- 标题
- 摘要
- 关键词
- 实验方案
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Dynamically stable continuous single frequency green ring laser
摘要： A single-frequency ring laser using two standard commercial diode-pumped Nd:YAG modules is demonstrated. Employing a dynamically stable resonator design, multi-longitudinal mode operation at 1064 nm with 53 W of output power was obtained. When inserting a LBO crystal in the resonator, 1.8 W of single-sided, single-frequency output at 532 nm was achieved. The measured linewidth was 3.6 MHz, close to the resolution limit of the scanning etalon used to measure the longitudinal mode structure.
关键词： dynamic stable resonators,Single frequency lasers,ring lasers,second harmonic generation
更新于2025-09-16 10:30:52
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Temporal profile measurements of ultrafast pulsed laser systems
摘要： Ultrafast pulsed lasers can be used to measure the phenomena occurring at femtosecond (fs) (10?15 s) time scale which include photo synthesis, protein collapsing and sub-atomic vibrations. In normal course, the temporal pro?le of the nanosecond (ns) pulsed lasers can be estimated by using the standard detectors because the recombination time of the electron-hole pair is of the order of ns. Nevertheless, the electronic equipment and the standard detectors are insuf?cient to measure the temporal pro?le of the ultrafast pulsed lasers. In the present investigation, we compare various techniques to measure the temporal pro?le of the ultrafast lasers which is followed by the details of the experimental con?guration of an autocorrelation technique. The temporal pro?le of the ultrafast pulsed lasers has shown various pulse width values in the experimental set-up when recorded at different con?gurations.
关键词： Second harmonic generation,Nonlinear optics,Autocorrelation measurement,Ultrafast spectroscopy,Ultrafast pulses
更新于2025-09-16 10:30:52
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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) - Zn:MgO:PPLN Waveguides for Rb Cold Atom Trap Based Quantum Gravitometry in a CubeSat
摘要： Satellite based experiments require laser systems that are compact and efficient, which are robust against vibration, radiation and thermal cycling. Supported by Innovate UK’s Quantum Technology ‘Cold Atom Space PAyload (CASPA)’ project we have fabricated PPLN (Periodically Poled Lithium Niobate) ridge waveguides to act as efficient frequency converters for rubidium atom cooling via second harmonic generation (SHG) of telecoms lasers. CASPA is a technology demonstrator for magneto-optical cooling within a micro CubeSat laying the foundations for novel gravitometry and global positioning techniques. With respect to the particular environment of operation we have developed single mode ridge waveguides with metal indiffusion and dicing. We fabricate PPLN ridge waveguides by firstly high-voltage poling of z-cut magnesium doped lithium niobate, then deposit and thermally indiffuse Zn to create planar optical confinement, followed by ultra-precision ductile dicing to define ridge waveguides and coupling facets. Our non-AR coated waveguides have produced optical to optical efficiencies of up to 22.0 %, producing 44.7 mW of SHG with 203 mW of transmitted pump. The 2nd moment MFD was calculated to be 10.8 and 10.0 μm in the x and y axes, respectively, allowing efficient mode matching to standard telecommunication fibre. With a free space launch we have measured an average insertion loss, over multiple dies, of -1.3 dB, for 4 cm long waveguides that are non-AR coated. When comparing to other ridge PPLN waveguides this is a 3.7 dB improvement over competing examples of a 5 cm bonded and thinned device and a 1.9 dB improvement for a 1 cm proton exchange device. These low insertion losses can be attributed to both the symmetric pump mode of the waveguides enabling efficient mode matching and low amounts of optical scattering from waveguide sidewall roughness. We have shown ductile dicing to produce an average surface roughness of 0.29 nm (Sa) on waveguide facets in a single processing step.
