Optical Power Research Articles

Compact Low Loss Ribbed Asymmetric Multimode Interference Power Splitter

Optical power splitters (OPSs) are utilized extensively in integrated photonic circuits, drawing significant interest in research on power splitters with adjustable splitting ratios. This paper introduces a compact, low-loss 1 × 2 asymmetric multimode interferometric (MMI) optical power splitter on a silicon-on-insulator (SOI) platform. The device is simulated using the finite difference method (FDM) and eigenmode expansion solver (EME). It is possible to attain various output power splitting ratios by making the geometry of the MMI central section asymmetric relative to the propagation axis. Six distinct optical power splitters are designed with unconventional splitting ratios in this paper, which substantiates that the device can achieve any power splitter ratios (PSRs) in the range of 95:5 to 50:50. The dimensions of the multimode section were established at 2.9 × (9.5–10.9) μm. Simulation results show a range of unique advantages of the device, including a low extra loss of less than 0.4 dB, good fabrication tolerance, and power splitting ratio fluctuation below 3% across the 1500 nm to 1600 nm wavelength span.

Standard Response Calculation of Electric Dipole Polarizability and Specific Optical Rotation Power Densities.

A time-dependent method has been developed to solve the standard response equation for the calculation of dynamic molecular property densities, endowed with the characteristic of being origin-invariant, entirely in the atomic orbital basis at both HF and DFT level of theory. The method has been tuned in particular for the calculation of origin-independent electric dipole polarizability density and specific rotation power density. Some demonstrations are given for the hexabenzocoronene molecule and the Tröger base.

Evaluating keratometry and corneal astigmatism data from biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism.

To compare results from different corneal astigmatism measurement instruments; to reconstruct corneal astigmatism from the postimplantation spectacle refraction and toric intraocular lens (IOL) power; and to derive models for mapping measured corneal astigmatism to reconstructed corneal astigmatism. Retrospective single centre study involving 150 eyes treated with a toric IOL (Alcon SN6AT, DFT or TFNT). Measurements included IOLMaster 700 keratometry (IOLMK) and total keratometry (IOLMTK), Pentacam keratometry (PK) and total corneal refractive power in 3 and 4 mm zones (PTCRP3 and PTCRP4), and Aladdin keratometry (AK). Regression-based models mapping the measured C0 and C45 components (Alpin's method) to reconstructed corneal astigmatism were derived. Mean C0 components were 0.50/0.59/0.51 dioptres (D) for IOLMK/PK/AK; 0.2/0.26/0.31 D for IOLMTK/PTCRP3/PTCRP4; and 0.26 D for reconstructed corneal astigmatism. All corresponding C45 components ranged around 0. The prediction models had main diagonal elements lower than 1 with some crosstalk between C0 and C45 (nonzero off-diagonal elements). Root-mean-squared residuals were 0.44/0.45/0.48/0.51/0.50/0.47 D for IOLMK/IOLMTK/PK/PTCRP3/PTCRP4/AK. Results from the different modalities are not consistent. On average IOLMTK/PTCRP3/PTCRP4 match reconstructed corneal astigmatism, whereas IOLMK/PK/AK show systematic C0 offsets of around 0.25 D. IOLMTK/PTCRP3/PTCRP4. Prediction models can reduce but not fully eliminate residual astigmatism after toric IOL implantation.

Fiber Bragg grating sensing system for temperature measurements based on optically injected DFB-LD with an OEO loop

A novel fiber Bragg grating (FBG) sensing system, based on an optically injected distributed feedback laser diode (DFB-LD) with an optoelectronic oscillating (OEO) loop, is proposed and experimentally demonstrated for temperature measurements with high and tunable sensitivity. The FBG sensor device works as an edge filter to adjust the optical power of the injected beam in response to temperature variations. The optically injected DFB-LD works at Period-one (P1) oscillating state, and the central wavelength of the oscillating mode of the DFB-LD can be tuned by the variable power of the injected beam. Furthermore, an OEO loop is implemented to improve the signal quality of the generated P1 microwave signal. Hence, the sensing parameter of temperature is converted to the frequency variation of the generated P1 microwave signal in the proposed sensing system. In the proof-of-concept experiment, a series of P1 microwave signals are generated while different temperatures are applied to the FBG sensor. The sensitivity of the proposed FBG sensing system for temperature measurements can be tuned from 0.44322 GHz/°C to 1.25952 GHz/°C. The stability and repeatability experiments are also performed, demonstrating the high measurement accuracy (0.0629°C) and low error of the system. The proposed FBG-based sensing and interrogation system exhibits high sensitivity, large tunability, good linearity, and flexible sensing generality.

