Spectroscopic Investigation of Tm3+-Dy3+ Co-Doped KY3F10 Crystals for $3\ \mu\mathrm{m}$ Laser Applications

Mid-infrared lasers operating in the
$2-5\ \mu\mathrm{m}$
region have been attracting a great deal of interest due to their usage in many diverse fields such as range finding [1], remote sensing [2], and medicine [3]. In the case of surgical intervention, efficient energy transfer between the laser and the tissue is required, therefore high absorption in the tissue is necessary. Strong absorption of water at
$2.94\ \mu\mathrm{m}$
[4] then sets the laser wavelength, especially for surgery applications. The most commonly used lasers are
$2.94-\mu\mathrm{m}$
Er
³⁺
:YAG lasers, producing ∼3-4 J/pulse energies with
$\mu\mathrm{s}$
pulse durations. As an attractive alternative, D
y
3+ ion possesses broad emission bands centered around
$2.9\ \mu \mathrm{m}$
, but usually suffers from low photon quantum efficiency
$(\lambda_{p}/\lambda_{L})$
. Alternatively, co-doping with ions such as ytterbium (Yb
³⁺
) [5] and thulium (Tm
³⁺
) [6] can potentially provide a direct diode pumping possibility. In this study, we investigated the potential energy transfer mechanisms between Tm
³
+ and D
y
3+ ions for Tm
³
+ in-band pumping using several concentration combinations in KY
3
F
10
crystals.