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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Lasing and saturation of CAEP THz FEL facility
摘要： A high power THz free electron laser (FEL) facility is under construction at China Academy of Engineering Physics (CAEP) since October, 2011. The radiation frequency of the FEL facility is designed in range of 1~3 THz and the average output power is about 10 W. First lasing of the CAEP THz FEL (CTFEL) facility was obtained in August 29, 2017. Then the saturation operation is observed in September 20, 2017. The radiation frequency is sequentially as 1.99THz, 2.41THz and 2.92THz. And the average output power is larger than 10 W; the largest output power is about 20W. The peak power of micro-pulse is larger than 0.5MW. The optical resonator of CTFEL is optimized to ensure wavelength tunable in a wide range and high power operation. In this paper, the main designed and present status of the facility is given.
关键词： free electron laser,lasing,CAEP,saturation,FEL,THz
更新于2025-09-23 15:21:01
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Coherent phonon lasing in a thermal quantum nanomachine
摘要： The notion of nanomachines has recently emerged to engage and use collective action of ensembles of nanoscale components or systems. Here we present a heat-gradient driven nanomachine concept which through appropriate coupling between quantum nanosystems is capable of realizing and maintaining an inversion. Based on a Lindblad form of the quantum master equation with a semiclassical coupling to the lattice displacement phonon field we show that this positive inversion can be harnessed to generate coherent optomechanical oscillations and phonon lasing.
关键词： heat-gradient,nanomachines,quantum nanosystems,quantum master equation,Lindblad form,phonon lasing
更新于2025-09-23 15:21:01
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Lighta??Emitting Nanophotonic Designs Enabled by Ultrafast Laser Processing of Halide Perovskites
摘要： Nanophotonics based on resonant nanostructures and metasurfaces made of halide perovskites have become a prospective direction for efficient light manipulation at the subwavelength scale in advanced photonic designs. One of the main challenges in this field is the lack of large-scale low-cost technique for subwavelength perovskite structures fabrication preserving highly efficient luminescence. Here, unique properties of halide perovskites addressed to their extremely low thermal conductivity (lower than that of silica glass) and high defect tolerance to apply projection femtosecond laser lithography for nanofabrication with precise spatial control in all three dimensions preserving the material luminescence efficiency are employed. Namely, with CH3NH3PbI3 perovskite highly ordered nanoholes and nanostripes of width as small as 250 nm, metasurfaces with periods less than 400 nm, and nanowire lasers as thin as 500 nm, corresponding to the state-of-the-art in multistage expensive lithographical methods are created. Remarkable performance of the developed approach allows to demonstrate a number of advanced optical applications, including morphology-controlled photoluminescence yield, structural coloring, optical-information encryption, and lasing.
关键词： metasurfaces,structural coloration,lasing,halide perovskites,light emission,nanostructures
更新于2025-09-23 15:19:57
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Origin of Light Scattering in Dye Doped Polymeric Waveguides and the Dependence of Excitation Geometry on Coherent Random Lasing
摘要： We present an experimental investigation on the origin of coherent random laser (RL) emission from 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminos-tyryl)-4H-pyran (DCM) doped polyvinyl alcohol (PVA) thin film (DCM-PVA) planar waveguide using various characterization techniques. Absorption and fluorescence spectra of the DCM-PVA thin film confirm the presence of aggregates at dye concentrations greater than 0.08 wt. %. Time correlated single photon counting measurements were perfomed to confirm the presence of dye aggregates in PVA matrix. X-ray diffraction studies reveal the semi-crystalline nature of the DCM-PVA thin film. The optical gain coefficient was determined by the variable stripe length method under 532 nm pulsed laser excitation and was found to be 2.1 cm-1 using the one-dimensional amplifier model for the 0.08 wt. % thin film. The RL emission of the planar waveguide depends on the geometry of the excitation spot. The emission spectrum consists of randomly positioned narrow spectral lines under stripe excitation geometry whereas, a smooth spectrum lacking the narrow peaks is observed under circular spot excitation, both above the lasing thresholds. The origin of weak scattering in DCM-PVA waveguide is attributed to the formation of dye aggregates and inhomogeneities created by the semi-crystalline nature of the film. The RL threshold decreases with an increase of the stripe length due to weak waveguiding in the planar film under stripe excitation. The high optical gain and low lasing thresholds attainable in DCM-PVA waveguides make them a promising candidate for the fabrication of polymer waveguide based photonic devices.
关键词： amplified spontaneous emission,Random lasing,polymeric waveguide
更新于2025-09-23 15:19:57
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On-chip single-mode CdS nanowire laser
摘要： By integrating a free-standing cadmium sulfide (CdS) nanowire onto a silicon nitride (SiN) photonic chip, we demonstrate a highly compact on-chip single-mode CdS nanowire laser. The mode selection is realized using a Mach-Zehnder interferometer (MZI) structure. When the pumping intensity exceeds the lasing threshold of 4.9 kW/cm2, on-chip single-mode lasing at ~518.9 nm is achieved with a linewidth of 0.1 nm and a side-mode suppression ratio of up to a factor of 20 (13 dB). The output of the nanowire laser is channelled into an on-chip SiN waveguide with high efficiency (up to 58%) by evanescent coupling, and the directional coupling ratio between the two output ports can be varied from 90 to 10% by predesigning the coupling length of the SiN waveguide. Our results open new opportunities for both nanowire photonic devices and on-chip light sources and may pave the way towards a new category of hybrid nanolasers for chip-integrated applications.
