Experimental Study On Light-control-light Characteristic Of SnS₂ Based Microfiber Knot Resonator

The microfiber ring is a resonator whitch made of micrometer-sized fiber.There are about three kinds of microfiber ring which are MLR?micro-loop resonator?,MCR?micro-coil resonator?and MKR?micro-knot resonator?.Due to its advantages of small size,simple manufacture,low cost and excellent resonance characteristics,it is widely employed in developing various fiber optic devices.Among different microfiber ring configurations,the performance of the MKR is the most stable one.Another significant character of the microfiber ring is the large fraction of evanescent light.This evanescent light is often combined with material whose property can be tuned by light,temperature,electric current and humidity in order to build all optical device with different functionality.Tin disulfide?SnS₂?,a two-dimensional dichalcogenide metal compound,has graphene-like two-dimensional structures.Thanks to the unique optical and electrical properties of SnS_2,it has wide applications in building optoelectronic devices such as photodetectors,biosensors and lasers.By the combination of the strong evanescent wave of micro-fiber ring and the large absorption properties of SnS₂,we report in this manuscript a study of light-control-light characteristic of MKR with SnS₂.In addition,the response time of this device are also measured.The experiment begins with a heat-flame taper-drawing fabrication of microfiber with a taper region of several millimeters.And then the microfiber?fiber diameter:d⁷?m?is elastically bent into a knot to form the MKR structure?ring diameter:D⁴80?m?.The characterization of the MKR begins with the stability test.For this,we pack the MKR separately on a conventional glass slides?refractive index¹.45?and a MgF₂?refractive index¹.37?substrate.Experimental results show that the MgF₂ substrate provides a better stability,which supports a resonance with higher Q,large extinction ratio and low loss.In order to deposit the SnS₂ onto MKR,we first fix the prepared MKR with the aid of translational stage.The deposition of the SnS₂ onto the areas away from the knot of the MKR is realized by means of drainage or by droplet diffusion of the tin disulfide suspension.In order to investigate the light-control-light characteristic of the SnS₂ coated onto MKR,we employed a 405 nm violet external pump light at different power shinning to the region with SnS₂.The optical output power variation with respect to different pump light power is recorded.When the violet light power increases as 0,5.1,10,15.3,20.2m W,the transmission power at the resonance dip position decreases.Correspondingly,the resonance extinction ratio decreases,with a maximum output power variation of⁴.5dB.The maximum sensitivity is about 0.22341dB/mW which is obtained at the wavelength of 1544.787nm.Whereas,the largest linear correlation between the output power versus pump light power is obtained at the wavelength of 1569.592nm,with a value of 0.9952.The multi-resonances nature of MKR enables us to demonstrate the relationship between output power variation rate and different resonance properties?such as Q,ER etc?simultaneously.It shows that a resonance with larger Q and higher ER can lead to a higher rate of output power variation.In addition,the response time of the device under different violet pump light power is also investigated.The results show that,a larger pump power can yield a higher photocurrent signal.Whereas,the response time has no dependence on the pump power,and the device can have a rise time as fast as 3.2 ms.The innovation of this work includes:1?Combining the MKR with SnS₂ and by means of a violet external pump light,we achieved in demonstrating an optical fiber devices with light-control-light functionality and with fast response time of³.2ms.2?Via the means of drainage,a MKR coated with tin disulfide?SnS₂?is obtained with a high quality factor Q and a high extinction ratio ER.Within the same experimental condition,we are able to experimentally investigate and analyze the relationship between the output power variation rate and resonance property?such as Q factor and ER?.