CsPbBr_3 perovskite quantum dots: saturable absorption properties and passively Q-switched visible lasers

This work presents the saturable absorption(SA) properties of CsPbBr_3 perovskite quantum dots(QDs). The perovskite QDs show excellent SA performance with a nonlinear absorption coefficient of-35 × 10^(-2) cm∕GW and a figure of merit of 3.7 × 10^(-14) esu cm. Further, their use as saturable absorbers in a passively Q-switched visible solid-state laser for the generation of soliton pulses is demonstrated. These results demonstrate thepotential for the perovskite QDs to act as saturable absorbers.

High-Power and High-Efficiency 650nm-Band AlGaInP Visible Laser Diodes Fabricated by Ion Beam Etching

High power and high-slope efficiency 650nm band real-refractive-index ridge w aveguide AlGaInP laser diodes with compressive strained MQW active layer are for med by pure Ar ion beam etching process.Symmetric laser mesas with high perpendi cularity,which are impossible to obtain by traditional wet etching method due to the use of a 15°-misoriented substrate,are obtained by this dry etching metho d.Laser diodes with 4μm wide,600μm long and 10%/90% coat are fabricated.Th e typical threshold current of these devices is 46mA at room temperature,and a s table fundamental-mode operation over 40mW is obtained.Very high slope efficien cy of 1.4W/A at 10mW and 1.1W/A at 40mW are realized.

Diode-pumped wavelength-switchable visible Pr^(3+):YLF laser and vortex laser around 670 nm

Here we developed a novel wavelength-switchable visible continuous-wave(CW)Pr^(3+):YLF laser around 670 nm.In single-wavelength laser operations,the maximum output powers of 2.60 W,1.26 W,and 0.21 W,the maximum slope efficiencies of 34.7%,27.3%,and 12.3%were achieved with good beam qualities(M^(2)<1.6)at 670.4 nm,674.2 nm,and 678.9 nm,respectively.Record-high output power(2.6 W)and record-high slope efficiency(34.7%)were achieved for the Pr^(3+):YLF laser operation at 670.4 nm.This is also the first demonstration of longer-wavelength peaks beyond 670 nm in the^(3)P_(1)→^(3)F_(3)transition of Pr^(3+):YLF.In multi-wavelength laser operations,the dual-wavelength lasings,including 670.1/674.8 nm,670.1/679.1 nm,and 675.0/679.4 nm,were obtained by fine adjustment of one/two etalons within the cavity.Furthermore,the triple-wavelength lasings,e.g.672.2/674.2/678.6 nm and 670.4/674.8/679.4 nm,were successfully demonstrated.Moreover,both the first-order vortex lasers(LG_(0)^(+1)and LG_(0)^(-1)modes)at 670.4 nm were obtained by off-axis pumping.

Saturable absorption and visible pulse modulation of few-layer topological nodal-line semimetal HfGeTe

Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses.Here,to the best of our knowledge,we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers.Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band,yielding the saturation intensities of 7.88,12.66,and 6.64μJ/cm^(2)at 515,640,and 720 nm,respectively.Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF_(4)gain medium,Q-switched visible lasers are also successfully achieved at 522,640,and 720 nm.The minimum pulse widths of the green,red,and deep-red pulsed lasers are150,125.5,and 420 ns,respectively.Especially for the green and red pulsed laser,the obtained pulse width is smaller than those of the low-dimensional layered materials.Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.

Few-layer Ti_(3)CN MXene for ultrafast photonics applications in visible band

Ti_(3)CN,as a typical hetero-MXene,has attracted tremendous attention for its unique properties.However,its ultrafast photonics applications are still rare.Here,the few-layer Ti_(3)CN MXene was successfully prepared by selective etching and molecular delamination technique.The nonlinear optical response of few-layer Ti_(3)CN MXene at 640 nm was studied using the open-aperture Z-scan technique.The asprepared Ti_(3)CN MXene sample exhibited excellent nonlinear saturable absorption characteristics,resulting in the nonlinear absorption coefficient b of
4.05×10^(-2)cm/GW,which was one order of magnitude larger than that of black phosphorus(BP)and molybdenum disulfide(MoS_(2)).For the optical modulation applications of few-layer Ti_(3)CN MXene,passively Q-switched(PQS)solid-state visible lasers based on Ti_(3)CN saturable absorber(SA)at 522 nm,607 nm,639 nm,and 721 nm were successfully realized.Furthermore,a Ti_(3)CN-based stable passively mode-locked Pr:YLF red laser was also successfully achieved with a pulse duration of 30 ps,and the corresponding repetition rate was 73.1 MHz.The optical modulation device based on few-layer Ti_(3)CN MXene shows good performance.Our work demonstrates that the tremendous prospects of the few-layer Ti_(3)CN MXene as a visible optical modulation device in ultrafast photonics applications.

Polymeric photonic molecule super-mode lasers on silicon

Optically coupled microcavities have emerged as photonic structures with promising properties for investigation of fundamental science as well as for applications.We report on the fabrication and spatially resolved spectroscopy of on-chip photonic molecule(PM)lasers consisting of two coupled,dye-doped polymeric microdisks on a silicon substrate.We investigate the fundamental lasing properties with focus on the spatial distribution of modes,the coupling dependent suppression of lasing modes,and in particular the application-oriented operation of these devices in aqueous environments.By depositing an additional polymer layer onto the lithographically structured cavities made of dye-doped poly(methyl methacrylate),coupling-gap widths below 150 nm with aspect ratios of the micro-/nanostructure exceeding 9:1 are achieved.This enables strong optical coupling at visible wavelengths despite relatively small resonator radii of 25 μm.The lasing properties of dye-doped PMs are investigated using spatially resolved micro-photoluminescence(μ-PL)spectroscopy.This technique allows for the direct imaging of whispering-gallery modes(WGMs)in the photonics molecules.For subwavelength coupling gaps,we observe lasing from delocalized eigenstates of the PMs(termed in the following as super-modes).Using size-mismatched cavities,the lasing mode suppression for different coupling-gap widths is investigated.We further demonstrate single-mode lasing operation in aqueous environments with PMs,which are realized on a low-cost,polymer-on-silicon platform.