Sellmeier equations, group velocity dispersion, and thermo-optic dispersion formulas for CaLnAlO_4 (Ln = Y, Gd) laser host crystals

Abstract

We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO₄ (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 μm. The group velocity dispersion (GVD) in CaGdAlO₄ is positive at ∼1 μm, 95 fs²/mm and negative at ∼2 μm, -40 fs²/mm. The GVD values for CaYAlO₄ are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO₄. dn/dT is negative at ∼1 μm, dn_o/dT=-7.8, and dn_e/dT=-8.7×10^-6 K^-1. Thermo-optic dispersion formulas were constructed. The obtained data are of key importance to the design of high-power mode-locked oscillators at ∼1 and ∼2 μm based on such laser hosts.

Advances of Yb:CALGO Laser Crystals

“…Notwithstanding the foregoing, researchers found that the quantum defect near zero regarding Yb 3+ ions can differ significantly from host to host [26]. Additionally, tetragonal rare-earth calcium aluminate CaGdAlO 4 /CALGO is a noteworthy member because of its disordered structure [27]. So, intuitively, the combination of Yb 3+ ions and CALGO may be of great promise.…”

Diode-pumped power scalable Kerr-lens mode-locked Yb:CYA laser

“…In addition, Yb:CYA crystal has relatively higher specific heat capacity, which means a larger optical damage threshold, while its thermal conductivity is moderate. Recently, Loiko et al investigated the Sellmeier equations, group velocity dispersion, and thermooptic dispersion formulas of CYA laser host crystal, showing that the thermo-optic properties of CYA are slightly better than those of CGA, which makes Yb:CYA promising for powerscalable lasers [15]. Benefiting from the above-noted advantages, Yb:CYA crystal attracts increasing interest in ultrashort pulse generation.…”

Wavelength-tunable Hermite–Gaussian modes and an orbital-angular-momentum-tunable vortex beam in a dual-off-axis pumped Yb:CALGO laser

“…x ; M 2 y 2m 1; 1. This consistency arises from the outstanding thermal-optical properties of Yb:CALGO [19], since thermal effects always lead to unwanted mixed modes [24]. Although HG 4;0 mode was hardly obtained by the off-axis method, it can be produced with the dual-off-axis pumping method by setting the off-axis displacements of OC and crystal at about x 1 ; y 1 ; x 2 ; y 2 −420 μm; 0; −400 μm; 0, as shown in Fig.…”

“…Yb:CaGdAlO 4 (Yb:CALGO), as a new laser crystal with outstanding optical properties [19], has the broadest emission bandwidth ever discovered among Yb 3 -doped crystals [20,21]. It has been used in high-efficiency and femtosecond lasers [22,23].…”

“…The end surfaces of Yb:CALGO were AR coated at 940-1080 nm, which was wrapped with indium foil and conductively water cooled through a copper heat sink at the temperature of 18°C. Yb:CALGO is an uniaxial crystal with a space group of I 4 ∕mmmD 17 4h , and the crystal used in our experiment is a-cut (c axis is in vertical direction), thus the lasing polarization is a stable linear σ-polarized light [19]. The linear cavity included a plane mirror (DM 1 :AR at 976 nm and HR at 1030-1080 nm) and a concave output mirror (OC: transmittance is 2% at 1030-1080 nm; the radius of curvature is 300 mm).…”