Mid-infrared Laser Generation Research Articles

Nonlinear pulse compression technique based on in multi-pass plano-cancave cavity

<sec>Ultrafast femtosecond laser system with hundreds of microjoules of energy, operating at a repetition frequency of several kilohertz, has very important applications in many fields such as medicine, mid-infrared laser generation, industrial processing, and vibrational spectroscopy. The chirped pulse amplification technique provides a feasible path to obtain light sources with those parameters. However, the use of chirped pulse amplification increases the technical complexity and cost of the laser system. Recently, the proposal of a multi-pass cell (MPC) nonlinear pulse compression technique has enabled us to obtain high power ultrafast femtosecond pulses with reduced technical complexity and cost. The device requires only two concave mirrors and a nonlinear medium in between. In the past seven years, the multi-pass cell nonlinear pulse compression technique has made great progress, making it possible to obtain ultrashort pulses with average power of more than a few kW and peak power of tens to hundreds of TW.</sec><sec>In this work, we achieve nonlinear pulse compression of a 100-W picosecond laser by using an improved nonlinear pulse compression scheme that combines a hybrid of a plano-cancave multi-pass cell and multi-thin-plate. Using fused silica plates in plano-cancave cavity, the spectral bandwidth (FWHM) of input picosecond laser is broadened from 0.24 nm to 4.8 nm due to self-phase modulation effect, the pulse is compressed to 483 fs by dispersion compensation using grating pairs, which corresponds to a compression factor of 22, and the final output power of 44.2 W is obtained. Compared with traditional MPC, the plano-cancave cavity scheme we developed is a very promising solution for nonlinear compression due to its compactness, more stability and large compression ratio.</sec>

Mid-Infrared Laser Generation of Zn1-xMnxSe and Zn1-xMgxSe (x ≈ 0.3) Single Crystals Co-Doped by Cr2+ and Fe2+ Ions-Comparison of Different Excitation Wavelengths.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 m, Q-switched Er:YAG laser at 2.94 m, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 m. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr or by Fe ions under direct excitation or indirectly by the Cr→ Fe energy transfer mechanism. Laser generation of Fe ions in Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 m at a temperature of 78 K was achieved, respectively. The excitation of Fe ions in both samples by direct 2.94 m as well as ∼4.05 m radiation or indirectly via the Cr→ Fe ions’ energy transfer-based mechanism by 1.73 m radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3–2.5 and ∼4.4–4.9 m) based on AB matrices was presented.

2.1 μm, 1.52 μJ square-wave noise-like pulse from an all-fiber figure-of-9 Ho-doped oscillator and single-stage amplifier.

A 2.1 μm, high energy square-wave noise-like pulse (NLP) in an all-fiber Ho-doped fiber laser is proposed, which consists of an oscillator and a single-stage amplifier. In the figure-of-9 oscillator, mode-locking is achieved based on the nonlinear amplifying loop mirror, employing a long gain fiber to provide sufficient gain in 2.1 μm band and optimizing the cavity length to obtain maximum pulse energy output. With appropriate pump power and polarization state, the oscillator emits a 175.1 nJ square-wave NLP with center wavelength of 2102.2 nm and spike width of 540 fs. The 3-dB spectral width and pulse envelope width are 11.2 nm and 6.95 ns, respectively. The single-stage amplifier employs a bi-directional pump scheme. After amplification, 5.8 W NLP with a slope efficiency of 56.8% is obtained. The pulse energy of NLP is scaled to 1.52 μJ, which is the highest pulse energy of NLP at 2.1 μm to the best of our knowledge. The obtained high-energy square-wave NLP-fiber laser has great potential in mid-infrared laser generation.

Structure design and numerical simulation of chirped periodically polarized lithium niobate crystal for broadband mid-infrared laser generation

Mid-infrared band 3–5 <inline-formula><tex-math id="M1">\begin{document}${\text{μm}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M1.png"/></alternatives></inline-formula> laser light source has important applications in many fields such as medical treatment, basic science, communication, and industry. Owing to the limitation to available efficient gain media in the mid-infrared band, the traditional methods of generating and amplifying lasers , such as regenerative amplification, are no longer applicable. In order to produce broadband and high-energy mid-infrared laser, in this work we combine quasi-phase matching technology and chirped periodically polarized lithium niobate (CPPLN) crystal for theoretical analysis and numerical design. The second-order nonlinear difference-frequency generation (DFG) process is used to implement the generation of mid-infrared laser via CPPLN. In the differential frequency process, the pump light used is 800 nm in wavelength and the wavelength range of signal light is 0.95–1.6 <inline-formula><tex-math id="M2">\begin{document}${\text{μm}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M2.png"/></alternatives></inline-formula>. By calculating the dispersion curve of CPPLN crystal, the phase mismatch of difference frequency generation processes with different light signals is obtained. Under the condition of quasi-phase matching, the CPPLN with deliberately poling structures is designed and used to provide phase mismatch compensation in a broad bandwidth. The designed structure can meet the generation of mid infrared laser in a 1.6–5<inline-formula><tex-math id="M3">\begin{document}$ {\text{μm}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M3.png"/></alternatives></inline-formula> band according to the numerical simulations. The conversion efficiencies of mid-infrared laser with different wavelengths at different positions in the crystal are obtained by using nonlinear coupled wave equations and fourth-order Runge-Kutta method. The results show that the mid-infrared laser in a wavelength range of 1.6–5 <inline-formula><tex-math id="M4">\begin{document}$ {\text{μm}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M4.png"/></alternatives></inline-formula> can be produced efficiently in a single CPPLN crystal, with an average conversion efficiency of about 15%. The theoretical analysis and numerical simulation for the designed CPPLN crystal can provide good schematic reference and theoretical support for further experimental exploration on generation of mid-infrared laser.

