Publications by authors named "Minglie Hu"

61 Publications

Caustic Interpretation of the Abruptly Autofocusing Vortex beams.

Opt Express 2021 Jun;29(13):19975-19984

We propose an effective scheme to interpret the abruptly autofocusing vortex beam. In our scheme, a set of analytical formulae are deduced to well predict not only the global caustic, before and after the focal plane, but also the focusing properties of the abruptly autofocusing vortex beam, including the axial position as well as the diameter of focal ring. Our analytical results are in excellent agreement with both numerical simulation and experimental results. Besides, we apply our analytical technique to the fine manipulation of the focusing properties with a scaling factor. This set of methods would be beneficial to a broad range of applications such as particle trapping and micromachinings.
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http://dx.doi.org/10.1364/OE.430497DOI Listing
June 2021

Orbital-angular-momentum-resolved diagnostics for tracking internal phase evolution in multi-bound solitons.

Opt Express 2021 May;29(11):16686-16694

The generation of multi-bound solitons is a fascinating subject of investigation in many conservative and dissipative systems, such as photonics, fluid mechanics, Bose-Einstein condensates, and so on. In this study, we demonstrate the successful extraction of phase dynamics between solitons in bound multiple solitons with up to seven constituents in a mode-locked Er laser system. By mapping the internal phase motions of multi-bound solitons to the spatial phase movement of cylindrical vector beams using orbital angular momentum (OAM)-based diagnostics, different categories of internal pulsations are revealed. We show that bound state of four solitons exhibits linear drifting relative phase evolution dynamics; while for bound multiple solitons with constituents from five to seven pulses, stationary relative phase dynamics are observed. These findings highlight the possibility of the OAM-based method access to the internal motion of multi-soliton molecules with more freedom of degrees and fuel the analogy with research on chemistry molecule complex.
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http://dx.doi.org/10.1364/OE.424602DOI Listing
May 2021

Orthogonally polarized tunable dual-wavelength femtosecond optical parametric oscillator.

Appl Opt 2020 Dec;59(34):10887-10891

We demonstrate a femtosecond optical parametric oscillator that can generate orthogonally polarized dual-wavelength femtosecond pulses. Two periodically poled lithium niobate (PPLN) crystals with mutually orthogonal crystal axes are pumped by a single femtosecond fiber laser. The central wavelength of the two orthogonally polarized signal pulses can be continuously tuned from 1387 to 1588 nm with a maximum frequency separation of 27 THz. Because of the orthogonal dual-crystal scheme, the system is immune to the coherent coupling effect, thus overcoming the limitation of minimum frequency separation.
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http://dx.doi.org/10.1364/AO.411301DOI Listing
December 2020

Route to stable dispersion-managed mode-locked Yb-doped fiber lasers with near-zero net cavity dispersion.

Opt Express 2020 Sep;28(20):29766-29774

We numerically investigate the stability of a dispersion-managed mode-locked Yb-doped fiber laser of near-zero net cavity dispersion. The instability is primarily due to the filtering effect of the chirped fiber Bragg grating. The size of the unstable region is dependent on the modulation depth of the saturable absorbers. At modulation depth higher than 30%, stable mode-locking can operate throughout the dispersion region. Based on the simulation results, stable mode-locking around zero cavity dispersion is experimentally viable by a SESAM with a 34% modulation depth. The fiber laser can generate laser pulses with a 17-nm spectral bandwidth and a 139-fs dechirped pulse duration.
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http://dx.doi.org/10.1364/OE.403456DOI Listing
September 2020

Direct femtosecond laser ablation of large-area TaSe, SnS, and TiS thick films by a back ablation procedure.

Appl Opt 2020 Sep;59(25):7606-7612

Direct ablation of large-area graphene-like two-dimensional (2D) materials, i.e., tantalum diselenide (), stannic disulfide (), and titanium disulfide (), by the back ablation method with a femtosecond laser with a repetition rate of 50 MHz and pulse width of 200 fs is studied for the first time to our knowledge. The ablation thresholds of the three kinds of materials are discussed. In addition, the optimization and ablation of narrow grooves on the films are demonstrated. Our work demonstrates the direct femtosecond laser ablation processing of the graphene-like 2D-material films and the potential of 2D-material-film-based devices.
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http://dx.doi.org/10.1364/AO.390667DOI Listing
September 2020

Dual-mode and two-signal-wavelength femtosecond optical parametric oscillator based on LiBO.

