Coupling quantum dots to optical fiber: Low pump threshold laser in the red with a near top hat beam profile

Direct coupling of the optical field in a similar to 244nm thick, CdSe/ZnS quantum dot film to an optical fiber has yielded lasing in the red (lambda similar to 644 nm) with a threshold pump energy density < 2.6 mJ cm(-2). Comprising 28-31 layers of similar to 8 nm diameter quantum dots deposited onto the exterior surface of a 125 mu m diameter coreless silica fiber, this free-running oscillator produces 134 nJ in 3.6 ns FWHM pulses which correspond to 37W of peak power from an estimated gain volume of similar to 4.5 x 10(-7) cm(3). Lasing was confirmed by narrowing of the output optical radiation in both the spectral and temporal domains, and the laser beam intensity profile approximates a top hat. (C) 2015 AIP Publishing LLC.