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In this work, experimental study for the chaotic dynamics of a quantum well semiconductor laser (SL) (1310 nm wavelength) with anoptical loop mirror is investigated. The spikesareintroduced by configuring this external cavity type. Making one arm from this cavity be attenuated led to retardation for it. Disturbance in longitudinal lasing mode resulted in chaotic spectrum. Bandwidth for this signal is very limited and changeable under the attenuation ratio. In comparison to pure optical feedback, the achieved signal is lower and evolved from kHz band (in 4.3 v bias voltage) to MHz band (with higher voltages i.e., 4.7 and 4.8 volt). The first range included 300% higher amplitudes for the lasing modes, while the later was equivalent to the random like signal amplitudes. Such a range can be employed for laser wavelength fine tuning applications with the benefit of not disturbing the laser medium. This results opens the door for mixing resulted signal with another oneprimary subjects to pure optical feedback. [ABSTRACT FROM AUTHOR]

In this experimental work, dynamics of laser diode (LD) with the presence of hybrid (triple) feedback is studied. Strategy is based on increase degrees of freedom for the single mode LD oscillator in order to increase its complexity. Hybrid implies the application of self both optoelectronic feedback (OEFB) and optical feedback (OFB) in additional to external optical injection (OI), this is under proper selection for controlling parameters. Realize of chaotic dynamics was happened in special running to the overall initial conditions. These conditions included; LD1 and LD2 current and voltage below and above free running threshold, attenuation of OEFB and OI, modulation frequency, uni-and bi-directional interaction via the transmission medium, the optical fiber. Results indicates robust chaotic dynamics with a moderate chaos bandwidth under the application of direct frequency modulation. [ABSTRACT FROM AUTHOR]

Nonlinear and chaotic dynamics for a continuous emission (CW) laser diode with Fabry-Perot cavity is studied experimentally. Uni-directional and Bi-directional fiber optical injection configuration was constructed in the absent of modulation. The optical injection itself mixed with optoelectronic feedback (OEFB) mode hopping and rout to chaos were observed. This optical injection is reversed to produce a pure optical injection (01), with observing dynamics generated in another identical laser diode (LD2). That's to say, at first, LD1 receives optical injection from LD2 (initially mixed in with self OEFB), then, in the second case, LD2 (operating with its self OEFB) receives pure optical injection came from LD1. a generation of mode-lock and for a specific bias current levels, unstable chaos generated is observed. Third case, experiment contained the mutual optical feedback. Results indicates a variety of nonlinearities associated with such a last three configurations, a mode shift achieved. Ratio of O1 was controlled and also OEFB strength. Mode hoping, multimode emission, mode lock and chaotic behavior all achieved experimentally. Additional tested parameter was the two lasers bias current. The chaotic pulse linewidth was around 300 MHz, with the ability to be boarder via changing detuning or injection ratio. Laser changed to emit in pulsation with rout to chaos status in which it has a FWHM around 0.1GHz. Reversing injection led to linewidth enhancing with a very sharp FWHM, 1.5 KHz. Laser emission perturbed due to mixed injection as if it works with OEFB, where the gain switches tends to drive the laser into pulsing states induced by that positive OEFB. For each achieved result them exist an application, such as; chaos shifts keying, frequency mixing, and up-conversion to a new frequency to reduce cost on high-speed electronics associated with optical communications. [ABSTRACT FROM AUTHOR]

An intra-cavity propagation delay effect in synchronization of coupled diode lasers is numerically investigated. A diode laser (master) with an optical feedback exhibits periodic, intermittent chaos, and chaotic dynamics in its output intensity at appropriate feedback rates, and the master's output is uni-directionally coupled to a solitary diode laser (slave). From the performance of cross-correlation analysis between master and slave's output, we observed that there exists an additional delay called intra-cavity propagation delay along with the coupling time delay between the lasers. We found that this intra-cavity propagation delay has an inverse relationship with synchronization quality and is observed for various laser's bias levels and spontaneous emission rates. [ABSTRACT FROM AUTHOR]

