Generation Of Mid-infrared Pulses Research Articles

Time-resolved ARPES with probe energy of 6.0 eV and tunable MIR pump at 250 kHz

In this paper, we present a laser source designed specifically for time- and angle-resolved photoemission spectroscopy (TR-ARPES) investigations of light-induced electron dynamics in quantum materials. Our laser source is based on a ytterbium-doped laser that seeds an optical parametric amplifier (OPA) followed by a difference frequency generation (DFG) stage. This configuration enables the generation of tunable near-infrared and mid-infrared laser pulses (1.5 to 8 μm - 0.82 to 0.15 eV) at 250 kHz of repetition rate, serving as the pump for TR-ARPES measurements. The remaining energy of the laser is used to generate the ultraviolet 6 eV probe pulses, which prompt the material to emit photoelectrons. We demonstrate the long-term stability of the source, as well as the characterization of the beam profiles and pulse durations. Additionally, we present preliminary TR-ARPES results obtained on Bi2Te3, a prototypical 3D topological insulator. This paper illustrates the capability of our laser source to probe electronic dynamics in quantum materials.

Modelling of long-wave mid-infrared ultrashort pulse generation via difference frequency generation

In this paper, a model of generating mid-infrared (MIR) ultrashort laser pulse through difference frequency generation (DFG) is established. The pulse evolution relationship among the pump, signal, and idler pulses during the DFG process, as well as the effects of crystal length, pulse energy of the pump and signal lights, pulse width, and other factors on the characteristics of the MIR pulse are explored. Furthermore, through simulations from the time domain to the frequency domain, the spectral characteristics and angular distribution of MIR were analyzed. DFG experimental data are also presented to support the model.

An optical fiber integrated device for nonlinear generation of femtosecond mid-infrared pulses

Compact and broadband mid-infrared (MIR) sources are in high demand because of a wide range of potential applications such as molecular sensing in the fingerprint region. The generation of coherent MIR radiation at arbitrary frequencies typically requires nonlinear mixing between at least two input waves, which is often cumbersome to implement. We present an integrated and, therefore, adjustment-free solution combining few-femtosecond pulse compression in a germanosilicate optical fiber and optical rectification. To this end, a 16-μm-thin GaSe crystal is directly mounted on the end facet of a highly nonlinear fiber assembly exploiting a focused ion beam. With input pulses of a minute energy of 5 nJ and a duration of 120 fs at the telecom wavelength of 1.55 μm, we directly obtain ultrabroadband and phase-stable output transients. Electro-optic sampling in free space reveals single-cycle pulses with spectral components covering the entire MIR from 10 to 120 THz.

1064 nm laser pumped optical parametric oscillator based on BaGa4Se7 crystal at 1 kHz repetition rate

In this work, a tunable mid-infrared optical parametric oscillator based on type I phase-matching BaGa4Se7 was demonstrated. Using a Nd:YAG master oscillator power amplifier system as pump source, we firstly achieve the 1064 nm pumped BGSe-OPO at 1 kHz repetition rate. With pump double-pass single resonant oscillator configuration, the maximum output power at 4.18 μm was 483 mW and the corresponding conversion efficiency is 8.78 %. Both temperature and angle tuning of BGSe-OPO were studied and widely tunable output in the range of 3.36–5.16 μm was obtained. The average power fluctuation measured within 30 min was 0.98 % root mean square. This study has unveiled the great potential of BGSe crystal in highly stable, widely tunable, high repetition rate mid-infrared pulse generation.

Mid-infrared pulse generation using multi-plate white-light generation and optical parametric amplification in LiGaS2 crystals

We demonstrate intense mid-infrared pulse generation with a pulse energy of up to 6.2 μJ and a tunable wavelength range of 5.3–7.4 μm. This light source is based on white-light generation by multi-plate pulse compression of the output of a commercial Yb:KGW laser pulse followed by intra-pulse difference frequency generation (DFG) and optical parametric amplification in LiGaS2 crystals. Due to the use of intra-pulse DFG, we were able to generate carrier-envelope phase (CEP)-stable mid-infrared optical pulses with a CEP standard deviation of 114 mrad, corresponding to a timing fluctuation of 360 attoseconds during the 5-hour-long measurement.

