Stable single longitudinal mode erbium-doped silica fiber laser based on an asymmetric linear three-cavity structure

We present a stable linear-cavity single longitudinal mode （SLM） erbium-doped silica fiber laser. It consists of four fiber Bragg gratings （FBGs） directly written in a section of photosensitive erbium-doped fiber （EDF） to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio （OSNR） of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer （OSA） for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.

A single-longitudinal-mode continuous-wave Ho-(3＋)：YVO4 laser at 2.05 μm pumped by a Tm-fibre laser

We present a single-longitudinal-mode continuous-wave Ho^3＋：YVO4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho：YVO4 laser is suitable for use as a seed laser in some Lidar systems（e.g., coherent Lidar or differential absorption Lidar）. To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho：YVO4 laser at 2.05 μm.

Simultaneous tailoring of longitudinal and transverse mode inside an Er:YAG laser

In this paper, we demonstrate a scheme to tailor both longitudinal and transverse modes inside a laser cavity and constitute an eye-safe single longitudinal mode Er∶Y_(3)Al_(5)O_(12)(Er:YAG) vector laser. A q-plate is employed as a spin-orbital conversion element to modulate the transverse mode and obtain cylindrical vector beams. An optical isolator is employed as a nonreciprocal element for the ring cavity to enforce unidirectional operation and achieve single longitudinal oscillation. The characteristics of power, transverse intensity, and polarization spectrum of the output beams are observed. The observed typical single longitudinal mode and highly matched special polarizations prove the successful tailoring of both longitudinal and transverse modes.

High order DBR GaSb based single longitude mode diode lasers at 2 μm wavelength

The GaSb-based distributed Bragg reflection（DBR） diode laser with 23 rd-order gratings have been fabricated by conventional UV lithography and inductively coupled plasma（ICP） etching. The ICP etching conditions were optimized and the relationship among etching depth, duty ratio and side-mode suppression ratio（SMSR） was studied. The device with a ridge width of 100 μm, gratings period of 13 μm and etching depth of 1.55 μm as well as the duty ratio of 85% was fabricated, its maximum SMSR reached 22.52 dB with uncoated cavity facets under single longitudinal operation mode at room temperature.

A novel hybrid Ⅲ–Ⅴ/silicon deformed micro-disk single-mode laser

A novel hybrid III-V/silicon deformed micro-disk single-mode laser connecting to a Si output wave- guide is designed, and fabricated through BCB bonding technology and standard i-line photolithography. Com- pared to a traditional circular micro-disk in multi-longitudinal-mode operation, unidirectional emission and single longitudinal-mode output from a Si waveguide are realized. In the experiments, an output power of 0.31 mW and a side-mode suppression ratio of 27 dB in the continuous-wave regime are obtained.