New method to determine the refractive index and the absorption coefficient of organic nonlinear crystals in the ultra-wideband THz region.
A method for simultaneously measuring the refractive index and absorption coefficient of nonlinear optical crystals in the ultra-wideband terahertz (THz) region is described. This method is based on the analysis of a collinear difference frequency generation (DFG) process using a tunable, dual-wavelength, optical parametric oscillator. The refractive index and the absorption coefficient in the organic nonlinear crystal DAST were experimentally determined in the frequency range 2.5-26.2 THz by measuring the THz-wave output using DFG. The resultant refractive index in the x-direction was approximately 2.3, while the absorption spectrum was in good agreement with FT-IR measurements. The output of the DAST-DFG THz-wave source was optimized to the phase-matching condition using the measured refractive index spectrum in THz region, which resulted in an improvement in the output power of up to a factor of nine.
Ohno
Seigo
S
RIKEN ASI, 519-1399 Aramaki, Aoba, Sendai 980-0845, Japan. sohno@riken.jp
Miyamoto
Katsuhiko
K
Minamide
Hiroaki
H
Ito
Hiromasa
H
D000042:Absorption; D003460:Crystallization / Q000295:instrumentation; D004867:Equipment Design; D007259:Infrared Rays; D008872:Microwaves; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D055053:Terahertz Radiation