Hybrid meta/refractive lens design with an inverse design using physical optics

Hybrid lenses are created by combining metasurface optics with refractive optics, where refractive elements contribute optical power, while metasurfaces correct optical aberrations. We present an algorithm for optimizing metasurface nanostructures within a hybrid lens, allowing flexible interleaving of metasurface and refractive optics in the optical train. To efficiently optimize metasurface nanostructures, we develop a scalar field, ray-wave hybrid propagation method. This method facilitates the propagation of incident and derived adjoint fields through optical elements, enabling effective metasurface optimization within the framework of adjoint gradient optimization. Numerical examples of various lens configurations are presented to illustrate the versatility of the algorithm and showcase the benefits offered by the proposed approach, allowing metasurfaces to be positioned beyond the image space of a lens. Taking a F/2, 40° field-of-view, midwave infrared lens as an example, the lens exhibits an average focusing efficiency of 38% before the integration of metasurfaces. Utilizing the new algorithm to design two metasurfaces—one in the object space and one in the image space—results in significant enhancement of the average focusing efficiency to over 90%. In contrast, a counterpart design with both metasurfaces limited to the image space yields a lower average focusing efficiency of 73%.

Secure high-density constellation mapping OTFS modulation scheme with low PAPR

In this paper, a secure orthogonal time-frequency space (OTFS) modulation transmission system based on 3D dense constellation mapping (DCM) geometric shaping is proposed, and a selective reduction amplitude algorithm (SRA) for DCM to reduce peak average power ratio (PAPR) is presented. The DCM is based on regular tetrahedron construction to improve its space utilization efficiency. The proposed SRA involves reducing high PAPRs transmitter and restoring them at the receiving end, which only requires an additional 0.57% of the total transmission capacity. The algorithm reduces PAPR while ensuring the bit error rate performance of the system, so it is suitable for systems that need to process large amounts of transmitted data quickly. By verifying the actual transmission performance on a 2 km of 7-core optical fiber transmission system, the optical transmission with a bit rate of 33.93Gb/s is achieved. The experimental results show that when the bit error rate (BER) reaches the 3.8×10−3 threshold, the OTFS system using DCM and SRA could improve the receiver sensitivity by 3.7 dB compared with the OTFS system using concentric cube mapping and SRA, and 2.7 dB compared with the OFDM system using DCM. After adding the SRA, the PAPR of the OTFS system is reduced by more than 2.2 dB. When the received optical power reaches near the bit error rate threshold, the SRA valid data can be fully recovered by optimizing the SRA.

Nanophotonic integrated active-passive InP membrane devices and circuits fabricated using ArF scanner lithography

We present a novel fabrication approach to an integrated nanophotonic platform, based on a III-V membrane bonded to a Si substrate with benzocyclobutene (BCB). The process incorporates a hybrid lithography strategy combining deep-UV and electron-beam lithography on the same wafer. We report for the first time the usage of deep-UV scanner lithography for the fabrication of the active-passive tapers and sub-micron waveguides on the same wafer, which enables better critical dimension control, uniformity, and reproducibility. The platform uses an active-passive butt-joint interface and includes components such as distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, electro-optical (EO) and electro-absorption (EA) modulators, and sub-micron ultra-confined passive waveguides, all monolithically integrated into a single membrane layer. The active devices have a heat sink achieved by ultra-thin BCB bonding. Lasers demonstrate up to 26 mW of optical power in the waveguide and a direct modulation bandwidth of up to 21 GHz. The modulators show static extinction up to 28.8 dB.

