in the Constant-Murley scores at the final follow-up between patients with and without subacromial osteolysis (SMD, -0.17; 95% CI, -0.50 to 0.15; P= 0.294). CONCLUSIONS: Subacromial osteolysis has a relatively high and variable incidence, and the primary factor influencing the reported incidence is the radiological assessment method. The current analysis suggests CC ligament reconstruction as an effective surgical approach for decreasing the incidence of subacromial osteolysis. The presence or absence of subacromial osteolysis did not significantly impact the functional outcomes observed during the final follow-up period.

Effect of Ultrasound-Guided Erector Spinae Plane Block on Pain After Laparoscopic Transabdominal Preperitoneal Repair: A Prospective, Double-Blind, Randomized Controlled Study.

Objective: The present study was performed to evaluate the effect of ultrasound-guided erector spinae plane block (ESPB) on pain after laparoscopic transabdominal preperitoneal (TAPP) repair. Therefore, improved postoperative pain management is crucial for enhancing the overall patient experience and recovery. Methods: This prospective, double-blind, randomized controlled trial enrolled 40 male patients with a unilateral inguinal hernia at Xi'an Aerospace General Hospital from November 1, 2020, to February 1, 2021. Participants were assigned through a random number table at a 1:1 ratio to receive either ESPB with 20 ml 0.5% ropivacaine in the experimental group (Group E) or ESPB with 20 ml normal saline in the control group (Group C), with 20 cases in each group. The primary outcome was assessed using visual analogue scale (VAS) scores for exercise pain at 2h, 6h, 12h, 18h, and 24h postoperatively. Secondary outcomes included time lapses before patient-controlled intravenous analgesia (PCIA) use, intraoperative remifentanil usage, additional sufentanil, postoperative nalbuphine consumption, analgesic remedies at 24h postoperatively, and incidence of postoperative adverse events. Results: Group E provided more pain mitigation for patients than Group C, as evidenced by the significantly lower VAS scores during exercise pain at 2h (Group C: 1.95±1.19; Group E:4.00±1.38), 6h (Group C: 2.00±1.12; Group E:3.90±1.37), and 12h (Group C: 2.05±1.05; Group E:3.55±1.36) postoperatively (P < .05), and the pain mitigation for Group C was significant only at 18h and 24h postoperatively compared to at 2h postoperatively (P < .05). Group E resulted in significantly reduced intraoperative use of remifentanil and, additional sufentanil and postoperative nalbuphine consumption versus Group C (P < .05). Group E exhibited a better pain tolerance than Group C, as demonstrated by the longer time lapse before the use of PCIA (RR value=5.709, t=8.446, P < .05). Group C required more analgesic remedies within 24 h after surgery than Group E (P < .05). Group E did not increase the risk of postoperative adverse events, given the absence of statistical significance in the intergroup comparison (P > .05). Conclusion: Ultrasound-guided ESPB demonstrates notable benefits by decreasing intraoperative and postoperative anesthetic drug requirements, enhancing pain management, and elevating postoperative comfort and quality of life for patients. While acknowledging the study's limitations, it is crucial to highlight the potential clinical implications of these findings. The incorporation of ESPB with ropivacaine into postoperative pain management protocols could represent a significant advancement in clinical practice. The observed improvements in pain management and reduced reliance on anesthetic drugs may lead to more tailored and efficient postoperative care, potentially enhancing patient recovery experiences. Further research and practical implementation studies are warranted to fully elucidate the specific impact and optimal integration of ESPB with ropivacaine within broader clinical settings.

Complicated Bosworth fracture-dislocation: A case report and review of the literature.

Bosworth fracture and dislocation is relatively rare, accounting for about 1% of ankle fractures. It is characterized by the proximal fibula fracture embedded in the posterolateral distal tibia. Due to an insufficient understanding of this fracture, it is easy to cause missed diagnosis and misdiagnosis in clinical practice. Due to the insertion of the fracture, it is challenging to perform closed reduction, and improper treatment is easy to cause complications. Surgical treatment is recommended for this type of fracture. In order to improve the understanding of orthopedic surgeons about Bosworth fracture and dislocation, this paper reports the diagnosis and treatment of 2 cases of Bosworth fracture and dislocation, and reviews the literature on Bosworth fracture's mechanism, diagnosis, classification, complications, and treatment options in recent years.

