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Extremely high-brightness tapered photonic crystal diode laser with narrow-emitting aperture
摘要： High-brightness tapered photonic crystal diode lasers in the 980 nm range are investigated. The tapered lasers with a 20 μm wide light-emitting aperture achieved 2.55 W at 3.2 A. The beam quality factor M2 in the vertical and lateral directions are 1.16 and 1.48 at 2.5 A. Maximum brightness ?2 · sr at the second moment level is achieved. The devices also shows a narrow far-field of 17.1° × 6.5° in the vertical and lateral directions and a high efficiency of 53%. The proportion of the first-order mode in the lasing emission is also investigated based on the measured beam quality factor.
关键词： high-brightness,beam quality factor,far-field,tapered photonic crystal diode laser,narrow-emitting aperture
更新于2025-09-11 14:15:04
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Transmission characteristics of photonic crystal waveguide with array square Al2O3 rods lattice in millimeter wave
摘要： In this work, the transmission characteristics of a millimeter wave photonic crystal waveguide formed by square lattice Al2O3 ceramic rods array are numerically and experimentally investigated. Based on the numerical simulations of photonic crystals, the corresponding experiments are performed, which are consistent with the numerical results. The transmission efficiency of photonic crystal waveguide with three-dimensional model is studied using finite element method. The measured transmission efficiency of the prototype photonic crystal waveguide is better than ?1.5 dB in frequency range 23.6–29.8 GHz. Since the designed photonic crystal waveguide is wide band, low loss and easy integration; it is potential to be applied in millimeter communication systems.
关键词： Defects,Millimeter wave,Photonic crystal structure
更新于2025-09-11 14:15:04
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Quasi-all-fiber structure CW mid-infrared laser emission from gas-filled hollow-core silica fibers
摘要： A quasi-all-?ber structure CW mid-infrared ?ber lasers based on gas-?lled hollow-core ?bers (HCFs) is ?rstly reported here. Through a thermally tapered single-mode ?ber, the CW tunable 1.5 μm ?ber pump light is coupled into an acetylene-?lled anti-resonance HCFs, and the coupling point is sealed with epoxy glue to ensure the stability and gas tightness, then the HCFs is ?lled with acetylene gas by a specially designed small gas cell, just like an end cap. When the pump is precisely tuned to the resonance with the absorption lines of acetylene, CW mid-infrared emission around 3.1–3.2 μm is generated at room temperature with maximum power of ~180 mW and slope e?ciency of ~14%. The laser threshold is also discussed as function of acetylene pressure. This work opens new opportunities for all-?ber mid-infrared lasers of new wavelengths those unavailable for traditional rare-earth-doped ?bers.
关键词： Molecular gas lasers,Infrared and far-infrared lasers,Fiber lasers,Photonic crystal ?bers
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Lviv, Ukraine (2019.7.2-2019.7.6)] 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Surface and Bulk Wave Modes of Two Dimensional Photonic Crystal Waveguide
摘要： Electrodynamical characteristics of the two-dimensional photonic crystal waveguide are considered. Effect of the width of hollow waveguide channel on the dispersion characteristics and spatial distribution of electric field is analyzed. Slow wave localized modes with phase velocity less than speed of light are supported by photonic crystal waveguide and can be used for synchronization with linear electron beams in the terahertz beam-wave systems. Widening of the waveguide hollow channel does not result in significant decrease of the electric field intensity on the axis of waveguide as occur in metallic slow-wave systems.
关键词： spatial harmonics,dispersion characteristics,two-dimensional photonic crystal waveguide,terahertz range,slow wave modes
更新于2025-09-11 14:15:04
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Ordered Arrays of Ge(Si) Quantum Dots Incorporated into Two-Dimensional Photonic Crystals
摘要： Two different approaches to the integration of self-assembled Ge(Si) quantum dots into two-dimensional photonic crystals are considered. One approach includes the synthesis of an ordered array of Ge(Si) quantum dots on the textured surface of a substrate followed by the formation of a photonic crystal on this array. In the other approach, the photonic crystal itself serves as a template for the ordered growth of quantum dots. It is shown that, by varying the diameter of holes of photonic crystals in the second approach, it is possible to implement the growth of quantum dots in two modes, in which quantum dots are formed inside or outside the holes of the photonic crystal. For structures with ordered quantum dots incorporated into a photonic crystal, an increase in the photoluminescence signal intensity is detected at room temperature in the spectral range 0.9–1.2 eV. This increase is attributed to the interaction of emission from the structure with radiation modes of the photonic crystal.
