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- 摘要
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- 实验方案
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Multi-octave spanning, Watt-level ultrafast mid-infrared source
摘要： We present a source of brilliant mid-infrared radiation, seamlessly covering the wavelength range between 1.33 and 18 μm (7500–555 cm?1) with three channels, employing broadband nonlinear conversion processes driven by the output of a thulium-fiber laser system. The high-average-power femtosecond frontend delivers a 50 MHz train of 250 fs pulses spectrally centered at 1.96 μm. The three parallel channels employ soliton self-compression in a fused-silica fiber, supercontinuum generation in a ZBLAN fiber, and difference-frequency generation in GaSe driven by soliton self-compressed pulses. The total output enables spectral coverage from 1.33 to 2.4 μm, from 2.4 to 5.2 μm, and from 5.2 to 18 μm with 4.5 W, 0.22 W and 0.5 W, respectively. This spatially coherent source with a footprint of less than 4 m2 exceeds the brilliance of 3rd-generation synchrotrons by more than three orders of magnitude over 90% of the bandwidth.
关键词： intra-pulse difference frequency generation (DFG),ultrafast optics,supercontinuum generation,mid-infrared generation,ZBLAN optical fibre,nonlinear optics
更新于2025-09-23 15:19:57
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[IEEE 2019 6th International Conference on Instrumentation, Control, and Automation (ICA) - Bandung, Indonesia (2019.7.31-2019.8.2)] 2019 6th International Conference on Instrumentation, Control, and Automation (ICA) - A Portable Surface Roughness Measurement System Using Laser Speckle Imaging Based on GLCM
摘要： This paper summarizes the generation of sub-single-cycle infrared (IR) pulses through a laser filament and the detailed properties of the generated pulses. The fundamental (ω1) and second harmonic (ω2) of 30-fs Ti:sapphire amplifier output were focused into nitrogen gas and produced phase-stable broadband IR pulses (ω0) by four-wave difference frequency generation (ω1 + ω1 ? ω2 → ω0) through filamentation. The spectrum spread from 200 to 5500 cm?1, corresponding to ～3.5 octaves. The waveform of the sub-single-cycle pulse was completely characterized with the frequency-resolved optical gating capable of a carrier-envelope phase determination. The pulse duration was measured as 6.9 fs, which was 0.63 times the period of the carrier frequency, 3000 cm?1. The carrier-envelope phase of the IR pulse was passively stabilized, and the instability of the phase was estimated as 154-mrad rms over 2.5 h. We also summarize a particular behavior of the spectral phase of the sub-single-cycle pulse; the phase of high-frequency components of the generated pulses changes continuously and linearly with the relative phase between the two-color input pulses, whereas the phase of the low-frequency components takes only two discrete values. The phase behavior is a unique feature of single-cycle pulses generated with a passive carrier-envelope phase stabilization scheme.
关键词： single-cycle pulse,infrared,ultrashort pulse,four-wave difference frequency generation,Filamentation
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Difference-frequency generation in the cavity of a dual-wavelength semiconductor disk laser: Effect of absorption of the short-wavelength radiation in the a??long-wavelengtha?? active region on the operation point stability
摘要： A difference-frequency generation in the external cavity of a dual-wavelength semiconductor disk laser (SDL) is numerically studied. The dual-wavelength SDL itself has been designed to emit two optical beams simultaneously – the short-wavelength beam (usually referred to as the pump) and the long-wavelength beam (signal). The study is performed with the help of the mathematical model based on a set of ordinary differential equations with a time delay. The model takes into account possible absorption of the pump radiation in the active region designed to provide gain for the signal. The steady state operation point, its stability, and transient dynamics of intra-cavity difference-frequency generator (ICDFG) are analyzed. As the pump radiation absorption exceeds the critical value, the operation point is shown to lose the stability within the certain interval of the primary pomp power. The steady-state instability of the ICDFG develops to the multi-scaled oscillations of high amplitude.
关键词： semiconductor disk laser,difference-frequency generation,intracavity nonlinear optical interaction
更新于2025-09-23 15:19:57
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Determination of the electric field and its Hilbert transform in femtosecond electro-optic sampling
摘要： We demonstrate time-domain sampling of mid-infrared electric ?eld transients and their conjugate counterparts exploiting the dynamical Pockels effect. To this end, the complete polarization change of few-femtosecond probe pulses is studied. An intuitive picture based on a phasor representation is established before gaining quantitative understanding in experiment and theory. In the standard version of electro-optic sampling, the electric ?eld is determined by analyzing the change of ellipticity of the probe polarization. Beyond this, we ?nd that a temporal gradient of the input electric ?eld manifests itself in a rotation of the polarization ellipsoid of the probe. The relative contribution of sum- and difference-frequency mixing processes and their spectral distribution over the near-infrared probe bandwidth are identi?ed as key aspects. If one of these processes dominates, detecting ellipticity changes and polarization rotation as a function of time delay results in two wave forms which are Hilbert transforms of each other. Such conditions may be achieved by angle phase matching in birefringent materials or spectral ?ltering of the probe after the nonlinear interaction. In this case, a static phase introduced by birefringence or re?ection at metallic mirrors results in a speci?c phase shift of both time traces with respect to the input electric ?eld. Contributions from sum- and difference-frequency generation are found to be equivalent when using electro-optic sensors with isotropic refractive index. Polarization rotations in the low- and high-frequency parts of the probe then tend to cancel out. In this limit, spurious additional phase shifts do not change the phase of the detected transients. This fact leads to a robust recovery of the carrier-envelope phase of the input wave form. Clarifying the role of imperfections of superachromatic phase retarders completes our survey on proper determination of the electric ?eld and its conjugate variable.