Opt Lett 2020 Jul;45(14):3985-3988

We demonstrate a tunable femtosecond dual-beam-mode (cylindrical vector beam [CVB] and Gaussian beam [GB]), dual-signal-wavelength optical parametric oscillator based on a temperature-tuned lithium triborate crystal, synchronously pumped by a frequency-doubled mode-locked Yb-doped fiber laser. When fixing the CVB wavelength at 780 nm, the central wavelength of the GB signal could be continuously tuned from 664 to 722 nm. The maximum total signal output power is 515 mW at a 4 W pump with dual-wavelength operation (664 and 780 nm). All the measured signal pulse durations are around 150 fs. Moreover, sum-frequency-generation with Gaussian mode tuning from 548 to 588 nm is obtained, with the maximum power of 52 mW at 548 nm. Thanks to the dual-channel configuration, the wavelengths of a CVB and GB can be tuned independently. Such a flexible and versatile configuration makes it a practical tool for many applications such as high-resolution microscopy and high-capacity optical communication.
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http://dx.doi.org/10.1364/OL.397032DOI Listing
July 2020

22.7  W mid-infrared supercontinuum generation in fluorotellurite fibers.

Opt Lett 2020 Apr;45(7):1882-1885

In this Letter, we demonstrate 22.7 W mid-infrared (MIR) supercontinuum (SC) generation in all-solid fluorotellurite fibers. All-solid fluorotellurite fibers based on ${{\rm TeO}_2} {\text -} {{\rm BaF}_2}{\text -}{{\rm Y}_2}{{\rm O}_3}$TeO-BaF-YO and ${{\rm TeO}_2}$TeO modified fluoroaluminate glasses are fabricated by using a rod-in-tube method. By using a 0.6 m long fluorotellurite fiber with a core diameter of 11 µm as the nonlinear medium and a high-power 1.93-2.5 µm SC fiber laser as the pump source, we obtain 22.7 W SC generation from 0.93 to 3.95 µm in the fiber for a pump power of 39.7 W. The 10 dB bandwidth is about 1633 nm, and the corresponding spectral range is from 1890 to 3523 nm. The optical-to-optical conversion efficiency is about 57.2%. Our results show that all-solid fluorotellurite fibers are promising nonlinear media for constructing high-power MIR SC light sources.
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http://dx.doi.org/10.1364/OL.383642DOI Listing
April 2020

Optical frequency comb noise spectra analysis using an asymmetric fiber delay line interferometer.

Opt Express 2020 Mar;28(7):9232-9243

A simple and practical apparatus enabling repetition rate (frep) noise, carrier-envelope frequency (fceo) noise and n optical comb mode (νn) noise spectra measurements with high precision is established. The frep and νn noise spectra are measured by a fiber delay line interferometer, while fceo noise spectrum is measured by an f-2f interferometer. We utilize this apparatus to characterize the noise performance of an Er-fiber optical frequency comb (OFC) and analyze the origin of dominant noise sources. Moreover, this apparatus provides a powerful tool for diagnosing noise dynamics intrinsic in mode-locked lasers and OFCs. To this end, we uncover the anti-correlation between frep and fceo noise as well as the impact of servo loops on noise characteristics in the stabilized OFC.
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http://dx.doi.org/10.1364/OE.386231DOI Listing
March 2020

High-power femtosecond cylindrical vector beam optical parametric oscillator.

Opt Express 2019 Nov;27(23):33080-33089

We report on high-power femtosecond cylindrical vector beam (CVB) generation from a Gaussian-pumped optical parametric oscillator (OPO). By introducing a half waveplate and a vortex half-wave plate of m = 1 to realize intracavity polarization modulation to the resonant Gaussian signal, the OPO could deliver broadband signal beam in CVB profile, i.e., radially and azimuthally polarized beam profile. The central wavelength of the generated CVB signals can be tuned continuously from 1405 to 1601 nm, while the corresponding pulse durations are all around 150 fs. A maximum average output power of 614 mW at 1505 nm is obtained. Moreover, our OPO cavity design can be extended to generate high order CVB by simply changing the vortex half-wave plate with different orders. Such a high-power CVB OPO configuration has the advantages of flexible control and wide tuning range, making it a practical tool for applications in super-resolution imaging, optical communication and quantum correlations.
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http://dx.doi.org/10.1364/OE.27.033080DOI Listing
November 2019

THz polarization-sensitive characterization of a large-area multilayer rhenium diselenide nanofilm.

