- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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) - Determination of the Residual Amplified Spontaneous Emission in Single-Mode Semiconductor Optical Amplifiers
摘要： The Master-Oscillator-Power-Amplifier (MOPA) is a laser light source best suited to provide high power, stable frequency, and narrow linewidth emission. In state-of-the-art MOPA systems, semiconductor optical amplifiers (SOAs) with single-mode lateral waveguides provide a compromise between the demands for high power on one side and excellent beam quality and small astigmatism of the optical mode on the other. The amplified spontaneous emission (ASE) in SOAs remains a limiting factor for the deployment of the MOPA systems in quantum technology applications. The presence of ASE reduces the carrier density and hence the device efficiency, increases the noise in the output signal, and adds incoherent background radiation that is critical, for example, for atom interferometry applications. It is therefore important to understand the dependence of the ASE on the design and operating conditions of an SOA in detail in order to develop SOAs optimized for applications that require spectrally very pure radiation. In this work, the coherent and the residual ASE power of ridge waveguide (RW) SOAs are experimentally determined as a function of the seed power (optical power at the input of the SOA) and the SOA current. The experiment provides essential information about the suppression of the ASE background and the saturation behaviour of the optical amplifier. The measurement setup is depicted in Fig. 1 (a). The seed laser (ECDL, TE-polarized at 871 nm) is operated far above its threshold to avoid amplification of the spontaneous emission of the seed laser by the SOA. An acousto-optic modulator (AOM) is used to set the seed power. The laser beam is then fed into the 6 mm long SOA. A non-polarizing beam splitter (BS) cube divides the output beam into two parts. One part (reference beam) is detected using a power meter (PM). The spectrum of the second part is recorded using an Advantest Q8347 optical spectrum analyser (OSA). The measured data is analysed using the correlation between optical power measured with the power meter and the optical spectrum. The ASE power is reconstructed from the remaining ASE (fitted) spectrum after removing the coherent part. Fig. 1(b) shows the measured total output, ASE and coherent powers retrieved from the spectrum as a function of the seed power. The measured quantities in Fig. 1(b) are compared to theoretical values which are calculated using a SOA model similarly as described in [2]. The carrier-density dependent spectra of the gain and the spontaneous emission are obtained from a microscopic model taking into account the waveguide structure [3]. The comparison shows good qualitative agreement between theory and measurement. We show how the experimental findings are used to validate and calibrate the model and how the model can be applied to compare the performance (coherent power, ASE background, saturation behaviour) of SOAs at different seed powers, injection current setting, different lengths or different lateral geometries.
关键词： ridge waveguide SOAs,semiconductor optical amplifiers,Master-Oscillator-Power-Amplifier,quantum technology applications,amplified spontaneous emission
更新于2025-09-12 10:27:22
-
[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) - Nd,Gd:SrF <sub/>2</sub> Laser Generating 600 fs Pulses at 0.9 W of Pump Power
摘要： Fluoride crystals (CaF2, SrF2) doped with neodymium Nd3+ and codoped with non-active ions as Y3+, La3+, or Gd3+ for breaking clusters of active ions, have become recently interesting active media for the diode-pumped mode-locked lasers. They possess broader emission spectra as well as longer fluorescence lifetime in comparison with widely used crystals such as Nd:YAG or Nd:YVO4. The femtosecond Nd,Y:SrF2 laser generating 97 fs pulses was reported in the Ti:sapphire pumped system [1]. We have reported continuously mode-locked operation of this laser pumped by a 2 W multimode laser diode and mode-locked using a semiconductor saturable absorber generating pulses with the duration of 258 fs [2]. In laser systems with La3+ codoped crystals, which have wider tunability than Y3+ codoped crystals, passively mode-locked 354 to 1200 fs and continuous-wave 1044 to 1081 nm tunable operation was reported in the system pumped by 4 W laser diode [3]. Recently a new Nd,Gd:SrF2 