Master Laser Research Articles

Cascaded injection of semiconductor lasers in period-one oscillations for millimeter-wave generation.

Period-one (P1) oscillations in semiconductor lasers are applicable in photonic millimeter-wave (mm-wave) generation. P1 oscillation can be invoked by optically injecting a laser, where the phase noise can be suppressed by modulation. To increase the frequency range of mm-wave generation, cascaded injection is investigated for enhancing the P1 oscillation harmonics. Relative to the optical frequency of the injection from a master laser, P1 oscillation at frequency f0 is induced in a primary slave laser which, in turn, injects a secondary slave laser for enhancing the harmonic at 2f0. Experimentally, photonic mm-wave generation at 2f0=72 GHz is demonstrated using P1 oscillations at f0=36 GHz. Subharmonic locking by modulation at f0/4=9 GHz can suppress the output phase noise to -87 dBc/Hz at 10kHz offset. The mm-wave power can be strengthened by the coherent addition from the master laser. The mm-wave frequency can be tuned by varying the operating conditions of the lasers. Extension to higher frequencies is possible using the approach of cascaded injection.

Problem of nuclear-laser power engineering and methods of their solution

The concept of a high power reactor-laser system based on a nuclear pumped optical quantum amplifier (OKUYaN) was formulated at IPPE in the mid-1980-ies. The idea amounted to the use of wide-aperture OKUYaN as an amplifier within the already well-known “master laser – two-pass amplifier with phase conjugation” scheme. The structure of such an amplifier includes a system of two neutron-coupled units – an ignition reactor (RB) and a nuclear pumped laser amplifier (LB). The ignition unit is a compact multi-core pulsed fast neutron reactor. The laser amplifier unit operates on thermal neutrons and, with regard to the neutronics, it is a subcritical booster zone of the ignition reactor unit. Unique reactor-laser complex incorporating demonstration sample of a pulsed reactor-laser system based on OKUYaN (test facility “Stand B”) having no analogues anywhere in the world, was developed and put into operation at IPPE in 1999 for the purpose of substantiation of basic principles of the OKUYaN concept and demonstration of the possibility of its practical implementation, as well as verification of calculation codes and development of relevant equipment elements. Problems overcome in the development and construction of “Stand B” test facility, the choice and justification of the neutronics and laser characteristics of the OKUYaN demonstration sample are discussed in the present paper. Provided are the results of a detailed computational-experimental study of the demonstration sample characteristics, the data from systems studies of direct conversion of nuclear fission energy into laser radiation energy in complex reactor-laser devices and the results of examination of prospects for the development of nuclear-laser power engineering.

Stochastic polarization switching induced by optical injection in bimodal quantum-dot micropillar lasers.

Mutual coupling and injection locking of semiconductor lasers is of great interest in non-linear dynamics and its applications for instance in secure data communication and photonic reservoir computing. Despite its importance, it has hardly been studied in microlasers operating at μW light levels. In this context, vertically emitting quantum dot micropillar lasers are of high interest. Usually, their light emission is bimodal, and the gain competition of the associated linearly polarized fundamental emission modes results in complex switching dynamics. We report on selective optical injection into either one of the two fundamental mode components of a bimodal micropillar laser. Both modes can lock to the master laser and influence the non-injected mode by reducing the available gain. We demonstrate that the switching dynamics can be tailored externally via optical injection in very good agreement with our theory based on semi-classical rate equations.