Influence of the nonlinear gain (NLG) and nonradiative recombination life time ratio (NRRLTR) on the rout to chaos and noise characteristics of semiconductor lasers (SLs) subject to optical feedback (OFB) are investigated. The analyses are performed in terms of the temporal trajectory of the photon numbers, bifurcation diagrams and relative intensity noise (RIN). Variations of the fluctuations of the photon number are statistically analyzed. The corresponding frequency dependence of RIN is characterized. The simulation results show that, NLG and NRRLTR can cause significant changes in the rout to chaos of the SLs and probability distribution of the photon numbers. We found that the value of the OFB rate at which the transition from CW to periodic oscillation (PO) or chaos state occur increases, as the value of the NLG/NRRLTR is increased/decreased. The RIN is found to be suppressed when the laser is operated in CW or PO region and at relatively higher/lower values of the NLG/NRRLTR. We believe that, the instability of the SLs can be reduced by operating it under OFB and by increasing/decreasing the values of the NLG/NRRLTR parameter. [ABSTRACT FROM AUTHOR]

Optical feedback driving schemes can enable accurate ageing and pixel brightness non-uniformity corrections in AMOLED displays. Here, we report on a pixel driver utilizing a metal-insulator-semiconductor (MIS) sensor for luminance control of the OLED element. In the proposed pixel architecture for bottom-emission AMOLEDs, the embedded MIS sensor shares the same layer stack with back-channel etched a-Si:H TFTs to maintain the fabrication simplicity. Performance characteristics of the MIS sensor are presented and analyzed to demonstrate its feasibility. Details on the pixel circuit functionality including the sensing and programming operations are also discussed. [ABSTRACT FROM AUTHOR]

A self-sustained Radiation-Pressure driven MEMS ring OptoMechanical Oscillator (RP-OMO) attaining an anchor-loss-limited mechanical Q-factor of 10,400 in vacuum has posted a best-to-date phase noise of −102 dBc/Hz at a 1 kHz offset from a 74 MHz carrier, more than 15 dB better than the best previously published mark [1]. While enhanced optical and mechanical Q both serve to lower the optical threshold power required to obtain oscillation, it is the mechanical Q that ends up having the strongest impact on phase noise [2], much as in a traditional MEMS-based oscillator [3]. This motivates a focus on increased mechanical Q — a challenge in previous such devices measured in air — and requires measurement in the absence of gas-damping using a custom optical vacuum measurement system. The improved phase noise performance of these RP-OMOs is now on par with many conventional MEMS-based oscillators and is sufficient for the targeted chip-scale atomic clock application. [ABSTRACT FROM PUBLISHER]

In order to resolve the issue of large-scale assembly for quasi-LIGA micro-parts, the purpose of this paper is to propose a novel method of orthogonal optical precise alignment. The micro-assembly experiment system set-up was constructed according to the principle of the orthogonal precise alignment. One single-position consists of three components: 3-DOF micro motion worktable, micro force feedback automatic feeding mechanism and optical alignment micro stereovision feedback control unit. The results indicate that orthogonal optical precision alignment could be used for the assembly of non-silicon MEMS devices with flat structure. The orthogonal optical alignment error is theoretically analyzed and calculated. When the prism orthogonal alignment mechanism produces the error of 1/1000°, the theoretical deviation was less than 0.9µm and the actual experimental micro-assembly platform assembly accuracy exceeded 15µm. [ABSTRACT FROM PUBLISHER]

Optical Network-on-Chip (ONoC) architectures are emerging as a new paradigm to interconnect a large number of processing cores at chip level, thereby enabling to meet the pressing demands for extremely high bandwidth and low power consumption. Some existing ONoC architectures are implemented in an electronic-controlled way in a two-layer 3D chip based on TSV (Through-Silicon Via). However, on-chip thermal effect is an inherent deficiency and chip temperature can fluctuate spatially, which can affect the operation of silicon nanophotonic devices. This leads to significant influence on the reliability of communications. To minimize the thermal impacts and improve the reliability, we propose a novel approach by adding a tunable wavelength converter (TWC) in the router for mesh-based ONoC. Simulation results show that our proposed approach can increase the signal-to-noise ratio (SNR) effectively. [ABSTRACT FROM PUBLISHER]