crystal has been investigated and the dual wavelength mode-locked picosecond operation was reported for pump power higher than 3.8 W [4]. We reported femtosecond operation of laser with this crystal and obtained pulses as short as 228 fs with output power of 2 x 50 mW in system pumped by 2 W laser diode for absorbed pump power of 1320 mW [5]. In the present contribution we report on operation of this novel laser with a Brewster cut crystal in passively mode locked regime for extremely low pump power. Laser system schematic is similar as in ref. [5] and is shown in Fig. 1. A 5 mm long Brewster cut 0.5%Nd, 5%Gd:SrF2 crystal was pumped by a multimode 2 W laser diode at 796 nm and passively mode-locked using a semiconductor saturable absorber mirror (SAM). Using a chirped mirror M3 with GDD equal to -650 fs2 it was possible to achieve continuously mode locked regime at absorbed pump power of only 320 mW, with output power of 2 x 12 mW behind the mirror M4 in linearly polarized beams with nearly Gaussian spatial profile and pulse duration of 740 fs (assuming sech2 pulse shape). For higher absorbed pump power of 632 mW (905 mW incident on the crystal) the total output power of 2 x 20 mW was achieved with a pulse duration of 600 fs. The autocorrelation curve is shown in Fig. 2 together with the measured spectrum 3.3 nm wide, and centered at 1051.5 nm. The absorbed pump power is 2 - 4 times smaller in comparison with our previous results. The calculated time-bandwidth product of 0.536 gives potential to get shorter pulses (down to 352 fs) with optimum GVD compensation.
关键词： diode-pumped,semiconductor saturable absorber mirror,femtosecond pulses,Nd,Gd:SrF2,mode-locked lasers
更新于2025-09-12 10:27:22
-
Photoluminescence mechanism of phosphorene quantum dots (PQDs) produced by pulsed laser ablation in liquids
摘要： Phosphorene quantum dots (PQDs) with high photoluminescence (PL) quantum yield were fabricated through pulsed laser ablation of black phosphorus in liquids. The PL emission showed excitation wavelength-independent features due to the suf?cient passivation by oxygen-containing substituents derived from the ablation-decomposed solvent molecules. There were four peaks in the PL pro?le showing a multi-frequency PL effect, which provided a viable route to investigate the PL mechanism via the detailed structures of the PL pro?le. The two peaks at shorter wavelengths were attributed to the intrinsic PL transitions. The two peaks at longer wavelengths were assigned to the transitions from the lowest unoccupied molecular orbital to the two-surface states. The positions of the four peaks are redshifted with increasing solvent molecular chain length due to the passivation effect. The intense, excitation wavelength-independent, multifrequency and blue-violet PL emissions indicate the potential application in semiconductor light sources.
关键词： semiconductor light sources,pulsed laser ablation,photoluminescence,phosphorene quantum dots
更新于2025-09-12 10:27:22
-
A computational approach to study the optoelectronic properties of F-BODIPY derivatives at the bulk level for photovoltaic applications
摘要： The Dipyrrin compounds are recognized as imminent and hi-tech organic semiconductor materials (OSMs) designed for photovoltaic applications owing to low-cost, flexible, and eco-friendly nature. In a latest study, several optoelectronic properties of conjugated F-BODIPY derivatives were studied by using the density functional theory (DFT) at (GGA/PBE) level. This analysis classifies Comp_1 (5,5-difluoro-1,37,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinine) as a direct band-gap semiconductor with a band-gap of 2.81 eV. The band-gap of Comp_2 (2-ethyl-5,5-difluoro-1,3,7,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinine) and Comp_3 (2,8-diethyl-5,5-difluoro-1,3,7,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f] [1,3,2] diazaborinine) are reduced by 1.25 and 1.09 eV, respectively in comparison with parent molecule Comp_1 owing to the influence of p- orbitals of all atoms in crystal structures. The reduction in energy and density of states (DOS) for these compounds in this study validated that band-gap could be improved to a required value for optoelectronic applications by derivatives modeling. Additionally, optoelectronic properties at the solid-state bulk level were also computed. Several features of interest at solid-state bulk level exposed the F-BODIPY derivatives as competent compounds for organic semiconductor devices applications.