Evaluation and application of a Chinese version symptom questionnaire for visual dysfunctions (CSQVD) in school-age children

ObjectiveTo develop and evaluate a Chinese version of the Symptom Questionnaire for Visual Dysfunctions (CSQVD) to quantify visual dysfunction symptoms in school-age children with various eye diseases, and to explore the relationship between ophthalmological disorders and visual dysfunction symptoms. MethodsFollowing standard scale adaptation procedures, the Symptom Questionnaire for Visual Dysfunctions (SQVD) was translated into Chinese (CSQVD). We employed random sampling to survey 198 outpatients aged 7–18 to assess the psychometric properties of the CSQVD. Using the reliable and validated questionnaire, we evaluated the determinants of visual dysfunction symptoms among 406 school-age patients at an eye center. The CSQVD scores were correlated with demographic and clinical variables, including gender, age, eye position, refractive power, and best-corrected visual acuity. Univariate analysis identified potential risk factors, followed by binary logistic regression and multiple linear regression analysis on factors with a P-value <0.05. ResultsThe CSQVD scale's critical ratio (CR) values ranged from 6.028 to 10.604. The Cronbach's Alpha coefficient was 0.779, and Spearman-Brown split-half reliability was also 0.779. The I-CVI varied from 0.83 to 1.000, the S-CVI/Ave was 0.857, and the KMO value was 0.821. Multifactorial regression analysis indicated that high myopia (OR ​= ​5.744, 95% CI [1.632, 20.218], P ​= ​0.006) and amblyopia (OR ​= ​9.302, 95% CI [1.878, 46.058], P ​= ​0.006) were significant predictors of CSQVD symptoms. Multiple linear regression analysis showed that BCVA of amblyopic eyes (B ​= ​−5.052, 95% CI [−7.779, 2.325], P ​= ​0.000) and SE power (B ​= ​−0.234, 95% CI [−0.375, 0.205], P ​= ​0.001) significantly affected the CSQVD scale scores. ConclusionsThe Chinese version of the SQVD scale (CSQVD) demonstrates good feasibility, discriminatory power, validity, and reliability in assessing Chinese school-aged children. Furthermore, those who have severe myopia and amblyopia reported more visual dysfunction symptoms.

OpSAVE: Eviction Based Scheme for Efficient Optical Network-on-Chip

For on-chip networks, nanophotonics has been considered a strong alternative owing to its high speed (due to low latency) and high bandwidth (due to wavelength division multiplexing). However, the major hurdle in the adoption of nanophotonic-based on-chip networks is their high static power consumption. Various proposals are there in the literature which try to reduce the static power consumption either by modulating the laser or by allowing the on-chip stations to share the photonic channels. In this paper, we propose OpSAVE— an optical NoC that combines the above two strategies to effectively reduce static power consumption. It proposes a superior prediction mechanism based on the eviction details from the private caches. It explains how shared channels can be used to dynamically balance the load and at the same time handle mispredictions. It allows the optical stations to share both the power and the available bandwidth to increase their utilization. Moreover, OpSAVE proposes to use a double pumping strategy to improve the system performance. We compared our scheme with the state-of-the-art proposals in this domain and the results show that our scheme consumes 4.4X less optical power and at the same time improves the performance by nearly 28%. In the evaluation, we have considered the multicore benchmarks from the Splash and Parsec benchmark suites.

Accuracy of 20 Intraocular Lens Power Calculation Formulas in Medium-Long Eyes.

The aim of this work is to compare 20 intraocular lens (IOL) power calculation formulas in medium-long eyes (24.50-25.99mm) in terms of root mean square absolute error (RMSAE), median absolute error (MedAE), and percentage of eyes with prediction error (PE) within ± 0.50 D. The data of patients who underwent uneventful phacoemulsification between January 2017 and September 2023 were reviewed. Pre-surgery IOL power was calculated using Holladay1, SRK/T, Hoffer Q, Holladay 2, and Haigis. Three months after phacoemulsification, refraction was measured. Post-surgery IOL power calculations were performed utilizing the following formulas: Barrett Universal II, Kane, K6, Olsen (OLCR), Olsen (standalone), PEARL-DGS, Ladas Super Formula AI (LSF AI), T2, EVO, VRF, Hoffer QST, Castrop, VRF-G, Karmona, and Naeser 2. RMSAE, MedAE, and percentage of eyes with PE within ± 0.25 D, ± 0.50 D, ± 0.75 D and ± 1.00 were calculated. One hundred twenty-four eyes with axial length ranges between 24.52 and 25.97mm were studied. The SRK/T formula yielded the lowest RMSAE (0.206) just before Holladay 1 (0.260) and T2 (0.261). In terms of MedAE, the best outcome was obtained by SRK/T (0.12) followed by Barrett Universal II (0.15) and LSF AI (0.15). The highest percentage of eyes with prediction error within ± 0.50 D was achieved by SRK/T, T2, and Holladay 1 (97.58, 93.55, and 93.55%, respectively). Third-generation formulas (SRK/T, Holladay 1) provided highly accurate outcomes in medium-long eyes and still can be wildly used to calculate IOL power.

