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A coupled class‐B laser system is presented to obtain a nonlinear emitter. Its bistability was theoretically predicted, and numerically illustrated to demonstrate by a typical bistable curve diagram. The bistable system exhibits some typical nonlinear dynamic behaviours, such as hyperchaos, quasi‐period as well as coexistent scenarios, and shows a route to a single‐period away from hyperchaos. The hyperchaotic states are diagnosed to find by Lyapunov exponent. The hyperchaotic four‐scroll strange attractor was illustrated to be characterized by ergodicity, complexity, and randomness. The result has a reference value for a bistable optical device, a hyperchaotic emitter, and their applications. [ABSTRACT FROM AUTHOR]

The authors experimentally demonstrated the generation of mode‐locked pulses from all‐fibre erbium‐doped fibre laser cavity by using organic material, Alq3, as a saturable absorber (SA). The SA film was integrated into a ring fibre laser cavity to act as a mode‐locker. A mode‐locking operation was achieved in three different experiments with pulse width/repetition rate of 1.26 ps/3.36 MHz, 970 fs/3.36 MHz and 820 fs/4.9 MHz by using cavity length/optical coupler (OC) of 61.5 m/80:20 OC, 61.5 m /95:5 OC and 42 m/80:20 OC, respectively. All the experiments produced a soliton and a very stable mode‐locking operation at central wavelength of ∼1561 nm. The experiments confirmed that organic material can readily be used as SA for a mode‐locked operation in the 1.5 μm region. This demonstration might shed new insights into the potentials and techniques for developing ultrafast fibre lasers by using organic materials as SAs. [ABSTRACT FROM AUTHOR]

The stability of the central wavelength of the erbium‐doped fibre source (EDFS) is one of the most important parameters to ensure the accurate operation of navigation systems based on high‐accuracy fibre optic gyroscopes (FOGs). In this study, the method of stabilisation of the EDFS as a part of the FOG is presented. The main advantage of this method is the possibility of quick and simple matching of temperature‐compensating spectral filters by changing the pump ratio without modifying the optic scheme. The EDFS optic scheme based on the double‐pass bidirectional pumping configuration. It makes it possible to obtain the world‐class stability of the central wavelength of the EDFS as a component of different devices with the spectral selectivity and set the constant value of the optic power of the output light (OL). Also, this is the first study of the dependence of the temperature coefficient of the central wavelength on the pump ratio. The proposed method allows compensating the spectral characteristics of the FOG, achieving the OL central wavelength stability around 0.7 ppm/°C and the FOG scale factor stability around 0.73 ppm/°C. [ABSTRACT FROM AUTHOR]

Q‐switched and mode‐locked fibre lasers have been successfully demonstrated in ytterbium‐doped fibre laser cavity by taking an advantage of the optical absorption of antimony telluride (Sb2 Te3) material. The Sb2 Te3 was embedded into polyvinyl alcohol to function as a saturable absorber (SA). A Q‐switching pulses train was obtained by incorporating the SA into the laser ring cavity configured with 3 dB coupler. The Q‐switching pulse repetition rate increases from 24.4 to 55 kHz as the pump power is increased from the threshold of 75.4–96.2 mW. The maximum pulse energy of 252.6 nJ is obtained at 82.3 mW pump power. On the other hand, by changing the output coupler to 10 dB coupler, a stable self‐started mode‐locking operation was then generated at pump power range from 47.8 to 89.4 mW with a fixed repetition rate of 24.2 MHz. At 89.4 mW pump power, the maximum output power and pulse energy are obtained to be around 18.6 mW and 0.8 nJ, respectively. The authors results display that the Sb2 Te3 material could also be developed as an effective SA for both Q‐switched and mode‐locked fibre lasers. [ABSTRACT FROM AUTHOR]

Abstract: Stable and phase‐locked emission in an extended topological supermode of coupled laser arrays, based on concepts of non‐Hermitian and topological photonics, is theoretically suggested. A non‐Hermitian Su–Schrieffer–Heeger chain of coupled microring resonators is considered, and it is shown that application of a synthetic imaginary gauge field via auxiliary passive microrings leads to all supermodes of the chain, except one, to become edge states. The only extended supermode, that retains some topological protection, can stably oscillate suppressing all other non‐topological edge supermodes. Numerical simulations based on a rate equation model of the semiconductor laser arrays confirm stable anti‐phase laser emission in the extended topological supermode and the role of the synthetic gauge field to enhance laser stability. [ABSTRACT FROM AUTHOR]

Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. [ABSTRACT FROM AUTHOR]