In this paper, we present a self-mixing double-head laser diode velocimeter. Analyzes are performed to evaluate the sensitivity to misalignment for this setup and calculate errors due to this misalignment. The analyses and calculations are verified by experimental results. [ABSTRACT FROM AUTHOR]

An optical feedback interferometer has been used as a sensor for measuring the deformation of the beams under dynamic loading. The compactness, non-contact nature, high accuracy (below half wavelength of the laser) and the cost-effectiveness of this sensor makes it a suitable choice for material deformation measurements. A general procedure of the measurement is described in detail, including the proposed solution to deal with the speckle effect which appears when large deformations are presented. The performance of the proposed sensor has been compared and validated with a commercial contact LVDT sensor showing measurement differences below 20μm (2.9%). [ABSTRACT FROM AUTHOR]

Effect analysis of external optical feedback on waveform and spectrum of semiconductor laser autodyne signal has been performed. The method of nanovibration amplitude determination has been described. The method involves measuring ratio of the first spectral components of nanovibration autodyne signal to one of the additional mechanical vibrations, taking into account the level of external optical feedback. It has been experimentally shown, that taking into account external optical feedback can significantly improve the accuracy of nanovibration measurements. [ABSTRACT FROM AUTHOR]

This paper presents simulation results for an underwater optical wireless communication system based on light emitting diode (LED) and integrated detector preamplifier (IDP). Both the position and the orientation of the transmitter and the receiver change during the swimmer's actions. The simulation results showed the line of sight (LOS) communication link and the non line of sight (NLOS). The effect of air bubbles in water which was studied by the authors previously was included in the simulation as a swimmer generates a huge amount of bubbles during swimming. The received power and the link margins for two different LEDs were calculated to check the availability of the system. It was proven that the half power beam width (HPBW) and the bubbles are important factors in the link budget calculations and this is important for the link availability. The simulation results for the optical wireless system using a superflux LED and OPT101 receiver achieved more than 1 m communication link underwater with and without the effect of air bubbles. [ABSTRACT FROM PUBLISHER]

In this paper, we present an example of control system design based on negative imaginary (NI) system theory. The system under consideration is an optical cavity system. A dynamical model of the cavity system is obtained through system identification of applied to experimental input output frequency response data obtained using a digital signal analyzer (DSA). The identified model satisfies NI property. An integral resonant controller is designed based on the NI system theory. [ABSTRACT FROM PUBLISHER]

Optical wedge is one kind of prism with small vertex angle and its characteristic of refraction can be used to deflect optical path. In this way, optical wedge can provide the light sources in different angular position. If rotating two optical wedges with certain angular velocity, the imaging point will be adjusted contiguously. Based on this, we propose an imaging guidance system that can utilize this feature to change the system optical axis and realize the target tracking or searching. In this system, servo motors are applied to drive optical wedges through the feedback loop. According to attitude information from carrier IMU (Inertial Measurement Unit), the optical system is located on one rotating frame which is controlled to isolate roll-channel disturbance from carrier. The decoupling in pitch and yaw channels can be done by cooperative rotation of the optical wedges. In this work, the image-forming principle of double wedges is analyzed and related control method is discussed. [ABSTRACT FROM PUBLISHER]

A simple and low cost remote up conversion (RUC) scheme is proposed using only one optical modulator. The baseband (BB) data and local oscillator (LO) signal are electrically coupled to drive a commercial intense modulator (IM). The laser source and IM can be shared by both BB data and LO signal. With less than 0.3dB power penalty, the 2.5Gbps on-off keying (OOK) data over 50km single mode fiber (SMF) is successfully distributed in a 60GHz ROF system without any chromatic dispersion compensation. The low cost and low power penalty suggest that such scheme is suitable for low cost 60GHz optical-wireless networks. [ABSTRACT FROM PUBLISHER]

