Single Continuous Wave Research Articles

Amphibious Hybrid Laser Tweezers for Fluid and Solid Domains.

Optical trapping is a potent tool for achieving precise and noninvasive manipulation of small objects in a vacuum and liquids. However, due to the substantial disparity between optical forces and interfacial adhesion, target objects should be suspended in fluid environments, rendering solid contact surfaces a restricted area for conventional optical tweezers. In this work, by relying on a single continuous wave (CW) laser, we demonstrate an optical manipulation system applicable for both fluid and solid domains, namely, amphibious hybrid laser tweezers. The key to our system lies in modulating the intensity of the CW laser with duration shorter than the dynamic thermal equilibrium time within objects, wherein strong thermal gradient forces with ∼6 orders of magnitude higher than the forces in optical tweezers are produced, enabling moving and trapping micro/nano-objects on solid interfaces. Thereby, CW laser-based optical tweezers and pulsed laser-based photothermal shock tweezers are seamlessly fused with the advantages of cost-effectiveness and simplicity. Our concept breaks the stereotype that CW lasers are limited to generating tiny forces and instead achieve ultrawide force generation spanning from femto-newtons (10-15 N) to (10-6 N). Our work expands the horizon of optical manipulation by seamlessly bridging its applications in fluid and solid environments and holds promise for inspiring optical manipulation techniques to perform more challenging tasks, which may unearth application scenarios in diverse fields such as fundamental physical research, nanofabrication, micro/nanorobotics, biomedicine, and cytology.

Comparative Evaluation of Three Rotary Retreatment Systems for Apical Extrusion of Root Canals Obturated with Different Techniques

The aim of this study was to evaluate the quantitative amount of apically extruded debris after endodontic retreatment using three retreatment rotary systems D-RaCe, R-Endo, and EdgefileXR in the teeth obturated by two techniques (single cone and continuous wave compaction). Sixty human mandibular premolars with single straight root canals were prepared by 2Shape endodontic rotary system with file size (25/0.04). After that, samples were divided into two groups according to the technique of obturation used (n=30/group): A: single cone and B: continuous wave compaction. Then, further random subdivision for each group into three sub groups according to the system used for retreatment (n=10/group) as follow: A1,B1:D-RaCe, A2,B2:R-Endo, and A3,B3: EdgefileXR. Preweighed Eppendorf tubes were used to collect the apical extruded material during endodontic retreatment. Then, Eppendorf tubes were stored in an incubator at 68C for 5 days. The weight of extruded debris was calculated by subtracting the weight of the empty tube from the weight of the tube containing the extruded debris. Data were analyzed statistically using one way ANOVA analysis of variance and post hoc Duncan test. EdgeFileXR and R-Endo were significantly not different, but significantly different from D-race in two obturation technique. Also, result showed that the same system exhibited no difference in both obturation techniques. All retreatment techniques resulted in apical extrusion debris. Also, it was concluded that the techniques of obturation had no significant effect in the amount of apical extruded debris by different retreatment systems used in this study.

Generating acoustic signals of varying intensities via modulating continuous-wave lasers scanning in air

This report describes the generation of acoustic signals via laser-interference-based heating. Sound signals of varying intensities were generated by modulating two continuous-wave (CW) laser beams interfering in air. In this study, we discovered that the acoustic signals generated by two spatial-frequency-modulated CW lasers scanning in air are significantly stronger than those of a single CW laser. The intensity of photoacoustic signals is proportional to the diameter of the laser beam. Furthermore, our investigation showed that modulating the spatial frequency of the two laser beams can change the intensity of the acoustic signal. In addition, we found that the two beams stack better against a single beam when scanned vertically in three dimensions.