Owing to unstable multi‐wavelength lasing, robust measurement is difficult with a fibre Bragg grating (FBG) laser sensor system that uses FBGs as laser cavity mirrors as well as sensors. A stabilising technique is essential for proper data acquisition. Here, it is demonstrated that polarisation scrambling (PS) stabilises the output of laser sensor system in combination with a spectrometer demodulation. The state of polarisation (SOP) of a fibre‐optic laser cavity is changed by a 1 MHz PS. A 5 kHz spectrometer traces the distribution of output laser wavelengths. The rapid changes in SOP make all the FBG wavelengths lase as long as necessary to determine the Bragg wavelength shifts in the sampling windows of a photo‐diode array. A laser sensor system with eight FBG sensors is used to demonstrate robust measurement and data collection under environmental perturbations. [ABSTRACT FROM AUTHOR]

The pulse repetition rate (RR) tuning and locking range (LR) as well as the pulse train timing stability of passively mode‐locked quantum‐well (QW) semiconductor lasers (SCLs) subject to single‐cavity optical self‐feedback (OFB) are investigated experimentally and by simulations. A simple and universal stochastic time‐domain model confirms the experimentally observed RR control and LR as well as timing jitter (TJ) improvement in QW SCLs subject to very long OFB cavities with lengths up to 73.1 m. In particular, the model allows predicting control potential and limits of the RR tuning, locking and TJ improvement depending on the choice of OFB delay length for time‐delay mode‐locked semiconductor laser stabilisation experiments. [ABSTRACT FROM AUTHOR]

An evaluation of the amplitude jitter and timing jitter for a regeneratively mode‐locked fibre laser via the use of the harmonic analysis approach is presented. The RF power spectrum of four harmonics derived from a 10 GHz mode‐locked pulse train was measured with high resolution. From a detailed analysis of the noise pedestal present in these harmonics, an amplitude jitter of ∼0.3% and an absolute timing jitter of ∼41 fs are obtained. [ABSTRACT FROM AUTHOR]

A microsquare dual wavelength laser has been fabricated and applied to sub‐THz emission by beating two modes. An 18 × 18 μm square AlGaInAs/InP microsquare laser combined with an optimised uni‐travelling‐carrier photodiode has demonstrated stable emission at 103.2 GHz. [ABSTRACT FROM AUTHOR]

A 10 GHz mode‐locked fibre laser has been treated to improve its stability and the quality of generated pulses. An unpumped 3 m erbium‐doped fibre (EDF) is incorporated outside the cavity at the output of the mode‐locked laser and a setup is designed so as to form the strong standing waves inside the EDF that leads to spatial hole burning effect. This reduces the phase noise of the mode‐locked laser, resulting in the timing jitter reduction from 260 to 130 fs. [ABSTRACT FROM AUTHOR]

The authors experimentally demonstrate an ultra-low repetition rate passive mode-locked fibre ring laser with a semiconductor optical amplifier works like as a gain medium and non-linear polarisation rotation. A unidirectional erbium-doped fibre amplifier provides additional gain to increase cavity power. By exploiting non-linear polarisation rotation combined with dispersion management stable 5.18 ps optical pulses with 67.2 kHz repetition rate and energy of 1.75 nJ were generated with an extinction ratio >35 dB. The central wavelength is 1557.89 nm and the optical 3-dB bandwidth 1.82 nm very appropriate for optical applications that often require high-peak-power, low repetition rate and picosecond pulses. [ABSTRACT FROM AUTHOR]

980 nm vertical‐cavity surface‐emitting lasers (VCSELs) operating error‐free at 38 Gbit/s at 85°C with record 177 fJ of dissipated heat per bit are presented. The VCSELs are particularly well suited for short, very‐short and ultra‐short‐reach interboard, chip‐to‐chip and intrachip optical interconnects, where temperature stability, bandwidth and VCSEL density and the minimisation of waste heat are critical. Error‐free operation at 40 Gbit/s at 75°C and at 42 Gbit/s at 25°C is achieved. To date, 980 nm VCSELs are the most energy‐efficient of all VCSELs at 85°C at any wavelength. [ABSTRACT FROM AUTHOR]

Distributed‐feedback ridge‐waveguide lasers emitting around 670 nm have been fabricated and experimentally characterised. Wavelength stabilisation is provided by 40th Bragg order surface gratings dry‐etched into the p‐GaAs–AlGaAs–AlGaInP layer structure. The large grating period of 4.2 µm allows the injection of the current between the grooves of the grating without sacrificing the electrical and optical properties noticeably. The 1.5 mm long devices achieve an output power of 50 mW at an injection current of 180 mA. The side mode suppression ratio is 50 dB at 150 mA. [ABSTRACT FROM AUTHOR]

Presented is a study on a single‐drive dual‐parallel Mach‐Zehnder modulator implementation as a single sideband suppressed carrier generator. High values of both extinction ratio and sidemode suppression ratio were obtained at different modulation frequencies over the C‐band. In addition, a stabilisation loop had been developed to preserve the single sideband generation over time. [ABSTRACT FROM AUTHOR]