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A recent study conducted at Linkoping University focused on improving brain tumor needle biopsies by utilizing in situ optical guidance to enhance diagnostic accuracy and reduce complications. The study found that real-time feedback on fluorescence, microcirculation, and tissue characteristics led to more precise tissue sampling and fewer trajectories, ultimately reducing operation time. The researchers concluded that the integrated optical guidance system improved the certainty and precision of diagnostic tissue sampling during brain tumor biopsies. For more information, readers can access the full article titled "In situ optical feedback in brain tumor biopsy - a multiparametric analysis" in Neuro-Oncology Advances published by Oxford University Press. [Extracted from the article]

Researchers from Goethe-University Frankfurt have developed an all-optical closed-loop voltage clamp system for precise control of muscles and neurons in live animals. This system combines non-invasive imaging with electrophysiology control capabilities, allowing for high-throughput, contact-less electrophysiology in individual cells. The study concluded that this technology paves the way for true optogenetic control in behaving animals. The research was funded by Deutsche Forschungsgemeinschaft and Max-Planck-Gesellschaft, and the findings were published in Nature Communications. [Extracted from the article]

Currently, optical chaos comb generation primarily relies on dielectric nonlinear micro-cavities on-chip, which require a high quality-factor. This increases complexity, cost, and potential compatibility issues with photonic integration. Here, we propose and experimentally verify a novel and simplified scheme for generating chaotic combs. We utilize a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) connected to a single ferrule connector with physical connection to generate a wideband chaotic comb. It is possible to achieve over 70 chaotic carrier channels, covering a spectral range exceeding 40 nm. The effective bandwidth of the single channel chaotic signal reaches 15.43 GHz. The Pearson correlation coefficient between randomly selected two-channel time series is −0.0033, indicating an almost negligible level of correlation. The cross-correlation among the 15 channels in the wavelength range of 1546.4–1554.5 nm is all within 0.05, meeting orthogonality requirements and distinguishing it from traditional FPLD with external feedback. The offline random bit sequences generated by single-channel chaos have been validated using the National Institute of Standards and Technology Special Publication 800-22 Statistical Test suite, thereby confirming the practicality of our proposed scheme. Since each chaotic carrier can be used as an independent chaotic entropy source after filtering and extraction, so the data throughput of the offline random number sequence generated by this scheme is expected to reach 22.40 Tbits/s (320 Gbits/s × 70 = 22.40 Tbits/s). Furthermore, III-V-based WRC-FPLDs offer the advantage of monolithic integration, which makes them potentially capable of achieving miniaturization, cost-effectiveness, massively parallel high-speed random bit generation, and parallel chaotic LiDAR and WDM chaotic secure communication in the future. [ABSTRACT FROM AUTHOR]

A patent application for a keratoscope relay mechanism for an OCT scanner adapter has been filed by inventors Mehran GHOFRANI and Robert H. HART. The invention aims to improve the optical design of OCT adapters to allow for a more compact form factor, both laterally and vertically. The relay mechanism includes a ring arrangement of light emitting diodes (LEDs) that replicate the arrangement of keratoscope LEDs of a microscope. The mechanism also includes photo detectors and a light sealing gasket, which activate the corresponding keratoscope state of the LEDs based on the detection of the keratoscope state of the microscope LEDs. The invention addresses the issue of current under carriage mounted OCT scanners obscuring the keratoscope illumination, rendering it unusable. [Extracted from the article]

Robustness and reliability are two key requirements for developing practical quantum control systems. The purpose of this article is to design a coherent feedback controller for a class of linear quantum systems suffering from Markovian jumping faults so that the closed-loop quantum system has both fault tolerance and $H^\infty$ disturbance attenuation performance. This article first extends the physical realization conditions from the time-invariant case to the time-varying case for linear stochastic quantum systems. By relating the fault-tolerant $H^\infty$ control problem to the dissipation properties and the solutions of Riccati differential equations, an $H^\infty$ controller for the quantum system is then designed by solving a set of linear matrix inequalities. In particular, an algorithm is employed to introduce additional quantum inputs and to construct the corresponding input matrices to ensure the physical realizability of the quantum controller. Also, we propose a real application of the developed fault-tolerant control strategy to quantum optical systems. A linear quantum system example from quantum optics, where the amplitude of the pumping field randomly jumps among different values due to the fault processes, can be modeled as a linear Markovian jumping system. It is demonstrated that a quantum $H^\infty$ controller can be designed and implemented using some basic optical components to achieve the desired control goal for this class of systems. [ABSTRACT FROM AUTHOR]

