Random numbers play an important role in many fields, such as computation, simulation and cryptography. The randomness inherent in quantum mechanics is a perfect source of entropy for a true random number generator. Nevertheless, many QRNG schemes require post-processing work to ensure randomness. On the other hand, the bit number of the QRNG is limited, which hamper its further applications. Here, we demonstrate a novel 5-bit all free space optical quantum random number generator based on a time-division-multiplexed degenerate optical parametric oscillator (DOPO), which does not need a complicated experimental environment and tedious post-processing work. By inserting a multi-pass cell into the optical parametric oscillator, the equivalent cavity length is calculated to be as long as 15 m, which corresponds to fifth of the separation times of pump pulses. As a result, 5 identical DOPO pulses are generated simultaneously. The randomness comes from phase responses of degenerate OPOs. Under threshold, the photons produced by optical parametric down conversion have random initial phase, while above threshold, stable oscillations occurs in one of the two possible phase states. Random number is reliably verified by measuring the relative phase states between DOPO output pulses and the original pump pulse using a fast response photodiode. All spatial structures have the advantages of higher stability and are less sensitive to temperature fluctuation. The bit number can be readily multiplied by increasing the cavity length of DOPO or the repetition rate of the pump laser source.
Pulsed digital holography, which combines femtosecond pulsed laser and digital holography, is a novel technology for detecting ultrafast transient processes in real-time. Pulsed digital holography can obtain a series of amplitude and phase information of the ultrafast process in one shot at the femtosecond or picosecond order, and comprehensively characterize the whole picture of the ultrafast process. However, the system of pulsed digital holography currently has the defects of complexing, poor stability, small number of pulse frames, and low utilization of space bandwidth, which seriously limits practical applications. In this work, a real-time detection system is designed for ultrafast transient processes, which has the property of high stability, femtosecond or picosecond time order resolution, and adjustable pulse frames. The pulsed lasers are used instead of traditional continuous lasers. The proposed system design provides a competitive approach to ultrafast transient imaging.
Soliton molecules, exhibiting similarities to molecular-like behavior, have attracted tremendous attention. With the dramatic recent advances in real time spectroscopic techniques as well as time-domain probes, the detailed nature of various soliton molecular has been revealed. Particularly, time-stretch dispersive Fourier transform (DFT) technique has been applied to unveil the complex internal dynamics of bound states. Nevertheless, the observation time frame of such technique is limited to hundreds of micro seconds mainly confined by the storage capability of the real time oscilloscopes, as well as by the number and the distribution of soliton pulses. Here, we experimentally demonstrate a new probing concept, orbital angular momentum (OAM)-resolved method, for visual extraction of long-term internal phase motions within soliton molecules produced by a mode locked laser.
Optical vortices, which carry orbital angular momentum, offer special capabilities in a host of applications. A single-laser source with dual-beam-mode output may open up new research fields of nonlinear optics and quantum optics. We demonstrate a dual-channel scheme to generate femtosecond, dual-wavelength, and dual-beam-mode tunable signals in the near infrared wavelength range. Dual-wavelength operation is derived by stimulating two adjacent periods of a periodically poled lithium niobate crystal. Pumped by an Yb-doped fiber laser with a Gaussian (lp = 0) beam, two tunable signal emissions with different beam modes are observed simultaneously. Although one of the emissions can be tuned from 1520 to 1613 nm with the Gaussian (ls = 0) beam, the other is capable of producing a vortex spatial profile with different vortex orders (ls = 0 to 2) tunable from 1490 to 1549 nm. The proposed system provides unprecedented freedom and will be an exciting platform for super-resolution imaging, nonlinear optics, multidimensional quantum entanglement, etc.