关键词： Bandgap,Bulk level,Photovoltaic application,F-BODIPYs,Organic semiconductor
更新于2025-09-12 10:27:22
-
Integrated color photodetectors in 40 nm standard CMOS technology
摘要： For the further integration of receivers in multi-color visible light communication systems, a novel color photodetector (PD) was designed and fabricated by using a 40 nm standard complementary metal oxide semiconductor (CMOS) process without any process modifications. The PD consists of CMOS photodiode and two-dimensional (2D) polysilicon subwavelength grating above the photodiode. The 2D polysilicon grating is controlled in structural parameters to realize color filtering, based on guided-mode resonance, for the first time in a standard CMOS process. Here three kinds of color PDs were designed to respond to the three primary colors. The measured results demonstrate that the color PDs exhibit wavelength selectivity in the visible range (400-700 nm) and the maximum peaks in the spectral response curves of them are at 660 nm (red), 585 nm (green) and 465 nm (blue), respectively. In addition, the added 2D polysilicon grating almost does not reduce the responsivity of the photodiodes.
关键词： two-dimensional polysilicon subwavelength grating,Color photodetector,visible light communication,complementary metal oxide semiconductor (CMOS)
更新于2025-09-12 10:27:22
-
[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) - XUV Coherence Tomography with Nanoscale Resolution Driven by High Harmonic Generation
摘要： Optical coherence tomography (OCT) is a well-established method to retrieve three-dimensional, cross-sectional images of biological samples in a non-invasive way using near-infrared radiation. The axial resolution of OCT is on the order of the coherence length lc ∝ λ 2 /Δλ which depends on the central wavelength λ0 and the spectral width Δλ of the light source. As a consequence, the axial resolution only depends on the spectrum rather than the geometrical properties of the radiation. OCT with broadband visible and near-infrared sources typically reaches axial (depth) resolutions on the order of a few micrometers [1]. Here we present extreme ultra violet (XUV) coherence tomography (XCT) [2], which takes advantage of the fact that the coherence length can be signi?cantly reduced if broadband XUV and soft X-ray (SXR) radiation is used. XCT can display its full capabilities when used in the spectral transmission windows of the sample materials. For instance, the silicon transmission window (30-99 eV) corresponds to a coherence length of about 12 nm, thus suggesting applications for semiconductor inspection. In the water window at 280-530 eV, a coherence length as short as 3 nm can be achieved and highlights possible applications of XCT for life sciences. XCT utilizes a variant of the Fourier-domain OCT scheme that completely avoids a beam splitter. In the experiment, broadband XUV from a lab-based high-harmonic generation light source [3] is focused onto the surface of the sample. The re?ected spectrum is measured with a grating spectrometer (see Fig. 1 left side). The top layer re?ection assumes the role of a reference beam. Previously, this simpli?cation led to artifacts [2]. Here we show a novel one-dimensional phase retrieval algorithm (PR) to mitigate such disadvantages and enable artifact-free so-called PR-XCT [4]. The right side of Fig. 1 shows a 3D-tomogram of a nondestructive XCT scan of two nanometer thin laterally structured gold layers embedded in silicon. An axial resolution of 24 nm could be reached in the silicon transmission window with the table-top system. Another remarkable result is the high material sensitivity of XCT. At a depth of about 160 nm, a Silicon dioxide layer (blue) was detected which developed during the production process of the sample and has a thickness of a few nanometers only. This layer could not be detected with a SEM in a thin slice cut out of the sample, and even in a TEM image it is only barely visible. Furthermore, the PR-XCT algorithm is capable of extracting material information about the materials inside of the sample. We will present ?rst results on material-resolved XCT.
关键词： optical coherence tomography,high harmonic generation,XUV coherence tomography,nanoscale resolution,life sciences,semiconductor inspection
更新于2025-09-12 10:27:22
-
[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - High performance lasers on Si
摘要： We review our recent progress on high performance heterogeneously integrated and directly grown semiconductor light sources on Si, with an emphasis on sub-kilohertz narrow linewidth lasers and high-channel-count comb lasers.