Laser chirp controlled relativistic few-cycle mid-infrared pulse generation

Abstract Relativistic few-cycle mid-infrared (mid-IR) pulses are unique tools for strong-field physics and ultrafast science, but are difficult to generate with traditional nonlinear optical methods. Here, we propose a scheme to generate such pulses with high efficiency via plasma-based frequency modulation with a negatively chirped laser pulse (NCLP). The NCLP is rapidly compressed longitudinally due to dispersion and plasma etching, and its central frequency is downshifted via photon deceleration due to the enhanced laser intensity and plasma density modulations. Simulation results show that few-cycle mid-IR pulses with the maximum center wavelength of $7.9\;\unicode{x3bc} \mathrm{m}$ and pulse intensity of ${a}_{\mathrm{MIR}}=2.9$ can be generated under a proper chirp parameter. Further, the maximum energy conversion efficiency can approach 5.0%. Such a relativistic mid-IR source is promising for a wide range of applications.

Nonlinear optical properties of porous monoclinic BiVO4 at 2.3 µm for the passively Q-switching laser

In this work, we report the nonlinear optical response of porous monoclinic bismuth vanadate (m-BiVO4) at 2.3 µm for the first time. We adopted the conventional open/closed aperture (OA/CA) Z-scan techniques to systematically investigate the nonlinear optical (NLO) behavior. The effective nonlinear absorption coefficient βeff was −6.4 ± 0.02 cm MW−1, the nonlinear refractive index n2 was 9.88 ± 0.08 × 10-1 cm2 GW−1, and the NLO third-order susceptibility |χ(3)| was 2.69 × 10-7 esu. These NLO properties allowed it to be used as a fantastic saturable absorber for the generation of mid-infrared (MIR) pulses. As an application, we implemented a passively Q-switched Tm:YAP laser with the prepared porous m-BiVO4 saturable absorber for the first time. A minimum pulse duration of 349 ns and a maximum pulse repetition frequency of 193 kHz were achieved, resulting in a maximum pulse energy of 1.18 µJ. Our findings suggest that the porous m-BiVO4 could provide a route to the MIR optoelectronic applications.

Efficient generation of mid-infrared few-cycle pulses by the intrapulse difference-frequency generation in YCOB.

Yttrium calcium oxyborate (YCOB) crystals have been widely applied for generating intense near-infrared laser pulses by optical parametric amplification. Here, we show that the YCOB crystals oriented in both the XZ and XY principal planes possess broadband phase-matching property of intrapulse difference-frequency generation in the mid-infrared region. Few-cycle pulses tunable from 2 to 4 µm are experimentally produced by using a 7.5-fs pump laser at 800 nm, in which the conversion efficiency can be as high as 2.5%. With a large-size crystal and high-power pump laser, intrapulse difference-frequency generation based on YCOB may provide a new route for directly producing intense few-cycle mid-infrared pulses.

Synthesis of core-shell polyhedron ZIF-8@ZIF-67 as saturable absorber for passive Q-switching operation in Tm:YAP laser at 3H4→3H5 transition

In this paper, we synthesized a novel core-shell polyhedron ZIF-8@ZIF-67 nanocomposites with a size of around 150 nm. Then the core-shell structure ZIF-8@ZIF-67 as a saturable absorber to passively Q-switch the Tm:YAP laser was demonstrated for the first time at 2.3 μm based on the Tm3+3H4 → 3H5 transition. ZIF-8@ZIF-67 possessed the excellent nonlinear optical absorption features with a large modulation depth of 6.7% at 2.3 μm. The obtained stable shortest pulse width was 208 ns with a repetition rate of 128 kHz. Moreover, to fully understand the nonlinear optical properties of the core-shell ZIF-8@ZIF-67 nanocomposites, the coupled rate equations were setup to simulate the 3H4→3H5 Q-switching operation. The numerical simulation results agreed well with the experimental results. It demonstrated that the ZIF-8@ZIF-67 core-shell nanocomposites feature great potential as saturable absorber candidate for the mid-infrared pulse generation.

Nanosecond mid-infrared pulse generation modulated by platinum ditelluride nanosheets

We demonstrated the generation of nanosecond mid-infrared (MIR) pulse from an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser modulated by platinum ditelluride nanosheets experimentally. The platinum ditelluride nanosheets exhibit strong nonlinear absorption with the saturation intensity 46.5 GW cm−2 and modulation depth 27.8% at 2.8 μm wavelength, respectively. With the saturable absorber mirror fabricated by depositing the platinum ditelluride nanosheets on a gold mirror, we have obtained the stable Q-switched pulses with repetition rate of 173.4 kHz and pulse duration of 600 ns at 2.8 μm wavelength under the pump power of 5.6 W. In addition, the maximum average output power and pulse energy reach 591 mW and 3.41 μJ, respectively. The experimental results confirm that the platinum ditelluride nanosheets exhibit excellent nonlinear optical behavior towards the MIR spectral range, and may make inroads towards MIR photonics with group-10 transition-metal dichalcogenides.

