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High speed antimony-based superlattice photodetectors transferred on sapphire
摘要： We report the substrate transfer of InAs/GaSb/AlSb based type-II superlattice (T2SL) e-SWIR photodetector from native GaSb substrates to low-loss sapphire substrate in order to enhance the frequency response of the device. We have demonstrated the damage-free transfer of T2SL-based thin-films to sapphire substrate using top–down processing and a chemical epilayer release technique. After transfer the ?3 dB cut-off frequency increased from 6.4 GHz to 17.2 GHz, for 8 μm diameter circular mesas under ?15 V applied bias. We also investigated the cut-off frequency verses applied bias and lateral scaling to assess the limitations for even higher frequency performance.
关键词： high speed,photodetectors,substrate transfer,antimony-based superlattice,sapphire
更新于2025-09-19 17:13:59
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Thermally annealed wafer-scale h-BN films grown on sapphire substrate by molecular beam epitaxy
摘要： The effect of high temperature annealing (HTA) on crystalline quality improvement of h-BN films grown on sapphire substrates has been investigated. It is found that BN grown using conventional molecular beam epitaxy is disordered due to the growth temperature below 1000 °C. By annealing at a temperature of 1700 °C, thermodynamically stable crystalline h-BN could be obtained at wafer scale, where diffusion of atoms in the as-grown BN film is enhanced and the structural defect density decreases. The crystalline h-BN has been confirmed by x-ray diffraction, Raman scattering, and atomic force microscopy measurements. This work demonstrates that HTA is a simple and effective way to achieve wafer-scale crystalline h-BN films, which have numerous potential applications in next-generation two-dimensional devices and flexible III-nitride optoelectronic devices.
关键词： crystalline quality,molecular beam epitaxy,sapphire substrate,h-BN films,high temperature annealing
更新于2025-09-19 17:13:59
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TE/TM mode full-spatial decomposition of AlGaN-based deep ultraviolet light-emitting diodes
摘要： The full-spatial decomposition of transverse electric (TE) / transverse magnetic (TM) mode in AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) has been experimentally investigated, by introducing self-built light intensity test system mainly composed of angle resolution bracket, Glan-Taylor prism and spectrometer. By means of roughening the sapphire sidewall, the extraction efficiency of DUV-LED is improved, for both TE and TM mode light with no polarization selectivity. The introduction of self-built light intensity metrology system has been reflected via scribing the sapphire sidewalls using various laser conditions, which show a reliability in the enhancement validation of the light extraction efficiency. More importantly, the self-built light intensity test system enables effective feedback on epitaxial structures and chip structure design and provides a new perspective to design high efficiency AlGaN-based DUV-LEDs.
关键词： AlGaN,TE/TM mode light,sapphire sidewall roughening,deep ultraviolet light emitting diodes
更新于2025-09-19 17:13:59
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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) - Comparison of SC Fibers for fs Ti:Sapphire Based Hyperspectral CARS Microscopy
摘要： Hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy is a rapidly developing field enabling label-free, chemically selective bio-imaging based on Raman signatures. A significant factor limiting its clinical application is the complexity of current laser sources. A solution immediately relevant to two-photon excited fluorescence imaging laboratories is coherently broadening a fs Ti:Sapphire laser seed in a fiber to provide the Raman wavelengths via spectral-focusing (SF) CARS. The NKT fiber with two Zero Dispersion Wavelengths (ZDWs) is one option but the spectrum exhibits low Power Spectral Density (PSD) because of the large (>800 nm) spectral broadening. Here we perform the first systematic comparison sweeping (i) input pump power, (ii) pump wavelength and (iii) fiber length comparing the coherent SC from a femtoWHITE-CARS (2 ZDWs) fiber, a fiber with one ZDW offset above the seed wavelength, and an all-normal dispersion (ANDi) fiber. Starting with the seed laser polarisation aligned to a principal fiber axis, we show the total experimentally measured spectral output and importantly the polarisation resolved spectral component on the orthogonal axis, which is a measure of the nonlinear power-dependent depolarisation. This orthogonal component will degrade the efficiency of the CARS signal but still contributes to the bio-toxicity that limits the maximum power for imaging. Finally, we show representative SF-CARS microscopy images to showcase the power of this technique.
关键词： fiber optics,spectral-focusing,Ti:Sapphire laser,Hyperspectral CARS microscopy,supercontinuum generation
更新于2025-09-16 10:30:52
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Conceptual Design of a Laser Driver for a Plasma Accelerator User Facility
摘要： The purpose of the European project EuPRAXIA is to realize a novel plasma accelerator user facility. The laser driven approach sets requirements for a very high performance level for the laser system: pulse peak power in the petawatt range, pulse repetition rate of several tens of Hz, very high beam quality and overall stability of the system parameters, along with 24/7 operation availability for experiments. Only a few years ago these performances were considered unrealistic, but recent advances in laser technologies, in particular in the chirped pulse ampli?cation (CPA) of ultrashort pulses and in high energy, high repetition rate pump lasers have changed this scenario. This paper discusses the conceptual design and the overall architecture of a laser system operating as the driver of a plasma acceleration facility for di?erent applications. The laser consists of a multi-stage ampli?cation chain based CPA Ti:Sapphire, using frequency doubled, diode laser pumped Nd or Yb solid state lasers as pump sources. Speci?c aspects related to the cooling strategy of the main ampli?ers, the operation of pulse compressors at high average power, and the beam pointing diagnostics are addressed in detail.