Pulse combination and compression in hollow-core fiber for few-cycle intense mid-infrared laser generation

The generation of high-peak-power, few-cycle mid-infrared (MIR) pulses using coherent beam combination and nonlinear pulse compression techniques simultaneously is demonstrated. The two pulses, with identical pulse energy of 2.8 mJ and pulse duration of 160 fs, are coherently combined at the input end of a krypton-filled hollow-core fiber (HCF), and then the bandwidth of the combined pulse is broadened to near an optical octave due to strong phase modulations, and the temporal width is compressed into a few-cycle regime. Finally, a 2.7 mJ, 22.9 fs, 20 Hz laser at 4 μm can be obtained, and the pulse peak power is greatly enhanced compared with that of conventional single-channel optical parametric chirped pulse-amplification systems. Furthermore, the peak power generated from this system has the prospect of further scaling up through use of more channels of coherent combination, which can pave a way to generate higher peak power ultra-intense MIR pulses for strong-field physics.

High-peak-power 1.7 µm pulse generation by cascaded second- and third-order nonlinearity

We report an efficient and novel method for generating high-peak-power 1.7 µm laser pulses by cascaded optical parametric oscillation (OPO) and stimulated Raman scattering (SRS). The 1064 nm fundamental wave was first converted to 1535 nm by the KTA OPO, and further extended to 1.7 µm by a SRS process. The configuration of OPO + SRS can provide high-intensity pumping light for subsequent Raman conversion, and allows for better wavelength expansibility benefitting from the non-phase-matching requirement of SRS. Two types of Raman conversion using the low-frequency Raman shift in KY(WO4)2 and high-frequency Raman shift in YVO4 were further studied. Up to the 8th-order cascaded KY(WO4)2 Raman laser (KRL) using the high gain 87 cm−1 Raman mode and a YVO4 Raman laser (YRL) using the 890 cm−1 Raman mode emitting at 1.7 µm were realized, respectively. The output wavelengths at 1556, 1577, 1599, 1622, 1646, 1670, 1695, 1720 nm and the output wavelength at 1778 nm were observed in the KRL and YRL, respectively. The maximum total average output powers of 1.26 W and 1.05 W, minimum pulse widths of 8.4 and 24 ns and maximum pulse peak powers of 33.3 kW and 9.4 kW were obtained respectively from the KRL and YRL, enabling the 1.7 µm laser source to have practical applicability in medical imaging, industrial processing, and mid-infrared laser generation.

Wavelength, repetition rate, and pulse width tunable high average power narrow linewidth 1.5 μm fiber amplifier

Abstract Here, a wavelength, repetition rate, and pulse width tunable high average power narrow linewidth 1.5 μm all-fiber amplifier has been achieved by directly modulating a continuous-wave single-frequency diode laser using an acousto-optic modulator. The laser wavelength can be precisely tuned from 1530 nm to 1570 nm. The repetition rate and pulse width are also conveniently tunable. The maximum output average power is more than 2.5 W and the laser linewidth is at the range of 150–500 MHz. It has wide applications in tunable mid-infrared hollow-core fiber gas lasers, mid-infrared laser generation by nonlinear frequency conversion, fiber radar, coherent combination, and so on.

Efficient cascaded wavelength conversion based on Stark-chirped rapid adiabatic passage

We demonstrate a highly efficient process of cascaded wavelength conversion among three states that is based on the Stark-chirped rapid adiabatic passage technique, and enables the achievement of nearly complete wavelength conversion in the mid-infrared laser generation process. By analyzing the relevant parameters in the model, we identify various factors that affect the efficiency of the conversion process. Compared with traditional cascaded wavelength conversion based on the technique of stimulated Raman adiabatic passage, the new conversion process not only maintains a high efficiency but also keeps the intermediate frequency strength low along the interacting length and achieves better stability when the relevant parameters change.

