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Article

Passively Mode-Locked Tm:YAP Laser Utilizing a Mo2TiAlC2 MAX Phase Saturable Absorber for Modulation

by
Chen Wang
,
Tianjie Chen
,
Zhe Meng
,
Sujian Niu
,
Zhaoxue Li
and
Xining Yang
*
Xinjiang Key Laboratory for Luminescence Minerals and Optical Functional Materials, School of Physics and Electronic Engineering, Xinjiang Normal University, Urumqi 830054, China
*
Author to whom correspondence should be addressed.
Photonics 2025, 12(6), 610; https://doi.org/10.3390/photonics12060610
Submission received: 8 May 2025 / Revised: 6 June 2025 / Accepted: 11 June 2025 / Published: 13 June 2025
(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)
Browse Figures
Versions Notes

Abstract

This study reports a novel MAX phase material, Mo2TiAlC2, as a passively mode-locking (PML) saturable absorber (SA) for a Tm:YAP laser operating in the 2 μm wavelength range. The systematic characterization of its nonlinear optical properties was quantitatively analyzed using I-scan methodology, demonstrating a significant modulation depth of 3.5%, which indicated strong nonlinear optical activity. Within the realm of optimal cavity conditions, a remarkable performance by the PML configuration can be discerned. A stable pulsed emission was manifested at 1937 nm, wherein an average output power reaching 620 mW was achieved. A pulse temporal span of 989.5 ps was acquired with a corresponding repetition frequency of 103.1 MHz, indicating robust mode-locked synchronization. Notably, the beam quality factors (M2) along the orthogonal spatial axes were observed with values measuring 1.12 and 1.18, respectively, indicating propagation characteristics close to those of diffraction-limited beams.

1. Introduction

Recent advancements have sparked growing interest in mid-infrared lasers, particularly those operating within the 2 μm wavelength region. This interest stems from their strategically significant spectral position, which coincides with both the water molecules’ absorption peak and atmospheric transmission allowance [1,2]. Instances reveal that pulsed laser systems at this particular wavelength emitting picosecond- or femtosecond-scale pulse durations—characterized by remarkable peak power, exceptional temporary steadiness, substantial energy per pulse, and superb beam form—are versatile across multiple applications spanning industrial processing, medical treatment modalities, and ecological monitoring, among others [3,4,5]. Notably, within this band lies an efficient pump locus for optical parametric oscillators (OPOs), facilitating mid-infrared radiation generation, thereby opening avenues for producing varied mid-infrared wavelengths. Henceforth, potential advances in nonlinear optical endeavors rest promisingly on ultrashort laser pulses at 2 μm [6,7].
Within this domain, mode-locking presents itself as an essential technique to achieve said ultrafast pulse formation; it is broadly divided into active mode-locking (AML) and PML. It is from observations that AML requires the incorporation of external modulating instruments, entailing considerable expenses coupled with complicated production procedures. Curiously enough, PML offers simpler cavity compositions, allowing focused narrowing of pulse widths. Its implementation predominantly relies on SAs acting as nonlinear optic manipulators. In newer exploration fields, most commercially accessible SAs are comprised largely of semiconductor saturable absorber mirrors (SESAMs), while SAs founded upon low-dimensional substrates arise alternatively. The evaluation of SESAM usage reveals the prerequisites for advanced fabrication techniques while also highlighting the limitations imposed by the narrow nonlinear optical bandwidth availability [8]. Consequently, the development of two-dimensional (2D) materials has emerged as an attractive alternative, offering both economic advantages and superior saturation absorption capabilities, and is gradually replacing conventional SESAM-based methodologies [9,10].
Among the commonly employed 2D materials are single-walled carbon nanotubes (SWCNTs), graphene, black phosphorus (BPs), and transition metal dichalcogenides (TMDs) [11,12,13,14]. The limitations of these materials are significant, as indicated by their low optical transmittance and insufficient oxidation resistance. Additionally, the complexity of their synthesis processes further restricts their application potential in practical domains [15,16,17]. In recent years, various artificial SAs, such as Mamyshev oscillators, have been continuously developed, and they have great potential in generating high-energy femtosecond pulses [18,19]. In contrast, the material-based SA still plays an indispensable role in 2 μm pulsed solid-state lasers due to its advantages of not requiring active modulation and external seeding signals. Meanwhile, MAX phase materials have received significant attention these days and are perceived as a promising alternative. They possess a unique combination of properties that overcome many of the shortcomings associated with conventional 2D materials. Their distinctive structural and optical characteristics make them an ideal candidate for next-generation SAs in ultrafast laser systems. The MAX phase materials represent a family of 2D ceramic compounds consisting of ternary, hexagonal nitrides or carbides, following the general formula Mn+1AXn (where n takes values such as 1, 2, 3, and so on). The M component corresponds to transition metal elements, including but not limited to molybdenum, scandium, chromium, titanium, zirconium, hafnium, niobium, vanadium, and tantalum. The A component refers to elements from groups III to VI in the periodic table, such as aluminum, germanium, gallium, indium, tin, thallium, silicon, phosphorus, and arsenic. The X component represents either carbon atoms, nitrogen atoms, or combinations thereof [20,21,22]. Compared to other 2D materials, MAX phase materials exhibit excellent mechanical damage tolerance, notable electrical conductivity, high thermal resistance, and superior oxidation resistance [23,24,25,26]. However, the application spectrum of MAX phase materials as SAs remains largely limited to Tm3⁺-doped or Tm3⁺/Ho3⁺-codoped passively mode-locked all-fiber lasers. In contrast to their fiber-based counterparts, solid-state lasers demonstrate significantly reduced occurrences of nonlinear pulse splitting phenomena. This characteristic inherently limits the practical applicability of MAX phase materials in the context of 2 μm solid-state laser systems, as evidenced by comparative analyses [27,28,29]. Currently, only a limited number of MAX phase materials, such as Cr2AlC, Ta4AlC3, and Ta2AlC, have been employed as modulators in 2 μm solid-state lasers [30,31]. This suggests their promising potential for applications as modulators within the 2 μm waveband. Mo2TiAlC2 is an emerging MAX phase material that exhibits rapid carrier dynamics coupled with broad nonlinear optical reactivity, spanning wavelengths from the visible to the mid-infrared spectrum. Consequently, it has garnered considerable academic interest. A review of its current applications indicates that Mo2TiAlC2-based SA used for modulating ultrafast PML solid-state lasers remains largely unexplored in the literature [32,33,34].
In this work, the SA based on the Mo2TiAlC2 MAX phase was successfully prepared by the spin-coating technique. By conducting comprehensive simulations of the cavity dynamics and stability, an optimized configuration methodology was systematically identified and implemented, leading to the successful construction of an M-shaped mode-locked resonant cavity. By utilizing a Mo2TiAlC2-based SA, modulation enabled the realization of ultrashort pulse generation. Under an absorbed pump power of 2.88 W, the laser achieved a mean output power of 620 mW, with a pulse duration of 989.5 ps. This corresponded to a pulse repetition frequency (PRF) of 103.1 MHz, emitting a central wavelength of 1937 nm. Additionally, the beam quality factors (M2) were measured to be 1.12 along the x-axis and 1.18 along the y-axis.

