D. M. Kane

Unlocking dynamical diversity : optical feedback effects on semiconductor lasers

List of Contributors. Preface. Acknowledgements. 1 Introduction (Deborah M. Kane and K. Alan Shore). 1.1 Semiconductor Laser Basics. 1.2 Nonlinear Dynamical Systems. 1.3 Semiconductor Lasers with Optical Feedback. 1.4 Landmark Results: Theory and Experiment. 1.5 Overview of Feedback Response: Regimes I-V. 1.6 Outline of Applications. References. 2 Theoretical Analysis (Paul Spencer, Paul Rees and Iestyn Pierce). 2.1 Introduction. 2.2 Basic Model: Single Mode Lasers with Weak Optical Feedback. 2.3 Steady State Analysis of the Lang-Kobayashi Equations. 2.4 Multimode Iterative Analysis of the Dynamics of Laser Diodes Subject to Optical Feedback. 2.5 Cavity Length Effects. 2.6 Coupled Cavity Analysis. 2.7 Conclusion. References. 3 Generalized Optical Feedback: Theory (Daan Lenstra, Gautam Vemuri and Mirvais Yousefi). 3.1 Varieties of Optical Feedback. 3.2 Compound-Cavity Analysis: Validity of Lang-Kobayashi Approach. 3.3 Filtered Optical Feedback. 3.4 Phase-Conjugate Feedback. 3.5 Conclusion. Acknowledgements. Note. References. 4 Experimental Observations (A. Tom Gavrielides and David W. Sukow). 4.1 Introduction. 4.2 Experimental Apparatus. 4.3 Extremely Weak Feedback Effects - Regime I. 4.4 Very Weak Feedback Effects - Regime II. 4.5 Weak Feedback Effects - Regime III-IV. 4.6 Moderate Feedback Effects - Low Frequency Fluctuations. 4.7 Short Cavity Regime. 4.8 Double-Cavity Systems. 4.9 Multimode Effects. 4.10 Control. 4.11 Feedback and Modulation. 4.12 Phase Conjugate Feedback. 4.13 Conclusion. References. 5 Bifurcation Analysis of Lasers with Delay (Bernd Krauskopf). 5.1 Introduction. 5.2 Bifurcation Theory of DDEs. 5.3 Numerical Methods. 5.4 Bifurcations in the COF Laser. 5.5 Bifurcations in the PCF Laser. 5.6 Conclusion. Acknowledgements. References. 6 Chaos Synchronization (Siva Sivaprakasam and Cristina Masoller Ottieri). 6.1 Introduction. 6.2 Synchronization of Unidirectionally Coupled Semiconductor Lasers. 6.3 Synchronization of Mutually Coupled Semiconductor Lasers. 6.4 Conclusion. References. 7 Laser Interferometry (Guido Giuliani and Silvano Donati). 7.1 Introduction. 7.2 Laser Diode Feedback Interferometry: Theory and Basic Experiments. 7.3 Application to Measurements. 7.4 Laser Diode Diagnostics Using Self-Mixing Techniques. 7.5 Conclusion. Acknowledgements. References. 8 Single Frequency and Tunable Single Frequency Semiconductor Laser Systems (Esa Jaatinen). 8.1 Introduction. 8.2 Effect of Frequency Filtering the Feedback for Robust Single Frequency Operation. 8.3 Tunable Semiconductor Laser System Designs and Operating Characteristics. 8.4 Frequency Stabilization. 8.5 Tunable Semiconductor Laser System Applications. 8.6 Conclusion. References. 9 Chaotic Optical Communication (Junji Ohtsubo and Peter Davis). 9.1 Introduction. 9.2 Communication Using Synchronized Laser Chaos. 9.3 Methods for Modulation and Recovery of Messages. 9.4 Mechanisms for Synchronization and Signal Recovery. 9.5 Parameter Sensitivity, Robustness and Security for Synchronized Chaos Communication. 9.6 Communication Bandwidth. 9.7 Conclusion. Acknowledgements. References. Index.

