  Multi-wavelength switchable single-frequency microlasers in a broad spectral
range are highly desirable for integrated photonic applications due to their
dynamic switching functionality, narrow linewidth, and high
side-mode-suppression-ratio (SMSR). Here, a strategy based on highly efficient
successive excitation of different stimulated multi-photon hyper-Raman
scattering (SMPHRS) processes is proposed to generate multi-wavelength
switchable single-frequency hyper-Raman microlasers. This is achieved through
collective precise dispersion management for arranging excitation wavelengths
to trigger different phase-matched SMPHRS processes in order, mode-hopping-free
tuning of the pump wavelength within a wide range of 0.75 nm by leveraging
strong thermo-optical broadening of ultra-high Q modes, and simultaneously
suppressing harmonics generation in a lithium niobate microcavity with high
second-order nonlinearity. As a result, under continuous-wave laser pump at a
low level of only 3.9 mW, SMPHRS processes from two- to five-photons emerged
step by step and almost depleted previously generated multi-photon Raman
signal. Consequently, four-wavelength dynamically switchable single-mode lasing
from near infrared (857 nm) to ultraviolet (350 nm) spanning beyond the record
range (~500 nm) with high SMSRs >35 dB is reported.