Reduction of the chromatic dispersion and chirping effects by using an injection-locked and directly intensity-modulated Fabry–Pérot laser in point-to-point optical access networks

We present recent improvements achieved for two important transmission parameters—dispersion, induced by the optical fiber, and the chirp parameter of the laser source—in a directly modulated system based on an injection-locked and directly modulated Fabry–Pérot laser diode for high-speed optical access networks with a point-to-point topology. Measurements in the 20-GHz range of the frequency response for distances up to 35 km are conducted by carefully adjusting the optical power and frequency detuning of the distributed master laser in the central office, thereby overcoming the problem of chromatic dispersion in high-speed optical access. Moreover, the enhancements make it possible to increase the transmission distance when a 1550-nm Fabry–Pérot laser is used as the light source in the central office of a point-to-point optical access network by distributing the seed light into numerous downstream lasers. This improvement to the injection-locked Fabry–Pérot laser is expected to extend the length of already-built, fiber-to-the-home, point-to-point networks with a simple upgrade in the central office without prejudicing the terminal equipment.

Tunable single-mode microwave signal generation utilizing an all-optical coupled microwave oscillator.

A tunable all-optical coupled microwave oscillator is proposed and experimentally demonstrated. This system has no any electrical microwave devices as well as photoelectric conversion and electro-optic modulation. In this scheme, a fiber ring laser not only provides a set of frequency references but also acts as an active optical resonator. The oscillation frequency selection is carried out by cavity modes transfer and injection locking process. Due to the mode pulling effect, a self-adapting oscillation frequency locking is achieved. Through the microwave envelope detection and feedback modulation in a semiconductor optical amplifier (SOA), a microwave signal can be generated by a pure optical oscillation. In the experiment, good quality and high stability single-mode microwave signals are obtained, whose frequencies can be tuned from 6.93 GHz to 25.54 GHz by simply adjusting the wavelength of the master laser. Under different operation frequencies, the measured single-sideband phase noises are approximately -95 dBc/Hz at a 10-kHz offset from the carriers.

Stochastic behavior of an external optically injected single-mode semiconductor laser including Langevin noise sources

In this paper the stochastic dynamics of an optically injected semiconductor laser (SCL) operating in the single mode are theoretically and numerically investigated in the framework of the Langevin approach. Novel modified analytical expressions for relative intensity noise (RIN) and frequency noise have been developed for both master laser and slave. The effective gain coefficient (EGC) parameter of this rate-equation model allows noise suppression of 65 dB to be achieved in addition to the diminution of RIN spectra achieved by classic decisive parameters. A modified Schawlow–Townes formula is also proposed for laser linewidth. Moreover the induced modulation of the FWHM by the mean EGC allows more significant reduction of the laser linewidth, unlike those of classic SCLs when the EGC is lower than 0.5, opening the route to the ideal laser linewidth, which is discussed. The impacts of linewidth enhancement factor, spontaneous emission factor and EGC are investigated in noise spectra around the threshold current.

Excitable interplay between lasing quantum dot states

The optically injected semiconductor laser system has proven to be an excellent source of experimental nonlinear dynamics, particularly regarding the generation of excitable pulses. Typically for low-injection strengths, these pulses are the result of a small above-threshold perturbation of a stable steady state, the underlying physics is well described by the Adler phase equation, and each laser intensity pulse is accompanied by a 2π phase rotation. In this article, we show how, with a dual-state quantum dot laser, a variation of type I excitability is possible that cannot be described by the Adler model. The laser is operated so that emission is from the excited state only. The ground state can be activated and phase locked to the master laser via optical injection while the excited state is completely suppressed. Close to the phase-locking boundary, a region of ground-state emission dropouts correlated to excited-state pulses can be observed. We show that the phase of the ground state undergoes bounded rotations due to interactions with the excited state. We analyze the system both experimentally and numerically and find excellent agreement. Particular attention is devoted to the bifurcation conditions needed for an excitable pulse as well as its time evolution.

Spectral purity transfer with 5 × 10−17 instability at 1 s using a multibranch Er:fiber frequency comb

In this work we describe the spectral purity transfer between a 1156 nm ultrastable laser and a 1542 nm diode laser by means of an Er:fiber multibranch comb. By using both the master laser light at 1156 nm and its second-harmonic at 578 nm, together with the 1542 nm slave laser, we investigate the residual noise between the main comb output, the octave-spanning output, and a wavelength conversion module including non-linear fibers, second-harmonic generation crystal and amplifiers. With an ultimate stability of the system at the level of at 1 s and accuracy of , this configuration can sustain spectral transfer at the level required by the contemporary optical clocks with a simple and robust setup.