关键词： CubeSat,rubidium atom cooling,second harmonic generation,ridge waveguides,PPLN
更新于2025-09-16 10:30:52
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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) - Second-Harmonic Generation in Monolithic Lithium Niobate Metasurfaces
摘要： Second harmonic generation (SHG) in nonlinear metasurfaces has proven as a versatile tool for novel ultra-thin light sources with engineered spatial wavefronts. However, the availability of second-order nonlinear materials suitable for fabrication of such metasurfaces has so far been mainly limited to III-V semiconductors (e.g. GaAs, AlGaAs, GaP). Such systems have a limited transparency range and unusual off-diagonal second-order susceptibility tensors. These constraints have driven the search for new material platforms, including lithium niobate as one of the most promising nonlinear materials. Various approaches, such as plasmonic cavities [1], bottom-up techniques [2] and lithium niobate on insulator [3], have been recently explored, however with limited applicability. Here we propose a new design concept for second-order nonlinear metasurfaces on a monolithic substrate, which is not limited by the availability of thin crystalline films and can be applied to any non-centrosymmetric material. Our approach enables blue SHG from a monolithic lithium niobate metasurface with a conversion efficiency above 10?5 using 1 GW/cm2 pump intensity, opening new opportunities for practical designs of nonlinear metasurfaces.
关键词： second harmonic generation,monolithic substrate,Mie-type resonances,lithium niobate,nonlinear metasurfaces
更新于2025-09-16 10:30:52
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From CuFeS <sub/>2</sub> to Ba <sub/>6</sub> Cu <sub/>2</sub> FeGe <sub/>4</sub> S <sub/>16</sub> : rational band gap engineering achieves large second-harmonic-generation together with high laser damage threshold
摘要： A new germanium-based sulfide, Ba6Cu2FeGe4S16, achieves a band-gap broadening of more than 1 eV relative to CuFeS2. Remarkably, Ba6Cu2FeGe4S16 exhibits excellent comprehensive NLO performance (SHG, 1.5 (cid:2) AgGaSe2; LDT, 2 (cid:2) AgGaSe2), satisfying the essential requirements of mid-IR NLO candidates.
关键词： laser damage threshold,mid-IR NLO materials,germanium-based sulfide,second-harmonic-generation,band-gap engineering
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - All-Dielectric Metasurfaces: Optical Nonlinearities and Emission Control
摘要： In this work we show our results on the harmonic generation and nonlinear frequency mixing enhanced by Mie modes in GaAs metasurfaces. Moreover, we show enhancement and directionality control of the quantum dot emission embedded in the metasurface.
关键词： nonlinear frequency mixing,semiconductor metasurface,all-dielectric metasurface,second harmonic generation
更新于2025-09-12 10:27:22
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Observation of a ferro-rotational order coupled with second-order nonlinear optical fields
摘要： Ferroic orders can be classified by the symmetry of their order parameters, and ferroelectric, ferromagnetic and ferro-toroidal orders have already been observed. The ferro-rotational order, whose order parameter is an axial vector invariant under both time-reversal and spatial-inversion operations, is the final ferroic to be identified and has a vector order parameter. This order is closely related to a number of phenomena such as polar vortices, giant magnetoelectric coupling and spin-helicity-driven ferroelectricity, but it has received little attention so far. Here, using high-sensitivity rotational-anisotropy second-harmonic generation, we have exploited the electric quadrupole contribution to the second-harmonic generation to directly couple to this centrosymmetric ferro-rotational order in an archetype of type-II multiferroics, RbFe(MoO4)2. We found that two domain states with opposite ferro-rotational vectors emerge with distinct populations at the critical temperature Tc ≈ 195 K and gradually evolve to reach an even ratio at lower temperatures. Moreover, we have identified the ferro-rotational order phase transition as weakly first order and have revealed its coupling field as a unique combination of the induced electric quadrupole second-harmonic generation and the incident fundamental electric fields.