Nanotechnology 2019 Dec 11;30(50):505203. Epub 2019 Sep 11.

School of Precision Instrument and Opto-electronics engineering, Key Laboratory of Opto-electronic Information Technology (Ministry of Education), Ultrafast Laser Laboratory, Tianjin University, Tianjin, People's Republic of China.

Recently, rhenium diselenide (ReSe) has attracted considerable attention due to its high anisotropy in the layer plane, which makes it a promising candidate for wide applications in electronics and optoelectronics. In this paper, we focus on the polarization-sensitive characteristics of a large-area multilayer ReSe nanofilm in the terahertz (THz) region under passive and active conditions by means of THz time-domain spectroscopy. We demonstrate the passive ReSe nanofilm with intrinsic THz polarization anisotropy. Maximum transmittance occurs only when the polarization direction of the incident THz wave is along the Re-chains direction. More importantly, THz polarization properties of the active ReSe nanofilm by an external electric field applied in a selected directions are also demonstrated. The modulation depth of the THz transmission is up to 16% and the response time is on the order of picoseconds. In addition, a comparative experiment is performed on three kinds of THz polarizers, i.e., ReSe nanofilm, carbon nanotubes (CNTs) and wire-gird, respectively. The results prove that the performance of the polarizer based on the active ReSe nanofilm is comparable with those of CNTs and the THz wire-gird polarizer. Based on these studies, we believe that the polarization-sensitive ReSe nanofilm can find important applications in ultrafast switches, filters and modulation devices in the THz region.
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http://dx.doi.org/10.1088/1361-6528/ab4377DOI Listing
December 2019

Photostimulation by Femtosecond Laser Activates Extracellular-signal-regulated Kinase (ERK) Signaling or Mitochondrial Events in Target Cells.

J Vis Exp 2019 07 6(149). Epub 2019 Jul 6.

School of Biomedical Engineering, Shanghai Jiao Tong University;

Direct control of cellular defined molecular events is important to life science. Recently, studies have demonstrated that femtosecond laser stimulation can simultaneously activate multiple cellular molecular signaling pathways. In this protocol, we show that through coupling femtosecond laser into a confocal microscope, cells can be stimulated precisely by the tightly-focused laser. Some molecular processes that can be simultaneously observed are subsequently activated. We present detailed protocols of the photostimulation to activate extracellular signal regulated kinase (ERK) signaling pathway in Hela cells. Mitochondrial flashes of reactive oxygen species (ROS) and other mitochondrial events can be also stimulated if focusing the femtosecond laser pulse on a certain mitochondrial tubular structure. This protocol includes pretreating cells before photostimulation, delivering the photostimulation by a femtosecond laser flash onto the target, and observing/identifying molecular changes afterwards. This protocol represents an all-optical tool for related biological researches.
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http://dx.doi.org/10.3791/59661DOI Listing
July 2019

Pulse dynamics manipulation by the phase bias in a nonlinear fiber amplifying loop mirror.

Opt Express 2019 May;27(10):14705-14715

Pulse dynamics controlling is of great importance for high quality pulse generation in ultra-short pulse fiber lasers. The pulse quality characteristics in terms of pulse duration, energy, chirp profile, tunability, as well as noise feature substantially depend on intracavity pulse propagation dynamics. Here we found that a nonlinear amplifying loop mirror mode-locked thulium-doped fiber laser can switch among enabling operation conventional soliton, stretched-pulse soliton and dissipative soliton regimes only by manipulating an intracavity phase bias device. This provides a simple approach to tailoring ultra-short laser characteristics to different applications.
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http://dx.doi.org/10.1364/OE.27.014705DOI Listing
May 2019

Intracavity cylindrical vector beam generation from all-PM Er-doped mode-locked fiber laser.

Opt Express 2019 Mar;27(6):8808-8818

We demonstrate a practical method that is used to generate on-demand first- and higher-order cylindrical vector beams, in the 1550 nm band, directly from an all polarization maintaining mode-locked Er-fiber laser. On demand typical 1st order CVBs, including the radially and azimuthally polarized beams, can be easily achieved by properly adjusting the angle of a half-wave plate with respect to the fast axis of the vortex wave plate. The spatial beam mode can be flexibly switched with no disturbance on the time domain mode-locking output. The laser outputs the desired vector beams at 1571 nm with a spectral bandwidth at full-width at half-maximum of 32 nm. The mode-locked laser pulses have a repetition rate of 74.9 MHz. Moreover, the proposed method can be easily extended to create higher-order CVBs. Our research provides a convenient way to generate ultrafast pulses in highly flexible-controlled structured modes, which is essential for optical fabrication and light trapping applications.
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http://dx.doi.org/10.1364/OE.27.008808DOI Listing
March 2019

910-MHz, watt-level, signal-power-enhanced, compact femtosecond optical parametric oscillator based on bidirectional pumping technique.

