Phase matching in RT KTP crystal for down-conversion into the THz range

Abstract

Dispersion of refractive index and absorption coefficients in flux-grown high-resistivity KTiOPO4 crystals between 0.2–2.5 THz are verified at room temperature by a THz-TDS. Measured dispersion components nx, ny and nz are approximated for the first time in the form of Sellmeier equations. Phase matching for down-conversion into the THz range under a visible and near IR pump is found possible only in the principle plane by and types of three-wave interactions. Low frequency THz generation is favorable due to the low absorption coefficient down to 0.2 cm−1, below 0.5 THz.

Optical Properties of KTP Crystals and Their Potential for Terahertz Generation

“…Corresponding Sellmeier equations for 81 K could be written as follows: Recorded dispersions were approximated in the form of Sellmeier equations by the best-fit method within the spectral range of 142 µm to 1500 µm at the room temperature [21]: Corresponding Sellmeier equations for 81 K could be written as follows:…”

“…Later, the results were supplemented by Raman spectroscopy measurements at the wavenumbers below 4000 cm −1 [17]. Recently, THz refractive index and absorption coefficient were directly measured using growingly accessible THz time-domain spectrometers (THz-TDS) [18][19][20][21]. The most comprehensive study of its THz optical properties for the waves polarized parallel to all three optical axes of the KTP crystals was carried out in [20].…”

“…The most comprehensive study of its THz optical properties for the waves polarized parallel to all three optical axes of the KTP crystals was carried out in [20]. The refractive index components at room temperature were approximated in the form of Sellmeier equations [21].…”

Terahertz Birefringence and Dichroism of KTA Crystal

“…KTA PM curves demonstrate analogous behavior to those of KTP crystal since both crystals show similar optical properties at THz range [15,16]. Especially, an asymptotic approximation to the V Z angle (an angle between the optic axis of the crystal and z-axis) is observed for longer wave generation.…”

Oxide nonlinear crystals: optical properties and phase-matching for terahertz wave generation

“…Several studies were devoted to measuring their optical properties (refractive index and absorption coefficient) in the terahertz domain [2][3][4][5]. Different schemes for IRto-THz and THz-to-THz conversion were investigated [6][7][8][9]. Besides nonlinear crystals another attractive materials such as metals and semi-metals were considered for efficient conversion of near-IR femtosecond pulses to terahertz radiation on their surface [10].…”