| High finesse fiber Fabry-Perot cavities(FFPC)have high quality factor(Q)and small mode volume(V),which effectively enhance the interaction between the light field and matter in the cavity.They have been extensively investigated and applied to the quantum systems such as atoms,ions,NV centers and quantum dots in recent decades.The high Q and small V are also the desired properties of low threshold and narrow-linewidth lasers.At the same time,the mode selection mechanism of the FFPC makes the output laser have single mode naturally.The short cavity length of the fiber cavity corresponds to the large free spectral range,giving the laser a larger tuning range.The laser wavelength can be tuned using the shear piezo to adjust the length of the cavity.The electrical tuning has a faster tuning rate than the thermal tuning of other microcavities.Based on the above advantages,the FFPC is used to fabricate a microcavity laser in this thesis,which has potential applications in optical communication,sensing,cw radar and high resolution imaging.Furthermore,due to the characteristics of short cavity length and high Q of the laser,the wavelength of the output laser is extremely sensitive to the change in cavity length.In this case,we demonstrate the application of the laser in active sensors.Finally,we study the self-pulse phenomenon of the microcavity laser and attempt to explain it using a polarization dynamic model.The main contributions in this thesis is as follows:(1)The laser processing system of in-situ detection is established to complete the fabrication of fiber end face with large radius of curvature(ROC)range.In this system,carbon dioxide laser is used to fabricate the precise surface shape on the fiber end,and the fiber end can be detected and analyzed in situ by using the profilometer integrated with the system.The ROC of the concave surface of the fiber end is extended to about 40-600 μm,and the concave surface with large ROC is a necessary component for the construction of long FFPC,which provides conditions for the experimental research of high finesse long FFPC.(2)The hybrid thermal expanded core single-mode fiber is realized,so that the FFPC output mode matches the fiber mode,thus effectively improving the output efficiency of FFPC.When FFPC is integrated with other quantum systems,in order to ensure the efficiency of the quantum system,it is necessary to match the mode of the fiber cavity with that of the single-mode fiber.The long cavity FFPC has a large beam waist and low coupling efficiency with the single-mode fiber.In this work,the mode field diameter of the fiber is expanded by thermal core expansion method,and eventually expanded by 3.5 times larger.(3)Based on the FFPC and rare earth ions doped glass,a fast and wide-tuned fiber microcavity laser is realized.A 1550 nm single-mode laser output is achieved by placing an Er3+/Yb3+co-doped gain medium in an FFPC with a 980 nm optical pump.The microcavity laser can achieve single longitudinal mode and single transverse mode output,THz-tuning range without mode hopping,frequency scanning rate up to 1.6 × 1017 Hz/s and other high performance,which can be used for active sensing,continuous wave radar,high resolution imaging and other applications.(4)The active acoustic sensor based on fiber Fabry-Perot microcavity laser is studied and demonstrated.The common phase-modulated fiber sensor needs to change its length to half wavelength to detect obvious signals,while the signal can be detected when the length of the micro-cavity changes by the magnitude of pm.Therefore,a high sensitivity(2.6 V/Pa)acoustic sensor experiment is carried out based on this laser.As an active sensor,the structure does not need additional lasers,resulting low cost.And because of the large FSR of the micro-cavity,the WDM can be used to realize the networking of multiple sensors.(5)Study on self-pulse phenomenon of the fiber microcavity laser.The phenomenon of laser self-pulse occurs when the optical fiber cavity concave does not meet the geometrical symmetry.Considering that the asymmetric concave surface can cause the splitting of polarization modes in the cavity,which leads to the chaotic effect of the output laser.Therfore,we construct a theoretical model of polarization dynamics to explain this phenomenon. |