Opt Lett 2019 Apr;44(7):1638-1641

We propose a high-efficiency and compact 910-MHz femtosecond optical parametric oscillator, which is harmonically pumped by a ∼101  MHz Yb doped fiber laser system. The OPO is capable of delivering watt-level, power-enhanced signals across the telecommunication waveband. The signal power enhancement is realized by exploiting the bidirectional pumping technique. A maximum signal power of 1.04 W at 1502 nm is obtained for an input pump power of 3.8 W. Tunable near-infrared signal pulses with a wavelength range between 1350 and 1610 nm are measured, and the pulse durations vary from 193 to 464 fs. This compact and economic design provides a solution for efficient high repetition rate pulse generation over a large wavelength span, which will be beneficial for a variety of practical applications.
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http://dx.doi.org/10.1364/OL.44.001638DOI Listing
April 2019

Higher-Order Mode Suppression in Antiresonant Nodeless Hollow-Core Fibers.

Micromachines (Basel) 2019 Feb 15;10(2). Epub 2019 Feb 15.

Ultrafast Laser Laboratory, School of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education), Tianjin University, Tianjin 300072, China.

Negative curvature hollow-core fibers (NC-HCFs) are useful as gas sensors. We numerically analyze the single-mode performance of NC-HCFs. Both single-ring NC-HCFs and nested antiresonant fibers (NANFs) are investigated. When the size of the cladding tubes is properly designed, higher-order modes (HOMs) in the fiber core can be coupled with the cladding modes effectively and form high-loss supermodes. For the single-ring structure, we propose a novel NC-HCF with hybrid cladding tubes to enable suppression of the first two HOMs in the core simultaneously. For the nested structure, we find that cascaded coupling is necessary to maximize the loss of the HOMs in NANFs, and, as a result, NANFs with five nested tubes have an advantage in single-mode guidance performance. Moreover, a novel NANF with hybrid extended cladding tubes is proposed. In this kind of NANF, higher-order mode extinction ratios (HOMERs) of 10⁵ and even 10⁶ are obtained for the LP and LP modes, respectively, and a similar level of 10⁵ for the LP modes. Good single-mode performance is maintained within a broad wavelength range. In addition, the loss of the LP modes in this kind of NANF is as low as 3.90 × 10 dB/m.
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http://dx.doi.org/10.3390/mi10020128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413180PMC
February 2019

Active f-to-2f interferometer for record-low jitter carrier-envelope phase locking.

Opt Lett 2019 Feb;44(4):1060-1063

The f-to-2f interferometer plays a key role for carrier-envelope phase (CEP) measurement and subsequent stabilization. The CEP measurement typically relies on the application of two optical nonlinearities, namely supercontinuum generation and second-harmonic generation. Then the cascadation of these nonlinearities often leads to signal levels on the order of a few photons per pulse. We experimentally demonstrate that the introduction of optical gain into the infrared arm of an f-to-2f interferometer can mitigate this detection bottleneck and improve signal-to-noise ratios by 20 dB compared to purely passive schemes. We further show that this measure allows for residual phase jitters between the carrier and envelope of about 10 mrad, corresponding to record-breaking timing jitters in the single attosecond regime. Moreover, the method appears generally applicable to a wide range of oscillators in the near-infrared and may enable stable CEP locking of mode-locked oscillators that so far have resisted stabilization. Finally, we propose a parametric variant of the active f-to-2f interferometer that can be used for laser amplifiers with kilohertz repetition rates and below.
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http://dx.doi.org/10.1364/OL.44.001060DOI Listing
February 2019

All-polarization-maintaining dual-wavelength mode-locked fiber laser based on Sagnac loop filter.

