Barry J. Koch

Single-mode vertical cavity surface emitting laser by graded-index lens spatial filtering

4.5 mW of power in a single spatial mode has been obtained from a vertical cavity surface emitting laser (VCSEL) in an external cavity setup, using a graded index (GRIN) lens with a spatial filtering high reflecting aperture deposited on its endface. The spatial filter on the GRIN lens endface forces a larger single transverse mode in the VCSEL than is obtained without it. A brightness of 5.1×105 W/cm2 str is demonstrated, which is 91% of the maximum achievable.

Single-mode vertical-cavity surface-emitting laser

Summary form only given. Numerous approaches have attempted to increase the single-transverse-mode output power of vertical-cavity surface-emitting lasers (VCSELs). These include external cavity, lossy or anti-guiding, and filtering approaches. For the purpose of commercial production, a monolithic, continuous wave (cw) device incorporating a lossless filter approach is desirable.

Reflection-mode sensing using optical microresonators

The authors present an approach for applying optical microring resonators to sensing. The approach relies on the interaction of the resonator with a nanoparticle taggant, which can induce coupling between forward and backward propagating traveling-wave resonant modes of the device. In the conventional four-port Add/Drop filter configuration, such coupling results in significant build-up of output intensity at ports that would normally be “dark.” Because the increased intensity occurs across a wide range of device resonances, the sensor may be interrogated using broadband excitation and with a broadband detector, enabling a low-cost, robust system.

Micro-optics in VCSEL and solid state laser resonators

Several unconventional laser resonators are described, and their application to various laser systems is explored. Spatial mode control of vertical cavity surface emitting lasers is enhanced by two spatial filtering methods. The first employs a GRIN lens with a patterned mirror designed to reflect power only from desired modes. The angular selectivity of a Fabry-Perot etalon is used in the second system to improve spatial modal discrimination. Diffractive optical elements are used with a solid-state laser for beam shaping and aberration correction. An analysis of the effects of fabrication errors shows that higher-order diffraction terms and phase errors can result in distorted modes. However, proper cavity design can help to reduce these effects and insure proper mode shape.