Nonlinear absorption properties of Co 2+ :MgAl 2 O 4 crystal

Passive Q-switching of erbium glass laser by magnesium aluminosilicate sitall with cobalt ions

“…The emission wavelength for the erbium glass laser (λ = 1.54 µm) corresponds to practically maximum absorption in this band. The bleaching relaxation time τ of the Co 2+ ions upon excitation of the transition 4 A 2 → 4 T 1 ( 4 F) by radiation with wavelength 1.54 µm is 320 ± 40 nsec and 370 ± 40 nsec for MAS and MAO [4,6]. Taking into account the measurement error, we can say that the bleaching relaxation times for the Co 2+ ions in the crystal and in the sitall virtually coincide and are equal to ≈350 nsec.…”

“…Taking into account the measurement error, we can say that the bleaching relaxation times for the Co 2+ ions in the crystal and in the sitall virtually coincide and are equal to ≈350 nsec. The measured times τ are determined by the lifetime of the excited state 4 T 2 , since the lifetime of the level 4 T 1 ( 4 F) of the Co 2+ ions in the studied materials is less than 15 picoseconds [4] (see Fig. 1b).…”

“…Such pulses can be obtained by operating the laser in passively Q-switched mode. Today the most efficient passive gate for erbium glass lasers, lasing at a wavelength of 1.54 µm, is a magnesium aluminum spinel containing divalent cobalt ions (Co 2+ :MgAl 2 O 4 ) [1][2][3][4]. In this material, the Co 2+ ions occupy positions with tetrahedral coordination and have a large ground state absorption (GSA) cross section (σ GSA ≈ (3-5)⋅10 -19 cm 2 ), a rather long bleaching relaxation time (τ = 300-400 nsec), and low excited state absorption (ESA) (σ ESA /σ GSA < 0.05) [1,4].…”

“…Today the most efficient passive gate for erbium glass lasers, lasing at a wavelength of 1.54 µm, is a magnesium aluminum spinel containing divalent cobalt ions (Co 2+ :MgAl 2 O 4 ) [1][2][3][4]. In this material, the Co 2+ ions occupy positions with tetrahedral coordination and have a large ground state absorption (GSA) cross section (σ GSA ≈ (3-5)⋅10 -19 cm 2 ), a rather long bleaching relaxation time (τ = 300-400 nsec), and low excited state absorption (ESA) (σ ESA /σ GSA < 0.05) [1,4]. At the same time, it has been demonstrated [5][6][7] that materials in the form of transparent glassceramic (sitall) containing divalent cobalt ions can be used as passive gates for lasers in the spectral range 1.3-1.6 µm.…”

Optical properties of transition metal ion‐doped MgAl2O4 spinel for laser application

“…It has a good thermal and mechanical properties, high hardness and low electrical loss. It can be easily activated by transition-metal ions like cobalt (Co 2+ ) or chromium (Cr 3+ ) for optical devices: with the saturable absorption in the eye-safe spectral range, Co 2+ -doped MgAl 2 O 4 crystals can be used as a media for passive Q-switch of lasers which operates in the spectral range of 1.3-1.6 µm, for example 1.32 µm Nd:YAG and 1.54 µm erbium glass lasers [1]. Cr 3+ -doped (MgO.nAl 2 O 3 ): stoichiometric (n = 1) or nonstoichiometric (n = 2.6) magnesium aluminate spinels have been well studied for tunable solid-state laser applications and fiber-optic thermometer [2,3].…”