Studies On The Er³⁺-doped Fiber Laser With A Microcavity-Based Add-drop Filter And It’s Applications

Fiber lasers have excellent stability,high efficiency and compact structure,and are widely used in industrial manufacturing,communications,scientific research and other fields.In order to realize a single-longitudinal-mode and narrow-linewidth fiber laser,we need to introduce an extra element for frequency stabilization and mode selection.Whispering Gallery Mode(WGM)microcavity,with characteristics of high quality factor(high Q value),large free spectral range(FSR)and small model volume,can be employed as a mode select element.In this thesis,an optical add-drop filter based on a silica microsphere with diameter greater than 600 μm is constructed and introduced into the traditional fiber-ring laser as a frequency stabilization element.Single longitudinal mode,high signal-to-noise ratio and ultra-narrow linewidth operation was achieved,and tunable single-mode and dual-mode fiber lasers were also presented by introducing an extra filter,a tunable FBG or filter for instances.By using the constructed tunable two-mode fiber laser,we proposed a scheme for the generation of optical comb with tunable repeat frequency where stimulated Brillouin scattering effect(SBS)is involved.1.Optical filter based on large-size quartz microspheresWe used a high-power CO2 laser to melt a spinning quartz rod with a diameter of 3 mm to produce a silica spherical cavity with diameter of 600μm.A high-quality adddrop filter is constructed based on a the fabricated spherical cavity and two tapered fiber waveguide.The microcavity-based add-drop filters are characterized by drop and transmission spectra.2.Ultra-narrow linewidth single longitudinal mode fiber laser based on microcavity ADF frequency stabilizationThe transmission and drop characteristics of the fabricated spherical-cavity-based ADF are analyzed,and the relationship between the drop efficiency and coupling parameters of waveguide,the mode Q value of the spherical cavity are studied.Based on the optical multiplexing and frequency stabilization of the constructed ADF,combined with a 0.2 nm linewidth FBG,a fiber laser with erbium-doped fiber as the gain medium is constructed.Single longitudinal mode,narrow linewidth(2.5 kHz),high signal-to-noise ratio(up to 67 dB)operations are achieved.The maximum output power is above 2 mW with a pump power at 20 dBm.Based on the super-mode resonances of microsphere,combined with optical bandpass filters or a Bragg fiber grating,stable single-and dual-frequency fiber lasers with a wavelength tuning range of 1525 nm to 1572 nm is achieved as well.3.Generation of optical frequency comb with a tunable repetition rate based on stimulated Brillouin scatteringWe propose a dual-mode Brillouin laser-pumped optical frequency comb(OFC)generation scheme.Based on the constructed dual-frequency fiber laser,the a length of high nonlinear fiber is introduced,and the Brillouin ring laser is constructed.Using the ring Brillouin laser as the pump source,the Brillouin laser pumped optical comb is obtained through the four-wave mixing(FWM)effect.The laser produces a backfoward optical frequency comb with a tunable repetition frequency ranging from 82.5GHz to 2.25THz.