High power surface emitting terahertz laser with hybrid second- and fourth-order Bragg gratings

Yuan Jin; Liang Gao; Ji Chen; Chongzhao Wu; John L Reno; Sushil Kumar

doi:10.1038/s41467-018-03697-9

High power surface emitting terahertz laser with hybrid second- and fourth-order Bragg gratings

Nat Commun. 2018 Apr 11;9(1):1407. doi: 10.1038/s41467-018-03697-9.

Authors

Yuan Jin¹, Liang Gao², Ji Chen², Chongzhao Wu², John L Reno³, Sushil Kumar⁴

Affiliations

¹ Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA, 18015, USA. yuj314@lehigh.edu.
² Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA, 18015, USA.
³ Sandia National Laboratories, Center of Integrated Nanotechnologies, MS 1303, Albuquerque, NM, 87185, USA.
⁴ Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA, 18015, USA. sushil@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.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.