High Modulation Depth Enabled by Mo2Ti2C3Tx MXene for Q-Switched Pulse Generation in a Mid-Infrared Fiber Laser.

Two-dimensional (2D) materials show great promise as saturable absorbers (SAs) for ultrafast fiber lasers. However, the relatively low modulation depth and poor stability of some 2D materials, such as graphene and black phosphorus, restrict their applications in the mid-infrared pulse generation. Herein, we first report a novel 2D double transition metal carbide, denoted as Mo2Ti2C3Tx MXene, as the saturable absorber (SA) for a passively Q-switched mid-infrared fiber laser. Due to the unique four-metal atomic layer structure, the Mo2Ti2C3Tx exhibits superior saturable absorption properties, particularly with a higher modulation depth (40% at 2796 nm) than most of the other reported 2D SA materials. After incorporating the MXene SA with an erbium-doped fiber system, the passively Q-switched pulses were achieved with a repetition rate of 157.3 kHz, the shortest pulse width of 370 ns, and single-pulse energy of 1.92 μJ, respectively. Such results extend the MXene-based SAs as promising candidates for advanced photonic devices.

Simple approach to broadband mid-infrared pulse generation with a mode-locked Yb-doped fiber laser.

Broadband mid-infrared (MIR) molecular spectroscopy demands a bright and broadband light source in the molecular fingerprint region. To this end, intra-pulse difference frequency generation (IDFG) has shown excellent properties among various techniques. Although IDFG systems pumped with 1.5- or 2-µm ultrashort pulsed lasers have been extensively developed, few systems have been demonstrated with 1-µm lasers, which use bulky 100-W-class high-power Yb thin-disk lasers. In this work, we demonstrate a simple and robust approach of 1-µm-pumped broadband IDFG with a conventional mode-locked Yb-doped fiber laser. We first generate 3.3-W, 12.1-fs ultrashort pulses at 50 MHz by a simple combination of spectral broadening with a short single-mode fiber and pulse compression with chirped mirrors. Then, we use them for pumping a thin orientation-patterned gallium phosphide crystal, generating 1.2-mW broadband MIR pulses with the -20-dB bandwidth of 480 cm-1 in the fingerprint region (760-1240 cm-1, 8.1-13.1 µm). The 1-µm-based IDFG system allows for additional generations of ultrashort pulses in the ultraviolet and visible regions, enabling, for example, 50-MHz-level high-repetition-rate vibrational sum-frequency generation spectroscopy or pump-probe spectroscopy.

Efficient and Broadband Generation of Mid-Infrared Pulses by Optical Parametric Amplification in Dispersion-Engineered Thin Film Lithium Niobate

Efficient and Broadband Generation of Mid-Infrared Pulses by Optical Parametric Amplification in Dispersion-Engineered Thin Film Lithium Niobate

Mid-infrared ultrashort pulse generation

Mid-infrared ultrashort pulse generation

Mid-infrared nanosecond pulse generation from a graphene modulated Er3+-doped fluoride fiber laser

We demonstrate a 2792.0 nm passively Q-switched Er3+-doped fluoride fiber laser using a graphene saturable absorber mirror (GSAM). Through optimizing the cavity design and the parameters of the GSAM, stable pulses are obtained with a repetition frequency ranging from 60.2 to 221.8 kHz. The shortest pulse duration is 238.2 ns, which, to the best of our knowledge, is the shortest passively Q-switching pulse obtained in 3 μm mid-infrared wavelength region. The maximum average output power is 535 mW, and the single pulse energy is 2.53 μJ. Further improvement of the pulse energy and pulse width is possible by optimizing the bleaching energy of the GSAM.

