"Anti" up the aperture

Abstract

C oupled vertical cavity surface-emitting laser (VCSEL) arrays are an attractive means to increase the coherent output power of VCSELs. Single-mode VCSELs, with output powers greater than 10 mW, would be useful as telecommunication transmitters (λ=1.3-1.55 µm) or sources for optical interconnects. Commercially available single-mode VCSELs, even at shorter wavelengths (λ=0.85 µm), are generally limited to a few milliwatts of output power. The conventional VCSEL structure incorporates a built-in positive-index waveguide, designed to support a single fundamental mode. Promising results in the 3-5 mW range (λ=0.85 µm) have been obtained from wet-oxidized, positive-index-guided VCSELs [1], [2] with small emission apertures (less than 3.5 µm-dia). The small aperture size leads to a high electrical resistance and high current density, which can impact device reliability.A larger emitting aperture is essential to reduce thermal rollover and achieve higher output powers with reliable operation. However, poor intermodal discrimination, gain-spatial-hole burning, and thermally induced self-focusing prevent single-mode outputs from larger aperture devices. Furthermore, to minimize nonlinear above-threshold effects, a relatively large built-in index step is desirable for mode stability in active devices. Unfortunately, positive-index-guided structures posses an inherent tradeoff between aperture size and index step, due to the modal cutoff conditions for single-mode operation.By contrast, antiguided VCSEL structures have shown promise for achieving larger aperture single-mode operation. To obtain high single-mode powers with a larger emitting aperture, the use of a negative-index guide (antiguide) is beneficial.

Single-Mode VCSELs

“…4.2) singlemode emission can only be achieved with a small aperture and a small index step. By contrast, with a negative index guide (antiguide), where the effective index of the core is smaller than that of the cladding, single-mode emission can be achieved from a larger aperture with a larger index step since such waveguides provide strong higher-order mode discrimination due to transverse radiation losses [66]. The larger index step also provides for mode stability against thermal and carrier-induced index variations.…”

Paraxial Hamiltonian for photons in two-dimensional photonic crystal microstructures

“…(a) Arrays of coupled index-guided microcavities (e.g., etched VCSEL arrays 53 ) or parallel waveguides (like in the cladding region of photonic band gap fibers 56 ). (b) Complementary, antiguided-array structures of microcavities defined by negative-index step (e.g., antiguided VCSEL arrays 54 ) or low-index core antiguides (like in photonic liquid crystal fibers 57 ). Λ is the lattice pitch, a is the pixel size.…”

“…2(b)] refractive index contrast are, respectively, etched VCSEL arrays 53 or matrices of antiguided VC-SEL resonators fabricated using a two-step organometallic chemical vapor deposition (OMCVD) growth. 54 As shown below, the approach based on Hamiltonian formalism (25) applies equally well to arrays of parallel waveguides 55 [Fig. 2(a)] and low-index-core antiguides [Fig.…”

Anti-resonant reflecting photonic crystal vertical-cavity surface-emitting lasers

“…High power, single mode vertical cavity surface emitting lasers (VCSELs) have attracted significant interest in the past years [1][2][3][4]. The conventional VCSEL structure incorporates a built-in positive-index waveguide, designed to support a single fundamental mode.…”

“…There are increasing demands for the larger aperture and higher continuous output powers. Due to the fact that multiple modes will exist in larger aperture waveguide, one of the solutions is to increase the modal discrimination and make the devices favour fundamental mode only [3]. Recently ring-type Anti-resonantreflecting optical waveguide (ARROW) VCSELs [4] have been reported to operate at single mode with emitting aperture .…”