Mid-infrared passively switched pulsed dual wavelength Ho3+-doped fluoride fiber laser at 3 μm and 2 μm

Abstract

Cascade transitions of rare earth ions involved in infrared host fiber provide the potential to generate dual or multiple wavelength lasing at mid-infrared region. In addition, the fast development of saturable absorber (SA) towards the long wavelengths motivates the realization of passively switched mid-infrared pulsed lasers. In this work, by combing the above two techniques, a new phenomenon of passively Q-switched ~3 μm and gain-switched ~2 μm pulses in a shared cavity was demonstrated with a Ho3+-doped fluoride fiber and a specifically designed semiconductor saturable absorber (SESAM) as the SA. The repetition rate of ~2 μm pulses can be tuned between half and same as that of ~3 μm pulses by changing the pump power. The proposed method here will add new capabilities and more flexibility for generating mid-infrared multiple wavelength pulses simultaneously that has important potential applications for laser surgery, material processing, laser radar, and free-space communications, and other areas.

Widely wavelength tunable gain-switched Er^3+-doped ZBLAN fiber laser around 28 μm

“…Besides, the simple and compact gain-switched laser is also the preference for the seeder of master oscillator power amplifier (MOPA). Therefore, gain-switching has drawn extensive interest and been employed in fiber lasers operating across the near-IR (845 nm) to Mid-IR (2.8 μm) [36][37][38][39][40][41][42][43][44][45][46]. In 2001, B. C. Dickinson et al reported a 2.7 μm pulsed Er 3+ -doped ZBLAN fiber laser pumped transiently on the 4 I 15/2 → 4 I 9/2 ground-state-absorption transition at 791 nm and achieved 1.9 mJ of output energy [43].…”

“…Here, the build-up time refers to the time delay of gain-switched pulse relative to pump pulse, reflecting the time needed for the photon density buildup. It is calculated from the front edge of the pump pulse envelope to that of the induced gain-switched pulse envelope and has been utilized in the previous reports [39,41]. This stable single-pulse gain-switched operation can be maintained until the pump power was increased to 705.6 mW.…”

A robust and tuneable mid-infrared optical switch enabled by bulk Dirac fermions

“…The rapid maturing of mid-infrared gain platforms91011 in recent years is calling for saturable absorbers with performance levels on par with their near-infrared counterparts. While being a powerful optical switching solution12131415, SESAMs nevertheless exhibit a relatively narrow nonlinear optical bandwidth and limited long-wavelength access, that is, typically ∼3 μm (ref. 16).…”

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

“…For example, by exploiting water absorption around 1900 nm, fiber lasers at this wavelength have been successfully applied for soft-tissue medicine and urinary stone ablation25. Moreover, lasers at 1900 nm are important for optical fiber communications which seek to exploit the transmission window from 1850 nm to 2100 nm67 and as pump sources to achieve emission further in the mid-infrared8.…”

“…In all of these demonstrations, two separate gain media are employed, which often leads to increased complexity in implementation and laser design. Li et al 8 reported passively Q-switched pulses at ~3000 nm and gain-switched pulses at ~2000 nm pulses with Ho 3+ -doped fluoride fiber and a semiconductor SA mirror; however, the use of bulk optics eliminates the advantages of an all-fiber configuration. A graphene SA has also been applied to obtain Q-switched pulses at 1190 nm and 3000 nm with Ho 3+ -doped ZBLAN fiber2122 while Q-switched pulses at 2780 nm and mode-locked pulses at 2800 nm were obtained with Er 3+ -doped ZBLAN fiber2324.…”