Comparison between Self-Raman Nd:YVO4 Lasers and NdYVO4/KGW Raman Lasers at Lime and Orange Wavelengths

The comparison of output powers between self-Raman Nd:YVO4 lasers and Nd:YVO4/KGW Raman lasers operating at lime and orange wavelengths is presented. We exploit the LBO crystal with cutting angle θ = 90° and φ = 8° for the lime wavelengths, and then we change the angle to θ = 90° and φ = 3.9° for the orange wavelengths. In self-Raman Nd:YVO4 lasers, experimental results reveal that thermal loading can impact on the output performances, especially at the high pump power. However, by using a KGW crystal as Raman medium can remarkably share the thermal loading from gain medium. Besides, the designed coating for high reflectively at the Stokes field on the surface of KGW also improved the beam quality and reduced the lasing threshold. For self-Raman Nd:YVO4 lasers, we have achieved the output powers of 6.54 W and 5.12 W at 559 nm and 588 nm, respectively. For Nd:YVO4/KGW Raman lasers, the output powers at 559 nm and 589 nm have been increased to 9.1 W and 7.54 W, respectively. All lasers operate at a quasi-CW regime with the repetition rate 50 Hz and the duty cycle 50%.

Investigation of defective hybrid cladding with silicon nanocrystal PCF for supercontinuum generation

Defective hybrid cladding through a silicon nanocrystal-core-structured photonic crystal fiber intended for high pump power supercontinuum proliferation is discussed in this paper. The cladding comprehends a hybrid approach of a hexagonal air hole in the outer section and a petal-structured air hole in the inner layer with a twisted pattern. Such a procedure with an air hole in the cladding section with a silicon nanocore displays high nonlinearity and negative dispersion at the communication window for varying pulse widths with 20 kW pump power. The impact of structural parameters of the proposed structure on the optical constraints is discussed, namely, dispersion, nonlinearity and group-velocity dispersion for wavelengths ranging from 0.45 µm to 1.85 µm. The proposed structure with optimized structural parameters provides high nonlinearity of about 6.38 × 106 W−1 km−1 with negative dispersion of −70.19 ps (nm km)−1 at 1550 nm.

Low-threshold and narrow-linewidth perovskite microlasers pumped by a localized waveguide source

For the widely used vertically pumped (VP) method with a free-space beam, very little pump power is absorbed by the gain materials in microlasers because of the large spatial mismatch of areas between laser modes and free-space pump beams together with small thicknesses of gain materials, resulting in a high pump power threshold. Here, an in-plane-waveguide-pump (IPWP) method with a localized waveguide source is proposed to reduce pump power threshold of perovskite microlasers. Owing to reduced spatial mismatch of areas between laser modes and localized waveguide sources as well as increased absorption distances, the pump power threshold of the IPWP method is decreased to approximately 6% that of the VP method. Moreover, under the same multiple of the pump power threshold, the laser linewidth in the IPWP method is narrowed to approximately 70% that in the VP method. By using the IPWP method, selective pumping two adjacent (separation 2 or 3 μm) parallel-located perovskite microlasers is experimentally demonstrated, and no crosstalk is observed. This IPWP method may have applications in low-energy and high-density microlasers and photonic integrated circuits.

Design of EDFA based 16 channel WDM system using counter directional high pump power

In this paper, design of erbium-doped fiber amplifiers (EDFA) based 16 channel wavelength-division multiplexing (WDM) system for different pump powers and input signal levels using counter propagating pumping scheme is reported. Wavelength range between 1548 and 1560 nm in C-band with channel spacing of 0.75 nm at a bit rate of 10 Gbps are used. Input power given to all the channels is taken between −20 and −35 dBm with 3 dBm variation. Pump power levels between 100 and 500 mW at 980 nm wavelength are used. Low gain flatness with high gains and low noise figures are achieved with the proposed scheme.

Power-efficient generation of two-octave mid-IR frequency combs in a germanium microresonator

Octave-spanning frequency comb generation in the deep mid-infrared (>5.5 μm) typically requires a high pump power, which is challenging because of the limited power of narrow linewidth lasers at long wavelengths. We propose twofold dispersion engineering for a Ge-on-Si microcavity to enable both dispersion flattening and dispersion hybridization over a wide band from 3.5 to 10 μm. A two-octave mode-locked Kerr frequency comb can be generated from 2.3 to 10.2 μm, with a pump power as low as 180 mW. It has been shown that dispersion flattening greatly enhances the spectral broadening of the generated comb, whereas dispersion hybridization improves its spectral flatness.