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IRG-I Highlight

Dynamic surface-emitting fiber lasers


Figure: Dynamic radial lasing is demonstrated as the dye doped fluid plug is moved along the hollow core SEFL.  The three photos correspond to three different instances in time.  The “AT MIT” logo in the background and the fiber are fixed in space, while the microliter fluid droplet moves along the fiber.  The green pump light is seen propagating along the fiber from the left and the orange surface emitting laser light is seen reflecting from the logo in the background.

Members of IRG-I of the MIT MRSEC have recently introduced a new concept in fiber lasers. Until now, emission from fiber lasers originated solely from the fiber ends in the axial direction with a spot size dictated by the core radius.  In contrast, these novel lasers, termed surface-emitting fiber lasers (SEFLs), emit radiation radially and are capable of dynamic tuning of both the gain-medium position along the fiber axis and the direction of emission[(Shapira et al, Optics & Photonics News 18(5), 27-31 (2007)]

These interesting results suggest that the direction of the laser beam can be controlled remotely just by rotating the pump polarization. Another key aspect of the SEFL is that the gain medium need not be fixed in place with respect to the fiber. By introducing a mobile gain medium into the fiber core, it is possible to engineer a SEFL with a highly-collimated dynamically tunable lasing position as shown in the Figure. Thus any point along the fiber may be utilized for lasing, as needed, in real time. Motion control is achieved from one end of the fiber by a series of electronically controlled microdispensing solenoid valves connected to a positive pressure source and a vacuum generator to allow displacement of the dye doped fluid-plug in both axis directions. SEFLs could provide enhanced capabilities for diverse technologies, including medical imaging, explosive vapor and chemical detection, photodynamic therapy, and fabric displays.

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