The Fabrication And Application Of A Single Mode Lassing Element Based On A Bottle Microcavity

Owing to its high-beam quality and spectral purity,single-mode lasing is of fundamental importance for various scientific and technical Applications.Owing to their high-quality factors and small-mode volumes,whispering-gallery mode(WGM)microresonators fabricated with different geometries and materials(for example,glass,semiconductor and polymer)have attracted increasing attention in various areas,including in lasing,sensing and optical communications.Generally,WGM lasers,which are generated through total internal reflection at the external cavity interface,are usually multimodal due to the lack of mode-selection strategies.Recently,bottle microresonators have attracted considerable interest in many applications such as compact optical delay lines,cavity optomechanics,optical frequency comb,lasing,electromagnetically induced transparency-like phenomenons,and nonlinear optics.Different from other shapes of WGM microcavities(for example,microdisks,microspheres and microtoroids),in bottle microresonators,the highly nondegenerated WGMs are spatially well-separated along the long-axis direction and provide mode selection according to their axial mode numbers.This paper first introduces the origin and development of whispering gallery mode optical micro cavity,and the research status of WGM single-mode laser;Then a simple,cheap and efficient method for the preparation of bottle microresonators is introduced;finally we propose and study two different ways for the realization of single-mode laser pumped bottle shaped micro cavity:(1)Single whispering-gallery mode lasing in polymer bottle microresonators via spatial pump engineering.First,the microcavity of the bottle is prepared by the polymer material,and the spatial intensity distribution of the space is produced by using the spatial pump light interference method.When their mode intensity profiles are spatially overlapped with the pump stripes,single-bottle WGMs can be efficiently selected to lase,with attractive advantages including a high SMSF(over 20 dB)and low-lasing threshold.Only two parameters,that is,the spacing between and positions of interference stripes,need to be adjusted.(2)Single-mode lasing via loss engineering in fiber-taper-coupled polymer bottle microresonators.The highly non-degenerated WGMs are spatially well-separated along the long-axis direction of bottle microresonators and the microfiber will losefluorescence at the coupling position both provide the possibility for the selection of lasing modes.we used the loss-engineering approach to suppress the higher-order WGMs and demonstrated single-mode lasing emission in small polymer bottle microresonators.By placing the fiber taper on the side surface of microresonator center and carefully adjusting the coupling position,the diameters of the fiber taper,and coupling angles,higher-order WGMs suffer greater losses,and single fundamental mode can be efficiently excited to lase.In addition,a single-mode lasing wavelength tuning over 8nm can be achieved by stretching the axis of the polymer bottle microresonators.the two methods to realize single-mode lasing is precise and reversibly controllable and does not need a complex facility design and expensive components.Therefore,our simple and general approach may have a variety of promising applications,ranging from tunable single-mode lasing and sensing to nonlinear optics.