Mapping the dynamic complexity of a semiconductor laser with optical feedback using permutation entropy

A semiconductor laser with delayed optical feedback is an experimental implementation of a nominally infinite dimensional dynamical system. As such, time series analysis of the output power from this laser system is an excellent test of complexity analysis tools, as applied to experimental data. Additionally, the systematic characterization of the range and variation in complexity that can be obtained in the output power from the system, which is available to be used in applications like secure communication, is of interest. Output power time series from a semiconductor laser system, as a function of the optical feedback level and the laser injection current, have been analyzed for complexity using permutation entropy. High resolution maps of permutation entropy as a function of optical feedback level and injection current have been achieved for the first time. This confirms prior research that identifies a coherence collapse region which is found to be uninterrupted with respect to any embedded islands with different dynamics. The results also show new observations of low optical feedback dynamics which occur in a region below that for coherence collapse. The map of the complexity shows a strong dependence on the delay time used in the permutation entropy calculation. Short delay times, which sample information at the complete measurement bandwidth, produce maps with drastically different systematic variation in complexity throughout the coherence collapse region, compared to maps generated with a delay time that matches the optical feedback delay. Evaluating the complexity with a permutation entropy delay equal to the external cavity delay produces results consistent with the notion of weak/strong chaos, as well as categorizing the dynamics as being of high complexity where the external cavity delay time is harder to identify. These are both desirable features for secure communication applications. The results also show permutation entropy as a function of delay time can be used to detect key frequencies driving the dynamics, including any that may exist due to, or arise from, technicalities of device fabrication and/or noise. A more complete insight into complexity as measured by permutation entropy is gained by considering multiple delay times.

A quantitative analysis of single pulse ultraviolet dry laser cleaning

Particles as small as 0.3 μm in diameter have been successfully removed from a glass surface using a single ultraviolet pulse from a frequency doubled copper vapor laser (255.3 nm). Quantitative analysis of the particle density before and after laser irradiation shows that laser cleaning occurs after a fluence threshold is reached. The cleaning efficiency after threshold follows a nonlinear trend with respect to fluence. A model is presented which reveals that the cleaning efficiency is a function of the irradiance distribution of the beam used. Results of modeling thermal expansion of the substrate and particles, and particle adhesion do not confirm a thermal expansion mechanism for laser cleaning in this study, in contrast with other recent reports.

High-pressure (>1 bar) dielectric barrier discharge lamps generating short pulses of high-peak power vacuum ultraviolet radiation

We have investigated the scaling of peak vacuum ultraviolet output power from homogeneous Xe dielectric barrier discharges excited by short voltage pulses. Increasing the Xe fill pressure above 1 bar provides an increased output pulse energy, a shortened pulse duration and increases in the peak output power of two to three orders of magnitude. High peak power pulses of up to 6 W cm−2 are generated with a high efficiency for pulse rates up to 50 kHz. We show that the temporal pulse characteristics are in good agreement with results from detailed computer modelling of the discharge kinetics.

Correlation dimension signature of wideband chaos synchronization of semiconductor lasers

Chaos data analysis has been performed on the chaotic output power time series data from a synchronized transmitter-receiver pair of semiconductor lasers. The system uses an asymmetric, bidirectional coupling configuration between the master (transmitter), which is a laser diode with optical feedback, and a stand-alone slave semiconductor laser. The correlation dimension of the chaotic time series has a minimum value of 4, which was obtained from high-bandwidth measurements. The correlation dimensions for both the master and the synchronized slave are identical when the cross-correlation coefficient of the synchronized chaos is above 0.9. These results establish correlation dimension analysis as an effective tool for the determination of the quality of wideband chaos synchronization.

Nonlinear dynamics of semiconductor lasers with feedback and modulation

The nonlinear dynamics of two semiconductor laser systems: (i) with optical feedback, and (ii) with optical feedback and direct current modulation are evaluated from multi-GHz-bandwidth output power time-series. Animations of compilations of the RF spectrum (from the FFT of the time-series) as a function of optical feedback level, injection current and modulation signal strength is demonstrated as a new tool to give insight into the dynamics. The results are contrasted with prior art and new observations include fine structure in the RF spectrum at low levels of optical feedback and non-stationary switching between periodic and chaotic dynamics for some sets of laser system parameters. Correlation dimension analysis successfully identifies periodic dynamics but most of the dynamical states are too complex to be extracted using standard algorithms.