KEYWORDS: Fiber lasers, Complex systems, Femtosecond fiber lasers, Femtosecond phenomena, Ultrafast lasers, Micromachining, High power lasers, High power fiber lasers, Laser applications, Laser systems engineering
Ultrafast laser sources with both high average power and high peak powers at a high repetition rate have many important applications in areas such as high-harmonic generation (HHG), micromachining, and high power optical parametric amplification. In recent years, with the development of high power fiber laser technology, the output of femtosecond fiber laser systems has reached average powers of thousands of watts and peak powers of several gigawatts. However, the pulse duration and pulse energy is limited by the accumulated nonlinear phase in the nonlinear propagation in the fiber, since it will distort the pulse shape and even break the femtosecond pulses. To enhance the performance of femtosecond fiber laser, the nonlinear phase accumulation and compensation is most important optimization factor. Pulse propagation dynamics control is the important method in femtosecond fiber system. This talk will demonstrate the few-cycle laser pulse generation in fiber system with nonlinear process manipulation.
Mitochondrial oxidative flashes (mitoflashes) are oxidative burst events in mitochondria. It is crosslinked with numerous mitochondrial molecular processes and related with pivotal cell functions such as apoptosis and respiration. In previous research, mitoflashes were found as spontaneous occasional events. It would be observed more frequently if cells were treated with proapoptotic chemicals. We show that multiple mitoflashes can be initiated by a single femtosecond-laser stimulation that was tightly focused on a diffraction-limited spot in the mitochondrial tubular structure. The mitoflash events triggered by different photostimulations are quantified and analyzed. The width and amplitude of mitoflashes are found very sensitive to stimulation parameters including laser power, exposure duration, and total incident laser energy. This study provides a quantitative investigation on the photostimulated mitoflashes. It may thus demonstrate such optical method to be a promising technique in future mitochondrial research.
All-optical pulse generation opens up a field for ultrawideband (UWB) applications. However, controllable pulse width and pulse type are still challenging. Here, we present a theoretical model and stimulated results of monocycle and doublet waveforms generation using programmable optical photon echo progress. We synthesized instantaneously monocycle and doublet waveforms by adjustment of pulse width, pulse amplitude, pulse position, and time interval of subpulses. We verified the possible application of the proposed method to design U.S. Federal Communications Commission-compliant UWB waveforms, and therefore, it may provide an avenue for waveform generation.
We report on a simple passive scheme to reduce the intensity noise of high-power nonlinear fiber amplifiers by use of the spectral-breathing parabolic evolution of the pulse amplification with an optimized negative initial chirp. In this way, the influences of amplified spontaneous emission (ASE) on the amplifier intensity noise can be efficiently suppressed, owing to the lower overall pulse chirp, shorter spectral broadening distance, as well as the asymptotic attractive nature of self-similar pulse amplification. Systematic characterizations of the relative intensity noise (RIN) of a free-running nonlinear Yb-doped fiber amplifier are performed over a series of initial pulse parameters. Experiments show that the measured amplifier RIN increases respect to the decreased input pulse energy, due to the increased amount of ASE noise. For pulse amplification with a proper negative initial chirp, the increase of RIN is found to be smaller than with a positive initial chirp, confirming the ASE noise tolerance of the proposed spectral-breathing parabolic amplification scheme. At the maximum output average power of 27W (25-dB amplification gain), the incorporation of an optimum negative initial chirp (-0.84 chirp parameter) leads to a considerable amplifier root-mean-square (rms) RIN reduction of ~20.5% (integrated from 10 Hz to 10 MHz Fourier frequency). The minimum amplifier rms RIN of 0.025% (integrated from 1 kHz to 5 MHz Fourier frequency) is obtained along with the transform-limited compressed pulse duration of 55fs. To our knowledge, the demonstrated intensity noise performance is the lowest RIN level measured from highpower free-running femtosecond fiber amplifiers.
A strip/slot hybrid horizontal silicon nitride slot waveguide is designed to provide an ultraflat and low dispersion. By optimizing the height and width of the structure, an ultraflat and low dispersion of ∼0±7 ps/nm/km over 812 nm wavelength range (from 1137 to 1949 nm) can be achieved. The waveguide with a 20-nm conformal overlayer has chromatic dispersion within ±1 ps/nm/km over 682-nm bandwidth. So the flatness is 0.0015, which is the lowest flatness in near-infrared regime of this kind of waveguide to our knowledge. The influence of the waveguide sidewall to dispersion is also discussed.
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