关键词： Ti:Sapphire lasers,Chirped Pulse Ampli?cation,laser driven plasma acceleration
更新于2025-09-16 10:30:52
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Attainment of a 40 TW peak output power with a visible-range hybrid femtosecond laser system
摘要： We report the results of investigations aimed at raising the peak output power of a THL-100 visible-range hybrid femtosecond laser system based on a XeF(C – A) photodissociation amplifier. The increase in power was achieved due to the shortening of the pulse duration at the system output by broadening the spectral profile of the second harmonic from 5.3 to 8 nm, which takes place in the transformation of a negatively chirped pulse of the fundamental frequency radiation in a nonlinear KDP crystal. After the KDP the radiation pulse was stretched to 1.8 ps in a prism stretcher and amplified in the XeF(C – A) amplifier. The energy obtained at the amplifier output was 1.2 J. After compression of the amplified output pulse, its duration was equal to 29.4 fs, which means that a peak output power of 40 TW was reached at the output of the laser system.
关键词： stretcher,chirped pulse,compressor,Ti : sapphire front end,hybrid laser system,XeF (C – A) photodissociation amplifier
更新于2025-09-16 10:30:52
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Radiation-resistant optical fiber Fabry-Perot interferometer used for high-temperature sensing
摘要： An optical fiber Fabry-Perot interferometer based on sapphire wafer for high-temperature sensing under Co-60 γ irradiation is designed. The sensing probe is composed by a thin sapphire wafer and a pure silica multi-mode fiber. In the experiment, the interferometer is exposed under the Co-60 γ irradiation with different irradiation time and absorbed dose rate. The irradiated optical fiber sensor underwent three temperature cycle tests up to 800°C and demonstrated excellent sensing performance at high temperature. The whole sensing system has the capability to survive in high temperature environment that surpasses 800°C. The interferometer can achieve the high sensitivity of 29.9 pm/oC at the wavelength around 1340 nm when the temperature is 800°C. The proposed sensor and sensing system has great potential to be applied under strong irradiation and high temperature.
关键词： optical fiber sensor,high temperature,sapphire wafer,radiation,Fabry-Perot interferometer
更新于2025-09-16 10:30:52
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A direct diode pumped continuous-wave Ti:sapphire laser as seed of a pulsed amplifier for high-resolution resonance ionization spectroscopy
摘要： Progress of the development of a tunable continuous-wave directly diode-pumped Ti:sapphire laser is reported. The pump diode system based on InGaN multimode emitters in the blue-green wavelength region is characterized in terms of beam quality and output power. A prototype bow-tie resonator with a short highly doped Brewster-cut Ti:sapphire crystal was investigated. Output power scaling with the number of pump diodes and output coupling ratio as well as wavelength tuning range using a three-plate birefringent filter was measured.
关键词： Laser spectroscopy,Laser,Resonance ionization,Ti:sapphire
更新于2025-09-16 10:30:52
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Laser-Inscribed Stress-Induced Birefringence of Sapphire
摘要： Birefringence of 3 × 10?3 is demonstrated inside cross-sectional regions of 100 μm, inscribed by axially stretched Bessel-beam-like fs-laser pulses along the c-axis inside sapphire. A high birefringence and retardance of λ/4 at mid-visible spectral range (green) can be achieved using stretched beams with axial extension of 30–40 μm. Chosen conditions of laser-writing ensure that there are no formations of self-organized nano-gratings. This method can be adopted for creation of polarization optical elements and fabrication of spatially varying birefringent patterns for optical vortex generation.
关键词： femtosecond laser,stress,birefringence,sapphire
更新于2025-09-16 10:30:52
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The Study on Tuning Photoluminescence of Colloidal Graphene Quantum Dots Synthesized through Laser Ablation
摘要： We report photoluminescence study of Colloidal Graphene Quantum Dots (GQDs) that synthesized from ablation of rGO solution. The rGO solution was ablated using 800 nm Ti-Sapphire femtosecond laser by varying the synthesize parameters such as laser power and ablation time. We observed that changing laser power 1 Watt to become 1.7 Watt and time ablation 20 minutes to become 60 minutes will alterate the Photoluminescence (PL) curve peak of GQDs. In case of ablation power variation, PL data shows that the PL curve peak excited by 280 nm laser changed from 369.09 nm to 371.02 nm, and when it excited by 290 nm the PL curve peak slightly changed from 388.17 nm to 393.8 nm. The alteration of Photoluminescence peak is also observed in the variation of time ablation experiment, The PL curve peaks from GQDs time ablation variation samples excited by 280 nm were slightly changed from 376.81 nm to 373.59 nm, and when it excited by 290 nm laser, the PL curve peak is 391.55 nm then changed to 392.11. The change of PL peak on laser power or time ablation variation shows that both parameters will alter either the size, shape, or the edge-type of GQDs.
关键词： Laser Ablation,Ti-Sapphire Femtosecond Laser,Graphene Quantum Dots,Photoluminescence,Reduced Graphene Oxide
更新于2025-09-16 10:30:52