Intelligent fault diagnosis and security early warning method of new power system based on system network situation

In the past few decades, China’s power demand has been increasing, and the power fiber plays a key role in ensuring the orderly dispatching of all links of the power system. The study used a wavelet decomposition and reconstruction method, which is a signal processing technique used to decompose complex optical power data into low-frequency and high-frequency signals with different frequency components. Through this decomposition, we can more clearly observe periodic fluctuations, trend changes, and noise components in optical power data. The study also examined different prediction models, including GRU, LSTM, ARMA), etc. The performance of these models in predicting optical power trends is then analyzed, taking into account their accuracy, stability, and computational efficiency. Finally, we carefully evaluated the GRU-ARMA combined prediction model and determined its superior performance in predicting optical power trends. The outcomes show that after adjusting the input data length of the gating cycle cell model and the relevant parameters of the autoregressive sliding mean model, the residual mean value was 0.0141. At the same time, the root mean square error calculated by the combined prediction model of the gating cycle unit-autoregressive moving mean model was 0.000618, which successfully improved the accuracy of predicting the optical power trend of power fiber. This research result provides an important reference for the aging state assessment of power fiber lines, and has an important practical application value for the maintenance of power fiber lines.

Engineering Graphene Phototransistors for High Dynamic Range Applications.

Phototransistors are light-sensitive devices featuring a high dynamic range, low-light detection, and mechanisms to adapt to different ambient light conditions. These features are of interest for bioinspired applications such as artificial and restored vision. In this work, we report on a graphene-based phototransistor exploiting the photogating effect that features picowatt- to microwatt-level photodetection, a dynamic range covering six orders of magnitude from 7 to 107 lux, and a responsivity of up to 4.7 × 103 A/W. The proposed device offers the highest dynamic range and lowest optical power detected compared to the state of the art in interfacial photogating and further operates air stably. These results have been achieved by a combination of multiple developments. For example, by optimizing the geometry of our devices with respect to the graphene channel aspect ratio and by introducing a semitransparent top-gate electrode, we report a factor 20-30 improvement in responsivity over unoptimized reference devices. Furthermore, we use a built-in dynamic range compression based on a partial logarithmic optical power dependence in combination with control of responsivity. These features enable adaptation to changing lighting conditions and support high dynamic range operation, similar to what is known in human visual perception. The enhanced performance of our devices therefore holds potential for bioinspired applications, such as retinal implants.

Harnessing the power of ML for robust SISO and MIMO FSO communication systems in fog weather

This study examines Free Space Optical (FSO) communication’s performance in different fog conditions, focusing on Single-Input Single-Output (SISO) and Multiple-Input Multiple-Output (MIMO) setups. In low fog, SISO handles signal degradation well. MIMO improves link robustness in moderate fog. High fog challenges traditional FSO, leading to ML integration to optimize communication parameters. For weather channel classification, a preprocessing scheme reduces features from 12 to 2 given that the 12 features are Bit Error Rate (BER), Quality Factor (Q-factor) and Received Optical Power (ROP) for different 4 users. A Gaussian Process Classifier (GPC) achieves an accuracy greater than 99%, surpassing SVM, Decision Tree, and Random Forest. GPC’s fit and predict functions execute in 0.15 s, outperforming NuSVM (0.2 s). This study highlights FSO, SISO, MIMO, and Machine Learning (ML) practicality in enhancing communication resilience in adverse weather, especially in fog-prone areas.