A novel microwave and millimeter wave signal generation system is proposed and numerically demonstrated using an optically pumped quantum dot (QD) spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL) with optical injection. Different from previous optical injection systems, the signal frequency in our proposed system is dominated by both the birefringence-splitting and injection detuning frequencies. By flexibly tailoring the frequency detuning and birefringence rate, the frequency ranges from a few gigahertz to nearly 150 GHz can be obtained. To evaluate the signal quality, the dynamical behaviors of the proposed system and the characteristics of the generated millimeter wave signal are evaluated including the center frequency, power, linewidth, and phase variance. We further adopt the optical feedback structure to improve the microwave and millimeter wave signal performance. Results show that the signal linewidth and phase variance can be optimized by three to four orders of magnitude. Compared to the case of a solitary QD spin-VCSEL, this work shows more stable performance, particularly in the frequency range above 90 GHz. This scheme offers an approach for high-purity microwave and millimeter sources in wireless communication and radar systems. • We achive microwave and millimeter wave (MMW) generation with broad frequency tunability via a QD spin-VCSEL under optical injection. • The nonlinear dynamical behaviors of the proposed system and the beating mechanism of MMW signal modes are elaborated. • The flexibility of the MMW frequency manipulating is demonstrated. • The optimization of the spectral purity of the MMW is studied. [ABSTRACT FROM AUTHOR]

Garrison Dental Solutions L.L.C. has been issued a patent for a dental curing light. The patent describes an instrument that applies light energy to a light-curable target, such as a dental composite. The instrument includes a controllable light source, a light sensor, and an optical feedback path. The controller adjusts the operating characteristic of the light source based on the light energy characteristic sensed by the light sensor, allowing for precise and controlled curing of dental restorative materials. The invention aims to improve the quality and safety of light cure exposure in dental procedures. [Extracted from the article]

A patent has been issued to Globus Medical Inc. for medical imaging systems that use robotic actuators. The patent describes methods for operating an imaging system using a contact imaging probe to generate imaging of a body. The robotic actuator can position the contact imaging probe at different locations on the body, allowing for different radial alignments with the imaging isocenter. This technology aims to provide non-radiation imaging options that can be used for 3D imaging at various locations on the patient's body. [Extracted from the article]

A patent has been issued for a system and method for stimulating nerve tissue. The patent, assigned to Medtronic Xomed Inc., describes a stimulation probe that can be used to apply electrical energy to a patient's nerve, stimulating nerve activity and resulting in muscle response. The system also includes a nerve monitoring system that can be used to monitor the integrity of the nerve during a procedure. The patent includes details about the design and functionality of the stimulation probe and the monitoring system. [Extracted from the article]

Turbulence is a complex spatiotemporal behavior and a fundamental concept in fluid dynamics, which has been extended to other systems out of equilibrium, such as nonlinear optics, chemistry, active matter, and economics. Fingerprint patterns with sustained spatiotemporal dynamics in a liquid crystal light valve with an optical feedback experiment are studied. We show that the light intensity field presents a dynamical regime simultaneously exhibiting phase and amplitude turbulence. This bi-turbulent behavior of patterns is characterized by power-law spectra with exponents close to − 2 and − 3 spatially and − 2 temporally, for the phase and amplitude respectively. The pattern orientation field also presents power-law spectra with exponents close to − 2 and − 3 / 4 , spatially and temporally. We characterize the observed chaotic dynamics by estimating the largest Lyapunov exponent. We provide a theoretical model of pattern formation that explains the experimental observations with good qualitative agreement. • Experimental evidence of universal power law spectra in fingerprint pattern turbulent-like dynamics. • Evidence of defects driven spatiotemporal chaotic dynamics by means of Lyapunov analysis tools. • Simplified model valid close to the critical point allows reproducing qualitatively the observed dynamics. [ABSTRACT FROM AUTHOR]

