Fluoride Glass Pulsed Laser in Middle Infrared Wavelength Range

Among all the techniques for achieving pulsed emission in rare-earth-doped fiber lasers, gain switching is particularly simple. It consists in modulating the optical gain of the active medium by employing a pulsed input pump with proper amplitude, repetition rate and duty cycle. In this work, a dysprosium-doped ZBLAN fiber is considered in order to investigate the generation of optical pulses at λs = 3.0 μm by employing in-band optical pumping at λ
_p
= 2.8 μm (
⁶
H
_15/2
→
⁶
H
_13/2
energy transition) [1]. The choice of this pumping configuration is due to its excellent performance in continuous-wave (CW) regime, as demonstrated in [2-5]. A home-made computer code exploiting a finite-difference time-domain (FDTD) algorithm is developed and several simulations are performed by varying the pulsed input pump characteristics to study the behavior of the device. The geometrical and spectroscopic parameters used in the simulation are realistic and are taken from [2]. In particular, the core and cladding radii are r
_co
= 6.25 μm and r
_cl
= 62.5 μm, respectively. The refractive index of ZBLAN glass is n = 1.48, measured at λ = 2.88 μm. Overall cavity losses are equal to about 0.9 dB/m. The dysprosium concentration is N
_Dy
= 2000 ppm.