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Recent increased interest in spin-polarised vertical-cavity surface-emitting lasers (spin-VCSELs) as potential high-speed sources has spurred research into the analysis of their dynamics. This has often been explored by combining the spin-flip model (SFM) with numerical methods. However, numerical simulation does not readily expose key dependencies and to date there is a lack of accessible closed-form analytical results for the steady-state solutions and dynamic stability boundaries. Thus in the present contribution we address this and show that, for zero dichroism, the five rate equations of the SFM can be reduced to a set of three. These can be solved in the steady-state in terms of the intensity and polarisation of the pump (optical or electrical), and the ellipticity of the output. Additionally, a small-signal analysis leads to analytic results for the boundaries between stable and unstable operation in the plane of pump ellipticity versus pump intensity. Comparison of the results from these expressions with those from numerical bifurcation and continuation methods shows very good agreement. The accuracy of the reduced set of equations is confirmed by comparing the results with those from the full set of SFM equations. In the limiting case of very high birefringence, as would be required for a potential THz source, a simple algebraic relation is derived for the spin relaxation rate in terms of other parameters. Hence we find that the range of spin relaxation rates to achieve THz oscillations is very limited. The relative simplicity of the present approach thus offers a rapid, intuitive and convenient route to study the dynamics of spin-VCSELs. [ABSTRACT FROM AUTHOR]

A newly-developed normal mode model of laser dynamics in a generalised array of waveguides is applied to extend the spin-flip model (SFM) to pairs of evanescently-coupled spin-VCSELS. The effect of high birefringence is explored, revealing new dynamics and regions of bistability. It is shown that optical switching of the polarisation states of the lasers may be controlled through the optical pump and that, under certain conditions, the polarisation of one laser may be switched by controlling the intensity and polarisation in the other. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the relative intensity noise of quantum dot lasers through a rate equation model taking into account both the spontaneous emission and carrier contributions. In particular, results show that the carrier noise originating from the ground and excited states significantly enhances the relative intensity noise of the laser, while that from the carrier reservoir does not. Simulations also point out that a large energy interval between the quantum confined levels is more suitable for low-intensity noise operation due to the reduced contribution from the carrier noise in the excited state. Finally, the carrier noise is found to have little impact on the frequency noise, thus being negligible for the investigation of the spectral linewidth. Overall, this paper is useful for designing low-noise quantum dot oscillators for high-speed communications, optical frequency combs, and radar applications. [ABSTRACT FROM AUTHOR]

We investigate the influences of ridge-waveguide shape and width on performances of InP-based coupled ridge waveguide laser arrays emitting at $2.1~\mu \text{m}$. Four devices with different shapes and widths of ridge elements are fabricated. The trapezoid ridges reduce the optical losses at regions between ridge elements in the trapezoid devices, thus enhances the optical coupling between ridge elements and lead to larger coherent output powers compared with the rectangular ones. Meanwhile, narrower ridges with the same shape give a stronger optical confinement to the lateral modes in every single ridge and improve the overall modal and far-field characteristics of the device. The results show that the trapezoid and narrower ridges can lead to a comprehensive improvement in the performances of the coupled ridge waveguide laser arrays emitting at $2.1~\mu \text{m}$. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the implementation of a 16-element array of heterodyning fiber grating laser sensors cascaded in a single optical fiber. Each laser consists of a Bragg grating pair inscribed in a short section of Er-doped fiber. The laser offers a RF-domain beat signal between orthogonally polarization modes and can act as a photonic sensor for the measurement of external perturbations, by monitoring the beat frequency. The laser sensors are wavelength multiplexed by inscribing fiber gratings with different pitches, and frequency multiplexed in RF domain by controlling the intracavity birefringence via CO2 laser side irradiation. The pump power depletion as a result of mode mismatch between the active and passive fibers is a main limitation factor for the multiplexing scale. We can multiplex ten laser sensors at most with a single pump laser with an output power of 130 mW and six more sensors can be multiplexed with an additional pump laser at the other end. The measurement ability of an individual laser sensor can be affected when multiplexed in array, in terms of abrupt frequency jumps and the raised noise level. As a result, the force resolution at 1 kHz is changed from 3 to 6 nN/√Hz, and the minimal detectable static force is changed from 68 to 120 μN. This is attributed to the off-resonance grating couplings and the reflections at the splicing points. This effect can be weakened by selecting mode-matching fibers and optimizing grating profiles, or simply using additional optical isolators. [ABSTRACT FROM PUBLISHER]