Quasi-analog operation for low photon flux detection with SiPM's standard and fast outputs

In this paper, we characterize the quasi-analog detection performance of silicon photomultiplier (SiPM) photodetector for optical wireless communications (OWC) at low photon flux signal intensity. In addition to analyzing the specificities of conventional anode-cathode standard output, it also highlights the unique capacitively coupled fast output feature of the off-the-shelf SiPM devices introduced by SensL, now ON Semiconductor (onsemi). Furthermore, the potential advantages of fast output are analyzed, and first propose the combined output model of standard and fast outputs. This combined output can be used to suppress ambient noise utilizing the bipolar characteristics of the fast output amplitude, e.g., the amplitude of the fast output can be up to ±30 mV under a useful signal light intensity of 94.1 nW, which can suppress the ambient noise amplitude of 30 mV and effectively improves signal-to-noise ratio. In addition, an approximate linear quantitative relationship between the standard output voltage amplitude and the SiPM chip received incident optical power was obtained, e.g., at different intensities of dark current and ambient current (1 nA and 2 nA), standard output voltage amplitudes of 90 mV and 50 mV correspond to optical powers of 50.5 nW and 21.3 nW or 34.7 nW and 5.7 nW. Finally, the potential performance of the proposed combined output schemes is confirmed by experimental and the measured Q-factor of the eye diagrams was optimised from 13.03 to 15.08. The proposed onsemi SiPM combined output schemes of standard and fast outputs can be selected to detection analog low-light link.

Hybrid pumped laser sources based hybrid traveling wave SOA and optical EDFA amplifies for signal quality improvement

Abstract This paper has demonstrated the hybrid pumped laser sources based hybrid traveling wave SOA and optical EDFA amplifies for the signal quality improvement. The previous effective noise figure and fiber loss variations are clarified against wavelength band with/without amplification. The related previous signal output power versus Raman/EDFA pumped amplification and signal power conversion efficiency are indicated versus the launched pump power with the Raman/EDFA pumped amplification. The signal quality factor/BER against the transmission distance with/without amplification after receiver side. The modified amplified light signal power is demonstrated after 300 km distance SMF channel with wavelength band variations. The modified amplified light signal power is clarified after 300 km distance SMF channel by using optical power meter. The modified amplified light signal power is clarified after 300 km distance SMF channel with time band variations. The modified amplified electrical signal power is demonstrated after 350 km distance SMF channel with frequency band variations. The modified amplified electrical signal power is clarified after 350 km distance SMF channel with time band variations. The modified amplified electrical signal power is demonstrated after 350 km distance SMF channel by using electrical power meter.

Modification of contact lenses via metal‐organic frameworks for glaucoma treatment

AbstractThe prevention of blindness from glaucoma requires multiple treatments to lower intraocular pressure. Here, human contact lenses are modified with highly porous metal‐organic frameworks with sustained release of brimonidine for prolonged glaucoma treatment. Various metal‐organic frameworks were screened for their attachment to lenses, loading with brimonidine, and drug‐release properties. Optimized therapeutic ocular lenses conjugated with MIL‐101(Cr) frameworks maintain optical transparency and power. Coating of lenses with MIL‐101(Cr) nanoparticles reduced brimonidine washout with tears and ensured a gradual and localized release of the drug into the eyeball through the cornea. The hybrid lenses provided a 4.5‐fold better decrease in eye pressure, compared by area under the curve (AUC) value to a commercially available brimonidine tartrate solution. Therapeutic lenses did not induce any notable eye irritation or corneal damage in vivo. The newly developed hybrid lenses are expected to provide a robust platform for the therapy and prevention of various ocular diseases.

Retinal image quality for multifocal lenses with on- and off-axis annular zones.

Multi-focal intra-ocular or contact lenses, intended to increase depth of focus, conventionally have annular zones of additional refractive power, generating wavefront rings of coaxial spherical surfaces. It is, however, possible to influence depth of focus by changing not only the curvature of the wavefront, i.e., refractive power, in the annulus, but also the tilt, i.e., circularly symmetrical linear radial deviation imposed on the spherical wavefront. Employing the example of a single annulus bifocal, retinal image light distributions in the two regimes are calculated, using standard diffraction theory. Four measures of retinal image quality in through-focus scans show that plus power additions and wavefront tilts operate almost interchangeably. In testing these lenses, attention needs to be paid to the detailed operating characteristics of measuring devices of the Shack-Hartmann type to ensure that their grain and precision is compatible with the framework of the analysis.

