V. Iakovlev

1.5-mW single-mode operation of wafer-fused 1550-nm VCSELs

We demonstrate 1.5-/spl mu/m waveband wafer-fused InGaAlAs-InP-AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting high single-mode power of 1.5 mW at room temperature with sidemode suppression ratio of over 30 dB and a full-width at half-maximum far field angle of 9/spl deg/. These devices have thermal resistance value below 1.5 K/mW and are emitting 0.2 mW at 70/spl deg/C. VCSELs with a wavelength span of 40-nm emission are produced from the same active cavity material, which shows the potential of realizing multiple-wavelength VCSEL arrays.

High-performance single-mode VCSELs in the 1310-nm waveband

High-performance vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1310-nm waveband are fabricated by bonding AlGaAs-GaAs distributed Bragg reflectors on both sides of a InP-based cavity. A 2-in wafer bonding process is optimized to produce very good on-wafer device parameter uniformity. Carrier injection is implemented via double intracavity contact layers and a tunnel junction. A 1.2-mW single-mode output power is obtained in the temperature range of 20/spl deg/C-80/spl deg/C. Modulation capability at 3.2 Gb/s is demonstrated up to 70/spl deg/C. Overall VCSEL performance complies with the requirements of the 10 GBASE-LX4 IEEE.802.3ae standard, which opens the way for novel applications of VCSELs emitting in the 1310-nm band.

Cavity Mode—Gain Peak Tradeoff for 1320-nm Wafer-Fused VCSELs With 3-mW Single-Mode Emission Power and 10-Gb/s Modulation Speed Up to 70

Room-temperature cavity mode red-shift of about 45nm from the photoluminescence peak is found to be optimal for tradeoff between high modulation bandwidth and good high-temperature performance for InAlGaAs(InP)-AlGaAs fused vertical-cavity surface-emitting lasers (VCSELs) employing tunnel junction carrier injection. Single-mode output power up to 5.4 and 3.1 mW, at 25 degC and 75 degC, respectively, and open eye diagrams exhibiting fall time values close to 40 ps at 10-Gb/s modulation up to at least 70 degC have been obtained for such VCSELs emitting at 1320-nm wavelength

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A widely-tunable single-mode 1.3 μm vertical-cavity surface-emitting laser structure incorporating a microelectromechanical system-tunable high-index-contrast subwavelength grating (HCG) mirror is suggested and numerically investigated. A linear tuning range of 100 nm and a wavelength tuning efficiency of 0.203 are predicted. The large tuning range and efficiency are attributed to the incorporation of the tuning air gap as part of the optical cavity and to the use of a short cavity structure. The short cavity length can be achieved by employing a HCG design of which the reflection mechanism does not rely on resonant coupling. The absence of resonance coupling leads to a 0.59 λ-thick penetration depth of the HCG and enables to use a 0.25 λ-thick tuning air gap underneath the HCG. This considerably reduces the effective cavity length, leading to larger tuning range and efficiency. The basic properties of this new structure are analyzed, and shown to be explained by analytical expressions that are derived in the paper. In this context, the penetration depth of the HCG is introduced and shown to be an important characteristic length scale. Throughout the tuning wavelength range, strong single mode operation was maintained and uniform output power is expected.

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A new generation of 10 Gb/s wafer fused VCSELs show high single mode output in excess of 2 mW at 80°C (6 mW at 20°C) in the 1310 nm band and 1.5 mW at 80°C (4 mW at 20°C) in the 1550 nm band. Error free transmission over 10 km of standard single mode fiber was performed with less than 1 dB penalty.

Broadband MEMS-Tunable High-Index-Contrast Subwavelength Grating Long-Wavelength VCSEL

We demonstrate the operation of bottom-emitting vertical cavity surface-emitting lasers (VCSELs) with linear mode polarization which is controlled in an arbitrary orientation by the use of patterned metallic mirrors on top of the VCSEL surface. The top mirror is made in the shape of a 200 nm pitch grating, composed of alternating high reflectivity (Au) and low reflectivity (Cr) metal lines, whose orientation determines the polarization of the laser mode. The gratings were fabricated by high-resolution (<50 nm) electron-beam lithography and lift-off technique, and were aligned with the other parts of the VCSEL structure (top electrode, ion-implanted zone) fabricated by conventional photolithography. Various types of mirror shapes and sizes were fabricated, including square and circular grating envelopes, as well as circular mirrors with an average (radial) Gaussian reflectivity.

10 Gbps VCSELs with High Single Mode Output in 1310nm and 1550 nm Wavelength Bands

1300-nm, 1550-nm, and 1480-nm wavelength, optically pumped VECSELs based on wafer-fused InAlGaAs/InP-AlGaAs/GaAs gain mirrors with intracavity diamond heat spreaders are described. These devices demonstrate very low thermal impedance of 4 K/W. Maximum CW output of devices with 5 groups of quantum wells shows CW output power of 2.7 W from 180  μm apertures in both the 1300-nm and the 1550-nm bands. Devices with 3 groups of quantum wells emitting at 1480 nm and with the same aperture size show CW output of 4.8 W. These VECSELs emit a high-quality beam with 𝑀 2 beam parameter below 1.6 allowing reaching a coupling efficiency as high as 70% into a single-mode fiber. Maximum value of output power of 6.6 W was reached for 1300 nm wavelength devices with 290  μm aperture size. Based on these VECSELs, second harmonic emission at 650 nm wavelength with a record output of 3 W and Raman fiber lasers with 0.5 W emission at 1600 nm have been demonstrated.

Vertical Cavity Surface Emitting Lasers Incorporating Structured Mirrors Patterned by Electron Beam Lithography

Self-ordered, strained InGaAs/GaAs quantum structures are grown on V-grooved GaAs substrates. The lateral patterning of these nonplanar heterostructures allows the growth of defect-free strained structures with thickness exceeding that achieved with planar epitaxy. Indium segregation at the bottom of the groove results in the formation of a vertical InGaAs quantum-well structure with In-enriched composition. We studied in detail the influence of nominal thickness and In content on the photoluminescence peak energy of these quantum wires. Room-temperature emission at 1.16 μm with a relatively narrow linewidth (30–35 meV) is achieved as a demonstration of the potential of this approach for fabricating long-wavelength semiconductor light sources on GaAs substrates.

Wafer-Fused Optically Pumped VECSELs Emitting in the 1310-nm and 1550-nm Wavebands

We report the fabrication and the performance of phase-locked VCSEL arrays emitting near 1310 nm wavelength. The arrays were fabricated using double wafer fusion by patterning a tunnel junction layer, which serves to define the individual single mode array elements. Phase-locking in both one-dimensional and two-dimensional array configurations was confirmed by means of far field and spectral measurements as well as theoretical modeling. CW output powers of more than 12 mW were achieved.

Effect of indium segregation on optical properties of V-groove InGaAs/GaAs strained quantum wires

Direct modulation at >25 Gbps is achieved with 1310 nm wavelength wafer fused VCSELs by adjusting the strain in the quantum well active region and the cavity photon lifetime. 25 + Gbps large signal modulation with 10-12 BER at 1310 nm across 10 km of standard single mode fiber is demonstrated.