A couple of amplifying arrays for the power scaling of the fiber lasers under diverse pumping modes are studied. The multifiber series distributed side-pumping arrangement and the cascade amplifier chains in the form of the end-pumped master oscillator fiber power amplifier (MOFPA) scheme are investigated accordingly. Those are numerically modeled based on the propagation rate equations associated with stimulated Brillouin scattering (SBS) as well as the consideration of coupling and splicing losses for large mode area fibers. The continuous wave double-clad Yb:silica fiber laser amplifier is analyzed in various amplifying stages for several cavity lengths at forward pumping regime. Despite the distributed mode exhibits a desirable beam quality, however, it suffers a low SBS threshold. On the other hand, high output power is achieved in the MOFPA configuration far from the onset of SBS. [ABSTRACT FROM AUTHOR]

Multiwavelength laser arrays (MWLAs) fabricated by a novel upper separate confinement heterostructure (SCH) layer selective area growth (SAG) technique are studied in comparison with laser arrays fabricated by the conventional multiquantum well (MQW) SAG technique. For MWLAs by the MQW SAG, the range of the laser emission of the array is smaller than the span of the PL wavelengths of the MQW active layers. In addition, the material quality of the MQW layer degrades greatly as the width of the SAG strips is increased. Thus, the MWLAs fabricated by the method have scattered L-I characters and large fluctuation of wavelength spacings. In contrast, the MWLAs fabricated by the novel SAG method have much better wavelength spacing uniformity than those by MQW SAG, which is comparable to or better than the MWLAs fabricated by E-beam direct writing. Furthermore, the upper SCH layer SAG technique is suitable for the fabrication of MWLAs with wavelength interval, which is a challenge even for E-beam technique. In the SCH layer SAG, the MQW layer is untouched, and the same is true for all the laser elements in an array. The metal organic vapor phase epitaxies ability to control the material properties with high accuracy can be fully utilized for the fabrication of MWLAs. Combined with partially gain-coupled distributed feedback structures, the technique is promising for the fabrication of low-cost, high-quality MWLAs. [ABSTRACT FROM PUBLISHER]

Strong optical and electrical interactions can occur between optoelectronic devices when the element-size and inter-element spacing are significantly reduced. In this paper, we study these interactions in the closely packed, positive index-guided sub-micrometer-ridge laser arrays, with element size of ∼0.8 μm, operating at a wavelength of ∼4.55 μm. From simulations, the structure is found to favor the in-phase lasing mode, which produces a single-main-lobe far-field profile. Next, this property is experimentally demonstrated in the fabricated device, which exhibits a near-diffraction-limited (beamwidth of 1.3 times diffraction-limit) single-main-lobe far-field operating at 2.6 times the threshold current. [ABSTRACT FROM AUTHOR]

We study the lasing eigen-modes and dynamics of circular array of coupled lasers in a rotating framework for ultrasensitive integrated optical rotation sensing applications. The dependence of the mode and frequency splitting on the array parameters and pumping level is studied in details. The impact of structure variations and disorder such as variations of the resonance wavelength of the individual cavities and the inter-cavity coupling is studied and found to generate a ldquodead-zonerdquo which limits the sensitivity of the sensor. [ABSTRACT FROM PUBLISHER]

Semiconductor lasers offer significant operational advantages due to their compactness and high electrical-optical conversion efficiency. The major drawback in considering semiconductor lasers for many applications is the relatively small emission power that can be obtained from a single semiconductor laser. Synchronization of laser arrays provides a unique solution to this limitation. In this paper, we describe our recent research on the synchronization of high-power broad-area semiconductor lasers and laser arrays. We demonstrate experimental results on 1) simultaneous injection locking of multiple broad-area lasers to achieve single longitudinal/transverse mode beams and 2) synchronization and coherent beam combination of an integrated 19 broad-area laser array based on a scalable external cavity. A number of issues in the synchronization of broad-area lasers have been addressed in this paper. These include the effects of laser coupling on the array synchronization performance and the gigahertz complementary intensity oscillations occurring at different transverse modes of broad-area lasers subject to the optical injection. [ABSTRACT FROM PUBLISHER]

An index-guided zinc oxide random laser array was designed and fabricated to achieve spatial overlapping of random spectral modes between the adjacent random cavities. Hence, the number of lasing spectral modes of the laser array can be limited by the phenomenon of spectral repulsion. In addition, the total spectrally coherent emission power can be enhanced by increasing the number of random cavities. [ABSTRACT FROM PUBLISHER]