Theoretical Modelling of Cascaded Er~(3+)-Doped,Tm~(3+)-Doped and Nd~(3+)-Doped Fibers for 0.4 to 2.0 μm Emission Spectra

We present a cascaded system designed with Er~(3+)-doped, Tm~(3+)-doped and Nd~(3+)-doped fibers to realize amplified spontaneous emission(ASE) spectra covering 0.4—2.0 μm. The system is excited with a pump laser emitting 808 nm photons with 500 m W pump power. The emission spectra of the cascaded system covering0.4—2.0 μm are realized with the Er~(3+), Tm~(3+)and Nd~(3+)ion doping densities optimized to 8 × 1019, 2 × 1020 and8 × 1020 ion/m3, respectively, and the fiber length optimized to 1 m. Numerical methods reveal that the peak ASE power for the cascaded system can reach 20.9 m W. A minimum ASE power of 4.39 m W is attainable. Using numerical calculations and analytical techniques, we provide a detailed insight into optimized Er~(3+)-doped, Tm~(3+)-doped and Nd~(3+)-doped fiber lengths and their doping concentrations for ASE power spectra covering 0.4—2.0 μm.We believe that the cascaded system can potentially provide significant applications in various optical fields which include but not limited to wavelength-division multiplexing, various optical communications and other salient medical imaging processes.     

Gain and Emission Spectrum Characteristics of 465 nm Laser Diode Pumped Tm~(3+)-Doped Telluride Glass Fibers

Gain and emission spectrum characteristics of Tm~(3+)-doped telluride glass fibers pumped with 465 nm lasers are analyzed. The rate and power propagation equation groups of the fibers are solved numerically and the effects of the fiber parameters including active ion concentration, length and pump power on the gain spectra and amplified spontaneous emission(ASE) spectra are analyzed. The results show that with a pump parameter of 465 nm/200 mW, a doping concentration of 2.5 × 10~(25) ion/m~3 and a fiber length of 16 m, the gain and ASE spectra can cover from 1.100 to 1.900 μm, and the gain and ASE power peaks can reach 52 dB and 8 mW, respectively.     

Theoretical Analysis of Er~(3+)-Doped Telluride Glass Fiber Amplifier for 2.700μm Laser Amplification

The rate equations and power evolution equations of erbium-doped telluride glass fiber amplifier for both 1.530 and 2.700 μm lasers are solved numerically, the dependences of gain spectra on fiber length, dopant concentration and pump power are analyzed, and the gain of 2.700 μm laser is calculated and compared with the experimental result from reference. The numerical analysis shows that with 8 × 10~(24)ion/m~3 erbium ion concentration, 5 m fiber length and 600 mW pump power, the gains at 1.530 and 2.700 μm may achieve 23 d B or so. With larger power pump and higher dopant concentration, a net gain of 17 dB is obtained from the Er~(3+)-doped telluride glass fiber amplifier for 110 mW input signal. This fiber amplifier is promising for both 1.530 μm signal amplification and 2.700 μm laser amplification.     

Gain Properties of Triply-Doped Graphene-Insulator-Graphene Nanosheet Waveguide

Er~(3+)-Tm~(3+)-Pr~(3+)triply-doped graphene-glass-graphene(GGG) nanosheet waveguide amplifier, which is a promising candidate for integrated photonic devices, is modelled and numerically analyzed. The designed waveguide is composed of a triply-doped tellurite glass core. The core is sandwiched between two graphene layers.The rate and power propagation equations of a heterogeneous multi-level laser medium are set up and solved numerically to study the effects of waveguide length and active ion concentrations on amplifier performance at five different input signal wavelengths(1.310, 1.470, 1.530, 1.600 and 1.650 μm). The analytical results show that rareearth ion dopant concentrations at an order of 10~(26) ion/m~3, waveguide length at 0.1 m and pump power at 100 m W can amplify 1.530 and 1.600 μm input signals with 1 μW power up to approximately 20.0 and 24.0 dB respectively.Finite-difference time-domain(FDTD) simulation results show that mode field radius of GGG waveguide is smaller than that of silicon waveguide. Consequently, GGG waveguide with the same pump and signal power and the same gain-medium length can produce higher gain than silicon waveguide.