Comparison of continuous pericapsular nerve group (PENG) block versus continuous fascia iliaca compartment block on pain management and quadriceps muscle strength after total hip arthroplasty: a prospective, randomized controlled study.

BACKGROUND: This investigation aimed to evaluate the impact of continuous pericapsular nerve group (PENG) block and continuous fascia iliac compartment block (FICB) on postoperative pain following total hip arthroplasty (THA). METHODS: This prospective, randomized, and controlled trial recruited a cohort of fifty-seven patients with unilateral femoral neck fractures from Xi'an Aerospace General Hospital in northwest China between July 2020 and November 2021. These patients were randomly assigned to two groups: the continuous PENG block group (PENG group, n = 29) and the continuous FICB group (FICB group, n = 28). Under ultrasound guidance, PENG block and FICB procedures were performed prior to spinal anesthesia, utilizing 20 ml of 0.25% ropivacaine for PENG block and 30 ml of 0.25% ropivacaine for FICB. Subsequently, a catheter was inserted. All study participants received a standardized postoperative multimodal analgesic regimen, including intravenous administration of 30 mg Ketorolac tromethamine every eight hours and patient-controlled neural analgesia (PCNA) after surgery. Numerical rating scale (NRS) scores at rest and during exercise were recorded at various time points: prior to block (T0), 30 min post-blockade (T1), and 6 h (T2), 12 h (T3), 24 h (T4), and 48 h (T5) postoperatively. Additional data collected encompassed postoperative quadriceps muscle strength, the time of initial ambulation after surgery, the number of effective PCNA activations, rescue analgesia requirements, and occurrences of adverse events (such as nausea and vomiting, hematoma, infection, catheter detachment, or displacement) within 48 h following surgery. RESULTS: In the PENG group, the resting NRS pain scores exhibited lower values at T1, T4, and T5 than those at T0. Furthermore, exercise NRS pain scores at T1-T5 were lower in the PENG group than in the FICB group. Similarly, during the same postoperative period, the PENG group demonstrated enhanced quadriceps strength on the affected side compared to the FICB group. Additionally, the PENG group displayed earlier postoperative ambulation and reduced occurrences of effective PCNA activations and rescue analgesia requirements compared to the FICB group. CONCLUSION: Continuous PENG block exhibited superior analgesic efficacy after THA compared to continuous FICB, promoting recovery of quadriceps strength on the affected side and facilitating early postoperative ambulation. TRIAL REGISTRATION: This clinical trial was registered in the China Clinical Trials Center ( http://www.chictr.org.cn ) on 20/07/2020, with the registration number ChiCTR2000034821.

Acousto-optic reconfigurable filter based on vector mode fusion in dispersion-compensating fiber.

An acousto-optic reconfigurable filter (AORF) is proposed and demonstrated based on vector mode fusion in dispersion-compensating fiber (DCF). With multiple acoustic driving frequencies, the resonance peaks of different vector modes in the same scalar mode group can be effectively fused into a single peak, which is utilized to obtain arbitrary reconfiguration of the proposed filter. In the experiment, the bandwidth of the AORF can be electrically tuned from 5 nm to 18 nm with superposition of different driving frequencies. The multi-wavelength filtering is further demonstrated by increasing the interval of the multiple driving frequencies. The bandpass/band-rejection can also be electrically reconfigured by setting the combination of driving frequencies. The proposed AORF gains the feature of reconfigurable filtering types, fast and wide tunability, and zero frequency shift, which is advantageous for high-speed optical communication networks, tunable lasers, fast optical spectrum analyzing and microwave photonics signal processing.

miR-181b promotes angiogenesis and neurological function recovery after ischemic stroke.

Promotion of new blood vessel formation is a new strategy for treating ischemic stroke. Non-coding miRNAs have been recently considered potential therapeutic targets for ischemic stroke. miR-181b has been shown to promote angiogenesis in hypoxia and traumatic brain injury model, while its effect on ischemic stroke remains elusive. In this study, we found that overexpression of miR-181b in brain microvascular endothelial cells subjected to oxygen-glucose deprivation in vitro restored cell proliferation and enhanced angiogenesis. In rat models of focal cerebral ischemia, overexpression of miR-181b reduced infarction volume, promoted angiogenesis in ischemic penumbra, and improved neurological function. We further investigated the molecular mechanism by which miR-181b participates in angiogenesis after ischemic stroke and found that miR-181b directly bound to the 3'-UTR of phosphatase and tensin homolog (PTEN) mRNA to induce PTEN downregulation, leading to activation of the protein kinase B (Akt) pathway, upregulated expression of vascular endothelial growth factors, down-regulated expression of endostatin, and promoted angiogenesis. Taken together, these results indicate that exogenous miR-181b exhibits neuroprotective effects on ischemic stroke through activating the PTEN/Akt signal pathway and promoting angiogenesis.