Secondary optics design in the past research only considered illuminance uniformity and ignored luminance uniformity and glare issue, which may result in serious security problem for vehicle drivers. A novel un-symmetric freeform LED lens designed for roadway lighting is proposed. Optical performance of un-symmetric lens will be compared with symmetric lens by optical software. The simulation results demonstrate that light intensity distribution curve (LIDC) of LED luminaire becomes un-symmetric and the overall roadway surface luminance uniformity with un-symmetric lens increases to 0.6, the longitudinal road surface luminance uniformity increases to 0.8, and light power density (LPD) drops to 0.7 W/m2. [ABSTRACT FROM PUBLISHER]

Recently, the size of digital content has continued to increase; therefore digital storage media have been required to increase capacity by narrowing the track pitch and the gap length between the optical head and the disk. On the other hand, anew optical disk has achieved a rotation speed of over 15,000 rpm. To meet these demands, several control systems for optical disks are proposed to achieve high-precision tracking control. In this paper, a high-precision focusing control system is proposed. The proposed control system consists of a feedback controller and a feedforward controller. The feedback controller design is based on a high-gain servo controller (HGSC). The feedforward controller design is based on a zero phase error tracking (ZPET) controller and an additional loop for suppressing multi-harmonic disturbances. The experimental results show the proposed control system has a fine focusing performance against fundamental periodic disturbances and high-order disturbances. [ABSTRACT FROM PUBLISHER]

In the robot systems and intelligent machines, the gear-box or mechanisms are connected with the motor to transmit the actuator torque to a distant joint. Generally, its elasticity causes resonance frequency in the system. By using the conventional PID controller, this method cannot perform well in this situation. Much research has proceeded with the aim of reducing vibration. A new effective control method, the resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for a position and force control. In this paper, two techniques are proposed for improving the performance of resonance ratio control: 1) A new multi encoder based disturbance observer (MEDOB) is shown to estimate the disturbance force on the load side. The proposed observer is not necessary to identify the nominal spring coefficient. 2) A coefficient diagram method (CDM) has been applied to calculate a new gain controller. A new resonance ratio gain has been presented as 2. The effectiveness of the method is verified by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The modes of a laser resonator experience optical amplification in the same gain medium, e.g. a laser crystal, in which they spatially overlap to a significant extent. This leads to the phenomenon of mode competition or gain competition, which can be studied extensively using the optical feedback mechanism. This paper analyses the existence of two modes in a laser system in the near infra red (NIR) range. Emphasis has been laid on the position and wavelengths of the two modes. Histogram analysis of the full width at half maximum (FWHM) of the modes mirrors remarkable upshots that have been elucidated in some detail. [ABSTRACT FROM PUBLISHER]

Photonic generation of microwave carriers by using a dual-frequency distributed feedback waveguide laser in ytterbium-doped aluminum oxide is demonstrated. A highperformance optical frequency locked loop is implemented to stabilize the microwave carrier. This approach results in a microwave frequency at ∼14 GHz with a phase noise of −75 dBc/Hz at 1 MHz offset from the center frequency. The frequency stability of the photonic microwave carrier has an Allan deviation of better than 1×10−10 for an averaging time of 1000 s with a loop settling time of 15 μs. [ABSTRACT FROM PUBLISHER]

This paper deals with the real time reconstruction of a self-mixing displacement signal under devices with limited resources. By implementing a first-order-hold interpolation used in digital-to-analog converters, the signal recovery problem has been reduced to the efficient usage of an adaptive filter with high potential of parallelism, suitable to meet hard timing constraints, low memory usage and easily integrable with other mitigation algorithms of the physical phenomena proper to laser behavior, towards the creation of a robust embedded displacement sensor. [ABSTRACT FROM PUBLISHER]

We present experimental results on the controlled vertical flight of a flapping-wing flying microrobot, in which for the first time an on-board sensing system is used for measuring the microrobot's altitude for feedback control. Both the control strategy and the sensing system are biologically inspired. The control strategy relies on amplitude modulation mediated by optical flow. The research presented here is a key step toward achieving the goal of complete autonomy for flying microrobots, since this demonstrates that strategies for controlling flapping-wing microrobots in vertical flight can rely on optical flow sensors. [ABSTRACT FROM PUBLISHER]

