• A
  • A
  • A
  • ABC
  • ABC
  • ABC
  • А
  • А
  • А
  • А
  • А
Regular version of the site

Article

Lasing in III–V microdisk core–TiO2 shell lasers

Journal of the Optical Society of America B: Optical Physics. 2019. Vol. 36. No. 8. P. 2285-2291.
Zhukov A, N. V. Kryzhanovskaya.

Microdisk lasers having a III–V core coated with a TiO2 shell are experimentally studied under optical pumping.
Initial core microdisk lasers with a 5–10 μm diameter comprising five layers of InAs∕In0.15Ga0.85As quantum dots
demonstrate room temperature lasing with excellent characteristics (threshold, quality factor) at the ground state
optical transition in the 1.28–1.30 μm spectral range. Deposition of the TiO2 dielectric shell results in a decimation
of the whispering gallery modes of the microdisk resonator and, for thicker (>100 nm) shells, in a blueshift
of the lasing wavelength. Using numerical analysis, we demonstrate that coating a III–V core microdisk with
a high-index shell causes strong penetration of the second and third radial modes into the shell, whereas the first
radial mode remains nearly undisturbed. Though optical loss added by the TiO2 dielectric shell is low (it does not
exceed 2 cm−1 even for a 250-nm-thick TiO2 layer), mode leakage to the TiO2 results in a decrease in the optical
confinement factor and an increase in the threshold pump power. This effect is more pronounced in microlasers of
the smallest diameter studied (5 μm). Thus, in addition to other applications, a TiO2 shell can be used for mode
selection in microdisk lasers or for selective outcoupling of the emission to the waveguide structure, which requires
proper adjustment of the TiO2 shell thickness and microdisk diameter.