Impact of high-sensitivity troponin elevation and dynamic changes on 90-day mortality in patients with acute ischemic stroke after mechanical thrombectomy: results from an observational cohort.

BACKGROUND: A study was undertaken to evaluate the impact of high-sensitivity cardiac troponin I (hs-cTnI) elevation and hs-cTnI dynamic changes on 90-day mortality in patients with acute ischemic stroke (AIS) treated with mechanical thrombectomy (MT). METHODS: Patients with AIS receiving MT were included in the study. Sixty hours after AIS onset, hs-cTnI levels were measured before and after MT to determine elevated and dynamic changes. Patients were stratified into either normal or hs-cTnI elevation groups according to the pre-MT hs-cTnI cut-off value of 0.03 ng/L. hs-cTnI dynamic changes were defined as an increase or decrease of more than 20% pre-MT and post-MT, and at least one hs-cTnI level >0.03 ng/L. Multivariate Cox regression models were used to investigate the association between hs-cTnI elevation, hs-cTnI dynamic changes, and 90-day mortality in patients with AIS after MT. RESULTS: A total of 423 patients with AIS after MT were included in our final analysis, of whom only 72 (17%) showed hs-cTnI elevation. Post-MT hs-cTnI retesting was performed in 354 patients, and 90 (25.4%) patients presented with hs-cTnI dynamic changes. 119 patients died within 90 days. After adjusting for potential confounding factors, the Cox regression model showed that patients with hs-cTnI dynamic changes, rather than hs-cTnI elevation, were associated with 90-day mortality (p<0.05). Compared with the hs-cTnI non-dynamic changes, these results showed that a statistical association was present between rising hs-cTnI dynamic changes and 90-day mortality (p>0.05). CONCLUSIONS: hs-cTnI dynamic changes, dominated by the rising pattern rather than hs-cTnI elevation, were independent factors associated with 90-day mortality in patients with AIS after MT, especially in elderly subjects.

Tens of hertz ultra-narrow linewidth fiber ring laser based on external weak distributed feedback.

We suggest and demonstrate a single-frequency fiber ring laser with an ultra-narrow linewidth based on an external weak distributed feedback. A π phase-shifted fiber Bragg grating (PSFBG) is used to improve mode selection and enable single-longitudinal mode (SLM) laser operation. The linewidth is then further strongly compressed using a signal generated by a weak distributed feedback structure (WDFS) and injected into the main laser cavity to suppress spontaneous emission. The resulting ultra-narrow linewidth fiber ring laser achieves a side-mode suppression ratio (SMSR) of ∼72 dB, and low white frequency noise of ∼10.3 Hz2/Hz, which correspond to an instantaneous linewidth of ∼32.3 Hz in the normal operating condition of the laser. Our linewidth compression mechanism not only solves the problems associated with deep linewidth compression in long-cavity fiber laser, but also fosters the development of practical and reliable all-fiber structures. Our laser source is characterized by low cost, high coherence, and low noise, which are highly desirable features in coherent optical detection, high-resolution spectrometers, microwave photonics, and optical sensing.

Ultra-narrow linewidth vertical-cavity surface-emitting laser based on external-cavity weak distributed feedback.

We demonstrate an ultra-narrow linewidth vertical-cavity surface-emitting laser (VCSEL) based on external-cavity weak distributed feedback from Rayleigh backscattering (RBS). A single longitudinal mode VCSEL with the linewidth as narrow as 435 Hz and a contrast of 55 dB are experimentally achieved by RBS fiber with a feedback level of RBS signal of -27.6 dB. By adjusting the thermal resistance of the VCSEL from 4.5 kΩ to 7.0 kΩ, the laser wavelength can be tuned from 1543.324 nm to 1542.06 nm with a linear tuning slope of -0.506 nm/kΩ. In the tuning process, the linewidth fluctuates in the range of 553-419 Hz.

Safety and efficacy of a new modified intravenous recombinant tissue plasminogen activator (rt-PA) regimen in Chinese patients with acute ischemic stroke: A descriptive retrospective cohort study with subgroup-analysis of different rt-PA dose.

