Direct imaging of optical cavity modes in ZnO rods using second harmonic generation microscopy.
Images of second harmonic generation (SHG) in needle-shaped ZnO rods obtained from individual structures show areas of enhanced second harmonic intensity along the longitudinal axis of the rod that are periodically distributed and symmetrically situated relative to the rod midpoint. The spatial modulation is a direct consequence of the fundamental optical field coupling into standing wave resonator modes of the ZnO structure, leading to an enhanced backscattered second harmonic condition that cannot be achieved in bulk ZnO. A more complicated second harmonic image is observed when excitation is below the band gap, which is attributed to whispering gallery modes. This physical phenomenon, which extends beyond just ZnO to many other optical materials, could pave the way to new applications that exploit the nonlinear optical properties of individual structures.
Mehl
Brian P
BP
Department of Chemistry, Caudill Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
House
Ralph L
RL
Uppal
Abhineet
A
Reams
Amanda J
AJ
Zhang
Chuan
C
Kirschbrown
Justin R
JR
Papanikolas
John M
JM