关键词： Mach-Zehnder interferometer,single-mode lasing,nanowire laser,on-chip nanophotonics,silicon nitride waveguide
更新于2025-09-23 15:19:57
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Tunable Microlasers Modulated by Intracavity Spherical Confinement with Chiral Liquid Crystal
摘要： Manipulation of laser emission offers promising opportunities for the generation of new spatial dimensions and applications, particularly in nanophotonics, super-resolution imaging, and data transfer devices. However, the ability to control laser modes and wavelength in a microcavity remains challenging. Here, a novel approach is demonstrated to control laser modes by manipulating the 3D-optical confinement, chirality, and orientations in a Fabry?Pérot microcavity with cholesteric liquid crystal droplets. Different configurations of intracavity micro-/nanostructures generate versatile dimensions of laser modes, while the significantly reduced laser mode volume further leads to single-mode lasing. Theoretical analysis is carried out to support this interesting discovery. Finally, switchable lasing wavelength with various surface anchoring forces and pH interactions is demonstrated. This novel concept not only provides a simple yet highly versatile method to manipulate laser emissions, but deepens insight into how molecules interact with and modulate laser light, laying the foundation for the development of tunable photonic devices at the molecular level. Promising applications include highly selective laser devices, laser-emission imaging, and bioinspired sensing.
关键词： tunable lasing,high-order laser mode,cholesteric liquid crystals,spherical confinement,intracavity interactions
更新于2025-09-23 15:19:57
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Lasing in a coupled hybrid double quantum dot-resonator system
摘要： We theoretically investigate the possibility of lasing in an electromagnetic resonator coupled to a voltage-biased hybrid double quantum dot comprised of a double quantum dot tunnel coupled simultaneously to a normal metal and a superconducting lead. Using a unitary transformation, we derive a resonator-double quantum dot interaction Hamiltonian in the rotating-wave approximation which reveals the fact that lasing in this system is mediated by electron transitions between Andreev energy levels in the system’s density of states. Moreover, by employing a Markovian master equation incorporating dissipation effects for the electronic and photonic degrees of freedom, we numerically calculate the steady-state reduced density matrix of the system from which we determine the average photon number and its statistics in the resonator in various parameter regimes. We ?nd that at some appropriate parameter con?gurations, lasing can be considerably enhanced due to the possibility of electron transitions between multiple Andreev levels in the system.
关键词： lasing,Andreev energy levels,hybrid double quantum dot,electromagnetic resonator,Markovian master equation
更新于2025-09-23 15:19:57
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Temperature dependence of an amorphous organic thin film polariton laser
摘要： Since its first observation, the polariton lasing threshold in organic films has been anomalously high, given that Bosonic condensation should occur at vanishingly small pumping powers. Here, we investigate the temperature dependence of a polariton laser employing an amorphous organic thin film, 2,7-bis[9,9-di(4-methylphenyl)-fluoren-2-yl]-9,9-di(4-methylphenyl)fluorene, in a vertical optical microcavity. An increase in laser threshold is observed at temperatures < 45 K, while the threshold remains unchanged as the temperature increases up to room temperature. In contrast, the energy dispersion characteristic of cavity polaritons is independent of temperature. At low temperature, an energy relaxation bottleneck along the polariton dispersion takes place below threshold. The bottleneck is found to be responsible for the anomalous increase in threshold with decreasing temperature. As the pumping power increases, amplified spontaneous emission (ASE) is observed prior to the onset of lasing. We also study the photoluminescence of the neat organic film versus temperature to explain the origin of the bottleneck in the exciton polariton dispersion.
关键词： exciton,polariton lasing,light-matter interaction,cavity,Strong-coupling
更新于2025-09-23 15:19:57
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Spectral Behaviors of Unidirectional Lasing from Various Semiconductor Square Ring Microcavities
摘要： Spectral behaviors of lasing from semiconductor square ring microcavities with structures for unidirectional laser oscillation were investigated. When a tapered structure was introduced, the lasing envelope shifted to a shorter wavelength region. Statistical estimate of the additional loss caused by the tapered structure was carried out by analyzing spectral data from many sets of cavities with various sizes. When a saw-edged structure was introduced, the unidirectional lasing functioned well but no apparent spectral shift was observed due to negligible additional loss.
关键词： Square ring,Microcavity,Cavity loss,Unidirectional lasing
更新于2025-09-23 15:19:57
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Amplified spontaneous emission and random lasing using CsPbBr3 quantum dots glass through controlling crystallization
摘要： By increasing the heat treatment temperature, the average size of CsPbBr3 quantum dots (QDs) in the glass matrix was increased, which contribute to the 5.5 folds increase of the optical gain coefficients. And the corresponding lasing threshold can decrease from 0.752 mJ/cm2 to 0.138 mJ/cm2.
关键词： CsPbBr3 quantum dots,glass matrix,heat treatment temperature,optical gain coefficients,lasing threshold
更新于2025-09-19 17:13:59