Co-amplification: An efficient spectral beam combination approach for high power, closely separated dual wavelength dye laser systems

Characteristics of an efficient spectral beam combination of two dye laser beams with wavelength difference of less than 10 nm are presented. Two dye laser oscillator beams were spatially and temporally combined with reduced losses before their co-amplification in a common power amplifier. Yellow and green beams of 9 kHz (pulse repetition rate) copper vapour laser (CVL) Master Oscillator Power Amplifier (MOPA) Chain were utilised to pump Rh 101 dye laser oscillators and DCM dye common amplifier respectively. The characteristics of green beam pumped DCM dye common amplifier were studied at various pump power and input power ratios. Combination losses for this configuration were 40% relative to individually amplified configuration. Input–output characteristics of the common amplifier were determined at various input power ratios. Composite dual wavelength dye laser beam having total power of 7.35W at 38.4 W pump power with extraction efficiency 16.5% was demonstrated.

Optical image encryption and transmission with semiconductor lasers

Optical chaos has great advantages in image encryption and optical message secure transmission, hence a novel image encryption and transmission system based on optical chaos is proposed. In this paper, we introduce optical chaos generated by the semiconductor laser in the encryption process. For increasing the chaotic complexity of slave lasers (SL1 and SL2), the master laser (ML) is subjected to the optical feedback and the external optical injection from the driven laser (DL). Then the SL1 and SL2 can generate the optical chaotic signal simultaneously, which can be used as chaotic carrier and the key for better security. The secret key and a new chaos sequence for the permutation can be structured by selecting randomly numbers from the optical chaos signal generated by the SL1 (or SL2). Furthermore, the result of color image encryption based on the Hilbert curve (HC) can be improved by introducing the optical chaos, after employing logistic chaotic map, the pixel positions and values of plain image are changed disorderly. The security analysis and simulation results can demonstrate the feasibility of proposed algorithms. Moreover, under the condition of chaos synchronization between the SL1 and SL2, the encrypted image can be modulated by using the chaos masking (CMS) technique and transmitted in 10 km single mode fiber (SMF) channel from the SL1 to SL2. The bit error rate (BER) can be for less than 4.22×10-20 and high quality factor (Q-factor) can be also for more than 9.

Optimizing optically injected semiconductor lasers for periodic dynamics with reduced sensitivity to perturbations.

Optically injected semiconductor lasers generate limit-cycle dynamics of period-one and period-two oscillations at microwave frequencies. At specific operating points, the periodic oscillations can be rendered insensitive to small-signal fluctuation in the operating conditions of the master and slave lasers. Periodic oscillations with low-sensitivity to fluctuation in the slave laser bias current, injection strength, or detuning frequency can be enhanced through tailoring the intrinsic laser parameters. Here, through numerical calculations, the effects of each intrinsic parameter on the various low-sensitivity operating points are demonstrated through detailed maps as functions of the operating parameters. For enhanced low sensitivity to bias-current and injection-strength fluctuations, a laser with a small linewidth enhancement factor is favored. Conversely, a large linewidth enhancement factor enhances low sensitivity to detuning-frequency fluctuations. Lasers with a more negative value of the gain saturation factor confine the regions of low sensitivity to fluctuations in the bias current and detuning frequency to the extrema of the periodic oscillation frequency. The laser relaxation rates that enhance the periodic-oscillation dynamic regions of an optically injected semiconductor laser, in turn, increases the regions of the various types of low-sensitivity operating points.

