Coupled Vertical Cavity Research Articles

Low Divergence Coherently Coupled Vertical Cavity Surface Emitting Laser Ring Arrays

We report the theory and experimental verification of a method to reduce beam divergence from coherently-coupled ring arrays of photonic crystal vertical cavity surface emitting lasers (VCSELs). The photonic crystal etched into the top distributed Bragg reflector defines the optically coupled array elements, each of which has independent current injection and thus independent gain. Using a 2-dimensional complex waveguide model we simulate the supermodes of a 6-element ring array of VCSELs. The influence of the photonic crystal, free carrier loss, laser gain, and carrier-induced index suppression arising from the spatially defined gain regions are included in our analysis. Our simulations show the latter enables preferred anti-guided supermodes with reduced beam divergence. Optical characterization of the spectral and beam characteristics of 6-ring photonic crystal implanted VCSEL arrays shows that when the arrays are current-tuned to quasi-single mode operation, we find the beam divergence angle approaches 2° consistent with our simulations. This method of reduced beam divergence may have advantages for high-brightness applications.

Mode Engineering in Linear Coherently Coupled Vertical-Cavity Surface-Emitting Laser Arrays

The supermode tuning of coherent 3 × 1 vertical-cavity surface-emitting laser arrays are characterized and simulated. The array elements are resonantly tuned to achieve coherent operation using selective current injection. Depending on the electrical bias, multiple coherent supermodes are observed above threshold. An effective index model is developed to account for the variable current injection and to simulate the supermodes of the linear array. Agreement between experimental near-field and far-field coherent modes and our model simulations are found both at and above lasing threshold.

垂直腔面发射激光器相干耦合阵列二维光束偏转

垂直腔面发射激光器相干耦合阵列二维光束偏转

高光束质量垂直腔面发射激光器同相耦合阵列

高光束质量垂直腔面发射激光器同相耦合阵列

Anticipation in the Polarization Chaos Synchronization of Uni-Directionally Coupled Vertical-Cavity Surface-Emitting Lasers With Polarization-Preserved Optical Injection

We investigate numerically the anticipated synchronization in the two uni-directionally coupled vertical-cavity surface-emitting lasers (VCSELs) as master and slave configuration. The master VCSEL is rendered chaotic state by an isotropic optical feedback and master’s chaotic output uni-directionally injected to a slave VCSEL under polarization-preserved optical injection. The synchronization quality and lag time between lasers are obtained by performing cross-correlation analysis. When the laser’s parameters are identical, a regime of anticipatory synchronization is found in both of the linearly polarized mode dynamics of the master and slave lasers, if the feedback delay time is greater than the coupling time. Anticipation is robust to a small variation in injection rate, frequency detuning, and laser’s internal parameter mismatches, but the synchronization is not complete. Injection-locking synchronization regime occurs between master and slave lasers for higher injection, positive detuning, and larger mismatch in the internal parameters. We show the mapping of synchronization quality, sustenance of anticipatory synchronization and switching of regimes in the injection rate and parameter mismatch plane. The anticipation maintained even for higher injection rates if mismatch is introduced in certain internal parameters.

单端反馈互耦合垂直腔面发射激光器混沌输出的时延特征和带宽分析

单端反馈互耦合垂直腔面发射激光器混沌输出的时延特征和带宽分析

Bottom-Emitting Coherently Coupled Vertical Cavity Laser Arrays

Two-dimensional coherently coupled photonic crystal ion-implanted bottom emitting vertical cavity surface emitting laser arrays are demonstrated. Subthreshold luminescence shows uniform current injection below threshold, benefiting from the improved contact alignment compared with the top emitting arrays. In-phase operation has been achieved in $2\times 2$ and $3\times 3$ arrays at lasing threshold. A remaining challenge is achieving uniform current distribution above lasing threshold for larger arrays due to the variation of series resistance through each of the elements of the arrays.