Vision is a vital cue for human navigation. Thus, visually impaired people encounter many challenges in day-today travelling. Identifying and avoiding obstacles in the environment is the most crucial among them. To empower blind navigation, numerous electronic travel aids were created in the past few decades, by using various obstacle sensing technologies such as sonar, infrared, and stereo vision. However, optical flow estimations based navigation, which is heavily used by insects and experimented in the field of robotics, has not been used in them. This project aimed to evaluate the potential optical flow estimation based techniques has in guiding a visually impaired person to avoid obstacles using auditory and tactile feedback. To demonstrate the researched core concepts, a prototype consisting of a virtual reality world was designed and developed. It also employs an existing optical flow algorithm for motion estimation, other image processing techniques, speech synthesis for auditory feedback and embedded programming for tactile feedback. The modular design of the prototype enables it to be used either in simulation mode, or as a standalone application in a real world environment. This work demonstrates the attractive possibilities of using optical flow estimations for visually impaired navigation. [ABSTRACT FROM PUBLISHER]

The insect visuomotor system combines a lightweight and high bandwidth sensor with fast processing algorithms for efficient information extraction that enables autonomous navigation in complex, obstacle laden environments. In this paper, an H∞ loop shaping controller synthesis framework is introduced to analyze an information extraction approach from patterns of optic flow based on analogs of wide field motion sensitive interneurons in the insect visuomotor system. Local proximity and velocity estimates are obtained with an optic flow model that is based on parameterization of typical three-dimensional urban environments. The insect inspired visual navigation technique combines proximity and speed estimates with an H∞ controller that provides robust stability in a cluttered environment as well as mitigates measurement noise and gusts. The loop shaping approach is used to demonstrate safe obstacle avoidance and terrain following behavior in simulation on an autonomous helicopter miro-air-vehicle for an urban-like environment subjected to gusts. [ABSTRACT FROM PUBLISHER]

There is evidence that flying animals such as pigeons, goshawks, and bats use optical flow sensing to enable high-speed flight through forest clutter. This paper discusses the elements of a theory of controlled flight through obstacle fields in which motion control laws are based on optical flow sensing. Performance comparison is made with feedback laws that use distance and bearing measurements, and practical challenges of implementation on an actual robotic air vehicle are described. The related question of fundamental performance limits due to clutter density is addressed. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a low complexity non decision directed blind carrier recovery algorithm (NDD-CRA) for 16-QAM optical coherent receivers. Through optimization of step size parameter (μ), we obtained similar performance compared to decision-directed phase estimation algorithm, however, our propose scheme has less complexity compared to the decision directed carrier recovery algorithm (DD-CRA) as the proposed scheme does not require any decision feedback module. From simulation, it is observed that the proposed scheme has less than 1.7 dB OSNR penalty at 10−3 BER and up to 200-kHz linewidth laser compared with the theoretical performance. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the viability of using self-mixing interferometer technique with a customized electro-optic phase modulator to detect the electrocardiographic signals on surface skin. The signals were recorded under two different optical feedback levels where the self-mixing technique operated under strong optical feedback regime was preferred due to the clear advantage of stability and linear relationship between the input and output signal. [ABSTRACT FROM PUBLISHER]

Optical orthogonal codes (OOCs) were introduced by Salehi, as signature sequences to facilitate multiple access in optical fibre networks. The existence of optimal (v, 3,1)-OOCs had been solved completely. For k ≥ 4, although there are some partial results, the existence of optimal (v, k, 1)-OOCs is far from settled. In this paper it is proved that if there exists a (g, 4, 1)-PDF, then (1) there exists an optimal ((g+2)v, 4, 1)-OOC for each integer v whose prime factors are all congruent to 1 modulo 4; (2) there exists an optimal ((g+1)v, 4, 1)-OOC for each integer v whose prime factors are all congruent to 1 modulo 6; (3) if g ≡ 1 (mod 48), then there exists an optimal ((g+7)v, 4, 1)-OOC for each integer v whose prime factors are all congruent to 1 modulo 6. By using the known results on (g, 4,1)-PDFs, many new optimal optical orthogonal codes with weight four are obtained. [ABSTRACT FROM PUBLISHER]