Mutually coherent dual-comb source generated from a free-running linear fiber laser

Abstract We demonstrate a simple scheme for mutually coherent dual-comb generation, in which two frequency combs are emitted from a linear polarization maintaining (PM) fiber laser. The employed master laser is simultaneously mode-locked along two cross-polarized axes. The cross-polarized pulses have different repetition rates, since PM fiber has intrinsic birefringence. A theoretical model is established to investigate the pulse generation and interplay between the two pulses. Moreover, excellent mutual coherence of the two cross-polarized mode-locked pulses and overlapping spectra are demonstrated, allowing us to resolve individual comb lines directly in dual-comb spectroscopy (DCS) without active stabilization. Furthermore, due to the compact structure of the setup, the laser has potential as a robust dual-comb source.

Direct Amplification of High Energy Pulsed Laser in Fiber-Single Crystal Fiber with High Average Power

A laser master oscillator power amplifier (MOPA) system consisting of a fiber amplifier and a two-stage Yb:YAG single crystal fiber (SCF) is experimentally studied. The nonlinear stimulated Raman scattering (SRS) is avoided by limiting the output power of the fiber preamplifier to 600 mW. Due to the benefit from the low nonlinearity and high amplification gain of the SCF, a laser pulse duration of 16.95 ps and a high average power of 41.7 W at a repetition rate of 250 kHz are obtained by using a two-stage polarization controlled double-pass amplification of Yb:YAG SCF, corresponding to an output energy of 166.8 μJ and a peak power of 9.84 MW, respectively. The polarization controlled SCF amplification scheme achieved a gain as high as more than 69 times. During the amplification, the spectra gain narrowing effect and the polarization controlled four-pass amplification setup are also studied. The laser spectrum is narrowed from over 10 nm to less than 3 nm, and the pulse width is also compressed to hundreds of femtosecond by dechirping the laser pulse. This compact-sized, cost-effective laser source can be used in laser micromachining, or as the seeder source for generating much higher power and energy laser for scientific research. For some applications which need femtosecond laser, this laser source can also be compressed to femtosecond regime.

High-Resolution Brillouin Optoelectronic Oscillator Using High-Order Sideband Injection-Locking

Microwave signals with high frequency, flexible tunability, and low phase noise are highly desired in signal processing and radar systems. In this letter, an optical injection-locking scheme using the high-order phase modulation sideband is introduced to realize a stable Brillouin optoelectronic oscillator (OEO). Pure microwave signals up to 40 GHz with low phase noise are obtained using an electrical drive signal below 5 GHz. A flexible frequency tuning with high resolution of 8 MHz is maintained by controlling the electrical drive signal and the slave laser, and the side mode suppression ratio is higher than 60 dB. The phase noise of the OEO-generated microwave signals under different master lasers is measured and compared to verify the significance of the master lasers with ultralow frequency noise. The maximum frequency drift of a 10.79-GHz signal is 1.4 kHz within 600 s, showing the stability of the proposed Brillouin OEO.

Microcontroller based scanning transfer cavity lock for long-term laser frequency stabilization.

We present a compact all-digital implementation of a scanning transfer cavity lock (STCL) for long-term laser frequency stabilization. An interrupt-driven state machine is employed to realize the STCL with the capability to correct for frequency drifts in the slave laser frequency due to measured changes in the lab environmental conditions. We demonstrate an accuracy of 0.9 MHz for master laser and slave laser wavelengths of 556 nm and 798 nm as an example. The slave laser is also demonstrated to dynamically scan over a wide frequency range while retaining its lock, allowing us to accurately interrogate atomic transitions.

Injection-Locked, Single Frequency, Multi-core Yb-doped Phosphate Fiber Laser

For the first time, we demonstrate injection locking and single frequency operation of a multi-core Yb-doped phosphate fiber laser (MCF). The 19 MCF laser cores operated in CW mode at 1030 nm. Each laser core was locked to the frequency and polarization of the single-frequency master laser, and produced milliwatts of power with similar lasing thresholds. The pump beam was homogenized with a simple technique to increase uniform lasing behavior of the cores. This behavior was verified using a MCF laser model developed in-house. This unique MCF laser can be useful for applications of coherent, coupled oscillator networks, for example in an all-optical coherent Ising machine configuration.