Efficient ground state cooling of a membrane by the combination of continuous-wave field and pulses

We present an approach that realizes the ground state cooling of the membrane-in-middle optomechanical system. Instead of straightforwardly using the continuous-wave (CW) or pulsed external drives, we consider the combinations of them for having a more efficient cooling process. Due to the dynamical nature of the joint action of both CW and pulse fields, it is necessary to explore the real-time evolutions of the system under various conditions, from which the optimal cooling can be found. Given such setup, the cooling limit previously discovered for the simple optomechanical systems under a single CW drive can be easily broken. The achieved cooling effect indicated by a defined cooling rate is one or more order lower than the cooling limit of a simple optomechanical systems, thus providing an efficient way of ground state cooling. Furthermore, the ground state cooling can be realized for a membrane with much lower mechanical quality factor and with the external drives of the lower intensities, to considerably relax the requirements for optomechanical cooling with the current experimental technology.

Single mode fiber-free space optic based hybrid $$32\times 2~\text{Gbps}$$ WDM-PON architecture employing optical frequency comb source and polarization multiplexing

In this paper, we propose a cost-efficient single mode fiber-free space optics (SMF-FSO) based hybrid $$32 \times 2~\text{Gbps}$$ wavelength division multiplexed passive optical network (WDM-PON) employing optical frequency comb (OFC) source and polarization multiplexing. OFC source is realized at optical line terminal (OLT) by modulating a single continuous wave (CW) laser source with radio frequency (RF) sinusoidal signal and dual-drive Mach–Zehnder modulator (DD-MZM). 16 coherent optical carriers are used to split into 32 x and y-orthogonal polarization states which are used to transmit the on-off keying (OOK) data of 32 channels to remotely located optical network units (ONUs). The performance of the channels is analyzed with bit error rate (BER) plots employing Gamma–Gamma (GG) FSO channel model at different turbulence regimes and lengths of FSO link. Moreover, the effect of varying the polarization mode dispersion (PMD) on BER is also evaluated. The cost of the proposed architecture is analyzed and compared with conventional PON architecture. The cost efficiency of the proposed architecture is demonstrated by the use of a single CW laser source to transmit the data of 32 users between remote node (RN) and ONUs through FSO links having reduced installation and maintenance costs.

Design and optimization of a microwave photonic filter exploiting differential mode group delay of a multi-mode fiber

A reconfigurable and application-specific tunable microwave photonic filter having finite impulse response is proposed. The filter exploits the differential mode group delays of linearly polarized modes in a multi-mode fiber to achieve single and multiple high-frequency passband response. The filter taps are realized using a single continuous wave laser source and differential delays among modes that are propagated through a single spool of graded index multi-mode fiber. Depending upon the application requirement, different values of free spectral range of the microwave photonic filter are obtained by employing fiber spools of different lengths. The reconfigurability of the microwave photonic filter is achieved by varying the number of linearly polarized modes. It has been shown that the passband ripple can be reduced by employing higher order spatial modes and unequal power ratio among different modes. The proposed filter enables application-specific free spectra range tunability and reconfigurability along with added advantages of easy implementation and passband optimization.

Thermo-responsive polymer encapsulated gold nanorods for single continuous wave laser-induced photodynamic/photothermal tumour therapy

Owing to strong and tunable surface plasmon resonance (SPR) effect and good biocompatibility, gold nanoparticles have been suggested to be a versatile platform for a broad range of biomedical applications. In this study, a new nanoplatform of thermo-responsive polymer encapsulated gold nanorods incorporating indocyanine green (ICG) was designed to couple the photothermal properties of gold nanorods (AuNRs) and the photodynamic properties of ICG to enhance the photodynamic/photothermal combination therapy (PDT/PTT). In addition to the significantly increased payload and enhancing photostability of ICG, the polymer shell in the nanoplatform also has thermo-responsive characteristics that can control the release of drugs at tumour sites upon the laser irradiation. On the basis of these improvements, the nanoplatform strongly increased drug aggregation at the tumour site and improved the photothermal/photodynamic therapeutic efficacy. These results suggest that this nanoplatform would be a great potential system for tumour imaging and antitumour therapy.