2. Nonlinear Optical Absorption Properties of the Mo2TiAlC2-Based SA

We successfully fabricated Mo2TiAlC2-based SAs and provided a detailed description of the preparation process in our prior study [35]. Additionally, extensive characterization and testing were carried out to comprehensively analyze their morphology and molecular structure features. Within the scope of this scholarly investigation, the nonlinear characteristics of optical absorption were examined for a Mo2TiAlC2-based SA. These investigations were conducted using an I-scan apparatus, which features a simpler structure, lower cost, and greater ease of operation compared to conventional methods. As illustrated in Figure 1, the spot radius converging at the Mo2TiAlC2-based SA was 194 μm. The initial transmittance of the Mo2TiAlC2-based SA, as determined by curve fitting, is 89.8%, whereas the transmittance at absorption saturation is 93.3%. This results in a modulation depth of 3.5%. The use of a self-constructed, actively Q-switched Ho:YAG laser, serving as the pump source for I-scan measurements, is evident. This apparatus operates at a PRF of 1 kHz with a pulse duration of 10 ns. Under this configuration, the central wavelength output achieves approximately 2091 nm. The experimental setup consisted of a half-wave plate (HWP), a beam splitter (BS), a focus lens (FL), and a 45° high reflectivity mirror (45° HR). The data were curve-fitted using the following mathematical relationship [36]:
T(I)=1 − ΔT × exp(−I/Isat) − Tns
In the equation under consideration, several parameters are represented: T(I) denotes transmittance; ΔT represents modulation depth; I indicates incident power intensity. Additionally, Isat refers to the saturation intensity, while Tns represents the nonsaturable loss, which is not subject to saturation [37]. This fitted curve corresponds to a nonlinear transmittance curve, indicating that the absorption of the Mo2TiAlC2-based SA reached saturation as the peak power density increased.