Dynamics of an Optically Injected Diode Laser Subject to Periodic Perturbation: Occurrence of a Large Number of Attractors, Bistability and Metastable Chaos

It is well known that during a certain interval of time, a molecule of gas in the beam path from the pump laser (master) to the injected laser (slave) can decrease the power injected [1]. In this contribution, we consider a well-known rate equation model of semiconductor laser to explore numerically the effect of a periodic perturbation from the pump laser (master) on the dynamical behavior of the injected laser (slave). Using nonlinear diagnostic tools such bifurcation diagrams, graph of maximum Lyapunov exponent, phase portraits, Poincare sections, basin of attraction and two parameter diagrams, the dynamical behavior of the model is analyzed in terms of its parameters. The coexistence of periodic and chaotic attractors as well as the occurrence of ten different attractors (symmetric and asymmetric) and transient chaos are demonstrated. Finally, PSpice simulations are performed to support numerical results.

Suppression of Intensity and Frequency Noise at Low-Sensitivity Operating Points of Period-One Dynamics of Optically Injected Semiconductor Lasers

Period-one (P1) dynamics induced by an optically injected semiconductor laser oscillate at microwave frequencies. The oscillation frequency of a P1 dynamic can be rendered nearly insensitive to small-signal parameter fluctuations and intrinsic laser noise at appropriate operating conditions of the master and slave lasers. In this paper, the noise-canceling properties of the various low-sensitivity (LS) operating points is demonstrated through their dependency on the noise fluctuation frequency and power. The three different types of LS operating points show their effectiveness in suppressing not only P1 intensity and frequency fluctuations caused by narrowband laser perturbations but also intensity and frequency noise caused by broadband intrinsic and extrinsic noise sources.

Generation of Tunable and Ultra-Broadband Microwave Frequency Combs Based on a Semiconductor Laser Subject to Pulse Injection From a Current Modulated Laser

We have experimentally demonstrated and characterized the generation of tunable and ultra-broadband microwave frequency combs (MFCs) based on a slave laser (SL) subject to regular pulse injection from a current modulated master laser (ML). Under modulation frequency fm = 1.2 GHz and modulation power Pm = 22 dBm, the current modulated ML is driven into a regular pulse state, and a seed MFC with 14.4 GHz bandwidth within a ±5 dB amplitude variation can be obtained. Such a seed MFC is then injected into the SL for producing final MFC with higher performances. For a fixed detuning frequency fi = 0 GHz and optimized injection power Pi = 2060 μ W, the bandwidth of the final MFC is increased to 33.6 GHz, and the single-sideband phase noises of all comb lines of the MFC within the bandwidth can be decreased to below –90.9 dBc/Hz@10 kHz. Additionally, the influences of Pi and fm on the MFC bandwidth are also analyzed. The experimental results are in agreement with numerical simulations to a certain extent.

Feed-forward comb-assisted coherence transfer to a widely tunable DFB diode laser.

The transfer of phase coherence from an ultrastable master laser to a distributed feedback diode laser, using an optical comb as a transfer oscillator, is obtained via a new scheme allowing continuous scanning across the whole tuning range of the slave laser together with absolute frequency determination. This is accomplished without phase lock loops, through a robust high-bandwidth feed-forward control acting directly on the slave laser output radiation. The correction is obtained by means of a dual-parallel Mach-Zehnder interferometer used as an optical single-sideband modulator. Coherence transfer across a master-slave frequency gap of 14 THz yields an ∼10 kHz linewidth providing high injection efficiency of an optical cavity with finesse 250 000. This allows demonstrating a cavity ring-down absorption spectrum of low-pressure ambient air over a 300 GHz spectral window.