Sensor networks that use line of sight (LOS) laser links can provide spatially efficient and physically secure connectivity. These features are advantageous for low-power communication networks over short distances in environments where LOS is available, and where radio frequency connectivity must be avoided because of interference, low data rates, or security problems. In order for optical wireless (OW) directional networks to provide viable short-range connectivity, the networks must provide signal coverage over an acceptable field of view and operate with efficient media access protocols to minimize random access times for the independent transmitting nodes within the network. In this paper, we focus on a unique design and the performance of a directional media access protocol for optical wireless sensor networks. The results are discussed with respect to efficiency of operation and optimized performance. [ABSTRACT FROM PUBLISHER]

In this paper we present results of a dynamic monochannel first-order polarization mode dispersion compensator, revisiting a simple compensation technique which deals separately with the state of polarization of the polarization controller output through a non-linear optimization technique and the differential group delay line compensation. [ABSTRACT FROM PUBLISHER]

The optical feedback self-mixing model is theoretical analyzed and numerical simulated when the external cavity of a semiconductor laser suffers a harmonic vibration, a micro-displacement measurement system is set up based on self-mixing effect. A method based on phase unwrapping is introduced to process the self-mixing power signal, which has a good reconstruction effect for different feedback level when the self-mixing signal suffers no noise and interference, and the maximum measurable amplitude error is 28nm peak to peak. [ABSTRACT FROM PUBLISHER]

The aim of this work is to study the dynamical behavior of a diode laser subject to optical feedback, using a Lang-Kobayashi model. At steady state, the effect of the optical feedback on threshold gain, on the oscillation frequencies and on the monomode operation will be shown. The light versus current characteristics for different amounts of optical feedback is given by using numerical simulations of the theoretical model. [ABSTRACT FROM AUTHOR]

The optical feedback characteristics of a single mode He-Ne laser with a quartz crystal plate in the external cavity are studied. The fringe frequency of the laser system can be doubled when a quartz crystal plate is put by a certain angle between the crystalline axis and the beam in the crystal plate. Theory analysis shows that the birefringent effect of the quartz crystal plate and the laser beam's second passing in the external cavity result in this phenomenon. The experimental results are in good agreement with the theory analysis. It can double the resolution of a self-mixing sensing system. [ABSTRACT FROM PUBLISHER]

A two-element laser phased array is implemented where two commercially available DFB lasers are phase locked to a reference laser using two heterodyne Electro-Optical Phase Locked Loops (EOPLL) with integrated CMOS electronics. Integrated frequency aided acquisition system increases the acquisition range of EOPLLs from 8 MHz to 980 MHz, improving the phase locking performance in presence of environment fluctuations. The phase of each laser is controlled by phase shifting of the radio frequency signal outside the PLLs, eliminating optical phase shifters. An external feedback loop using a voltage controlled oscillator is realized to compensate for the relative phase fluctuations between the output of locked lasers at the point of beam combining. By electronically adjusting the relative phase between lasers, beam steering over more than 1 mrad at the far field (corresponding to 1 mm beam spot displacement at one meter away from the phased array emitters) has been demonstrated. Use of integrated electronics enables realization of laser phased arrays with large number of elements. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel circuit-switched on-chip photonic interconnection network (CSPIN) architecture. Different from existing circuit-switched photonic networks, CSPIN eliminates the electronic control layer but employs optical signaling to control the circuit switching functions. To implement CSPIN, the CSPIN router is proposed which uses electro-optical tuned micro-ring resonators. The analysis based on the synthesis result of the CSPIN router shows that significant savings in power and path-setup latency are achieved by the proposed CSPIN architecture. [ABSTRACT FROM PUBLISHER]

We demonstrate the first active stabilization of a microring-based device within a thermally volatile environment. The proposed design is CMOS integratable and leverages low-speed power monitoring and a feedback loop circuit for dynamic thermal correction. [ABSTRACT FROM PUBLISHER]

Coherent Interleaved FDMA (IFDMA)-PON uplink transmission with 30Gbps-8PSK format over 20km SSMF is experimentally demonstrated. Digital carrier frequency offset pre-compensation technique enables coherent orthogonal subcarrier multiple access of 2 ONUs with free-running sources. [ABSTRACT FROM PUBLISHER]

