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Writing Bragg Gratings in Multicore Fibers
Published on: April 20, 2016
High power surface emitting terahertz laser with hybrid second- and fourth-order Bragg gratings
Yuan Jin1, Liang Gao2, Ji Chen2
1Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA, 18015, USA. yuj314@lehigh.edu.
Abstract:
A surface-emitting distributed feedback (DFB) laser with second-order gratings typically excites an antisymmetric mode that has low radiative efficiency and a double-lobed far-field beam. The radiative efficiency could be increased by using curved and chirped gratings for infrared diode lasers, plasmon-assisted mode selection for mid-infrared quantum cascade lasers (QCLs), and graded photonic structures for terahertz QCLs. Here, we demonstrate a new hybrid grating scheme that uses a superposition of second and fourth-order Bragg gratings that excite a symmetric mode with much greater radiative efficiency. The scheme is implemented for terahertz QCLs with metallic waveguides. Peak power output of 170 mW with a slope-efficiency of 993 mW A-1 is detected with robust single-mode single-lobed emission for a 3.4 THz QCL operating at 62 K. The hybrid grating scheme is arguably simpler to implement than aforementioned DFB schemes and could be used to increase power output for surface-emitting DFB lasers at any wavelength.
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