Evidence for effects of the dose of recombinant tissue plasminogen activator(rt-PA) in Asian populations is inconclusive. The standard dose may cause drug waste and increase economic burden in developing country. Therefore, we preliminarily describe the safety and efficacy of a new modified dose of rt-PA regimen(0.6 or 0.9 mg/kg, with a maximum dose of 50 mg) in real world settings. 265 consecutive patients with ischemic stroke were treated with intravenous(IV) rt-PA alone from all the 323 consecutive patients treated with reperfusion therapy between January 1, 2017 and March 31, 2020. Safety and Efficacy was assessed by early neurological improvement(ENI), early neurological deterioration(END), symptomatic intracranial hemorrhage(sICH) and 90-day outcome defined by modified Rankin scale(mRS). Subgroup analysis was conducted to draw comparisons between different dose groups ([0.5,0.6)mg/kg, [0.6,0.7)mg/kg, [0.7,0.8)mg/kg, [0.8,0.9]mg/kg). Among the 265 patients, 150(56.60%) had a favorable outcome at 3 months(3 M); Mortality occurred in 17(6.40%) in 3 M; sICH in 12(4.50%); ENI in 70(26.40%); END2 in 29(10.90%) and END4 in 18(6.80%). In subgroup analysis, there was a significant difference in sICH that more patients developed sICH in [0.8-0.9]mg/kg group(P = 0.044) in univariate analysis of different dose. After adjusting, there was no significant difference between 4 dosage groups. Significant differences were seen in gender, atrial fibrillation and baseline NIHSS in the multivariable model of favorable outcome at 3 M. Our study preliminarily shows a good safety and efficacy of our modified rt-PA regimen, indicating that this regimen should be worthy of further study especially in developing country to reduce the financial burden of patients and avoid drug waste.

Ultra-narrow-linewidth DFB laser array based on dual-cavity feedback.

Herein, we propose a structure to simultaneously compress the distributed feedback (DFB) laser array's linewidth. The proposed structure is meticulously designed to ensure single longitudinal mode operation via the interference phenomenon between the laser's primary cavity and the dual-cavity feedback. Given the weak feedback effect for each wavelength in the laser array, the proposed structure could realize the intense compression of the laser linewidths. The study results show that the side-mode suppression ratios of each DFB laser are over 40 dB, and the linewidths have been compressed from 3 MHz to ∼800 Hz. Thus, we believe the idea of an overall compression linewidth scheme in the present study can be adopted for integrated laser arrays.

Control of polarization switching in a VCSEL via resonant feedback from a whispering-gallery-mode cavity.

We report a method for flexibly switching the dominant polarization of a vertical-cavity surface-emitting laser (VCSEL) by introducing polarization-resolved resonant optical feedback from a whispering-gallery-mode (WGM) cavity to the lasing cavity. Switching between the originally dominant mode and a side mode is experimentally demonstrated under different bias currents once one of them is locked to the resonance mode of the WGM cavity. In addition to a controllable polarization state, the reported VCSEL also demonstrates a linewidth as narrow as tens of kilohertz, which is highly desirable for many applications, including high-speed data communication, light detection and ranging (lidar), and absorption spectroscopy.

Simultaneous self-injection locking of two VCSELs to a single whispering-gallery-mode microcavity.

Simultaneous self-injection locking of two vertical-cavity surface-emitting lasers (VCSELs) to a single whispering-gallery-mode (WGM) microcavity is experimentally demonstrated. The linewidths of the two VCSELs are compressed from 3.5 MHz and 5 MHz to 20.9 kHz and 24.1 kHz, which is on the same order of magnitude as that of locking each VCSEL to the microcavity separately. Moreover, the frequency noises of the two simultaneously locked VCSELs are suppressed by more than 60 dB below the offset frequency of 100 kHz compared to that of the free-running VCSELs. The method demonstrated here might be used in the multi-wavelength laser array with low phase and frequency noises, especially the VCSELs with the unique architecture of a two-dimensional array.

Narrow linewidth VCSEL based on resonant optical feedback from an on-chip microring add-drop filter.