External cavity laser diodes with frequency-shifted feedback

Abstract Two infrared diode lasers, with one low reflectance facet of 4.5% or 0.1% have been evaluated in an external cavity diode laser (ECDL) with frequency-shifted feedback, with the aim of generating large frequency bandwidth superfluorescent output. A feedback level dependent linewidth broadening up to 750 MHz and 6 GHz respectively, has been observed for single chip mode operation. Both systems show multiple chip mode operation, with increasing frequency-shifted feedback, increasing in bandwidth to greater than 1 THz. The onset of multiple chip mode operation can be suppressed to higher levels of frequency-shifted feedback by the use of a diffraction grating rather than an external mirror in the ECDL.

Automated correlation dimension analysis of optically injected solid state lasers

Nonlinear lasers are excellent systems from which to obtain high signal-to-noise experimental data of nonlinear dynamical variables to be used to develop and demonstrate robust nonlinear dynamics analysis techniques. Here we investigate the dynamical complexity of such a system: an optically injected Nd:YVO(4) solid state laser. We show that a map of the correlation dimension as a function of the injection strength and frequency detuning, extracted from the laser output power time-series data, is an excellent mirror of the dynamics map generated from a theoretical model of the system. An automated computational protocol has been designed and implemented to achieve this. The correlation dimension map is also contrasted with prior research that mapped the peak intensity of the output power as an experimentally accessible measurand reflecting the dynamical state of the system [Valling et al., Phys. Rev. A 72, 033810 (2005)].

Nonlinear dynamics of a laser diode with optical feedback systems subject to modulation

The nonlinear dynamic behavior of a direct frequency-modulated diode laser with strong optical feedback is examined and compared to a laser diode subject to electro-optically modulated, strong optical feedback. Direct modulation is achieved by sinusoidal modulation of the diode laser injection current. Electro-optic modulation is achieved by applying a sinusoidal voltage to an intracavity phase modulating element. The output state (characterized by the output power versus time, the intensity noise spectrum and the optical frequency spectrum) for both types of modulation is dependent on the ratio of the modulation frequency to the external cavity resonant frequency, and the modulation power. A number of distinct states are observed: conventional amplitude modulation (with FM spectra); multimode, low-noise amplitude modulation; multimode, high-noise amplitude modulation; periodic limit-cycle operation; quasi-periodicity; chaos; low-frequency fluctuations; and mode-locking. There are significant differences between the direct and electro-optic frequency-modulation cases. The onset of the dynamic instability is characterized as a noisy period-one oscillation for direct modulation and a low-frequency fluctuation for intracavity electro-optic modulation. Phase portraits produced experimentally with the use of a digital phosphor oscilloscope are shown to agree well with those constructed from output power versus time data. This represents an experimental method for examining the dynamics phase portraits in real-time.

Reduced threshold ultraviolet laser ablation of glass substrates with surface particle coverage: A mechanism for systematic surface laser damage

A recent study of ultraviolet laser cleaning of silica glass surfaces contaminated with medium density alumina particles has shown a systematic type of laser-induced surface damage. This is characterized as a pit which increases in diameter and depth with increasing irradiating fluence. The damage pit occurs at lower fluence levels when smaller contaminant particles are used. The pits are due to laser ablation of the particle coated glass surface. The threshold for this laser ablation is well below that for a sample of the glass in its uncontaminated condition and the efficiency of ablation is estimated as being about 1000 times greater than that for silica. This laser damage is difficult to visualize by standard optical microscopy and could easily go undetected in laser cleaning studies. It may have general implications in the application of the new laser cleaning technologies to a variety of surfaces, including dielectrics and semiconductors, where medium to high densities of contaminant particles are p...