Opt Express 2018 Oct;26(22):28302-28311

We demonstrate an all polarization-maintaining (PM) fiber based dual-wavelength mode-locked Er-fiber laser. A nonlinear amplifying loop mirror (NALM) with an intracavity nonreciprocal phase shifter is used for self-started mode-locking. A short segment of PM fiber is angle-spliced to the NALM, functioning as a PM Sagnac loop filter, thus enabling dual-wavelength mode-locking. The wavelength separation is solely determined by the angle-spliced PM fiber length. Stable dual-wavelength mode-locking operation is switchable between 1570/1581 nm and 1581/1594 nm. The two-color pulse trains oscillating in the same cavity have an inherent offset repetition rate of ~1 kHz owing to cavity dispersion, allowing future high precision dual-comb applications with a simple and robust configuration.
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http://dx.doi.org/10.1364/OE.26.028302DOI Listing
October 2018

Femtosecond laser pulse generation with self-similar amplification of picosecond laser pulses.

Opt Express 2018 Oct;26(20):26411-26421

Compressing picosecond laser pulses to the femtosecond level is an attractive shortcut for obtaining femtosecond laser pulses. However, dechirped pulses generated by nonlinear compression with self-phase modulation (SPM) show obvious pedestals, which are induced by nonlinear chirp accumulation in spectral broadening process and cannot be easily suppressed. Here, we report systematic numerical simulations and experimental studies on self-similar amplification of picosecond pulses in a short gain fiber for obtaining ~100-fs laser pulses with nearly transform-limited (TL) temporal quality. It is demonstrated that self-similar amplification with picosecond seed pulses is only sensitive to pulse duration and pulse energy. Based on this optimization guideline, we built a compact self-similar amplification fiber system with a picosecond fiber laser as the seed source. This system outputs 66-fs pulses with 6.1-W average power at a repetition rate of 30 MHz. Due to the linear chirp produced in self-similar evolution process, compressed pulses show nearly TL temporal quality. It promises an efficient way of obtaining high-quality femtosecond laser pulses from a picosecond laser source.
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http://dx.doi.org/10.1364/OE.26.026411DOI Listing
October 2018

Generation of 3.9-cycle pulses from the coherent synthesis of two continuous-wave injection seeded optical parametric amplifiers at 53  MHz.

Opt Lett 2018 Nov;43(22):5579-5582

A high repetition-rate, few-cycle light pulse is of great importance due to its potential for a variety of applications, including two-dimensional infrared spectroscopy and time-resolved imaging of molecular structures, which benefit from its ultrabroadband spectrum and ultrashort pulse duration. The generation of an ultrabroadband coherent spectrum is one of the frontiers of ultrafast optics, and accessing such few-cycle pulses is presently under active exploration. Here, we demonstrate a simple yet effective pulse synthesizer. It is based on two continuous-wave (cw) injection-seeded high-repetition-rate optical parametric amplification systems and the following self-phase-modulation dominated spectra-broadening processes. The combined spectrum spans from 1250 to 1670 nm, and a near Fourier-transform-limited 3.9-cycle (19.2 fs) synthesized pulse with a central wavelength of 1470 nm is obtained accordingly.
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http://dx.doi.org/10.1364/OL.43.005579DOI Listing
November 2018

High-detectivity optical heterodyne method for wideband carrier-envelope phase noise analysis of laser oscillators.

Opt Lett 2018 Jul;43(13):3108-3111

Broadband characterization of the carrier-envelope phase (CEP) noise spectral density of free-running mode-locked lasers is essential for advanced low-noise optical frequency comb designs. Here we present a direct method that utilizes an optical heterodyne beat between a pair of repetition-rate-locked mode-locked lasers for CEP noise characterization, without requiring an f-2f interferometer or nonlinear optical conversion steps. A proof-of-principle experiment in a femtosecond Yb-fiber laser achieves CEP noise spectral density characterization with >270  dB dynamic range over a Fourier frequency range from 5 mHz to 8 MHz. The measurement noise floor is well below 1  μrad/√Hz, enabling dependable detection down to a quantum-limited noise floor. The method can resolve various noise mechanisms that cause specific CEP noise spectral shapes. The underlying mechanisms are further analyzed in terms of spurious temporal correlation to distinguish between technical and stochastic noise signatures. Moreover, a Hadamard deviation analysis reveals a varying degree of frequency stability in the measured CEP time series.
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http://dx.doi.org/10.1364/OL.43.003108DOI Listing
July 2018

Quantitative analysis of mitoflash excited by femtosecond laser.

J Biomed Opt 2018 06;23(6):1-6

Tianjin Univ., China.