In response to the possibility of time delay (TD) signatures (TDSs) leakage becoming a serious problem in chaotic optical communication, from the perspective of improving the security of chaotic optical communication, this paper proposes a chaotic secure optical communication system based on dispersion keying, which generates signals with TDSs concealment characteristics. In this scheme, a common laser is used to drive chaotic synchronization between the transmitter and the receiver. The complex chaotic signal is generated by the combination of all-optical feedback and optical injection, and the TDSs are hidden by using the structure of dual filters and setting the parameters of each device reasonably. The switch is controlled by binary message to connect fiber Bragg gratings (FBGs) with different dispersion coefficients and maps different symbols to different chaotic attractors instead of the traditional way of directly sending messages to the channel. In addition, the generated signal no longer suffered from return map attacks. FBGs can compress and expand signals in the time domain to enhance the complexity of chaotic signals, and the dispersion value is an important key to effectively increasing the key space. Finally, the performance of TDSs concealment, sensitivity of parameter mismatch, and return map attack in this scheme are discussed in detail. The scheme still achieves a bit error rate (BER) of 1.74 × 10−4 when transmitting at a rate of 10Gbit/s under harsh communication environments such as 10 dB signal-to-noise ratio (SNR), which provides a reference for realizing high-speed and secure optical communication at the physical layer. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigate the intensity time series in a pair of mutually coupled laser oscillators, which display some essential patterns observed in the neuronal oscillations in the brain of mammals. An asymmetry is implemented by a mismatch among the laser pump parameters, while the coupling scheme is induced by fast saturable absorbers, which interact with a beam that coherently combines the electric fields of both lasers. The laser oscillator with the smaller pump level exhibits mixed-mode oscillations (MMOs), a class of large amplitude oscillations (LAOs), while the other one displays small amplitude oscillations (SAOs). An additional relevant neuronal oscillatory pattern is the frequency of oscillations, which is higher for the SAOs compared to that of the MMOs. Depending on the coupling parameters, these two robust patterns can emerge as a result of a boundary crisis or an interior crisis. In both cases the dynamics display robust hyperchaotic behavior with two positive Lyapunov exponents of similar order of magnitude in the intensity time series. Nevertheless, in these time series the correlation dimension remains essentially unchanged. These two robust patterns, which are also found in many systems displaying chimera states, persist in the coupled lasers as the phase mismatch changes in the beam combining fields. • The intensity time series in two mutually coupled lasers are studied. • These time series display essential patterns observed in the brains of mammals. • The laser oscillations display two positive Lyapunov exponents. • The oscillations basic properties are robust with respect to the lasers phase shifts. [ABSTRACT FROM AUTHOR]

The article presents the magazine's top 20 photonics technology for 2020. First on the list is advances in fiber optics which includes hollow-core optical fiber and pico- and femto-second fiber lasers. Second on the list is improvements in the observation capabilities of instruments, including superresolution optical-fluctuation imaging, light-sheet fluorescence microscopy and white-light interferometry. Also included in the list is photonic devices for quantum and other uses.

This paper presents a high sensitivity and dynamic range 25 Gbaud optical receiver including the CMOS transimpedance amplifier (TIA) and Ge-on-Si photodetector. In the TIA with a DC bypassing path, instead of deploying a voltage-controlled path with a fixed feedback strength, a current-controlled path with $g_{\mathrm {m}}$ -adjusting ability is proposed to minimize the noise amplified by the feedback loop and achieve high sensitivity. In addition, in the optical part, a Ge-on-Si photodetector with cube-shape Ge is proposed to boost the responsivity, which therefore overcomes the noise contribution from the TIA and enhance the overall sensitivity of the cascaded optical receiver. The CMOS transimpedance amplifier includes a 3-stage transimpedance pre-amplifier, a 4-stage post amplifier, a CML buffer stage and a DC offset cancellation block. Measurement results show a transimpedance of 66–71 dB $\Omega $ , a SDD21 bandwidth of 18.5 GHz, an input-referred noise current density of 11.1 pA/ $\surd $ Hz, a BER of $1\times 10^{-{12}}$ @ $26~\mu \text{A}$ and a power consumption of 105 mW. The FOM is 5.2 which is the lowest, to the best of the authors’ knowledge. The photodetector achieves a responsivity of 0.57 A/W at 1550 nm and a bandwidth of 40 GHz. The optical receiver achieves an optical sensitivity of −11.7 dBm. Compared with the prior arts, the proposed receiver demonstrates distinct sensitivity and FOM enhancement. [ABSTRACT FROM AUTHOR]

The article announces photonics products and applications recognized at the 3rd annual Innovators Awards Program, including the Platinum-Level award to MV.X Embedded-Vision Hyperspectral Imaging System from Photonics, the Gold-Level award to DuraChill Portable Recirculating Chiller from Polyscience, and the Silver-Level award to Multijunction Semiconductor Laser Diodes from Seminex Corp.

A recent report from Soochow University in Suzhou, China discusses the formation and control of rare ultrahigh pulses, known as rogue waves (RWs), in semiconductor laser systems. The researchers used numerical simulations to analyze the evolution of these extreme events (EEs) in the system and found that optical injection can potentially control EEs, which could optimize the performance of chaotic laser systems. This research provides new insights into the understanding and prediction of EEs in laser systems. The study was funded by the National Natural Science Foundation of China and other organizations. [Extracted from the article]

The article offers review of several products including Tor XS Q-switched laser by the Cobolt Laser; MityCAM-C50000 imaging system by the Critical Link; and infrared (IR) high-power SMT components by the Osram Opto Semiconductors.