We demonstrate a narrow linewidth vertical-cavity surface-emitting laser (VCSEL) by injecting resonant optical feedback into the lasing cavity. A single longitudinal mode VCSEL with a Lorentzian linewidth of 32.6 kHz and a purified optical spectrum is experimentally achieved by an on-chip microring add-drop filter with a quality factor of 1.36 million, where the feedback level is ${-}{47.77}\;{\rm{dB}}$. The frequency noise spectrum of the VCSEL demonstrates that the thermo-optic effect in the microring resonator can also stabilize the lasing frequency. A VCSEL with narrow linewidth and stable frequency provides a high-performance light source for a single VCSEL or VCSEL array-based application.

Plasma Exosomal MiRNAs Expression Profile in Mesial Temporal Lobe Epilepsy With Hippocampal Sclerosis: Case-Control Study and Analysis of Potential Functions.

BACKGROUND: To explore an expression profile in plasma exosomal miRNAs of mesial temporal lobe epilepsy with hippocampal sclerosis (mTLE + HS) patients and investigate the associated clinical significance and putative pathways involved. METHODS: Plasma exosomal miRNAs were measured in six mTLE + HS patients who were confirmed with pre-surgical stereo-electroencephalography and six without hippocampal sclerosis (mTLE-HS) using Illumina HiSeq 2500. Then six dysregulated miRNAs were chosen for validation in an independent sample of 18 mTLE + HS patients and 18 mTLE-HS controls using RT-qPCR. Receiver operating characteristic curve was conducted to evaluate the diagnostic value of miRNAs in HS. Bioinformatic analyses were conducted to reveal in which pathways these miRNAs were involved. RESULTS: We revealed that a total of 42 exosomal miRNAs were differentially expressed in mTLE + HS. Among them, 25 were increased and 17 decreased. After validation, hsa-miR-129-5p, -214-3p, -219a-5p, and -34c-5p were confirmed as being upregulated, while hsa-miR-421 and -184 were significantly downregulated in mTLE + HS. Moreover, hsa-miR-184 had the best diagnostic value for discriminating mTLE + HS with 88.9% sensitivity and 83.3% specificity. These six miRNAs regulated several genes from neurotrophin-, hippo-, p53-, TGF- beta-, HIF- 1-, mTOR-related pathways. CONCLUSION: Six miRNAs were dysregulated in mTLE + HS patients and targeted several genes. This result might facilitate pathological mechanistic studies of miRNAs in HS and represent potential diagnostic biomarkers. These provided the rationale for further confirmation studies in larger cohorts of prospective patients.

A fluorometric optical fiber nanoprobe for copper(II) by using AgInZnS quantum dots.

An optical fiber nanoprobe is presented for fluorometric determination of copper(II). The method based on the use of water-dispersible AgInZnS quantum dots (QDs) deposited at the end of an optical fiber in a poly(vinyl alcohol) matrix. The fluorescnece of the QDs, best measured at excitation/emisssion wavelengths of 365/570 nm, is quenched by Cu(II) due to both static and electron transfer from the QDs to Cu(II). This is experimentally confirmed by photoluminescence and UV-vis absorption spectra, and measurement of luminescence lifetimes. The probe is highly selective and possesses a linear detection range that extends from 2.5 to 800 nM. Graphical abstractSchematic representation of an optical fiber nanoprobe based on hydrophilic AgInZnS quantum dots for fluorometric determination of copper(II). The fluorescence is quenched by Cu(II) due to static quenching and dynamic quenching. It has a detection range of 2.5-800 nM.

Plasmon-enhanced linear and second-order surface nonlinear optical response of silver nanoparticles fabricated using a femtosecond pulse.

We present the plasmon-enhanced linear and second-order surface nonlinear optical response of silver nanoparticles (Ag NPs) fabricated using a femtosecond pulse. Theoretical analysis indicates Ag NPs with a diameter of ∼100 nm have excellent linear response within the visible band, and the electric field intensity enhancement factor reaches ∼105 under excitation of continuous light of 632.8 nm. Meanwhile, the simulation result of second-order surface nonlinear optical response shows that the second harmonic conversion efficiency of the Ag NPs dimer is two orders of magnitude higher than that of a single Ag NP, under excitation of a femtosecond pulse. In experiment, the linear response of Ag NPs is examined using surface-enhanced Raman spectroscopy (SERS) with a Raman enhancement factor of ∼1.7 × 1010, revealing the excellent linear optical response of Ag NPs. Moreover, the spectra of the second harmonic can be measured clearly under conditions of an average pump power of 40 µW, revealing the excellent second-order surface nonlinear optical response of Ag NPs.