H. Pakarzadeh, S. Hosseinabadi, I. S. Amiri,
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11205/1120504/Designing-a-silicon-waveguide-for-tunable-wavelength-conversion-in-terahertz/10.1117/12.2548203.short?SSO=1
Terahertz (THz) radiation, as a low-risk and
high-efficient radiation has attracted especial attention and development of
compact and efficient THz sources for various applications is of considerable
interest. Wavelength conversion in the standard optical fibers was first
observed and investigated based on the nonlinear phenomenon known as the scalar
modulation instability (SMI). Compared with standard silica-based optical
fibers, silicon waveguides have advantages such as higher refractive index and
lower absorption loss over the THz region. The SMI can be analyzed based on the
FWM process and in order to satisfy the phase-matching condition, the
dispersion characteristics of the silicon waveguide must be well engineered. To
this end, the pump wavelength must be adjusted very close to the zerodispersion
wavelength (ZDW) of the waveguide. There are many methods which can be used to
engineer the dispersion curve; one of them is changing geometrical parameters
of the waveguide. In this paper, a silicon waveguide based on the photonic
crystal idea is designed for the first time, and using the SMI phenomenon,
tunable wavelength conversion for generation of THz radiation is simulated. By
changing the geometrical parameters such as the air hole diameter of the photonic
crystal, dispersion and nonlinear characteristics of the waveguide are
controlled and hence the generated THz radiation is tuned. The results show
when the pump wavelength is set at λp=5.60 μm in the normal
dispersion regime and for the fixed lattice pitch of Λ= 4.80μm, as the air hole
diameter is changing from d=4.60μm to d=0.86μm, the converted wavelength is
tuned from λ=2.15μm to λ=326.17μm, respectively.
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