The article offers review of several products including Hyperion VUV femtosecond laser source by the KMLabs; Ultrafast laser driver by the Osram Opto Semiconductors; and Corona fiber laser by the nLight.

In this paper, a fully-integrated transimpedance amplifier with ultra-large dynamic range and automatic gain control function is presented. By first deploying three AGC-controlled current paths in the low noise pre-amplifier, the transimpedance amplifier (TIA) can accommodate a significantly enlarged input current. Meanwhile, the range of automatic transimpedance adjustment is enhanced utilizing the automatic gain control (AGC) circuit, tunable pre-amplifier (PrA), and variable gain amplifier (VGA). Besides the above blocks, the TIA with a size of $1.26\times 1.33$ mm2 also integrates level shifter, post-amplifier, buffer, DC offset cancellation (DCOC), bandgap reference (BGR), and low-dropout regulator (LDO). With a single 3.3-V external supply voltage, the fully integrated TIA in $0.11~\mu \text{m}$ CMOS achieves a measured input dynamic range up to 7.4 mA@2.5 Gb/s, an input referred noise as low as 137.3 nA and a differential trans-impedance gain of 10 $\text{k}\Omega $. Taking the bandwidth, dynamic range, and trans-impedance gain into account, the fabricated CMOS TIA demonstrates the largest input dynamic range with maintaining competitive comprehensive performance. [ABSTRACT FROM AUTHOR]

Highlights • We demonstrate theoretically the existence of slow chaotic spiking sequences in QD-LEDs with optical feedback. • We reported evidence of complex dynamics with feedback. • Our results show that small OFBS (less than 0.03) lead to a good controlling of dynamics as evidenced by bifurcation diagram. • Increasing of the delay time leads to an increase in the period of chaotic. • Moreover, bias has a clear effect and greater than the OFBS. • There is existence of a number of important states transition between periodic and chaotic with adding the grating mirror. • Clear effecting of delay time with large value of the bias while the turn-on dynamic show damping relaxation oscillations, phase shift appears with speedy threshold of first pulsing under delayed feedback and turn-on examination. Abstract In this work a four-variable dimensionless model of a quantum dot light emitting diode (QD-LED) under optical feedback effect is studied. Depending on the optical feedback (OFB) strength a complex bifurcation scenarios for the photon intensity were completely determined by the variation of the OFB in the QD as well as time series, inter-spike interval (ISI) and phase plane of all dynamic variables of the QD-LED. Our results show that small OFB lead to a good controllability of QD-LED dynamics as evidenced by the bifurcation diagram. The delay time leads to delay control of dynamics. Moreover, bias has a clear and greater effect than that of OFB. By adding a grating mirror as a special technique to suppress unwanted frequencies, there is an important transition between periodic and chaotic states. Delayed feedback and turn-on dynamics are studied. [ABSTRACT FROM AUTHOR]

The article discusses that SRS remains a major development challenge for multikilowatt fiber lasers used in industrial applications. Topics discussed include focuses on stimulated Raman scattering (SRS) remains a major development challenge for multikilowatt fiber lasers used in industrial applications; and reliability is key in end-user industrial applications, especially when considering increasing throughput with more powerful lasers.

Researchers at the University of Basel in Switzerland have developed a multimodal feedback system to improve the safety and accuracy of laser osteotomy, a type of bone surgery. The system integrates optical feedback systems with an Er:YAG laser, including a real-time visual feedback system to monitor and control the depth of laser-induced cuts, and a tissue sensor to differentiate tissue types based on their chemical composition. The system was tested on pig femur bone specimens and demonstrated successful tissue differentiation and visualization without thermal damage. The researchers believe that this integrated approach has the potential to enhance minimally invasive surgery and should be further investigated and developed. [Extracted from the article]

Samsung Electronics Co. Ltd has been issued a patent for a laser device and method of transforming a laser spectrum. The invention aims to stabilize laser frequency and narrow the laser spectrum by using a resonant optical feedback from an external optical element. The device utilizes multiple longitudinal mode lasers locked to high-Q microresonators to generate powerful narrow laser lines or optical frequency combs. The patent describes the technical details and components of the laser device, including the use of high-Q microresonators and a tuner to match frequencies and reduce linewidths. The invention has potential applications in various fields, including spectroscopy, LIDAR, and holographic interferometry. [Extracted from the article]