Comparative study of the reptilian cornea's microstructure

BackgroundThe cornea of various vertebrate is considered a major part in the glop, which acts as a powerful lens, providing a sharp retinal image, and meantime acts as an excellent defensor for other corneal layers.ResultsThe four reptilian families [Scincidae (Chalcides ocellatus); Chamaeleontidae (Chameleon chameleon); Cheloniidae (Chelonia mydas) and Testudiniae (Testudo kleinmanni)] investigated in the current study were gathered across Egypt. After being taken out of the orbit, the cornea under inquiry was ready for light, specific stain and scanning electron microscopy. The epithelium, stroma, and endothelium are the three corneal layers that are common to all four species of reptiles. All other species lack Bowmen's and Descemet's membranes, with the exception of C. ocellatus and T. kleinmanni. The latter layers of Chalcides ocellatus display a strong affinity for Periodic Acid Schiff stain. Epithelial cells with a variety of forms, from hexagonal to atypical polygonal cells, cover the outer corneal surface. These epithelial cells are coated in short microplicae, microvilli, and microholes of varied diameters. There are a few blebs scattered around their surface.ConclusionThe current study concluded that various habitats have various significant effects on the cornea's microstructure characteristics and its physiological trends to accommodate different environmental surroundings.

Sliced chaotic encrypted transmission scheme based on key masked distribution in a W-band millimeter-wave system

In order to guarantee the information of the W-band wireless communication system from the physical layer, this paper proposes the sliced chaotic encrypted (SCE) transmission scheme based on key masked distribution (KMD). The scheme improves the security of free space communication in the W-band millimeter-wave wireless data transmission system. In this scheme, the key information is embedded into the random position of the ciphertext information, and then the ciphertext carrying the key information is encrypted by multi-dimensional chaos. Chaotic system 1 constructs a three-dimensional discrete chaotic map for implementing KMD. Chaotic system 2 constructs complex nonlinear dynamic behavior through the coupling of two neurons, and the masking factor generated is used to realize SCE. In this paper, the transmission of 16QAM signals in a 4.5 m W-band millimeter-wave wireless communication system with a rate of 40 Gb/s is proved by experiments, and the performance of the system is analyzed. When the input optical power is 5 dBm, the bit error rate (BER) of the legitimate encrypted receiver is 1.23 × 10−3. When the offset of chaotic sequence x and chaotic sequence y is 100, their BERs are more than 0.21. The key space of the chaotic system reaches 10192, which can effectively prevent illegal attacks and improve the security performance of the system. The experimental results show that the scheme can effectively distribute the keys and improve the security of the system. It has great application potential in the future of W-band millimeter-wave wireless secure communication.

Bias-drift insensitive full-field frequency response characterization of a thin-film lithium niobate-based intensity modulator.

We propose a rapid and precise scheme for characterizing the full-field frequency response of a thin-film lithium niobate-based intensity modulator (TFLN-IM) via a specially designed multi-tone microwave signal. Our proposed scheme remains insensitive to the bias-drift of IM. Experimental verification is implemented with a self-packaged TFLN-IM with a 3 dB bandwidth of 30 GHz. In comparison with the vector network analyzer (VNA) characterization results, the deviation values of the amplitude-frequency response (AFR) and phase-frequency response (PFR) within the 50 GHz bandwidth are below 0.3 dB and 0.15 rad, respectively. When the bias is drifted within 90% of the Vπ range, the deviation fluctuation values of AFR and PFR are less than 0.3 dB and 0.05 rad, respectively. With the help of the full-field response results, we can pre-compensate the TFLN-IM for the 64 Gbaud PAM-4 signals under the back-to-back (B2B) transmission, achieving a received optical power (ROP) gain of 2.3 dB. The versatility of our proposed full-field response characterization scheme can extend to various optical transceivers, offering the advantage of low cost, robust operation, and flexible implementation.