Polarization stabilization in vertical-cavity surface-emitting lasers through asymmetric current injection

We present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting lasers (VCSELs) stabilizes the polarization of the emitted light. Anisotropies in the gain and loss mechanisms introduced by asymmetric current injection are considered to explain this effect. The design scheme opens perspectives to obtain actual polarization control in VCSEL

Hole transport effects in p-Ge lasers

Applied Science

Current crowding in oxide-confined intracavity-contacted VCSELs

An important problem for intracavity-contacted oxide-confined Vertical-Cavity Surface-Emitting Lasers (ICOC-VCSELs) is current crowding at the inner edges of the oxide current constrictions, which introduces extra losses and leads to excitation of unwanted higher-order transverse modes. We have proposed novel ’asymmetric’ ICOC-VCSELs, where the contact metallisations are restricted to opposite mesa sides, for more homogeneous current injection and polarisation control. Here, results of simple 2D drift-diffusion calculations are presented for symmetric and asymmetric ICOC-VCSELs. Current crowding in our ’asymmetric’ devices is reduced, but depends on the design of the layer structure

High-Q BAW resonator on Pt/Ta2O5/SiO2 based reflector stack

This paper discusses the design and optimization of high-Q Bulk-Acoustic-Wave resonators using a Pt/Ta2O5/SiO2 reflector stack. It can be shown that by properly designing the reflector stack and boundary conditions, large performance improvements can be realized. In this paper the characterization and design of the reflector stack is described and its results are presented

High-resolution study of composite cavity effects for p-Ge lasers

The temporal dynamics, spectrum, and gain of the far-infrared p-Ge laser for composite cavities consisting of an active crystal and passive transparent elements have been studied with high temporal and spectral resolution. Results are relevant to improving the performance of mode-locked or tunable p-Ge lasers using intracavity modulators or wavelength selectors, respectively. It is shown that an interface between the active p-Ge crystal and a passive intracavity spacer causes partial frequency selection of the laser modes, characterized by a modulation of their relative intensities. Nevertheless, the longitudinal mode frequencies are determined by the entire optical length of the cavity and not by resonance frequencies of intracavity sub-components. Operation of the p-Ge laser with multiple interfaces between Ge, Si, and semi-insulating GaAs elements, or a gap, is demonstrated as a first step toward a p-Ge laser with an external quasioptical cavity and distributed active medi

A tunable-MMI-coupler-based wavelength adjustable laser

This paper introduces a novel integrated widely tunable laser, the tunable multimode interference (T-MMI) laser, with as tunable component an MMI coupler with a wavelength adjustable transmission spectrum. Experiments demonstrate up to 150 nm of tuning range for the T-MMI component and operation of a widely tunable T-MMI laser is demonstrated over a wavelength range of 38 nm

Processing of intra-cavity VCSELs in structures with doped DBRs

Standard GaAs-based VCSEL structures with doped DBR mirrors are processed into intra-cavity contacted VCSELs with asymmetric current injection to investigate their polarisation behaviour. The processing requires reflectometry measurements during etching of the first and second mesa. The p- and n-contacts are deposited on an AlGaAs layer with the lowest Al-content of the upper and bottom DBR respectively. A dichromate solution was used to etch selectively the higher Al-content layer of the DBRs before depositing the contacts

Controlled polarisation switching in VCSELs by means of asymmetric current injection

We have investigated the potential of asymmetric current injection for polarisation switching in GaAs-based intra-cavity contacted vertical cavity surface emitting lasers using two sets of p- and n-type contacts per device. When using the contacts set along the [110 ] axis, the polarisation was set along [011] while using the contacts along [011] the polarisation switches from the direction along [011] to a direction making an angle of 25 to 90° towards [011]