P Dowd

Mode control in vertical-cavity surface-emitting lasers by post-processing using focused ion-beam etching

Single-mode emission is achieved in previously multimode gain-guided vertical-cavity surface-emitting lasers (VCSELs) by localized modification of the mirror reflectivity using focused ion-beam etching. Reflectivity engineering is also demonstrated to suppress transverse mode emission in an oxide-confined device, reducing the spectral width from 1.2 nm to less than 0.5 nm.

Linewidth narrowed vertical-cavity surface-emitting lasers for millimeter-wave generation by optical heterodyning

Narrow beat-note linewidths as low as 190 kHz have been obtained by optically heterodyning two vertical-cavity surface-emitting lasers (VCSELs) whose linewidths are minimized by optical feedback. Narrow line operation has been achieved stably at frequencies up to a detector limited value of 25 GHz for both free space and fiber-loop arrangements.

Mode-Controlled Vertical Cavity Surface Emitting Lasers for Bandwidth Enhancement of Multimode Fibre Links

A GaAs Vertical Cavity Surface Emitting Laser (VCSEL) that generates controlled modes offset from the center is described. The device is modulated with a 27-1 pseudo-random bit sequence and its output is transmitted along a 1 km length of multimode fiber (MMF). Open eyes are obtained for data rates as high as 1.4Gb/s. The transmission bandwidth increases by a factor of 4 over over-filled launch (OFL). This enhancement is stable against environment influences on the fiber.

Post-processing of vertical-cavity surface-emitting lasers for transverse mode and polarization control

The operation on how high quality single-mode operation can be readily attained on etching circles in multimode devices is discussed. Arrays of such spots can also be envisaged. Control of the polarization state is also achieved by use of deep line etches. The output filaments and beam shapes of the conventional multimode vertical cavity surface emitting lasers (VCSEL) is shown to be engineered in terms of their positions, widths, and polarizations by use of focused ion beam etching (FIBE). Several GaAs quantum well top-emitting devices with cavity diameters of 10 μm and 18 μm were investigated.

Beam control and manipulation in vertical cavity surface emitting lasers

This paper reviews novel techniques which are used to modify the properties of the optical beam generated by vertical cavity surface emitting laser diodes. The main emphasis within the paper concerns the use of etches applied to the device surface either adjacent to or across its optical aperture. Such etches can be used to modify facet reflectivities sufficiently to pin the optical mode precisely and reduce the onset of higher order modes. In addition, single polarization operation is achieved by using deeper etches placed outside the light emitting region. Using this technique, previously multimode components may be transformed to single mode components with precisely fixed polarization states. The effect of these etches on other lasing properties such as spectral performance and power efficiency is also discussed.