Large Vertical-cavity Surface-emitting Lasers Research Articles

Injection locking and coupling the emitters of large VCSEL arrays via diffraction in an external cavity.

Networks of semiconductor lasers are the foundation of numerous applications and fundamental investigations in nonlinear dynamics, material processing, lighting, and information processing. However, making the usually narrowband semiconductor lasers within the network interact requires both high spectral homogeneity and a fitting coupling concept. Here, we report how we use diffractive optics in an external cavity to experimentally couple vertical-cavity surface-emitting lasers (VCSELs) in a 5×5 array. Out of the 25 lasers, we succeed to spectrally align 22, all of which we lock simultaneously to an external drive laser. Furthermore, we show the considerable coupling interactions between the lasers of the array. This way, we present the largest network of optically coupled semiconductor lasers reported so far and the first detailed characterization of such a diffractively coupled system. Due to the high homogeneity of the lasers, the strong interaction between them, and the scalability of the coupling approach, our VCSEL network is a promising platform for experimental investigations of complex systems, and it has direct applications as a photonic neural network.

Structure modifications of oxide‐confined GaInNAs VCSELs for the second‐generation optical‐fibre communication

AbstractFor the second‐generation optical‐fibre communication, lasing sources emitting stable single‐fundamental‐mode (SFM) 1.3‐μm radiation are required. Then oxide‐confined GaAs‐based GaInNAs quantum‐well (QW) vertical‐cavity surface‐emitting lasers (VCSELs) seem to be the best solution. But possibility to reach their efficient 1.3‐μm low‐threshold SFM operation is usually questionable. Therefore the comprehensive fully self‐consistent simulation VCSEL model is used to find the most promising VCSEL structure for this application. It has been concluded from our analysis, that the best performance may be reached in the VCSEL structure in which the proper detuning of the cavity mode towards longer wavelengths and the proper step‐like active‐region QW structure are simultaneously applied. Then the stable 1.3‐μm SFM operation is reached for temperatures exceeding 305 K in the relatively large VCSEL with the 12‐μm diameter activity region. Its threshold current is only somewhat higher than 6 mA at the ambient temperature of 350 K. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Evolution of high-speed long-wavelength vertical-cavity surface-emitting lasers

High-speed buried tunnel junction (BTJ) vertical-cavity surface-emitting lasers (VCSELs) covering the long-wavelength range from 1.3 µm to 1.6 µm have been developed in the last decade and achieved remarkable performance. The InP-based monolithic approach with a BTJ as a current aperture and an integrated gold heat sink, which originated at the Walter Schottky Institute, is reviewed in this review. Cutting-edge device performance like error-free operation at 25 Gb s−1 data rate, large VCSEL arrays with high output powers, widely tunable devices, or novel nano-photonic device concepts could be realized.

Performance of a prototype atomic clock based on lin‖lin coherent population trapping resonances in Rb atomic vapor

We report on the performance of the first table-top prototype atomic clock based on coherent population trapping (CPT) resonances with parallel linearly polarized optical fields (lin||lin configuration). Our apparatus uses a vertical cavity surface emitting laser (VCSEL) tuned to the D1 line of 87Rb with current modulation at the 87Rb hyperfine frequency. We demonstrate cancellation of the first-order light shift by proper choice of rf modulation power, and further improve our prototype clock stability by optimizing the parameters of the microwave lock loop. Operating in these optimal conditions, we measured a short-term fractional frequency stability (Allan deviation) 2*10^{-11} tau^{-1/2} for observation times 1s<tau< 20s. This value is limited by large VCSEL phase noise and environmental temperature fluctuation. Further improvements in frequency stability should be possible with an apparatus designed as a dedicated lin||lin CPT resonance clock with environmental impacts minimized.

Mesa-size dependence characteristics of vertical surface-emitting lasers

The vertical-cavity surface-emitting laser (VCSEL) is the most suitable light source for many optoelectronic applications because of its planar nature. The design of large VCSEL arrays requires accurate modeling of device characteristics. In this paper, we present a thermal model to analyze the dependence of VCSEL threshold current and light-output characteristics on aperture size. For both 850-nm and 980-nm VCSELs, a linear dependence of threshold current on device area is observed for oxidized aperture sizes with diameters between 5 µm and 25 µm. Good agreement between theoretical and experimental light-output characteristics is observed using a simple thermal model.

1.55-μm InGaAs/InGaAlAs MQW vertical-cavity surface-emitting lasers with InGaAlAs/InP distributed Bragg reflectors

High-performance InGaAs/InGaAlAs multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) with InGaAlAs/InP distributed Bragg reflectors are proposed for operation at the wavelength of 1.55 μm . The lasers have good heat diffusion characteristic, large index contrast in DBRs, and weak temperature sensitivity. They could be fabricated either by metal-organic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE) growth. The laser light-current characteristics indicate that a suitable reflectivity of the DBR on the light output side in a laser makes its output power increase greatly and its lasing threshold current reduce significantly, and that a small VCSEL could output the power around its maximum for the output mirror at the reflectivity varying in a broader range than a large VCSEL does.

Large area multitransverse-mode VCSELs for modal noise reduction in multimode fibre systems

The first operation is reported of large area multitransversemode vertical cavity surface emitting lasers (VCSELs) to reduce the effect of modal noise in multimode fibre systems. A BER &lt; 10−13 is measured with a 25 μm VCSEL operated at 1 Gbit/s in a multimode optical link with 10 dB of mode selective loss at 16 m. The reduction in modal noise is from a decrease in the coherence of the large VCSELs with multitransverse-mode operation.