关键词： photonic crystal,microphotoluminescence,quantum dots,heterostructures
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Non-Invasive Real-Time Characterization of Hollow-Core Photonic Crystal Fibres using Whispering Gallery Mode Spectroscopy
摘要： Single-ring hollow-core photonic crystal fibre (SR-PCF), consisting of a ring of thin-walled glass capillaries surrounding a central hollow core, can offer remarkably low transmission loss [1], and is finding applications in, e.g., wavelength conversion and pulse compression in gases, high-power beam delivery and circular dichroism [2]. As with all microstructured fibres, it is highly desirable to continuously measure the internal structural parameters (e.g. the capillary diameter) during fibre drawing. This would improve the yield of useful fibre lengths, as well as offering better control of structural uniformity along the fibre. Successful tapering of hollow-core fibres also requires a non-destructive method of verifying structural integrity along the taper. We here report for the first time a non-invasive technique for monitoring the capillary diameter in SR-PCF during the draw. The technique relies on excitation of whispering gallery modes (WGMs) in the capillary walls. The frequency spacing between successive WGMs fulfils the well-known condition: (cid:16)(cid:81)(cid:81)1l(cid:14)l(cid:32)cLcap(cid:173)(cid:176)(cid:174)(cid:176)(cid:175)lnl(cid:14)1,m1(cid:14)((cid:81)l(cid:14)1,(cid:16))mnl,m(cid:81)l,m(cid:189)(cid:176)(cid:190)(cid:176)(cid:191)(cid:124)cLncapWGM(cid:81)(1) where c is the speed of light in vacuum, Lcap is the circumference (~2(cid:652)R, where R is the mean radius), l the azimuthal and m the radial mode order, and nl,m is the effective index of the mode. Both approximate analytical solutions to nl,m and full numerical simulations show that, for the SR-PCFs studied, the approximation in Eq.(1) is accurate to within ±0.9% if nWGM is set to 1.484. As illustrated in Fig. 1 (right), the fibre is illuminated transversally by a broadband light source, thereby exciting WGMs inside selected capillaries. By placing a light collection fibre (400 μm core diameter) at a suitable position ~1 cm from the SR-PCF, the WGM spectrum originating from one of the capillaries could be selectively measured. A fast Fourier transform could then be used, together with Eq. (1), to compute the effective capillary diameter 2R in real-time with sub-micron accuracy. The results shown in Fig. 1 (left) were made at a fibre drawing speed of 32.3 m/min and a spectrometer integration time of 70 ms, corresponding to an axial resolution of <4 cm. We also used the technique to measure the diameter of individual capillaries at points along a tapered hollow-core fibre (not shown here).
关键词： Non-invasive,Hollow-core,Real-time,Characterization,Whispering Gallery Mode Spectroscopy,Photonic Crystal Fibres
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controllable Photon-Pair Spectral Correlations
摘要： Photon-pair states, whether spectrally correlated or separable, can all be very useful in quantum technology applications. For example, the former are used for improving the security of quantum key distribution, whilst the latter are the backbone in heralded single photon sources. It has been shown that the amount of spectral correlations is well-described by the shape of the Joint Spectral Amplitude function (JSA), which mostly depends on the relative group velocity relation between the pump, signal and idler photons within the source medium [1]. Here, we report on a photon-pair source whose states can be controlled from separable to spectrally entangled. The source is based on four-wave mixing nonlinear effect within a gas-filled hollow-core photonic crystal fiber (HCPCF). It combines three important properties: (1) Raman-free generation thanks to the use of a noble gas and to a minute overlap with silica within the hollow-core [2]; (2) strong efficiency nonlinear medium and (3) a high versatility in the phase-matching conditions thanks to the fiber microstructuration and gas pressure tunability. The inhibited-coupling HCPCF (see Fig.1a) filled with xenon, was designed to operate at wavelengths that are convenient for heralded single photon sources; the idler lies in the telecom wavelength range (~ 1545 nm), while the signal wavelength is in the range of atomic transitions and Silicon single photon detectors (~ 778 nm). More importantly, we show how the multiband dispersion profile (see Fig. 1b) of such medium allows to tailor phase- and group velocity relations and possibly at any given wavelength from the UV to infrared [3]. We demonstrate experimentally an active control over the generated photon spectral-correlation that allows spectrally entangled and factorable states to be obtained within the same device (examples in Fig. 1c). More specifically, a gallery of different JSI, including exotic shape, is measured by tuning various parameters: gas pressure, pump spectral FWHM, spectral chirp and pump spectral envelope. Such a versatile photon-pair source can target both applications requiring factorable (heralded single photon) and correlated states (spectral entanglement) and paves the way to spectro-temporal mode encoding [4]. Furthermore, the photon-pair state is generated over an unprecedented tunable frequency-range that span well over tens of THz. We will present complete theoretical and experimental results demonstrating the full capacity of this platform to generate photon pair with controllable spectral properties.
