Long-wavelength VCSELs Research Articles

AMand RIN of a Long-Wavelength Tunable MEMS VCSEL

AMand RIN of a Long-Wavelength Tunable MEMS VCSEL

Low-temperature performance of InP-based long-wavelength VCSELs

We have studied, for the first time, the parameters of long-wavelength InP-based buried tunnel junction (BTJ) VCSELs with substrate temperature varied in the range between 150 and 330 K. The BTJ-VCSELs with threshold currents <1 mA were designed by VERTILAS (Germany) to operate near 1512 nm and 1577 nm at room temperature (models VL-1512 and VL-1577, respectively). Reducing the substrate temperature of the lasers from room temperature to 150 K resulted in more than a fourfold increase of the threshold injection current accompanied with threefold and twofold increases in output power and slope efficiency, respectively. We have observed continuous single-mode tuning over intervals up to ∼20 nm (VL-1512) and ∼22 nm (VL-1577) at constant injection currents and substrate temperatures varied in a 180 K range. The emission wavelength was found to shift linearly with temperature with rates of 0.11 nm/K and 0.12 nm/K for lasers VL-1512 and VL-1577, respectively. The single-mode laser output reached ∼3 mW for both lasers cooled down to 173 K. Gas sensors based on BTJ-VCSELs can be temperature tuned over wide spectral intervals using either a cooler or a low ambient temperature to control laser substrate temperature. Ultra-sensitive gas concentration measurements under low ambient temperatures may include chemical analysis of the lower earth stratosphere and of the martian atmosphere.

High-Speed Subcarrier Based on High-Resistivity Silicon for Long-Wavelength VCSEL Array

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose a chip-to-chip optical interconnection using a silicon (Si) subcarrier integrated with a long-wavelength vertical-cavity surface-emitting laser (LW-VCSEL) array. As the basic study of that, we examined the microwave and optical characteristics of the Si subcarrier. Finally, a demonstrator that mounted the four channels and 1550-nm LW-VCSEL array on the subcarrier has been shown with no kink L-I curves and with clear 2.5-Gb/s eye diagrams. </para>

Analysis of VCSEL distributed Bragg reflectors by the Floquet-Bloch theory

In this paper, the Floquet-Bloch formalism is applied to the investigation of distributed Bragg reflectors in vertical cavity surface emitting lasers. A number of comparisons with other largely used methods are presented. Performance predictions for long-wavelength VCSELs with a GaInAsP active region are derived, showing the accuracy of our approach.

Frequency tuning of long-wavelength VCSELs

Tuning properties of long-wavelength VCSELs have been studied experimentally, for the first time to our knowledge. Injection current and temperature tuning rates of two VCSELs operating near 1512 and 1577 nm have been measured using a Fabry–Perot etalon with free spectral range 0.056 cm −1. A 100-Hz saw-tooth modulation with depths of modulation of ∼10% or less was superimposed on a direct injection current (dc bias) to tune lasers in narrow spectral intervals (0.3–1.2 cm −1) around a central frequency set by the dc bias. The lasers have been found to be capable of being tuned faster at higher levels of dc bias. The enhancement factors were up to ∼2 and ∼3 for the 1512- and 1577-nm lasers, respectively, as compared with their tuning rates measured at the levels of the dc bias close to the threshold of lasing. A linear dependence between injection current tuning rates and the levels of dc bias has been observed. Temperature tuning coefficients have been proved to be independent of the laser heat sink temperature and of the dc bias. Frequency tuning curves were approximated with a second-order polynomial. The frequencies of more than 40 absorption lines of CO, CO 2, H 2O and NH 3 known from spectral databases were compared with the calculated frequencies. The accuracy of the approximation was found to be within 0.2 cm −1 for spectral intervals up to 38 cm −1. The dependence of current tuning rates of the VCSELs on dc bias was shown to be taken into account for accurate analysis of absorption line profiles. The results obtained can be used for precise spectroscopic measurements with long-wavelength VCSELs.

Long-wavelength InAlGaAs VCSELs with Al2O3 embedded current-confinement apertures

Long-wavelength InAlGaAs VCSELs with Al/sub 2/O/sub 3/ embedded current-confinement structures are reported. Using atomic layer deposition, the current confinement structures are fabricated by depositing Al/sub 2/O/sub 3/ on airgap surfaces of undercut apertures, which are formed by laterally etching the active region. 1.57 /spl mu/m VCSELs showing an output power of over 1 mW and direct modulation characteristics at 4 Gbit/s are reported using these current-confinement apertures.

