Tuning of near-infrared-to-near-infrared luminescence from one-photon to two-photon anti-Stokes shift in Ca_3Ga_2- _xCr_xGe_3O_12 via varying Cr^3+ content

Abstract

Near-infrared-to-near-infrared (NIR-to-NIR) anti-Stokes luminescence from Cr³⁺ singly doped Ca₃Ga₂Ge₃O₁₂ (CGGG) occurs under the excitation of an 808 nm diode laser. The anti-Stokes processes vary from one photon to two photon, depending on the Cr³⁺ content (x) in Ca₃Ga_2-xCr_xGe₃O₁₂. The results suggest that phonon-assisted anti-Stokes excitation and cooperative energy transfer are involved in the observed upconversion (UC) processes of CGGG:Cr³⁺. The relevant Cr³⁺-doping-concentration-dependent NIR-to-NIR anti-Stokes luminescent mechanism, either one-photon or two-photon UC, is investigated. Such an observation on modulating the UC process via varying the doping concentration is helpful in broadening the understanding of UC phenomena.

A broadband near‐infrared Sc1−x(PO3)3:XCr3+ phosphor with enhanced thermal stability and quantum yield by Yb3+ codoping

“…Compared to the lanthanide ions (Nd 3+ , Yb 3+ , Er 3+ , Tm 3+ ), Cr 3+ ion can be served as a preferable NIR emitter, because it has a broadband absorption in the visible region (well matched with the blue‐emitting chips), and an intense sharp‐line emission (typically located around 690 nm) from the 2 E→ 4 A 2 transition in a strong crystal field, or a broadband emission from the 4 T 2g (4 F)→ 4 A 2 transition in a weak crystal field 12–18 . Thus, seeking for efficient Cr 3+ ‐doped broadband NIR phosphors has become a hot topic in the field of luminescent materials 19–27 .…”

“…10,11 Compared to the lanthanide ions (Nd 3+ , Yb 3+ , Er 3+ , Tm 3+ ), Cr 3+ ion can be served as a preferable NIR emitter, because it has a broadband absorption in the visible region (well matched with the blue-emitting chips), and an intense sharp-line emission (typically located around 690 nm) from the 2 E→ 4 A 2 transition in a strong crystal field, or a broadband emission from the 4 T 2g (4 F)→ 4 A 2 transition in a weak crystal field. [12][13][14][15][16][17][18] Thus, seeking for efficient Cr 3+ -doped broadband NIR phosphors has become a hot topic in the field of luminescent materials. [19][20][21][22][23][24][25][26][27] Until now a great progress has been made for the phosphors with emission peak wavelength less than 850 nm, which have a high internal and/or external quantum efficiency (IQE/EQE), superior thermal resistance quenching, and striking electro-optical efficiency.…”