关键词： photon-pair states,hollow-core photonic crystal fiber,spectral correlations,quantum technology,spectral entanglement,four-wave mixing
更新于2025-09-11 14:15:04
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Photonic crystal for graphene plasmons
摘要： Photonic crystals are commonly implemented in media with periodically varying optical properties. Photonic crystals enable exquisite control of light propagation in integrated optical circuits, and also emulate advanced physical concepts. However, common photonic crystals are un?t for in-operando on/off controls. We overcome this limitation and demonstrate a broadly tunable two-dimensional photonic crystal for surface plasmon polaritons. Our platform consists of a continuous graphene monolayer integrated in a back-gated platform with nano-structured gate insulators. Infrared nano-imaging reveals the formation of a photonic bandgap and strong modulation of the local plasmonic density of states that can be turned on/off or gradually tuned by the applied gate voltage. We also implement an arti?cial domain wall which supports highly con?ned one-dimensional plasmonic modes. Our electrostatically-tunable photonic crystals are derived from standard metal oxide semiconductor ?eld effect transistor technology and pave a way for practical on-chip light manipulation.
关键词： graphene plasmons,tunable,infrared nano-imaging,Photonic crystal,surface plasmon polaritons
更新于2025-09-11 14:15:04
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Development of Non-Mechanical Beam Steering and LiDAR Based on Photonic Crystal and Si Photonics
摘要： LiDAR is crucial for future robots/drones, autonomous vehicles, etc. Photonic crystal and Si photonics technologies have potential of non-mechanical beam steering and coherent FMCW LiDAR. We report the current status of their development.
关键词： slow light,FMCW,LiDAR,photonic crystal,beam steering
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dual-Colour-Pump Broadband CARS in Single-Ring Gas-Filled Photonic Crystal Fibre
摘要： Selective detection and chemical analysis of trace gases at concentration levels of parts per million (ppm) and below is of critical importance in environmental monitoring and medicine. Spectroscopic techniques offer high gas-type selectivity and are widely used for measuring the concentration of specific molecular species. Raman spectroscopy provides two key advantages. First, the pump wavelength can be freely chosen, independently of the absorption lines of the gas. Second, the highest Raman frequency shift of any gas is the vibrational transition of H2 at 125 THz, which means that all known Raman active molecules can be detected with one spectrometer. We report coherent anti-Stokes Raman spectroscopy (CARS) in single-ring hollow-core photonic crystal fibre (SR-PCF) using a dual-colour pump. The long collinear path-length offered by SR-PCF strongly enhances the efficiency of the Raman interactions, and furthermore the gas-filled SR-PCF has a zero dispersion wavelength which is pressure tuneable. By selecting an appropriate pressure, the dispersion can be arranged to be anomalous in the visible and at the same time normal in the ultraviolet. Under these circumstances, by fine-tuning the pressure to minimize dephasing, the Raman coherence prepared by seeded pumping in the visible can be used for phase-matched generation of an anti-Stokes signal from a second pump in the ultraviolet. This spectrally separates the 'preparation' pump from the 'read-out' pump. The low dephasing rate in the ultraviolet permits efficient generation, along the whole fibre length, of anti-Stokes signals from all known Raman-active gas molecules, which is a significant advantage compared to other spectroscopic techniques. The dual-colour pump scheme allows the main detection limit of CARS imposed by the non-resonant background (NRB) to be overcome. It exploits the fact that the NRB is a quasi-instantaneous effect, present only when pump and seed pulses overlap. Although this is also a requirement of Raman excitation, the resulting coherence wave has a lifetime of nanoseconds before it relaxes through intermolecular collisions. Therefore, by appropriately delaying the read-out pump pulse, it is possible to suppress the NRB. Figure 1(a) shows the CARS spectrum for two trace gases, H2 (500 ppm) and CH4 (600 ppm), mixed with the buffer gas N2, measured when the read-out pump overlaps with the Stokes seed. Figure 1 (b) shows the CARS spectrum for 20 ppm of H2 and 350 ppm of CH4, measured when the pump was delayed by 2 ns with respect to the Stokes seed. As can be seen from Fig.1, the dual-colour-pump CARS scheme in SR-PCF reduces the NRB by 120 dB, improving the detection limit by 15 dB and allowing detection of trace gas concentrations as low as 20 ppm with only 20 kW of peak pump power. This novel dual-colour-pump CARS approach has great potential in environmental monitoring and medical applications, offering high sensitivity, short acquisition times (several seconds) and simultaneous multi-species sensing.
关键词： Raman spectroscopy,photonic crystal fibre,dual-colour pump,CARS,trace gas detection
更新于2025-09-11 14:15:04