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.
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http://dx.doi.org/10.1117/1.JBO.23.6.065005DOI Listing
June 2018

Single-polarization large-mode-area fiber laser mode-locked with a nonlinear amplifying loop mirror.

Opt Lett 2018 Jun;43(12):2848-2851

The generation of high-power ultrashort pulses from a passively mode-locked fiber laser is reported based on the combination of a single-polarization large-mode-area (LMA) photonic crystal fiber with a nonlinear amplifying loop mirror design. The introduction of a non-reciprocal phase shift in the loop mirror enables self-starting of the mode-locked laser, while the polarizing LMA fiber supports environmentally stable high-power operation. Mode locking in the soliton-like, stretched-pulse, and all-normal-dispersion regime is characterized. The laser generates stable pulses with up to 2 W average power at a 72 MHz repetition rate, corresponding to a single-pulse energy of 28 nJ. The output pulses are dechirped to a near transform-limited duration of 152 fs. The proposed fiber oscillator presents an alternative approach to high-power ultrafast laser sources, along with environmental stability.
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http://dx.doi.org/10.1364/OL.43.002848DOI Listing
June 2018

Dielectric-mirror-less femtosecond optical parametric oscillator with ultrabroad-band tunability.

Opt Lett 2018 May;43(10):2316-2319

We demonstrate a high average power, widely tunable, dielectric-mirror-less optical parametric oscillator (OPO) based on MgO:PPLN (MgO-doped periodically poled lithium niobate), which is synchronously pumped by a 1040 nm femtosecond fiber laser. The OPO does not require any dielectric coating mirrors. By exploiting the four-prism sequence system, combined with the gold mirrors, the oscillating laser pulses could span the spectral regions in both the signal and idler, and the output pulses of OPO can be tuned across 1367-1914 nm in the signal, and 2152-4480 nm in the idler as well. This device can deliver as much as 1.2 W of average power at 1482 nm in the signal and up to 411 mW at 3487 nm in the idler, respectively. The ultrabroad-band spectra tunability, along with the high average output property, makes the dielectric-mirror-less OPO an attractive alternative to conventional OPOs.
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http://dx.doi.org/10.1364/OL.43.002316DOI Listing
May 2018

Dual-comb spectroscopy with a single free-running thulium-doped fiber laser.

Opt Express 2018 Apr;26(8):11046-11054

We demonstrate dual-comb spectroscopy in the vicinity of 2 µm wavelength based on a single dual-wavelength dual-comb Thulium-doped fiber laser. The shared laser cavity ensures passively maintained mutual coherence between the two combs due to common mode environmental noise rejection. In a proof-of-principle experiment, the absorption characteristics caused by the water in the optical path that composes the dual-comb spectrometer are measured. The retrieved spectral positions of the water absorption dips match with the HITRAN database.
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http://dx.doi.org/10.1364/OE.26.011046DOI Listing
April 2018

Observation of subfemtosecond fluctuations of the pulse separation in a soliton molecule.

Opt Lett 2018 Apr;43(7):1623-1626

In this work, we study the timing instability of a scalar twin-pulse soliton molecule generated by a passively mode-locked Er-fiber laser. Subfemtosecond precision relative timing jitter characterization between the two solitons composing the molecule is enabled by the balanced optical cross-correlation (BOC) method. Jitter spectral density reveals a short-term (on the microsecond to millisecond timescale) random fluctuation of the pulse separation even in the robust stationary soliton molecules. The root-mean-square (rms) timing jitter is on the order of femtoseconds depending on the pulse separation and the mode-locking regime. The lowest rms timing jitter is 0.83 fs, which is observed in the dispersion managed mode-locking regime. Moreover, the BOC method has proved to be capable of resolving the soliton interaction dynamics in various vibrating soliton molecules.
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http://dx.doi.org/10.1364/OL.43.001623DOI Listing
April 2018

Intensity and temporal noise characteristics in femtosecond optical parametric amplifiers.

