Lateral Mode Selection Research Articles

Impact of an Antiresonant Oxide Island on the Lasing of Lateral Modes in VCSELs.

Use of antiresonant structures is a proven, efficient method of improving lateral mode selectivity in VCSELs. In this paper, we analyze the impact of a low-refractive antiresonant oxide island buried in a top VCSEL mirror on the lasing conditions of lateral modes of different orders. By performing comprehensive thermal, electrical, and optical numerical analysis of the VCSEL device, we show the impact of the size and location of the oxide island on the current-crowding effect and compute threshold currents for various lateral modes. If the island is placed close to the cavity, the threshold shows strong oscillations, which for moderate island distances can be tuned to increase the side mode discrimination. We are therefore able to pinpoint the most important factors influencing mode discrimination and to identify oxide island parameters capable of providing single-lateral-mode emission.

Simulations of the optical properties of broad-area edge-emitting semiconductor lasers at 1060 nm based on the PBC laser concept

The design principles of multi-stripe edge-emitting lasers based on the photonic band crystal (PBC) laser concept are evaluated numerically. The concept is based on a waveguide with a thick quasi-periodic sequence of alternating high- and low-index layers allowing mode expansion across the whole layer sequence. Effective ways to filter out higher-order modes via control of the confinement and leakage are demonstrated as well as enhanced lateral mode selectivity of multi-stripe lasers by changing their etching profile. Thus, for proper epitaxial and lateral design PBC lasers have an enormous potential to provide high-power/brilliance single-mode radiation with broad-area output spot size and nearly circular narrow far-field pattern.

Lateral-mode selectivity in external-cavity diode lasers with residual facet reflectivity

The relatively flat lateral gain profile across a wide-strip laser diode does not allow sufficient overlap with the Gaussian fundamental mode of an external resonator to achieve saturation of the gain in the wings of the mode profile. Thus, parasitic free-running oscillation of the diode in an external-cavity laser is permitted by residual facet reflectivity of the antireflection-coated diode, and degrades the lateral-mode-selectivity of the external resonator at injection currents exceeding the threshold of the solitary diode. A relation between the maximum injection current at which the external-cavity laser will operate in a single mode and the diode's facet reflectivity is given. >

Binary-optics miniature Talbot cavities for laser beam addition

A miniature external cavity has been fabricated from a single 4.5 mm substrate for coherent beam addition of a linear AlGaAs laser array. Binary-optics elements are fabricated on the front surface for laser beam collimation and onto the back surface for lateral mode selection. Near-diffraction-limited performance has been observed with up to 80% of the far-field power contained in the central lobe.

Lateral mode selection in semiconductor injection lasers

Various methods have been used to control the lateral modes of injection lasers. We report on lateral mode selection in continuous-wave double-heterojunction lasers using the differential diffraction losses of different modes at a narrow reflector stripe on one emitting facet. Power output curves and far-field beam patterns scanned in the lateral (junction) plane are shown both before and after an antireflection coating was deposited on one facet except in a narrow stripe. The stripe defines the mode-selecting reflective region. Calculations, based on a simple model of DH injection lasers, are made by estimating the magnitude of the effect. Output powers of 12 mW from one facet were obtained.