关键词： RbFe(MoO4)2,multiferroics,ferro-rotational order,second-harmonic generation,Landau theory
更新于2025-09-12 10:27:22
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A New Optical Angle Measurement Method Based on Second Harmonic Generation with a Mode-Locked Femtosecond Laser
摘要： This paper proposes a new optical angle measurement method based on second harmonic generation with a mode-locked femtosecond laser source by taking use of the unique characteristic of high peak power and high-intensity electric field of the femtosecond laser pulses. The angle is measured from the second harmonic wave intensity, which is a function of the angle between the laser beam axis and the optic axis of a nonlinear crystal attached to the target of interest. It is found that the beta barium borate (BBO) crystal is suitable as the nonlinear crystal for this purpose through theoretical simulation. As the first step of research, an experimental demonstration is also carried out in such a way that a change of the second harmonic wave intensity due to the angular displacement of BBO crystal is measured to verify the feasibility of the proposed principle of the angle measurement method.
关键词： Angle measurement,Second harmonic generation,Femtosecond laser
更新于2025-09-12 10:27:22
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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) - Periodic Poling with Short Period for Thin Film Lithium Niobate Waveguides
摘要： Lithium niobate (LN) is a favourable material for many applications, especially in integrated optics, due to its excellent electro-optic, acousto-optic, and nonlinear optic properties. One promising application of LN is second-harmonic generation (SHG). For enhancing the efficiency of SHG, phase matching between the interacting waves is needed, which is often realized by employing quasi-phase matching (QPM). QPM is typically realized by periodic poling of LN, i.e. the periodic flipping of the crystal orientation. The needed period is determined by the wavelengths as well as by the wave vectors of the fundamental- and the second-harmonic waves (FW and SH, respectively). For the case of backward SHG with a fundamental wavelength of 1.55 μm, where the SH wave travels in the opposite direction to the FW, typically sub-micrometer periods of the poled LN are required. Here, we demonstrate the realization of short-period QPM structures in LN-on-insulator (LNOI) thin-film substrates with a thickness of 600 nm. We aim to fabricate periodically poled LNOI (PPLNOI) waveguides with a periodicity as small as 1 μm, facilitating efficient nonlinear interaction due to the strong mode confinement.
关键词： periodic poling,second-harmonic generation,integrated optics,Lithium niobate,quasi-phase matching
更新于2025-09-12 10:27:22
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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) - Coherent Control of the Non-Instantaneous Response of Plasmonic Nanostructes
摘要： Nonlinear metamaterials have revolutionized nonlinear optics, allowing novel abilities that expand the current available nonlinear material capabilities. Due to their unique response, nanoparticles (NP's) have been the subject of research in numerous fields ranging from physics, engineering, biology, medicine and others. Understanding their physical mechanism and properties has enabled unprecedented capabilities in linear and nonlinear optics, sensing, theragnostic biomedical optics, material classifications of molecular structures as complicated as DNA or sensitive as oxygen singlets and much more [1-4]. A complete theoretical description, based on the nonlinear scattering theory, has been found suitable to describe the geometrical contribution of nanostructures (NSs) to their nonlinear response [5]. Yet, until now, a comprehensive theory has been investigated only for the instantaneous nonlinear response. A full response, including the resonant non-instantaneous behavior brought about by their resonant linewidth, has not yet been studied. We experientially demonstrate variance in the nonlinear response by coherently controlling the electric field. We show, for the first time to our knowledge, resonant non-instantaneous properties by coherent control measurements of nonlinear second harmonic generation (SHG) in resonant media. (see Figure 1). In contrary to common perception, we find that transform limited pulses do not yield the strongest nonlinearity in SHG. Approaching strong fields, a decrease in nonlinear behavior is not captures in traditional nonlinear models. We develop a theoretical framework, analogous to a resonant 3 level interaction, capturing non-instantaneous resonant phenomena portraying resonant effects beyond the weak field two-photon description. These include deviations from the conventional SHG nonlinearity which commonly is proportional to the square of the fundamental field intensity (see Figure 2.a). We also show that with changing the localized surface plasmonic resonant wavelength relative to the source's central wavelength, a shift in energy distribution and intensity emerges in the SH process pointing to the relative position of the resonant frequency (see Figure 2.b).
关键词： Nonlinear metamaterials,nanoparticles,second harmonic generation,nonlinear optics,plasmonic nanostructures
更新于2025-09-12 10:27:22