Martin Achtenhagen

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.

Lateral current spreading in ridge waveguide laser diodes

Lateral current spreading is experimentally and theoretically investigated in ridge waveguide laser diodes having various residual guide thickness outside the ridge region. It is found that a critical residual thickness exists below which the lasers emit in a single mode with a low threshold current. Above this critical value, the threshold rises rapidly and the lasers oscillate simultaneously in the two lowest order lateral modes. This critical thickness can be used to experimentally determine an average doping level of the upper waveguide layer. This doping level permits the control of the threshold current and series resistance.

1.55-/spl mu/m optically pumped wafer-fused tunable VCSELs with 32-nm tuning range

We demonstrate widely tunable InAlGaAs-InP-AlGaAs-GaAs optically pumped vertical-cavity surface-emitting lasers operating in the 1.55-/spl mu/m waveband. The tuning range of 32 nm is achieved by applying a low tuning voltage of 4 V. Maximum single-mode output power of 2 mW with less than 1.5-dB power variation over the whole tuning range and side-mode suppression ratio in excess of 30 dB have been obtained.

Coherent kinks in high-power ridge waveguide laser diodes

Coherent coupling of lateral modes is suggested to explain the phenomena associated with beam-steering kinks, which appear in the L-I curves of many ridge waveguide lasers. The analysis that is presented explains quantitatively the previously reported experiments.

Detuning characteristics of fiber Bragg grating stabilized 980 nm pump lasers

We investigate wavelength detuning effects between ridge waveguide 980 nm pump laser-fiber Bragg grating (FBG) pairs. A design point suppressing single-mode to multi-mode switching under coherence collapse is experimentally and theoretically developed.

Spectral Properties of High-Power Distributed Bragg Reflector Lasers

In this paper, spectral data of distributed Bragg reflector lasers emitting around 974 nm and 1084 nm are presented. The devices are fabricated by a single-growth molecular beam epitaxy step, and the gratings are defined by holographic interferometry. Spectral dependencies on the grating and gain section lengths are systematically investigated in the so-called cleaved-back experiments. Experimental data for the side-mode suppression ratio, mode spacing, and group refractive index are given for devices emitting around 974 nm. In addition, the coupling efficiency between the grating and gain section is derived experimentally for devices emitting around 1084 nm.

Threshold analysis of vertical-cavity surface-emitting lasers with intracavity contacts

A numerical analysis of vertical-cavity surface-emitting lasers (VCSELs) incorporating intracavity contacts and distributed Bragg reflectors (DBRs) is presented. The model considers polarization dependent reflection at the DBRs, current spreading, and nonuniform carrier density distribution self consistently. Analytic expressions for the current spreading and the corresponding series resistance for VCSELs incorporating intracavity contacts are derived. It is shown that current spreading strongly affects the lateral gain profile, the threshold current density, the transverse mode shape and the transverse mode discrimination through the creation of intracavity optical phase and gain apertures. The series resistance and the depth of the dip in the current density distribution are used as figures-of-merit to provide guidelines for device optimization, as illustrated by means of two examples of long wavelength VCSEL designs

Design of distributed Bragg reflector structures for transverse-mode discrimination in vertical-cavity surface-emitting lasers

An angular spectrum of plane-wave representation is employed to calculate the discrimination between the fundamental and higher order transverse modes in step-index-guided vertical-cavity surface-emitting lasers. The effect of material composition and number of layer pairs in the distributed Bragg reflectors, as well as mode size and structure, are examined with the goal of optimizing the mode discrimination for better mode stability and higher single-mode power. In particular, it is shown that decreasing the width of the distributed Bragg reflector stopband, by means of controlling the material composition, improves significantly the mode discrimination.

High-Power DBR Laser Diodes Grown in a Single Epitaxial Step

Spectral and output power data of distributed Bragg reflector lasers emitting in the technologically important wavelength range from 780 nm to 1083 nm are presented. These devices are fabricated in a single molecular beam epitaxy growth step, and the gratings are defined by holographic interferometry. Spectral dependencies on the grating and gain section lengths are systematically investigated. Experimental data for the side-mode suppression ratio, mode spacing, and thermal wavelength shift are given for devices emitting in the near infrared wavelength range between 780 nm and 1083 nm.

Three-dimensional analysis of mode discrimination in vertical-cavity surface-emitting lasers

Optical mode discrimination in vertical-cavity surface-emitting lasers that contain distributed Bragg reflectors (DBRs) and a spatially limited gain medium is analyzed numerically. It is assumed that the output field is linearly polarized owing to gain selectivity. The analysis employs a three-dimensional model and an angular spectrum of plane-wave decomposition with the proper polarizations. Two types of round aperture are considered, namely, a Gaussian aperture and a ring-peak aperture that represents gain saturation. Coupled with the DBRs, the former aperture yields nearly Laguerre-Gaussian modes, whereas the latter aperture significantly distorts the mode shapes. In both cases, narrowband DBRs provide the best mode discrimination.