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.

Observation of direction instability in a fiber ring laser

We report on the observation of a new phenomenon occurring in a fiber ring laser. This phenomenon is about the transition from an initially bidirectional emission of a reciprocal fiber ring laser to a unidirectional emission at a certain pump power threshold. In addition, the final direction is not predefined but appears to be randomly chosen every time the threshold is exceeded. Therefore, we term this new phenomenon direction instability. Furthermore, we provide a first discussion of how the instability threshold is influenced by the length and the loss of the cavity. We show that the threshold follows a power times length scaling, indicating a nonlinear origin.

Graphene Oxide Embedded In Polymer Film As Saturable Absorber For Q-switched Erbium-doped Fiber Laser

– We demonstrate a Q-switched Erbium-doped fiber laser (EDFL) using a newly developed Graphene Oxide (GO) based saturable absorber (SA). The SA was fabricated by embedding a GO material, which was obtained through chemical oxidation of graphite into polyvinyl alcohol (PVA) film. A small piece of the film was sandwiched between two fiber ferrules via a fiber adapter and incorporated in an EDFL cavity for generating a stable Q-switching pulse train. The EDFL operates at 1560.5 nm with a pump power threshold of 16.88 mW while a pulse repetition rate was tunable from 32.45 to 81.7 kHz, and the smallest pulse-width of 5.67 μs. The Q-switching pulse shows no spectral modulation with a peak-to-pedestal ratio of 61.76 dB indicating the high stability of the laser. These results show that the GO has a great potential to be used for pulsed laser applications.Key words: graphene oxide, passive saturable absorber, Q-switching, EDFL, GO