This paper reports a coherent random microcavity laser that consists of a disordered cladding(scattering) layer and a light-amplification core filled with dye solution. Cold cavity analysis indicates that the random resonance modes supported by the proposed cavity can be effectively excited. With introducing the gain material, random lasing by specific modes is observed to show typical features of coherent random lasers, such as spatially incoherent emission of random modes. By inserting a metal nanoparticle into the gain region, emission wavelength/intensity of the random lasers can be considerably tuned by changing the position of the inserted nanoparticle,opening up new avenues for controlling output of random lasers and sensing applications(e.g., small particleidentification, location, etc.).
Dissipative Kerr solitons in resonant frequency combs offer a promising route for ultrafast mode-locking,precision spectroscopy and time-frequency standards.The dynamics for the dissipative soliton generation,however,are intrinsically intertwined with thermal nonlinearities,limiting the soliton generation parameter map and statistical success probabilities of the solitary state.Here,via use of an auxiliary laser heating approach to suppress thermal dragging dynamics in dissipative soliton comb formation,we demonstrate stable Kerr soliton singlet formation and soliton bursts.First,we access a new soliton existence range with an inverse-sloped Kerr soliton evolution—diminishing soliton energy with increasing pump detuning.Second,we achieve deterministic transitions from Turinglike comb patterns directly into the dissipative Kerr soliton singlet pulse bypassing the chaotic states.This is achieved by avoiding subcomb overlaps at lower pump power,with near-identical singlet soliton comb generation over twenty instances.Third,with the red-detuned pump entrance route enabled,we uncover unique spontaneous soliton bursts in the direct formation of low-noise optical frequency combs from continuum background noise.The burst dynamics are due to the rapid entry and mutual attraction of the pump laser into the cavity mode,aided by the auxiliary laser and matching well with our numerical simulations.Enabled by the auxiliary-assisted frequency comb dynamics,we demonstrate an application of automatic soliton comb recovery and long-term stabilization against strong external perturbations.Our findings hold potential to expand the parameter space for ultrafast nonlinear dynamics and precision optical frequency comb stabilization.
Heng ZhouYong GengWenwen CuiShu-Wei HuangQiang ZhouKun QiuChee Wei Wong
Transverse localization of the optical Tamm plasmon(OTP) is studied in a metal-distributed Bragg reflector(DBR)structure with a one-dimensional disordered layer embedded at the interface between the metal and the DBR. The embedded disordered layer induces multiple scattering and interference of light, forming the light localization in the transverse direction. This together with the formation of Tamm plasmonic modes at the metal-DBR interface(i.e., the confinement of light in the longitudinal direction), gives birth to the so called transverse-localized Tamm plasmon. It is shown that for both transverse electric(TE) and transverse magnetic(TM) polarized light injection, the excited transverse-localized Tamm plasmon broadens and splits the dispersion curve due to spatial incoherence in the transverse direction, thus proving the stronger light confinement especially in the TE polarized injection. By adding the gain medium, specific random lasing modes are observed. The proposed study could be an efficient way of trapping and locally enhancing light on a subwavelength scale,which is useful in applications of random lasers, optical sensing, and imaging.
Photonic sensors that are able to detect and track biochemical molecules offer powerful tools for information acquisition in applications ranging from environmental analysis to medical diagnosis.The ultimate aim of biochemical sensing is to achieve both quantitative sensitivity and selectivity.As atomically thick films with remarkable optoelectronic tunability,graphene and its derived materials have shown unique potential as a chemically tunable platform for sensing,thus enabling significant performance enhancement,versatile functionalization and flexible device integration.Here,we demonstrate a partially reduced graphene oxide(prGO)inner-coated and fiber-calibrated Fabry-Perot dye resonator for biochemical detection.Versatile functionalization in the prGO film enables the intracavity fluorescent resonance energy transfer(FRET)to be chemically selective in the visible band.Moreover,by measuring the intermode interference via noise canceled beat notes and locked-in heterodyne detection with Hz-level precision,we achieved individual molecule sensitivity for dopamine,nicotine and single-strand DNA detection.This work combines atomic-layer nanoscience and high-resolution optoelectronics,providing a way toward high-performance biochemical sensors and systems.
A fiber-optic Raman spectrum sensor system is used for the fast diagnosis of esophageal cancer during clinical endoscopic examination.The system contains a 785nm exciting laser,a Raman fiber-optic probe with 7 large core fibers and a focus lens,and a highly sensitive spectrum meter.The Raman spectrum of the tissue could be obtained within 1 second by using such a system. A signal baseline removal and denoising technology is used to improve the signal quality.A novel signal feature extraction method for differentiating the normal and esophageal cancer tissues is proposed,based on the differences in half-height width(HHW)in 1200cm^-1 to 1400cm^-1 frequency band and the ratios of the spectral integral energy between 1600cm^-1-1700cm^-1 and 1500cm^-1- 1600cm^-1 band.It shows a high specificity and effectivity for the diagnosis of esophageal cancer.
The combination of optical fiber with graphene has greatly expanded the application regimes of fiber optics,from dynamic optical control and ultrafast pulse generation to high precision sensing.However,limited by fabrication,previous graphene-fiber samples are typically limited in the micrometer to centimeter scale,which cannot take the inherent advantage of optical fibers—longdistance optical transmission.Here,we demonstrate kilometers long graphene-coated optical fiber(GCF)based on industrial graphene nanosheets and coating technique.The GCF shows unusually high thermal diffusivity of 24.99 mm^(2) s^(-1) in the axial direction,measured by a thermal imager directly.This enables rapid thermooptical response both in optical fiber Bragg grating sensors at one point(18-fold faster than conventional fiber)and in long-distance distributed fiber sensing systems based on backward Rayleigh scattering in optical fiber(15-fold faster than conventional fiber).This work realizes the industrial-level graphene-fiber production and provides a novel platform for two-dimensional material-based optical fiber sensing applications.
The effects of gamma ray(γ-ray)radiation and electron beam(e-beam)radiation on Rayleigh scattering coefficient in single-mode fiber are experimentally investigated.Utilizing an optical time domain reflectometry(OTDR),the power distribution curves of the irradiated fibers are obtained to retrieve the corresponding radiation-induced attenuation(RIA).Based on the backscattering power levels and the measured RIAs,the Rayleigh scattering coefficients can be characterized quantitatively for each fiber sample.Under the given radiation conditions,Rayleigh scattering coefficients have been changed very little while RIAs have been changed significantly.Furthermore,simulations have been implemented to verify the validity of the measured Rayleigh scattering coefficient,including the splicing points.
In this paper,a cladding-pumped erbium-ytterbium co-doped random fiber laser(EYRFL)operating at 1550 nm with high power laser diode(LD)is proposed and experimentally demonstrated for the first time.The laser cavity includes a 5-m-long erbium-ytterbium co-doped fiber that serves as the gain medium,as well as a 2-km-long single-mode fiber(SMF)to provide random distributed feedback.As a result,stable 2.14 W of 1550 nm random lasing at 9.80 W of 976 nm LD pump power and a linear output with the slope efficiency as 22.7%are generated.This simple and novel random fiber laser could provide a promising way to develop high power 1.5μm light sources.