Flat Broadband Chaos in Mutually Coupled Vertical-Cavity Surface-Emitting Lasers

The flatness of chaos generated by mutually coupled vertical-cavity surface-emitting lasers (VCSELs) has been investigated experimentally in two configurations. Power variation between dc and the bandwidth frequency and flat bandwidth are used to quantitatively study the flatness of chaos. The power spectrum of chaos from a single VCSEL in both configurations is not flat due to a peak at relaxation oscillation frequency. This uneven nature will affect the application of chaos in random number generation. The experimental results show that the power spectra of chaos can easily be flattened by combining two uneven chaos. Flat bandwidth of the combined output can be 15 times higher than that of chaos from a single VCSEL at the optimum frequency detuning. The mechanism for this flattening is attributed to the frequency beating.

Modal Properties of 2-D Implant-Defined Coherently Coupled Vertical-Cavity Surface-Emitting Laser Array

We have investigated the dependence of modal behavior on the structures of 2-D implant-defined coherently coupled vertical cavity surface-emitting laser (VCSEL) arrays experimentally and theoretically. 2-D VCSEL arrays with different interelement spacing have been designed and fabricated. Through the experimental analysis of near-field and far-field distribution, in-phase and out-of-phase mode are obtained from the arrays, depending on the interelement spacing. Considering the effect of thermal and carrier injection, the refractive index distribution of the arrays under operation is calculated. Then, FDTD Solutions software is employed to calculate the near-field distributions of the arrays through establishing a simplified refractive index model. The simulation results agree well with the experiments. Meanwhile, according to the phase characteristics of in-phase and out-of-phase mode, as observed from the near-field profiles, the far-field distributions are calculated, in an excellent agreement with the experiments.

Conceal Time-Delay Signature of Mutually Coupled Vertical-Cavity Surface-Emitting Lasers by Variable Polarization Optical Injection

In this letter, we quantitatively investigate the time-delay (TD) signature of chaotic outputs generated by mutually coupled vertical-cavity surface-emitting lasers (VCSELs) with variable polarization optical injection (VPOI). The research is performed using a novel estimator, which calculates the peak-to-mean ratio on the basis of the autocorrelation function (ACF). It is shown that the TD signature of mutually coupled VCSELs with VPOI at intermediate polarizer angles can be better concealed than that of mutually coupled VCSELs with conventional polarization-selected optical injection. The effects of bias current and injection delay are also taken into account. The system is further discussed by applying a recent approach that computes the ACF from a phase of chaotic outputs.

Electronically Controlled Two-Dimensional Steering of In-Phase Coherently Coupled Vertical-Cavity Laser Arrays

Photonic crystal vertical-cavity surface-emitting laser arrays can be designed to lase only in the in-phase array supermode. By electronically addressing the array elements independently, the relative phases between the emission from each element can be altered. The shift in relative phase results in the angular deflection of the central peak of the in-phase array supermode. We demonstrate highly controllable steering of a coherent laser beam produced by a 2 2 array of emitters.

"Anti" up the aperture

Coupled vertical cavity surface-emitting laser (VCSEL) arrays are an attractive means to increase the coherent output power of VCSELs. Single-mode VCSELs, with output powers greater than 10 mW, would be useful as telecommunication transmitters /spl lambda/=1.3-1.55 μm) or sources for optical interconnects. Commercially available single-mode VCSELs, even at shorter wavelengths /spl lambda/=0.85 μm), are generally limited to a few milliwatts of output power. The conventional VCSEL structure incorporates a built-in positive-index waveguide, designed to support a single fundamental mode. Promising results in the 3-5 mW range (/spl lambda/=0.85 μm) have been obtained from wet-oxidized, positive-index-guided VCSELs with small emission apertures (less than 3.5 μm-dia). The small aperture size leads to a high electrical resistance and high current density, which can impact device reliability. By contrast, antiguided VCSEL structures have shown promise for achieving larger aperture single-mode operation. To obtain high single-mode powers with a larger emitting aperture, the use of a negative-index guide (antiguide) is beneficial. This paper discusses antiguided structures and some of their advantages when incorporated in 2-D VCSEL array structures.