FIG. 1. Refractive indices and absorption coefficients of a THz wave at 1 THz. (a) and (b) xy plane, (c) and (d) yz plane, (e) and (f) xz plane.
FIG. 2. THz frequencies versus θ with CPM for KTP with a pump wavelength of 1.064 μm. (a) s→f+s with θ < Ω and s→f+f with θ > Ω in the xz plane, (b) s→f+f in the yz plane.
FIG. 3. The effective nonlinear coefficient deff versus THz frequencies by a pump wavelength of 1.064 μm with θ of 5°, 30°, 45°, 60° and 90°.
FIG. 4. THz wave intensities versus crystal length with a pump wavelength of 1.064 μm. Pump intensity Ip = 10 MW/mm2, initial Stokes intensity Is = 10 W/mm2. (a) s→f+s with θ < Ω in the xz plane, θ = 5°, 10° and 15°, (b) s→f+f with θ > Ω in the xz plane, θ = 21°, 24° and 27°, (c) s→f+f in the yz plane, θ = 4°, 8° and 12°.
FIG. 5. The maximum THz wave intensity and optimal crystal length versus the angle θ with a pump wavelength of 1.064 μm. Pump intensity Ip = 10 MW/mm2, initial Stokes intensity Is = 10 W/mm2.
FIG. 6. THz wave intensities versus crystal length for s→f+f in the xz plane with a pump wavelength of 1.064 μm and θ of 5°. Pump intensity Ip = 10, 20, 30, 40 and 50 MW/mm2, initial Stokes intensities Is = 10 W/mm2.
FIG. 7. The maximum THz wave intensity and quantum conversion efficiency versus pump intensity Ip for s→f+s in the xz plane with a pump wavelength of 1.064 μm and θ of 5°. Initial Stokes intensity Is = 10 W/mm2.
TABLE 1. CPM conditions and the corresponding nonlinear coefficients for KTP with pump wavelength of 1.064 μm. Y indicates CPM can satisfy, and N indicates CPM cannot satisfy
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