GPS L1 C/A 신호를 위한 심층신경망을 이용한 단일 연속파 재밍 검출기법

In this paper, a novel deep neural network-based single continuous wave jamming detection scheme is proposed for Global Positioning System (GPS) L1 Coarse/Acquisition (C/A) signals, which are used most frequently in civilian satellite-based navigation systems. The main environmental variables considered are as follows: The effective jamming power-to-noise spectral density ratio (J/N0) has a range of 34 dB-Hz to 64 dB-Hz; the center frequency and Doppler frequency of a single continuous wave jamming occur uniformly within ± 1 KHz and within ± 10 KHz, respectively, based on the center frequency of the GPS L1 C/A signal. The designed deep neural network consists of six hidden layers and one SoftMax layer. In order to assess the performance of the proposed scheme, the energy detection scheme that is frequently used for the detection of single continuous wave jamming at pre-correlation level is considered as a conventional scheme. When the false alarm probability is set to 10<SUP>-5</SUP> via simulation, it was confirmed that the detection probability of the proposed scheme is approximately 98% or higher, while that of the conventional scheme is approximately 78% at an effective J/N0 of 61 dB-Hz.

Vital Sign Detection during Large-Scale and Fast Body Movements Based on an Adaptive Noise Cancellation Algorithm Using a Single Doppler Radar Sensor.

The non-contact detection of human vital signs (i.e., respiration rate (RR) and heartbeat rate (HR)) using a continuous-wave (CW) Doppler radar sensor has great potential for intensive care monitoring, home healthcare, etc. However, large-scale and fast random body movement (RBM) has been a bottleneck for vital sign detection using a single CW Doppler radar. To break this dilemma, this study proposed a scheme combining adaptive noise cancellation (ANC) with polynomial fitting, which could retrieve the weak components of both respiration and heartbeat signals that were submerged under serious RBM interference. In addition, the new-type discrete cosine transform (N-DCT) was introduced to improve the detection accuracy. This scheme was first verified using a numerical simulation. Then, experiments utilizing a 10-GHz Doppler radar sensor that was built from general-purpose radio frequency (RF) and communication instruments were also carried out. No extra RF/microwave components and modules were needed, and neither was a printed circuit board nor an integrated-chip design required. The experimental results showed that both the RR and HR could still be extracted during large-scale and fast body movements using only a single Doppler radar sensor because the RBM noises could be greatly eliminated by utilizing the proposed ANC algorithm.

Microwave photonic notch filter based on polarisation multiplexing and cross gain modulation in a semiconductor optical amplifier

A coherent interference-free tunable microwave photonic notch filter with a pair of negative and positive coefficients generated by employing polarisation multiplexing and cross gain modulation in a semiconductor optical amplifier is proposed and demonstrated through simulation results. The negative and positive coefficients of the notch filter are realised through two orthogonal polarisation states of a single continuous wave laser diode. The free spectral range of microwave photonic filter is tuned by varying the differential group delay of a birefringent single-mode fibre. The proposed filter shows good tunability, easy implementation and is cost-effective.

Receptivity Study of Hypersonic Boundary Layer under Freestream Finite Amplitude Continuous Entropy Disturbance with Single Frequency

The DNS method is used to calculate the unsteady flowfield around blunt cone under the action of a single frequency finite amplitude continuous entropy wave. The hypersonic flowfield response to single frequency finite amplitude entropy wave is investigated, and the hypersonic boundary layer receptivity features under single frequency finite amplitude disturbance are explored. The results find that the strong disturbance wave is produced by the interaction of freestream wave with shock wave and boundary layer, and there are regular high-entropy and low-entropy regions in the downstream evolution process. The frequency characteristics of boundary layer disturbance wave are directly related to freestream disturbance wave, and the frequency characteristics become weaker as the disturbance wave evolves downstream. During the development of disturbance downstream, the second, third and fourth (f2-f4) order modes in the boundary layer increase relatively. The central disturbance modes of the nose region are the fundamental mode in the boundary layer, and the main disturbance modes in the boundary layer of the downstream region of the flowfield are composed of the fundamental mode (f1) and the second, third and fourth (f2-f4) order modes.

Non-spherical particles in optical tweezers: A numerical solution.

We present numerical methods for modeling the dynamics of arbitrarily shaped particles trapped within optical tweezers, which improve the predictive power of numerical simulations for practical use. We study the dependence of trapping on the shape and size of particles in a single continuous wave beam setup. We also consider the implications of different particle compositions, beam types and media. The major result of the study is that for different irregular particle shapes, a range of beam powers generally leads to trapping. The trapping power range depends on whether the particle can be characterized as elongated or flattened, and the range is also limited by Brownian forces.