Correction to: Stable and Efficient Pulsed Mid-Infrared Laser Generation from an Er3+-Doped ZBLAN Fiber Laser

Correction to: Stable and Efficient Pulsed Mid-Infrared Laser Generation from an Er3+-Doped ZBLAN Fiber Laser

Exploration in Performance Scaling and New Application Avenues of Superfluorescent Fiber Source

Thanks to the unique properties such as spatially coherent, broadband emission spectrum, and high temporal stability, superfluorescent fiber source (SFS) has shown tremendous potential in wide applications of sensing, imaging, spectroscopy, and material processing. The fast development of active fiber and pump diode provides unprecedented opportunity for the performance scaling of SFS. In this paper, the new horizon opened by the recently developed SFS will be reviewed. First, the output power scaling of SFS with different architectures will be summarized, and a kilowatt-level high power SFS based on a tandem pumping technique will be demonstrated for the first time. Second, spectrum manipulation of SFS, including coverage extending and spectrum shaping, will be introduced in detail. What is more, the spectrum evolution of narrowband SFS in power scaling will be numerically modeled and evaluated. Third, several novel applications of SFS, including midinfrared laser generation, nonlinear effect suppression, sensing, and imaging, will be given, indicating the versatile performance of SFS compared with traditional fiber laser oscillators. Based on the new developed SFS, we will present the first hundred-watt level linearly polarized random fiber laser. In the last section, future endeavors on SFS will be presented.

Stable and Efficient Pulsed Mid-Infrared Laser Generation from an Er3+-Doped ZBLAN Fiber Laser

We demonstrate a stable and efficient passively Q-switched 2.8 μm Er3+-doped ZBLAN fiber laser with a broadband semiconductor saturable absorber mirror. Enabled by the broadband optical modulator, the stable Q-switched fiber laser can deliver a maximum average power over 700 mW with corresponding per-pulse energy of 8.19 μJ and a pulse width of 1.3 μs at a repetition rate of 88.6 kHz under an incident pump power of 3.8 W. In addition, the slope efficiency can reach 22.5%. To the best of our knowledge, this is the highest reported slope efficiency for the passively Q-switched Er3+-doped ZBLAN fiber laser.

High-Power Narrow-Linewidth Tunable 670.8-nm Master Oscillator Power Amplifier With High Efficiency

A highly efficient 670.8-nm high-power narrow-linewidth wavelength-tunable laser source with master oscillator power amplifier structure is demonstrated, which yielded CW output power of 4.5 W with spectral linewidth of 0.3 pm and mode-hop free tuning range of 52 pm (35 GHz). The total conversion efficiency of 20% was achieved. The developed narrow-linewidth tunable laser source can provide better performance than others ever reported at 670.8 nm for many applications, such as laser isotope separation, Bose–Einstein condensation experiments, and mid-infrared laser generation.

High Power Yb Fiber Laser With Picosecond Bursts and the Quasi-Synchronously Pumping for Efficient Midinfrared Laser Generation in Optical Parametric Oscillator

A fiber laser-pumped high-power burst-mode-operated picosecond mid-infrared (IR) laser at 3.8 $\mu\text{m}$ is reported. A gain-switched distributed Bragg reflector laser diode with a pulse repetition rate (PRR) of 138 MHz and pulse duration around 200 ps was applied as the seed laser of a master oscillator power amplifier (MOPA)-structured Yb fiber laser. The PRR of the MOPA was increased to about 1.1 GHz through a pulse multiplier consisting of four cascaded 2 $\times$ 2 fiber couplers. A fiber-pigtailed acousto-optic modulator was used to carve the pulse train into pulse bursts so that the peak power of the final linearly polarized fiber laser output could be optimized by adjusting the duty cycle of the pulse bursts correspondingly. The output of the fiber laser was directed to pump a periodically poled magnesium-oxide-doped lithium niobate-based optical parametric oscillator through the quasi-synchronized pump scheme. Efficient parametric conversion was realized with a maximum average power output of 7.3 W at 3.8 $\mu\text{m}$ under pump power of 45 W at 1.064 $\mu\text{m}$ with pump-to-idler conversion efficiency exceeding 16%.

Hundred-watt-level high power random distributed feedback Raman fiber laser at 1150 nm and its application in mid-infrared laser generation.

Two kinds of hundred-watt-level random distributed feedback Raman fiber have been demonstrated. The optical efficiency can reach to as high as 84.8%. The reported power and efficiency of the random laser is the highest one as we know. We have also demonstrated that the developed random laser can be further used to pump a Ho-doped fiber laser for mid-infrared laser generation. Finally, 23 W 2050 nm laser is achieved. The presented laser can obtain high power output efficiently and conveniently and opens a new direction for high power laser sources at designed wavelength.