The method of claim 11, comprising: providing a focusing lens to be included in the beam splitter, the focusing lens including a wavelength sensitive layer; and passing the laser beam and the optical response signal respectively through the focusing lens. The method of claim 1, comprising: providing a focusing lens to be included in the beam splitter, the focusing lens including a wavelength sensitive layer; and passing the first optical signal and the second optical signal respectively through the focusing lens. "In Example 9, the subject matter of Example 8 optionally includes, wherein the beam splitter includes: a first port coupled to the proximal end of the probe; and a second port configured to align with the optical path and configured to pass a second optical signal. [Extracted from the article]

Furthermore, it is possible to combine a number of acquisition parameters especially advantageously, wherein by a deflection of the lever arm from the rest position to the first end point a determination, (e.g., continuous determination), of a value of the combined acquisition parameters may be made possible. Furthermore, a first value of at least one acquisition parameter of the medical x-ray examination is able to be determined as a function of a measure of deflection of the deflection of the lever arm from the rest position to the first end point. In other words, the rest position represents a position of equilibrium of the lever arm in relation to at least one deflection direction, in which the lever arm finds itself without the effect of any force from outside the lever. Furthermore, a first value of at least one acquisition parameter of the medical x-ray examination is able to be determined as a function of a measure of deflection of the deflection of the lever arm from the rest position to the first end point. [Extracted from the article]

The article evaluates optics and photonics-related products, including the BP450 indigo bandpass filter from Midwest Optical Systems, the PLUTO-2.1 spatial light modulator from HOLOEYE Photonics, and the Opti-CAl software from Bristol Instruments.

External Optical feedback can severely change the stability and the performance of semiconductor ring lasers. To reduce the undesired effect of the optical feedback, we propose to use a second feedback to stabilize the wavelength and the intensity of the ring laser even in the presence of undesired external reflections. In this work, we numerically investigate the dynamical behavior of the semiconductor ring laser when it is subject to two optical feedback simultaneously using a two-directional mode rate equation model. The results show that the laser’s output is determined according to the competition between the longitudinal modes which are enhanced by the different feedback. The undesired changes of the dynamical behavior of the laser due to the effect of the one feedback can be minimized using a second controlled feedback. The second feedback has been chosen with a short delay line so it can be integrated on the same chip with the laser. This approach allows to avoid the complex integration process of magneto-optic materials which are normally required for on-chip isolation. The fabrication of the delay line and the control of the strength and the phase of the proposed feedback are currently supported and offered using standard building blocks by several integrated optics foundries. [ABSTRACT FROM AUTHOR]

Our news correspondents obtained a quote from the research from Nanjing Xiao Zhuang University: "In this chaotic laser system, a double-ring resonator model is employed, leveraging the laser self-mixing method. Keywords: Photonics; Science EN Photonics Science 566 566 1 09/04/23 20230908 NES 230908 2023 SEP 10 (NewsRx) -- By a News Reporter-Staff News Editor at Medical Devices & Surgical Technology Week -- Data detailed on photonics have been presented. [Extracted from the article]

In quantum engineering, faults may occur in a quantum control system, which will cause the quantum control system unstable or deteriorate other relevant performance of the system. This note presents an estimator-based fault-tolerant control design approach for a class of linear quantum stochastic systems subject to fault signals. In this approach, the fault signals and some commutative components of the quantum system observables are estimated, and a fault-tolerant controller is designed to compensate the effect of the fault signals. Numerical procedures are developed for controller design and an example is presented to demonstrate the proposed design approach. [ABSTRACT FROM AUTHOR]

We consider an asymmetric laser system which displays mixed-mode oscillations and hyperchaos. This system consists of two laser oscillators which are weakly and bidirectionally coupled, where the asymmetry is induced by a mismatch between the laser pump parameters. The coupling scheme via saturable absorbers, however, is built up with a beam combining process which incorporates the electric fields of both laser oscillators. This procedure, which is relevant in semiconductor and solid-state lasers, is implemented in the present molecular laser model. In our numerical simulations and time series analysis we show that for small enough coupling strength, below the chaotic phase synchronization threshold, the asymmetric laser system displays extreme rare events in one of the lasers whose occurrence can be mitigated and suppressed by optical feedback. These episodes are outliers in the time series from the laser intensity and the return time intervals, and are reminiscent of Dragon-Kings. We estimate the correlation dimensions and Lyapunov exponents from the time series, which suggest the ubiquity of hyperchaotic dynamics irrespective of the occurrence or lack of extreme rare events in these time series. [ABSTRACT FROM AUTHOR]

