Diode and fibre pumped Cr2+:ZnS mid-infrared external cavity and microchip lasers

Abstract

Demonstrations of CW and pulsed microchip lasing in Cr 2þ : ZnS and Cr 2þ : ZnSe crystals are reported. Slope efficiencies up to 53% with output power up to 150 mW for CW and energy up to 1 mJ for pulsed pumping were achieved. Two compact diode and Er fibre laser directly pumped external cavity Cr 2þ : ZnS lasers are also described. Crystal preparationBulk Cr 2þ : ZnS crystals can be obtained from melt [14] or vapour growth techniques [14] by including the dopant in the starting charge. Under atmospheric pressure ZnS is sublimed at a temperature higher than about 1180 8C before melting [15]. Therefore for melt growth, in addition to high temperature (1950 8C), it is necessary to apply high q IEE, 2003

Vapor deposited Cr-doped ZnS thin films: towards optically pumped mid-infrared waveguide lasers

“…The crosssection is plotted in Fig. 2(d) for one of the films (black, atomic density) and compared to a single crystal sample (red) [21]. The atomic density is used for the film because the low sample volume makes analysis of ionization states difficult.…”

Progress in Cr2+and Fe2+doped mid‐IR laser materials

“…It was because among all the known Cr doped chalcogenides Cr:ZnSe has one of the most favorable combination of thermal, optical, and spectroscopic properties. A short summary of initial progress in Cr:ZnSe lasers includes: first demonstration of the direct diode excitation [43][44][45]; CW lasing with efficiency exceeding 60% [45,46]; gain switched lasing with output power up to 18.5 W [47]; the range of tunability over 1880-3100 nm [48,49]; active [50] and passive modelocking [51,52]; first demonstration of sub 100 fs modelocked operation [53]; first microchip [54][55][56][57] and disk laser [58] operations; single-frequency operation [59]; random lasing [4]; multi-line and ultra-broadband operation in spatially dispersive cavities [60]; lasing via photoionization transitions [61]. The minimum laser threshold of 45 mW CW pump power was achieved in [62].…”

“…The laser operates around 2.4 μm and delivers up to 3 W of output power at about 7.5 W pump with 59% slope and 41% real optical efficiencies, and generates 20 nm broadband output spectrum. Gain switched microchip lasing was demonstrated using uncoated ZnSe and ZnS crystals with laser cavity formed by Fresnel reflections [57]. The best results were obtained using 5.5 mm Cr:ZnSe crystal with Cr concentration 6 × 10 18 cm −3 .…”

“…Possibility of electrical pumping of mid-IR semiconductor lasers based on TM doped II-VI structures was investigated in several publications [34,41,[88][89][90]. This new type of laser could possess some advantages in comparison with other mid-IR laser sources such as quantum cascade lasers; semiconductor diodes (InAsSbP/InAsSb/InAs), and systems based on nonlinear frequency conversions (optical parametric oscillation and difference frequency generation).…”

Femtosecond SESAM-modelocked Cr:ZnS laser

“…:ZnS active medium has later been shown to operate in tunable continuous-wave regime [5], as diodepumped [6], microchip [7], high-power [8], and tunable sources with over 1200 nm tuning range [9].…”