High singlemode output power from long-wavelength VCSELs using curved micro-mirrors for mode control

Concave curved micro-mirrors enable record high 2.8 mW singlemode emission from long-wavelength vertical-cavity surface-emitting lasers with large current apertures up to 12 µm. Higher-order transverse modes are suppressed by more than 48 dB, while polarisation control by a dominating mirror asymmetry is demonstrated after coupling 1.9 mW into a singlemode fibre.

A long-wavelength MEMS tunable VCSEL incorporating a tunnel junction

In this letter, we describe the performance of a microelectromechanical system tunable vertical-cavity surface-emitting laser operating at 1550 nm and incorporating a tunnel junction for improved current injection and reduced optical loss. These lasers exhibit single-mode powers greater than 0.28 mW over 10 nm of tuning. Peak single-mode powers are greater than 0.8 mW and minimum threshold currents are less than 1 mA.

Thermal Conductivity Analysis and Device Performance of 1.55 ?m InGaAlAs/InP Buried Tunnel Junction VCSELs

The thermal resistance of InGaAlAs/InP long-wavelength VCSELs with buried tunnel junctions is investigated by means of a heat flow finite element analysis. Because of the low thermal conductivity of InP based compound layers, a significant improvement is obtained for a top-down mounted structure with a hybrid dielectric-metal back mirror and an InP heat spreading layer. Experimental results for such lasers show cw operation up to 75 °C with a maximum power exceeding 2 mW at room temperature for 17 μm diameter. The temperature behavior of the threshold current indicates a substantial improvement for laser operation at values even far beyond room temperature by adjusting cavity mode and spectral gain.

Long-wavelength VCSELs advance in Asia

long-wavelength VCSELs advance in Asia

MOCVD InP/AlGaInAs distributed Bragg reflector for 1.55 [micro sign]m VCSELs

A new MOCVD InP/AlGaInAs distributed Bragg reflector for long-wavelength VCSELs is presented. The InP/AlGaInAs system presents a high potential for 1.55 /spl mu/m VCSELs owing to the combination of its high refractive index contrast (/spl Delta/n/spl sime/0.34) and its low conduction band discontinuity (/spl Delta/Ec/spl sime/150 meV). InP/AlGaInAs mirrors and one half VCSEL (bottom mirror and /spl lambda/ cavity) have been fabricated for the first time using AlGaInAs transparent to 1.55 /spl mu/m.

50 km error-free 10 Gbit/s WDM transmission using directly modulated long-wavelength VCSELs

The first long-wavelength VCSEL based WDM link over a distance of 50 km is demonstrated. Error-free transmission at a speed of 10 Gbit/s is achieved over 50 km of standard singlemode fibre. The link comprises four individually modulated L-band VCSELs each transmitting at a speed of 2.5 Gbit/s. No crosstalk is observed between channels. Our system is suitable for deployment in metro networks where low cost combined with high data rates are paramount.

Reactive ion etching of InAlAs and InAlGaAs with BCl3/Cl2/CH4/H2 mixtures for long-wavelength VCSELs

A novel reactive ion etching process for the InAlGaAs material system lattice matched to InP using BCl3/Cl2/CH4/H2 mixtures is presented. The etching speed is ~ 700 Å/min, which remains approximately the same for all InAlGaAs compositions. The smoothness and the anisotropy of the etched wall appear to be very good. The etching characteristics of InP and mask materials are also reported.

Room-temperature, CW operation of lattice-matched long-wavelength VCSELs

Continuous-wave operation of vertical-cavity surface-emitting lasers lattice matched to InP and grown with one epitaxial step is presented. These lasers combine highly reflective AlAsSb/AlGaAsSb mirrors with a double-intracavity contacted structure based on thick InP contact layers.

First demonstration of highly reflective and highly polarization selective diffraction gratings (GIRO-gratings) for long-wavelength VCSELs

We present experimental results on surface relief gratings in GaAs and InP with high reflectivity (>85%) and polarization selectivity to normal incidence from the semiconductor side. The potential for polarization stabilization with a reduced mirror complexity for long-wavelength VCSELs is discussed.