Plasmonic MoO3-x nanoparticles incorporated in Prussian blue frameworks exhibit highly efficient dual photothermal/photodynamic therapy.

Development of near infrared (NIR) light-responsive nanomaterials for high performance multimodal phototherapy within a single nanoplatform is still challenging in technology and biomedicine. Herein, a new phototherapeutic nanoagent based on FDA-approved Prussian blue (PB) functionalized oxygen-deficient molybdenum oxide nanoparticles (MoO3-x NPs) is strategically designed and synthesized by a facile one-pot size/morphology-controlled process. The as-prepared PB-MoO3-x nanocomposites (NCs) with a uniform particle size of ∼90 nm and high water dispersibility exhibited strong optical absorption in the first biological window, which is induced by plasmon resonance in an oxygen-deficient MoO3-x semiconductor. More importantly, PB-MoO3-x NCs not only exhibited a high photothermal conversion efficiency of ∼63.7% and photostability but also offered a further approach for the generation of reactive oxygen species (ROS) upon singular NIR light irradiation which significantly improved the therapeutic efficiency of the PB agent. Furthermore, PB-MoO3-x NCs showed a negligible cytotoxic effect in the dark, but an excellent therapeutic effect toward two triple-negative breast cancer (TNBC) cell lines at a low concentration (20 μg mL-1) of NCs and a moderate NIR laser power density. Additionally, efficient tumor ablation and metastasis inhibition in a 4T1 TNBC mouse tumor model can also be realized by synergistic photothermal/photodynamic therapy (PTT/PDT) under a single continuous NIR wave laser. Taken together, this study paved the way for the use of a single nanosystem for multifunctional therapy.

In Vitro Assessment of Apical Leakage of Bioceramic Endodontic Sealer with Two Obturation Techniques

Purpose: The aim of this study was to evaluate the apical sealing ability of Total Fill BC sealer and AH Plus sealer with single cone and continuous wave condensation obturation techniques using dye extraction leakage method. Materials and Methods: Eighty-four extracted human single-rooted teeth with round canals were decoronated at 12 mm length and instrumented using crown down technique with the iRace rotary file system to apical file size 40 with 0.04 taper. The roots were randomly divided into four experimental groups (n=20). Group (A1) contained roots which were obturated with Total Fill BC sealer with a single cone. Group (A2) contained roots which were obturated using Total Fill BC sealer with continuous wave condensation. Group (B1) contained roots which were obturated using epoxy resin sealer (AH Plus) with a single cone. Group (B2) contained roots which were obturated using AH Plus sealer with continuous wave condensation. Apical microleakage was assessed with dye extraction method where the absorbance of leaked 1% methylene blue dye was measured using a spectrophotometer. The absorbance values were converted into concentrations, and the data was analyzed using One way ANOVA test. Results: The mean dye concentration values were 0.012, 0.016, 0.011 and 0.015 for Group A1, Group A2, Group B1 and Group B2, respectively. One-way ANOVA indicated no significant difference in dye leakage between the investigated groups (F = 0.938). Conclusion: With the limitation of the study, it was concluded that Total Fill BC was equivalent to AH Plus in apical sealing ability when using single cone or continuous wave condensation. The single cone can provide a similar apical seal of canal filling as can be achieved by using continuous wave condensation methods, in the round canal.

Efficient continuous-wave noise spectroscopy beyond weak coupling

The optimization of quantum control for physical qubits relies on accurate noise characterization. Probing the spectral density $S(\omega)$ of semi-classical phase noise using a spin interacting with a continuous-wave (CW) resonant excitation field has recently gained attention. CW noise spectroscopy protocols have been based on the generalized Bloch equations (GBE) or the filter function formalism, assuming weak coupling to a Markovian bath. However, this standard protocol can substantially underestimate $S(\omega)$ at low frequencies when the CW pulse amplitude becomes comparable to $S(\omega)$. Here, we derive the coherence decay function more generally by extending it to higher orders in the noise strength and discarding the Markov approximation. Numerical simulations show that this provides a more accurate description of the spin dynamics compared to a simple exponential decay, especially on short timescales. Exploiting these results, we devise a protocol that uses an experiment at a single CW pulse amplitude to extend the spectral range over which $S(\omega)$ can be reliably determined to $\omega=0$.

Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors

Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is stopped. Also, FMCW radar cannot function when the detection object is near the sensor. Therefore, by implementing a single continuous wave (CW) radar for operating in dual-mode, the disadvantages in each mode can be compensated for. In this paper, a dual mode local oscillator (LO) is proposed that makes a CW radar operate as a Doppler or FMCW radar. To make the dual-mode LO, a method that controls the division ratio of the phase locked loop (PLL) is used. To support both radar mode easily, the proposed LO is implemented by adding a frequency sweep generator (FSG) block to a fractional-N PLL. The operation mode of the LO is determined by according to whether this block is operating or not. Since most radar sensors are used in conjunction with microcontroller units (MCUs), the proposed architecture is capable of dual-mode operation by changing only the input control code. In addition, all components such as VCO, LDO, and loop filter are integrated into the chip, so complexity and interface issues can be solved when implementing radar sensors. Thus, the proposed dual-mode LO is suitable as a radar sensor.

Quantitative and Spatially Resolved Measurement of Atomic Potassium in Combustion Using Diode Laser**Supported by the National Natural Science Foundation of China under Grant Nos 91541119 and 91541203.

A compact optical setup for quantitative and spatially resolved measurement of atomic alkali concentration in combustion is demonstrated. Tunable diode laser absorption spectroscopy and laser-induced fluorescence are combined using a single continuous wave diode laser to measure the line-integration concentration and the relative distribution simultaneously, thereby obtaining the absolute concentration distribution along the laser beam. The results indicate the good performance of this method for one-dimensional quantitative measurement.

Watt-Level Continuous-Wave Emission from a Bifunctional Quantum Cascade Laser/Detector.

Bifunctional active regions, capable of light generation and detection at the same wavelength, allow a straightforward realization of the integrated mid-infrared photonics for sensing applications. Here, we present a high performance bifunctional device for 8 μm capable of 1 W single facet continuous wave emission at 15 °C. Apart from the general performance benefits, this enables sensing techniques which rely on continuous wave operation, for example, heterodyne detection, to be realized within a monolithic platform and demonstrates that bifunctional operation can be realized at longer wavelength, where wavelength matching becomes increasingly difficult and that the price to be paid in terms of performance is negligible. In laser operation, the device has the same or higher efficiency compared to the best lattice-matched QCLs without same wavelength detection capability, which is only 30% below the record achieved with strained material at this wavelength.

Tunable optical frequency comb generation in a periodically poled lithium niobate waveguide based on stimulated Brillouin scattering

We propose and demonstrate a technique for the generation of an optical frequency comb (OFC) in a periodically poled lithium niobate (PPLN) waveguide based on stimulated Brillouin scattering. A single continuous wave laser is sent to a multi-wavelength Brillouin erbium fibre laser for generating a set of coherent and phase-locked multi-wavelength spectral lines. They are injected into a PPLN waveguide to obtain an OFC. We investigate the influence of the cavity structure on the OFC property in our two different schemes. The number of comb lines is affected by the 980 pump current and Brillouin pump power. The OFCs are tunable in a large range by changing their central wavelength.

UWB over fiber transmission to multiple radio access units using all-optical signal processing

An ultra-wideband over fiber architecture is proposed where multiple coherent pulsed optical signals are used for transmitting high data rate signals to five different radio access units (RAUs). The RAUs are placed in a star topology to form a broadcast distributive antenna system architecture. The architecture transmits $$5 \times 1.25$$5?1.25 Gbps data from control unit to the RAUs using a wavelength division multiplexed signal. The multiple pulsed optical carriers forming the wavelength division multiplexed signal are generated using a single continuous wave optical source. The data modulated coherent optical pulsed signals are all-optically converted to electrical Gaussian mono-cycle pulses at the RAUs. The proposed architecture is cost-efficient and gives good bit-error rate results.