The Coming Age of Pnictide and Chalcogenide Ternary Crystals in the Terahertz Frequency Regime

et al. 2023

ACS Appl. Opt. Mater.

Self Cite

An emerging crystal, CdSiP 2 , is shown to exhibit a higher nonlinearity than other key electro-optic sampling crystals, while also satisfying the electro-optic sampling phasematching conditions across the spectral range of ∼15−90 THz. Frequencies up to ∼65 THz are measured using an 800 nm central-wavelength probe electric field pulse and a (110) CdSiP 2 crystal; however, a higher central-wavelength (i.e., 1.3 μm) probe pulse can be used to record frequencies up to 90 THz. Given the high nonlinearity and electro-optic phasematching capabilities of CdSiP 2 , it is envisioned to emerge as the prominent crystal for detecting electric field waveforms within the high terahertz and infrared spectral regimes.

Section: ■ Theoretical Analysismentioning

confidence: 99%

CdSiP₂: An Emerging Crystal for Electro-Optic Sampling from Terahertz to the Infrared

Carnio

Zawilski

et al. 2023

ACS Appl. Opt. Mater.

Self Cite

“…Given that highly-nonlinear chalcopyrite crystals (e.g., ZnGeP 2 , CdSiP 2 , AgGaSe 2 , AgGaS 2 , etc.) have found great success in the mid-infrared regime 9 – 12 (not to mention the low THz frequency regime 13 ), these crystals are good candidates for the emission and sensing of phase-resolved electric fields in the high-frequency THz spectral range. Such chalcopyrite crystals are structurally robust, in contrast to the soft and flaky nature of GaSe (i.e.…”

Section: Introductionmentioning

confidence: 99%

Intra-pulse difference frequency generation in ZnGeP2 for high-frequency terahertz radiation generation

Carnio

Zawilski

et al. 2023

Sci Rep

The highly-nonlinear chalcopyrite crystal family has experienced remarkable success as source crystals in the mid-infrared spectral range, such that these crystals are primary candidates for producing high terahertz frequency (i.e., $$\gtrsim$$ ≳ 10 THz) electric fields. A phase-resolved terahertz electric field pulse is produced via intra-pulse difference frequency generation in a chalcopyrite (110) ZnGeP2 crystal, with phase-matching being satisfied by the excitation electric field pulse having polarizations along both the ordinary and extraordinary crystal axes. While maximum spectral power is observed at the frequency of 24.5 THz (in agreement with intra-pulse phase-matching calculations), generation nonetheless occurs across the wide spectral range of 23–30 THz. To our knowledge, this is the first time a chalcopyrite ZnGeP2 crystal has been used for the generation of phase-resolved high-frequency terahertz electric fields.

Intrinsic point defects (vacancies and antisites) in CdGeP2 crystals

Gustafson

Giles

Journal of Applied Physics

et al. 2023

Cadmium germanium diphosphide (CdGeP2) crystals, with versatile terahertz-generating properties, belong to the chalcopyrite family of nonlinear optical materials. Other widely investigated members of this family are ZnGeP2 and CdSiP2. The room-temperature absorption edge of CdGeP2 is near 1.72 eV (720 nm). Cadmium vacancies, phosphorous vacancies, and germanium-on-cadmium antisites are present in as-grown CdGeP2 crystals. These unintentional intrinsic point defects are best studied below room temperature with electron paramagnetic resonance (EPR) and optical absorption. Prior to exposure to light, the defects are in charge states that have no unpaired spins. Illuminating a CdGeP2 crystal with 700 or 850 nm light while being held below 120 K produces singly ionized acceptors (VCd−) and singly ionized donors (GeCd+), as electrons move from VCd2− vacancies to GeCd2+ antisites. These defects become thermally unstable and return to their doubly ionized charge states in the 150–190 K range. In contrast, neutral phosphorous vacancies (VP0) are only produced with near-band-edge light when the crystal is held near or below 18 K. The VP0 donors are unstable at these lower temperatures and return to the singly ionized VP+ charge state when the light is removed. Spin-Hamiltonian parameters for the VCd− acceptors and VP0 donors are extracted from the angular dependence of their EPR spectra. Exposure at low-temperature to near-band-edge light also introduces broad optical absorption bands peaking near 756 and 1050 nm. A consistent picture of intrinsic defects in II-IV-P2 chalcopyrites emerges when the present CdGeP2 results are combined with earlier results from ZnGeP2, ZnSiP2, and CdSiP2.