Nonlinear Optical Properties of CdSiP₂ Crystal at 1 μm

Cadmium silicon phosphide, CdSiP<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (CSP), is now recognized as a promising nonlinear optical material for deep-infrared (deep-IR) applications due to its unique properties such as wide transparency range extending from 1-6.6 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> and high nonlinearity <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(d_{36}\sim 84\ \text{pm}/\mathrm{V})$</tex>. These properties make CSP highly attractive for frequency conversion using the well-established pump laser technology based at 1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> to generate deep-Ir radiation at wavelengths as long as 6 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> [1]. In spite of the high nonlinear gain, the residual linear and nonlinear absorption at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 1\ \mu \mathrm{m}$</tex> significantly limit the power scaling potential of frequency conversion sources based on CSP. Further, recent commercial availability of high-power femtosecond Yb-fiber lasers emphasize the importance of investigating the nonlinear optical properties of CSP, including two-photon absorption coefficient <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\beta_{2})$</tex> and nonlinear refractive index <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(n_{2})$</tex> at ~1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> pump wavelength, to unlock its full potential of this material as a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\chi^{(2)}$</tex> nonlinear gain medium.