关键词： Semiconductor lasers,Photonic Integration,Si photonic and heterogeneous platform
更新于2025-09-12 10:27:22
-
Excellent ambipolar gas sensing response of Eu[Pc(OC4H9)8]2/acidified multiwalled carbon nanotubes hybrid at room temperature
摘要： A new hybrid material has been developed by mixing a sandwich-type double-decker, Eu[Pc(OC4H9)8]2 = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninate] with acidified multiwalled carbon nanotubes (aMWCNTs) through non-covalent interactions. The UV-vis spectrum, X-ray diffraction and scanning electron microscope have been employed to reveal the J-aggregate mode and optimized morphology of Eu[Pc(OC4H9)8]2 molecules in the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid material. The gas-sensing devices based on this hybrid material are fabricated by a simple solvent-processing quasi-Langmuir–Sh?fer (QLS) progress. The n-type and p-type response is shown by the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid film at room temperature. The detection limit of the hybrid for ammonia and nitrogen dioxide gas is 0.5 ppm and 0.3 ppm, respectively.
关键词： phthalocyanine,gas sensing,multiwall carbon nanotubes,ambipolar organic semiconductor,europium complex
更新于2025-09-12 10:27:22
-
Stronger Reductive Environment in Solvothermal Synthesis Leads to Improved Ga Doping Efficiency in ZnO Nanocrystals and Enhanced Plasmonic Absorption
摘要： The key parameter for degenerated semiconductor oxide plasmonic nanocrystals is the doping level. Hydrothermal and solvothermal approaches are considered to be less effective toward achieving high concentration of aliovalent donor dopants in a host oxide when compared to other synthesis methods that use long chain hydrocarbon solvents, fatty acids, and fatty amines as precursors. Because of this, although they have several advantages such as sustainability, ease of use, relatively inexpensive reagents and apparatus, and reduced environmental impact, they are excluded from the list of potential synthesis methods. Herein, an effective Zn2+ substitution with aliovalent Ga3+ in the ZnO host lattice is demonstrated, and it is achieved by increasing the reductive power of the solvothermal synthesis conditions by either solvent substitution or the addition of reducing agents. This increase results in an increased oxidation affinity of the medium. This in turn promotes Ga3+ incorporation into the ZnO lattice, by skewing the reaction equilibrium toward oxygen evolution.
关键词： plasmonic resonance,semiconductor nanocrystals,gallium-doped zinc oxide,degenerated oxide semiconductor nanocrystals
更新于2025-09-11 14:15:04
-
[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) - Non-Hermitian Broad Aperture Semiconductor Lasers Based on PT-Symmetry
摘要： In this paper we propose a novel configuration to regularize the complex spatiotemporal dynamics of broad area lasers into bright light beam. It has recently been shown that arbitrary non-Hermitian optical potentials based on local Parity-Time (PT-) symmetry may tailor and control the flow of light, due to the asymmetric mode coupling. We now provide a comprehensive analysis on how this can be applied to stabilize the emission from broad aperture semiconductor lasers. The mechanism relies on a non-Hermitian configuration of the laser potential achieved by simultaneous spatial modulation of the refractive index and gain-loss profiles. This allows concentrating the light into a bright and narrow output beam. We provide a numerical analysis on Vertical Cavity Surface Emitting lasers and Broad Area Semiconductor Lasers. The results indicate a significant intensity enhancement and concentration of the emitted stabilized beam. The proposed mechanism may be technologically achievable, and it is expected to be applicable to regularize the radiation of other broad aperture and microlasers, which typically emit quite random and irregular light patterns. Besides, the reported concentration effect is universal, and could be extended to random and quasi-periodic background potentials.
关键词： semiconductor lasers,VCSEL,local PT-symmetry,non-Hermiticity
更新于2025-09-11 14:15:04