In this contribution the CMOS photonics technology (LuxG) developed and commercialized by Luxtera is reviewed. The advantages of integration and usage of a standard CMOS foundry toolset/process/practice are discussed with mention to a newly developed 14Gbps transceiver chip. [ABSTRACT FROM PUBLISHER]

Carrier recovery is essential in optical coherent systems to track the phase noises of lasers. Feedback and feedforward schemes are described and the performances are compared. Cycle slips and its remedies are discussed. [ABSTRACT FROM PUBLISHER]

We present experimental and theoretical results on Vertical Cavity Surface Emitting Lasers (VCSELs) and microlasers with saturable absorber. Laser cavity solitons are experimentally demonstrated in a compact system, a broad-area VCSEL with intracavity saturable absorber. These states of light appear as 10 μm diameter self-localized microlasers that one can manipulate with external beams in the transverse plane of the laser. Cavity solitons (CS) can be thought of as optical bits for reconfigurable processing of information. We demonstrate incoherent manipulation of CS at a fast rate and present evidence of optical manipulation of self-pulsing states. Excitability is also demonstrated in a different parameter region. Excitability is characterized by: 1) existence of a threshold leading to an “all or nothing” type of response to an input perturbation, 2) appearance of a calibrated response above threshold. Excitable response is interesting for optical pulse reshaping and may be used to build logical gates. A chain of such coupled microlasers can also be used to demonstrate discrete nonlinear wave propagation, with application to e.g. optical delay lines or neuro-inspired processing. A novel scheme to attain self-pulsing in nanocavity lasers will also be presented, thus showing the possible scaling down of the previous system. [ABSTRACT FROM PUBLISHER]

We experimentally study the polarization dynamics in a quasi isotropic CO2 laser emitting on the TEM∗01 mode subjected to an optical feedback. We observe a complex dynamics in which spatial mode and polarization competition are involved. The observed dynamic is well reproduced by means of a model that provides a quantitative discrimination between the intrinsic asymmetry due to the kinetic coupling of molecules with different angular momenta and the anisotropy induced by the polarization feedback. Possible applications to polarization coding and synchronization will be presented [ABSTRACT FROM PUBLISHER]

In this report, we will first present the most recent experimental progress of small compact Ca-beam optical frequency standard at 657nm wavelength at Peking university. Second, we will discuss our new scheme, which combining pre-pumping, shelving detection, and sharp-angle velocity selection detection. Comparing previous schemes, we expect the short-term stability can be improved at least by a factor of 30, and an expected factor of 10 for uncertainty in our new scheme since Doppler effect can be calibricated with higher accuracy. [ABSTRACT FROM PUBLISHER]

Quasi-conformal Transformation Optics (QCTO) has been proposed as a design technique for flattened or compressed optical and RF lenses. QCTO devices may be realized using all-dielectric gradient-index structures, which simplifies implementation and improves bandwidth for structures at optical wavelengths by avoiding the requirement for metamaterial design and fabrication. However, replacing one or more conventional homogeneous optical lenses by a QCTO equivalent is not as simple as a single-step design from performance specification to a drop-in replacement lens. Optimizations must be performed over the QCTO transformation in order to achieve equivalent optical performance under index and fabrication constraints. This abstract presents an optimization procedure for QCTO lenses that makes use of a ray tracing tool that supports arbitrary numerically-specified GRIN profiles for electrically large structures. [ABSTRACT FROM PUBLISHER]

The effect of moderate external feedback on the gradual degradation of 808 nm emitting AlGaAs-based high-power broad-area diode lasers is analyzed. Eventually the quantum well that actually experiences the highest total optical load remains unaffected by the aging, while severe impact to the waveguide by point defects is observed. [ABSTRACT FROM PUBLISHER]

We demonstrate closed-loop control of a MEMS phased array using an optical interferometer designed for in-situ phase-measurement. Phase resolution is comparable with commercial interferometers and we achieve beamsteering without calibration. [ABSTRACT FROM PUBLISHER]