Opt Express 2017 Dec;25(25):31263-31272

We characterize the relative intensity noise (RIN) and relative timing jitter (RTJ) between the signal and pump pulses of optical parametric amplifiers (OPAs) seeded by three different seed sources. Compared to a white-light continuum (WLC) seeded- and an optical parametric generator (OPG) seeded OPA, the narrowband CW seeded OPA exhibits the lowest root-mean-square (RMS) RIN and RTJ of 0.79% and 0.32 fs, respectively, integrated from 1 kHz to the Nyquist frequency of 1.25 MHz. An improved numerical model based on a forward Maxwell equation (FME) is built to investigate the transfers of the pump and seed's noise to the resulting OPAs' intensity and temporal fluctuation. Both the experimental and numerical study indicate that the low level of noise from the narrowband CW seeded OPA is attributed to the elimination of the RIN and RTJ coupled from the noise of seed source, being one of the important contributions to RIN and timing jitter in the other two OPAs. The approach to achieve lower level of noise from this CW seeded OPA by driving it close to saturation is also discussed with the same numerical model.
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http://dx.doi.org/10.1364/OE.25.031263DOI Listing
December 2017

Scaling the abruptly autofocusing beams in the direct-space.

Opt Express 2017 Nov;25(24):30598-30605

We propose a simple technique to scale the abruptly autofocusing beams in the direct space by introducing a scaling factor in the phase. Analytical formulas are deduced based on optical caustics, explicitly revealing how the scaling factor controls location, peak intensity, and size of the focal spot. We demonstrate that the multiplication of a scaling factor on the phase is equivalent to the axial-scaling transformation under the paraxial approximation. Further numerical and experimental results confirm theoretical predictions. In addition, amplitude modulation using phase-only holograms is used to maintain the peak intensity level of the focal spots.
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http://dx.doi.org/10.1364/OE.25.030598DOI Listing
November 2017

Noise characteristics of high power fiber-laser pumped femtosecond optical parametric generation.

Opt Express 2017 Oct;25(20):24594-24603

We study, both numerically and experimentally, the relative intensity noise (RIN) and timing jitter characteristics of optical parametric generation (OPG) process in MgO-doped periodically poled LiNbO (MgO:PPLN) pumped by fiber femtosecond laser. We directly characterize the RIN, and measure timing jitter spectral density of the OPG process based on the balanced optical cross-correlator (BOC) technique for the first time as well, which are both in a fairly good agreement with numerical simulation. Both the numerical and experimental study reveals that OPG can suffer from a smaller intensity fluctuation but a lager temporal jitter when it is driven into saturation. Furthermore, we demonstrate that with a 30 mW CW diode laser injection seeding the OPG output results in superior noise performance compared to the vacuum fluctuations seeded OPG.
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http://dx.doi.org/10.1364/OE.25.024594DOI Listing
October 2017

Programmable controlled mode-locked fiber laser using a digital micromirror device.

Opt Lett 2017 May;42(10):1923-1926

A digital micromirror device (DMD)-based arbitrary spectrum amplitude shaper is incorporated into a large-mode-area photonic crystal fiber laser cavity. The shaper acts as an in-cavity programmable filter and provides large tunable dispersion from normal to anomalous. As a result, mode-locking is achieved in different dispersion regimes with watt-level high output power. By programming different filter profiles on the DMD, the laser generates femtosecond pulse with a tunable central wavelength and controllable bandwidth. Under conditions of suitable cavity dispersion and pump power, design-shaped spectra are directly obtained by varying the amplitude transfer function of the filter. The results show the versatility of the DMD-based in-cavity filter for flexible control of the pulse dynamics in a mode-locked fiber laser.
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http://dx.doi.org/10.1364/OL.42.001923DOI Listing
May 2017

Practical 24-fs, 1-μJ, 1-MHz Yb-fiber laser amplification system.

Opt Express 2017 Apr;25(7):7559-7566

We develop a practical femtosecond polarization-maintaining fiber laser amplification system with a standard double-cladding fiber technique, enabling 24-fs transform-limited pulses with 1-μJ pulse energy at a 1-MHz repetition rate. The laser system is based on a hybrid amplification scheme. Chirped-pulse amplification is employed in the pre-amplifier stage to supply high-quality pulses with enough energy for the main-amplifier, where nonlinear amplification is utilized to broaden the output spectrum. To obtain a dechirped pulse with high quality and short duration, a pre-shaper is inserted between the two amplification stages to adjust the pre-chirp, central wavelength, and pulse energy of the signal pulses in the main amplifier for optimizing pulse evolution. As a result, temporal pedestal free sub-ten-cycle high-energy laser pulses can be routinely obtained. In the end, the advantages of this novel laser source are demonstrated in the experiments on enhanced damage effect to cells co-cultured with gold nanorods.
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http://dx.doi.org/10.1364/OE.25.007559DOI Listing
April 2017
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