Multistable systems present rich dynamical behaviors of interfaces between the different equilibria. Close to the disappearance of bistability, i.e., transition between a bistable to a monostable region, we show that the speed of bistable fronts follows a square root law as a function of the bifurcation parameter. Analytically and numerically, we show this law for different prototype models of bistable systems. Based on a liquid crystal light valve experiment with optical feedback, we investigate the front speed close to the disappearance of bistability. Our results apply both to systems that do or do not follow energy minimization principles. Experimental findings show a quite fair agreement with the theoretical results. • The front speed follows a universal law near to the disappearance of bistability. • Nonlinear optical experiment (LCLV) near the saddle-node bifurcation. • Power law (square root) front speed behavior near saddle-node point. [ABSTRACT FROM AUTHOR]

The laser light source can be coupled to the beam splitter and can generate a laser beam. "In Example 2, the subject matter of Example 1 optionally includes a spectrometer optically coupled to the beam splitter, the spectrometer configured to receive from the beam splitter the second optical signal representative of the anatomical target and to provide spectral measurements representative of the anatomical target. The system of claim 1, comprising a light source optically coupled to the first port of the beam splitter, the light source configured to generate the first optical signal passing through the beam splitter and the probe and incident on the anatomical target. [Extracted from the article]

This paper theoretically investigates a secondary-encryption optical chaotic communication system scheme based on an optical injection structure with single optical feedback and dual-dispersion optical feedback lasers. In the scheme, a fiber reflector (FR) and Fabry–Perot interferometer (FPI) are selected as the laser feedback cavity and effectively conceals time delay signatures (TDSs) of the generated chaotic signals. By switching the responding laser connected to the driving laser with the message feeding method, messages directly participating in the process of encryption signal generation are avoided to generate the first encrypted chaotic sequence that can characterize a message. Subsequently, chaotic phase disturbance technology is used to complete the secondary encryption. By virtue of the spectral broadening effect of chaotic phase disturbance, the message rate and the randomness of the encrypted signal can be effectively enhanced. We use the synchronous power error to decrypt the message at the receiver, which simplifies the system structure and realizes the scheme with low hardware costs. The proposed scheme overcomes the shortcomings of existed schemes, which generate chaotic signal sensitive to channel noise and have complex system structures. In addition, the proposed scheme shows good robustness in terms of handling noise for transmitting digital signals, a bit error rate (BER) of 6.7 × 10−4 at a simulation signal-to-noise ratio of 10 dB, and good application prospects in harsh transmission environments, such as submarine optical fiber transmission. • A secondary encryption optical chaotic communication system is proposed, which show good robustness in terms of handling noise for transmitting digital signals. • By switching the responding laser connected to the driving laser as a message feeding method,the security of the system can be improved greatly. • The dispersion characteristic of F P I is used to widen the time delay signature pulse. • A bit error rate of 6.7×10-4 is achieved at the signal-to-noise ratio of 10dB in the simulation. [ABSTRACT FROM AUTHOR]

In this brief, we numerically demonstrate a photonic delay-based reservoir computing system, which processes, in parallel, two independent computational tasks even when the two tasks have unrelated input streams. Our approach is based on a single-longitudinal mode semiconductor ring laser (SRL) with optical feedback. The SRL emits in two directional optical modes. Each directional mode processes one individual task to mitigate possible crosstalk. We illustrate the feasibility of our scheme by analyzing the performance on two benchmark tasks: 1) chaotic time series prediction and 2) nonlinear channel equalization. We identify some feedback configurations for which the results for simultaneous prediction/classification indicate a good performance, but with slight degradation (as compared with the performance obtained for single task processing) due to nonlinear and linear interactions between the two directional modes of the laser. In these configurations, the system performs well on both tasks for a broad range of the parameters. [ABSTRACT FROM PUBLISHER]

We study the effect of delayed coherent optical feedback on the pulse timing jitter in passively-mode-locked semiconductor lasers with the help of a semi-analytical method which we develop to calculate the timing fluctuations in these lasers. Through the proposed method physical insights into the feedback dependence of the timing jitter are gained and the greatly reduced computation times allow for the investigation of the dependence of timing fluctuations over greater parameter domains. We show that resonant feedback leads to a reduction in the timing jitter and that a frequency-pulling region forms about the main resonances, within which a timing jitter reduction is observed. The width of these frequency-pulling regions increases linearly with short feedback delay times. We derive an analytic expression for the timing jitter, which predicts a monotonic decrease in the timing jitter for resonant feedback of increasing delay lengths, when timing jitter effects are fully separated from amplitude jitter effects. For long feedback cavities the decrease in timing jitter scales approximately as 1/τ with increasing feedback delay time τ. This behavior is not related to the stability of the system but is instead due to the influence of the noise, on the timing jitter, being reduced since the solution space is larger for increasing τ. [ABSTRACT FROM AUTHOR]