Mid-Infrared Few-Cycle Pulse Generation and Amplification

In the past decade, mid-infrared (MIR) few-cycle lasers have attracted remarkable research efforts for their applications in strong-field physics, MIR spectroscopy, and bio-medical research. Here we present a review of MIR few-cycle pulse generation and amplification in the wavelength range spanning from 2 to ~20 μm. In the first section, a brief introduction on the importance of MIR ultrafast lasers and the corresponding methods of MIR few-cycle pulse generation is provided. In the second section, different nonlinear crystals including emerging non-oxide crystals, such as CdSiP2, ZnGeP2, GaSe, LiGaS2, and BaGa4Se7, as well as new periodically poled crystals such as OP-GaAs and OP-GaP are reviewed. Subsequently, in the third section, the various techniques for MIR few-cycle pulse generation and amplification including optical parametric amplification, optical parametric chirped-pulse amplification, and intra-pulse difference-frequency generation with all sorts of designs, pumped by miscellaneous lasers, and with various MIR output specifications in terms of pulse energy, average power, and pulse width are reviewed. In addition, high-energy MIR single-cycle pulses are ideal tools for isolated attosecond pulse generation, electron dynamic investigation, and tunneling ionization harness. Thus, in the fourth section, examples of state-of-the-art work in the field of MIR single-cycle pulse generation are reviewed and discussed. In the last section, prospects for MIR few-cycle lasers in strong-field physics, high-fidelity molecule detection, and cold tissue ablation applications are provided.

Harmonic injection locking of high-power mid-infrared quantum cascade lasers

High-power, high-speed quantum cascade lasers (QCLs) with stable emission in the mid-infrared regime are of great importance for applications in metrology, telecommunication, and fundamental tests of physics. Owing to the intersubband transition, the unique ultrafast gain recovery time of the QCL with picosecond dynamics is expected to overcome the modulation limit of classical semiconductor lasers and bring a revolution for the next generation of ultrahigh-speed optical communication. Therefore, harmonic injection locking, offering the possibility to fast modulate and greatly stabilize the laser emission beyond the rate limited by cavity length, is inherently adapted to QCLs. In this work, we demonstrate for the first time the harmonic injection locking of a mid-infrared QCL with an output power over 1 W in continuous-wave operation at 288 K. Compared with an unlocked laser, the intermode spacing fluctuation of an injection-locked QCL can be considerably reduced by a factor above 1 × 10 3 , which permits the realization of an ultrastable mid-infrared semiconductor laser with high phase coherence and frequency purity. Despite temperature change, this fluctuation can be still stabilized to hertz level by a microwave modulation up to ∼ 18 GHz . These results open up the prospect of the applications of mid-infrared QCL technology for frequency comb engineering, metrology, and the next-generation ultrahigh-speed telecommunication. It may also stimulate new schemes for exploring ultrafast mid-infrared pulse generation in QCLs.

Gold nanospheres saturable absorber for 1.93 μm passively Q-switched laser generation

High-quality gold nanospheres (Au NPs) were transferred to a sapphire substrate. The balanced twin-detector measurement technique was used to study the saturable absorption properties of the Au NPs. With the as-prepared Au NPs as a saturable absorber (SA), an efficient passively Q-switched laser was realized at 1.93 μm. Under an absorbed pump power of 4.5 W, a maximum output power of 400 mW was obtained with the shortest pulse width of 410 ns and repetition rate of 126 kHz. The results indicate that Au NPs are promising candidates as SAs for mid-infrared laser pulse generation.

Mid-Infrared Ultra-Short Pulse Generation in a Gas-Filled Hollow-Core Photonic Crystal Fiber Pumped by Two-Color Pulses

We show numerically that ultra-short pulses can be generated in the mid-infrared when a gas filled hollow-core fiber is pumped by a fundamental pulse and its second harmonic. The generation process originates from a cascaded nonlinear phenomenon starting from a spectral broadening of the two pulses followed by an induced phase-matched four wave-mixing lying in the mid-infrared combined with a dispersive wave. By selecting this mid-infrared band with a spectral filter, we demonstrate the generation of ultra-short 60 fs pulses at a 3–4 µm band and a pulse duration of 20 fs can be reached with an additional phase compensator.

Few-cycle mid-infrared pulses from BaGa2GeSe6.

BaGa2GeSe6 (BGGSe) is a newly developed nonlinear material that is attractive for ultrabroad frequency mixing and ultrashort pulse generation due to its comparably low dispersion and high damage threshold. A numerical study shows the material's capacity for octave-spanning mid-infrared pulse generation up to 18 µm. In a first experiment, we show that a long crystal length of 2.6 mm yields a pulse energy of 21 pJ at 100 MHz with a spectral bandwidth covering 5.8 to 8.5 µm. The electric field of the carrier-envelope-phase stable pulse is directly measured with electro-optical sampling and reveals a pulse duration of 91 fs, which corresponds to sub-four optical cycles, thus confirming some of the prospects of the material for ultrashort pulse generation and mid-infrared spectroscopy.