关键词： polarization rotation,sum-frequency generation,difference-frequency generation,electro-optic sampling,Pockels effect,mid-infrared,Hilbert transform
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) - Systematically Varying the Active Material Volume in a Photonic Crystal Nanolaser
摘要： This paper summarizes the generation of sub-single-cycle infrared (IR) pulses through a laser filament and the detailed properties of the generated pulses. The fundamental (ω1) and second harmonic (ω2) of 30-fs Ti:sapphire amplifier output were focused into nitrogen gas and produced phase-stable broadband IR pulses (ω0) by four-wave difference frequency generation (ω1 + ω1 ? ω2 → ω0) through filamentation. The spectrum spread from 200 to 5500 cm?1, corresponding to ～3.5 octaves. The waveform of the sub-single-cycle pulse was completely characterized with the frequency-resolved optical gating capable of a carrier-envelope phase determination. The pulse duration was measured as 6.9 fs, which was 0.63 times the period of the carrier frequency, 3000 cm?1. The carrier-envelope phase of the IR pulse was passively stabilized, and the instability of the phase was estimated as 154-mrad rms over 2.5 h. We also summarize a particular behavior of the spectral phase of the sub-single-cycle pulse; the phase of high-frequency components of the generated pulses changes continuously and linearly with the relative phase between the two-color input pulses, whereas the phase of the low-frequency components takes only two discrete values. The phase behavior is a unique feature of single-cycle pulses generated with a passive carrier-envelope phase stabilization scheme.
关键词： single-cycle pulse,infrared,ultrashort pulse,four-wave difference frequency generation,Filamentation
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Sub-terahertz Quantum-cascade Laser Source based on Difference-frequency Generation
摘要： Authors report a sub-terahertz monolithic semiconductor source based on a high power, long-wavelength quantum cascade laser. In order to obtain higher nonlinear susceptibility in the sub-terahertz frequency region, we design long wavelength dual-upper-state active region in which transition dipole moments are substantially increased. A fabricated device with distributed feedback grating produces nearly watt-level infrared output power, and as a result, it exhibits a peak output power of 18.5 μW at room temperature, around a frequency of ~700 GHz. Besides, the device produces an output power of 103 μW at 110 K.
关键词： dual-upper-state active region,monolithic semiconductor source,difference-frequency generation,sub-terahertz,quantum-cascade laser
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Time-Domain Detection of the Electric Field and its Conjugate Variable in Ultrabroadband Electro-Optic Sampling
摘要： We demonstrate unambiguous detection of the conjugate variable to the electric field in a time-domain experiment. The polarization change induced by nonlinear mixing of probe and multi-THz fields via the Pockels effect is examined concerning changes in ellipticity and tilting of the polarization ellipsoid. Spectrally resolved measurements yield crucial insights into how sum and difference frequency generation processes shape the electro-optic signal for different detection crystals. This approach enables precise, even simultaneous, measurement of the electric field and its conjugate variable by combinations of different phase biases ((cid:2)/4 and (cid:2)/2) and spectral filtering.
关键词： sum and difference frequency generation,ultrabroadband electro-optic sampling,Pockels effect,electric field,conjugate variable
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Numerical Study of CO Laser Down-Conversion into the THz Range With ZnGeP <sub/>2</sub> crystal
摘要： Difference frequency generation of rotational-vibrational lines of nonselective CO laser in ZnGeP2 crystal was numerically studied. It was shown that a great number of difference frequency lines can densely cover spectral range from 50 to 1000 (cid:2)m and even up to 5000 (cid:2)m. An influence of ZnGeP2 crystal absorption on THz generation was studied.
关键词： THz generation,CO laser,difference frequency generation,ZnGeP2 crystal
更新于2025-09-12 10:27:22
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz surface phonon polariton generation in GaP photonic waveguide
摘要： Generation of THz wave using surface phonon polariton and difference frequency generation in GaP stripe is investigated. Here, we present our preliminary results and show that mixing a TE and a TM mid-IR mode propagating along a [100] crystal axis is more efficient than the usual optical configuration along a [110] axis under transverse pump modes for efficient THz generation.
关键词： photonic waveguide,surface phonon polariton,GaP,difference frequency generation,THz
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) - Broadband Infrared (2.7–20 μm) Generation Via Random Quasi-Phase-Matched Intra-Pulse Difference-Frequency Generation
摘要： Coherent mid-infrared (MIR) light has a plethora of important applications ranging from life-science to industrial processes. Simultaneous coverage of this region will enable the parallel detection of various chemicals and enhance the specificity of their detection [1]. One of the most popular broadband infrared generation methods is nonlinear down-conversion from the near-infrared. An effective conversion can be achieved by using phase-matching and quasi-phase-matching in birefringent crystals and crystals with periodically poled structure respectively. Random quasi-phase-matching (RQPM) in poly-crystals is an alternative method that has recently shown great promise [2,3], which results in a gradual growth of the generated signal linear to the propagation length. Compared to generic phase-matching schemes, RQPM offers an unparalleled phase-matching bandwidth that is insensitive to incident angle. In addition, unlike single-crystals, poly-crystals can easily be grown into larger dimensions to enable longer interaction lengths. Here we describe the generation of octave-spanning MIR continuum at over 20 mW of average power based on RQPM driven by a Ho:YAG thin-disk oscillator at 2.1 μm [4]. To the best of our knowledge, this is the first time RQPM has been implemented for intra-pulse difference-frequency generation (DFG). A 1 μm laser system based on a Yb:YAG thin-disk oscillator [5] was also tested as the driving source in this scheme.
关键词： ZnS,mid-infrared,Broadband infrared,random quasi-phase-matching,intra-pulse difference-frequency generation,ZnSe
更新于2025-09-12 10:27:22