Mutual Injection Locking Research Articles

Emulating the local Kuramoto model with an injection-locked photonic crystal laser array

The Kuramoto model is a mathematical model for describing the collective synchronization phenomena of coupled oscillators. We theoretically demonstrate that an array of coupled photonic crystal lasers emulates the Kuramoto model with non-delayed nearest-neighbor coupling (the local Kuramoto model). Our novel strategy employs indirect coupling between lasers via additional cold cavities. By installing cold cavities between laser cavities, we avoid the strong coupling of lasers and realize ideal mutual injection-locking with effective non-delayed dissipative coupling. First, after discussing the limit cycle interpretation of laser oscillation, we demonstrate the synchronization of two indirectly coupled lasers by numerically simulating coupled-mode equations. Second, by performing a phase reduction analysis, we show that laser dynamics in the proposed device can be mapped to the local Kuramoto model. Finally, we briefly demonstrate that a chain of indirectly coupled photonic crystal lasers actually emulates the one-dimensional local Kuramoto chain. We also argue that our proposed structure, which consists of periodically aligned cold cavities and laser cavities, will best be realized by using state-of-the-art buried multiple quantum well photonic crystals.

Chaotic regimes and synchronization in Tm3+-doped fiber laser with pump modulation

The dynamical behavior of a thulium-doped fiber laser (Tm-DFL) with pump modulation is investigated numerically. A rate equation model is used. Different routes to chaos are identified via intermittent-like or period-doubling regimes. Pulse width and pulse energy are extracted. In the second part, the dynamics of two parallel cavities with mutual injection-locking is studied. The lag synchronization between mutually coupled Tm-DFLs can be achieved. Under some conditions, the butterfly effect is demonstrated with this system, and the influence of coupling strength on time lag synchronization is detailed.

Modulation Characteristics Enhancement of Monolithically Integrated Laser Diodes Under Mutual Injection Locking

Modulation characteristics enhancement by mutual injection locking of monolithically integrated distributed feedback (DFB) lasers is studied. Locking bistability in mutually coupled integrated lasers is observed. Resonance frequency as high as 34.3 GHz is recorded, corresponding to more than fivefold enhancement over the relaxation oscillation frequency at free running state. The mutually injection-locked lasers exhibit reduced harmonics and third-order intermodulation distortion, as well as suppressed relative intensity noise near the relaxation oscillation frequency. The spurious-free dynamic range is improved from 75 to 80 dB·Hz2/3. Furthermore, alleviation of chirp-induced power fading in analog optical links has been demonstrated. To our knowledge, this is the first time that suppressed nonlinear distortion and noise as well as chirp reduction are simultaneously demonstrated for monolithic mutually injection-locked DFB lasers.

Single-Antenna Doppler Radars Using Self and Mutual Injection Locking for Vital Sign Detection With Random Body Movement Cancellation

This work presents a single-antenna self-injection-locked (SIL) radar to reduce the hardware complexity of continuous-wave (CW) Doppler systems. The theory provides a basis for determining the signal-to-noise spectral density ratio (SNDR) with the effects of clutter. Experimental results agree closely with the theoretical predictions, showing that the clutter does not affect the optimal SNR performance in an SIL radar. A single-antenna SIL radar array is designed to detect vital signs with random body movement cancellation. To this end, a subject is placed between two single-antenna SIL radars to measure the rates of respiration and heartbeat using Doppler shift, and the effects of random movement of the subject are cancelled by wireless mutual injection locking (MIL) of the two radars. In an experiment, a prototype of such a two-radar array with a spacing of 2 m was implemented at 2.4 GHz, providing accurate and reliable cardiopulmonary monitoring of a subject who jogged on a treadmill with random body motion of many centimeters.

Mutual Injection Locking of Monolithically Integrated Coupled-Cavity DBR Lasers

We present a photonic integrated circuit (PIC) composed of two strongly coupled distributed Bragg reflector (DBR) lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz. Mutual injection-locking and external injection-locking operation are compared.

Mutual injection locking and coherent beam combining of two thulium doped fiber lasers

We demonstrate which we believe the first investigation on mutual injection-locking and coherent combining of two thulium-doped fiber lasers. Mutual coherence between the two fiber lasers is established by means of mutual coupling through two 3 dB couplers. High combining efficiency of 99% for two fiber laser has been obtained, and the fringe contrast of the intensity pattern at the receiving plane is as high as 93%. The solution to scale to high power coherent beam combining is briefly discussed.

Effect of Coupling Phase on Mutual Injection Locking Range in Coupled Oscillator Arrays

The performance of a coupled oscillator array depends critically on the coupling network. Determination of the optimal coupling phase depends on the oscillator equivalent circuit and the location of mutual coupling between the oscillators. In this paper, the authors examine the effects of coupling phase on the mutual injection locking range. Three element coupled oscillator arrays (COAs) were mutually coupled at two different locations, with each coupling location presenting a different resonance to the coupling network, and the optimal coupling phase required to generate a linear phase shift in the range of -90deg to 90deg was determined. For each coupling location, when the coupling phase was off by 180deg , the arrays were shown to lock with a limited range and operate in a mode other than the in-phase mode.

Mutual injection-locking of two individual double-clad fibre lasers

Phase-locking and coherent beam combination of two individual double-clad fibre lasers by a novel extra-cavity mutual injection-locking method are proposed and experimentally demonstrated. Steady interference stripes with high contrast ratio (about 0.5) are observed. The output power of the phase-locked array exceeds 11 W and the power-combining efficiency is about 80%. No power-restriction optical components are utilised in the phase-locking experiment and the output power can be further up-scaled.

Mutual Injection-Locking and Coherent Combining of Two Individual Fiber Lasers

In this paper, mutual injection-locking and coherent combining are demonstrated with two individual erbium-doped fiber lasers that were coupled by two fiber splitters. Mutual injection-locking theory of two lasers is analyzed. In the free-running state, the far-field beam profile is a simple intensity superposition, as expected of two incoherent beams. Under mutual injection-locking, interference fringes with high contrast ratio are obtained, and the two fiber lasers lase at the same wavelength with a stable output power. We have found that the two fiber lasers are always in out-of-phase mode, which is consistent with theoretical analysis. Coherent beam combining by mutual injection-locking is realized without the need for length or amplitude control. This method can be easily scaled to combine more beams.

Research of Magnetron Phased Array with Mutual Injection Locking for Space Solar Power Satellite/Station

Research of Magnetron Phased Array with Mutual Injection Locking for Space Solar Power Satellite/Station

Theory of self-phase-locked optical parametric oscillators

The plane-wave dynamics of 3*omega => (2*omega, omega) subharmonic optical parametric oscillators containing a second harmonic generator of the idler wave omega is analyzed analytically by using the meanfield approximation and numerically by taking into account the field propagation inside the media. The resonant Chi(2):Chi(2) cascaded second-order nonlinearities induce a mutual injection-locking of the signal and idler waves that leads to coherent self phase-locking of the pump and subharmonic waves, freezing the phase diffusion noise. In case of signal-and-idler resonant devices, largely detuned sub-threshold states occur due to a subcritical bifurcation, broadening out the self-locking frequency range to a few cavity linewidths.