We report experimental bifurcation diagrams of a semiconductor laser, biased well above threshold, subjected to external optical feedback. As feedback is increased, we see a quasiperiodic route to chaos interrupted by several windows of periodicity corresponding to limit cycles, differing in frequency by multiples of the external-cavity free-spectral range that have developed around external-cavity modes (ECMs) whose frequency is slightly larger than that of the solitary laser. Successive windows correspond to the transition between two limit cycles either on the same or neighboring ECMs. For larger feedback, the laser operates in a chaotic regime around numerous negatively shifted external-cavity modes. These experimental observations detail the bifurcations leading to fully developed chaos in this system, and further provide detailed insight on the standard theoretical framework applied to these lasers. [ABSTRACT FROM AUTHOR]

We have demonstrated that a weak external optical feedback with delay can lead to the switching of the counterpropagating modes in a ring laser. The period of this switching is almost equal to the doubling delay time. This time should be longer than any system characteristic time. The equations describing the ring laser with the delayed optical feedback have been obtained and the analytical formula for the necessary external feedback strength was derived. We have shown that the effect can take place in semiconductor lasers on quantum dots. [ABSTRACT FROM AUTHOR]

In most manipulation techniques for optical tweezers, open-loop controllers are developed to move the laser source without consideration of the dynamic interaction between the cell and the manipulator of laser source. This technical note presents a simple PD control scheme for manipulation of cell using optical tweezers. We formulate a closed-loop setpoint control problem for optical tweezers and show that simple control law is effective for closed-loop manipulation, taking into consideration of the dynamic interaction between the laser beam and the cell. The use of closed-loop feedback control helps to enhance the trapping and also reduces the possibility of photodamage. The setpoint controller is also extended to a region reaching controller, where the desired objective is generalized to a region. Though the overall dynamics that involves the interaction between the cell and the manipulator is a fourth-order system, the proposed controllers do not require the use of acceleration and its derivative or the construction of any observer. Experimental results are presented to illustrate the performance of the proposed controllers. [ABSTRACT FROM AUTHOR]

We propose a new method to construct an optimal linear coherent quantum controller based on an evolutionary optimization method, namely a differential evolution algorithm. The aim is to provide a straightforward approach to deal with both nonlinear and nonconvex constraints arising in the coherent quantum controller synthesis. The solution to this control problem involves a complex algebraic Riccati equation, which corresponds to a physical realizability condition for the coherent quantum controller. The proposed method is demonstrated through an example of an entanglement control problem for a quantum network comprising two cascaded optical parametric amplifiers. [ABSTRACT FROM PUBLISHER]

The article reports about EPFL researchers demonstrate visible laser diodes with a photonic chip microresonator. Topics including By injection-locking the laser diode to a silicon nitride (Si3N4) photonic integrated circuit, Swiss Federal Institute of Technology Lausanne (EPFL; Lausanne, Switzerland) researchers achieved a laser intrinsic linewidth of ~1.15 MHz and more than 100x reduction in optical phase noise.

Purpose -- The purpose of this paper is to present the result of an experiment examining the effects of changing input and output channel variety in an optical feedback system and their potential to give rise to novelty, as some non-trivial systems do. Design/methodology/approach -- The experimental design is based on a digital computer connected to a digital photo camera (input channel), and to a monitor screen (output channel). The camera is pointed at the monitor to form a circular feedback system. Monitor and camera resolutions constitute the variable input and output variety of the system, allowing the visual investigation of effects of variety reduction and variety amplification in circular feedback systems. Findings -- Results suggest that variety amplification in input and/or output channels promotes the emergence of discernible novelty in the apparent absence of a creative/generative capability or agenda within the recursive system. Research limitations/implications -- An analogy between an optical feedback system and human novelty generation is shown, while generalisability of observations made beyond the described experiment remains to be established. Originality/value -- A new approach to the computational modelling of aspects of human creativity is presented. Photographic investigation of variety reduction and variety amplification is new, and hoped to be of value to those wishing to examine these theoretical concepts in concrete terms. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to develop a model reduction theory for linear quantum stochastic systems that are commonly encountered in quantum optics and related fields, modeling devices such as optical cavities and optical parametric amplifiers, as well as quantum networks composed of such devices. It is shown that subsystem truncation preserves the physical realizability property of linear quantum stochastic systems, and that the property of complete passivity is invariant under subsystem truncation. However, generic linear quantum stochastic systems need not have a balanced realization under symplectic transformations. Therefore, alternative notions of balancing, including so-called quasi-balancing, are developed, and necessary and sufficient conditions are derived. A truncation error bound is derived for quasi-balanceable linear quantum stochastic systems and it is shown that all asymptotically stable completely passive linear quantum stochastic systems have a quasi-balanced realization. An example is provided to illustrate model reduction in the context of low-pass optical filtering of coherent light using a network of optical cavities. [ABSTRACT FROM PUBLISHER]

We study theoretically the nonlinear polarization dynamics of vertical-cavity surface-emitting lasers in the presence of an external cavity providing delayed optical feedback and cross-polarized reinjection. We show that, far from the laser threshold, the dynamics remains confined close to the equatorial plane of a Poincaré sphere with a fixed radius. It entails that the evolution of the system is described by two phase variables: the orientation phase of the quasilinear polarization and the optical phase of the field. We explore the complex modal structure given by the double reinjection configuration and how it evolves between the cases of single cross-polarized reinjection and single optical feedback, hence disclosing the relationship with the Lang-Kobayashi model. We also reinterpret the square-wave switching observed by J. Mulet et al. [Phys. Rev. A 76, 043801 (2007)] in terms of phase kinks. [ABSTRACT FROM AUTHOR]

During the last 4 years, chaotic waveforms for random number generation found a deep interest within the community of analogue broadband chaotic optical systems. Earlier investigations on chaos-based RNG were proposed in the 90s and early 2000, however mainly based on piecewise linear (PL) 1D map, with bit rate determined by analog electronic processing capabilities to provide the PL nonlinear function of concern. Optical chaos came with promises for much higher bit rate, and entropy sources based on high complexity (high dimensional) continuous time (differential) dynamics. More specifically in 2009, Reidler published a paper entitled “An optical ultrafast random bit generator”, in which they presented a physical system for a random number generator based on a chaotic semiconductor laser. This generator is claimed to reach potentially the extremely high rate of 300 Gb/s. We report on analysis and experiments of their method, which leads to the discussion about the actual origin of the obtained randomness. Through standard signal theory arguments, we show that the actual binary randomness quality obtained from this method, can be interpreted as a complex mixing operated on the initial analogue entropy source. Our analysis suggests an explanation about the already reported issue that this method does not necessarily require any specific deterministic property (i.e., chaos) from the physical signal used as the source of entropy. The bit stream randomness quality is found to result from “aliasing” phenomena performed by the post-processing method, both for the sampling and the quantization operations. As an illustration, such random bit sequences extracted from different entropy sources are investigated. Optoelectronic noise is used as a non deterministic entropy source. Electro-optic phase chaotic signal, as well as simulations of its deterministic model, are used as deterministic entropy sources. In all cases, the extracted bit sequence reveals excellent randomness. [ABSTRACT FROM PUBLISHER]

Estimation of permutation entropy (PE) using Bayesian statistical methods is presented for systems where the ordinal pattern sampling follows an independent, multinomial distribution. The desired PE posterior distribution is demonstrated to closely approximate a standard Beta distribution whose hyperparameters can be computed directly from ordinal pattern counts. It is further shown that this Bayesian approach is a generalization of previously-published frequentist methods. Because Bayesian posterior distributions can be estimated for very short time series, this method enables PE analysis on data sets currently not compatible with existing methods due to their limited size. To demonstrate the power and flexibility of this technique, the PE of a semiconductor laser with optical feedback (SLWOF) is shown to be time-variant by visualizing how the PE posterior distribution varies over sequences of small (1000 point) partitions of the output time-series. • Estimation of permutation entropy and uncertainties using Bayesian methods. • Fast and efficient moment-based approach usable even on small (< 1000 pt) data sets. • Demonstrated generalization of prior frequentist estimation methods for iid data. • Detection of non-stationary permutation entropy in a chaotic laser output. • Source code referenced and made available for general use. [ABSTRACT FROM AUTHOR]

We report on a narrow linewidth laser diode system that is stabilized using both optical and electronic feedback to a spectral hole in cryogenic Tm:YAG. The large group delay of the spectral hole leads to a laser with very low phase noise. The laser has proved useful for quantum optics and sensing applications involving cryogenic rare-earth-ion dopants. [ABSTRACT FROM AUTHOR]