3. Experimental Setup

Prior to the physical construction of the resonant cavity, we designed an M-type 5-mirror folded cavity based on the ABCD matrix theory. The relevant parameters were determined as follows: M2-M1 = 220 mm, M3-M2 = 670 mm, M4-M3 = 470 mm, and OC-M4 = 50 mm. Additionally, by adjusting the angle of incidence, we enhanced the overlapping area between the meridian and sagittal surfaces, ultimately setting the angle of incidence θ to 8°. Under conditions where the pump wavelength is set at 792 nm and the crystal length is 7 mm, with the thermal lens effect neglected, results obtained from the use of self-programmed simulation software for optical path modeling are presented. It can be observed from this situation that Figure 2 presents these findings adeptly. In this figure, the three curves representing the sagittal surface, the meridian plane, and the modulus are nearly overlapped, indicating that the resonant cavity can form a stable laser output. The spot radii at M1 and OC are 130 µm and 89 µm, respectively. The SA is located adjacent to the OC, with a spot radius measured at 114 µm at the position of the SA. This value is sufficiently small to meet the power density requirement for achieving saturation in the SA. It can therefore be concluded that the designed M-type passively mode-locked cavity demonstrates a certain degree of feasibility.
As depicted in Figure 3, optical excitation was achieved using a laser diode characterized by a core diameter of 105 μm, an emission wavelength of 792 nm, and a numerical aperture of 0.22. The operational capabilities of the PML configuration were enabled by a gain medium consisting of a Tm:YAP crystal measuring 3 × 3 × 7 mm3 along the b-axis, doped with Tm3⁺ ions at a concentration of 3 at.%. To maintain experimental stability and thermal management, the Tm:YAP crystal was carefully encapsulated in indium foil to enhance thermal conductivity and minimize thermal fluctuations. Subsequently, the crystal was mounted within a water-cooled heat sink, maintaining a stable temperature of 15 °C throughout the entire experiment. This precise thermal control scheme was implemented with the aim of suppressing potential thermal drift phenomena and ensuring the accuracy of spectral measurements. To enhance optical performance, high-transmittance films were coated on both surfaces of the crystal, which are respectively applicable to the spectral ranges of 790–810 nm and 1900–2100 nm. M1 and OC were both flat mirrors. M1 served as the input coupler, featuring high transmittance (T > 90%) in the 790–810 nm range on its two surfaces and high reflectivity (R > 99%) at 1900–2100 nm on its internal surface. The OC was designed with a coating exhibiting high reflectivity in the 790–810 nm wavelength range and controlled partial transmittance (T = 2% or 5%) within the 1900–2100 nm waveband. The mirrors labeled M2, M3, and M4 are plano-concave, with radii of curvature measuring 300 mm for both M2 and M3 and 100 mm for M4. The spatial distances between the optical components are as follows: from M1 to M2 is 220 mm, from M2 to M3 is 670 mm, from M3 to M4 is 470 mm, and finally, from M4 to the OC is 50 mm. The power meter (PM, PM100D, Thorlabs, Newton, NJ, USA) was placed behind the OC to assess the output power. The SA was determined to be in close proximity to the OC to achieve two critical objectives: first, it facilitates the attainment of the PML threshold condition; second, it ensures that the SA operates at the optimal energy density for effective mode-locking performance [38]. This arrangement strikes a balance between enhancing nonlinear optical effects and preserving cavity stability.

4. Results and Discussion

Figure 4a illustrates the power output trajectories for both the PML mode and the continuous wave (CW) mode as dependent on absorbed pump power. The measurements were performed under two distinct OC conditions, with transmittance values of T = 2% and T = 5%. In the CW mode, as shown by the red and black lines, the laser exhibited threshold powers of 0.47 W at an OC transmittance of 2% and 5%. The data also revealed a maximum output power of 3.33 W and a lower output power of 2.13 W. These values were converted into slope efficiencies of 17.2% and 26.9%, respectively. Upon transitioning to the PML mode, as indicated by the blue and green lines, the threshold pump powers remained at 0.86 W and 0.663 W for the respective PML configurations, while the average output powers were measured to be 206 mW and 620 mW, respectively. This, in turn, led to a reduced slope efficiency of 3.09% and 7.8%, respectively. The observed variations in output power can primarily be attributed to the differences in transmission losses across various operational modes [39]. The significant reduction in output power observed during PML operation primarily results from the incorporation of the SA, which is composed of Mo2TiAlC2 MAX phase material, into the resonator cavity. This incorporation introduced non-negligible intracavity losses, thereby attenuating the overall power output. At a specific absorbed pump power of 2.88 W, the system, while maintaining stable PML operation, achieved a mean output power of 620 mW. During the experiment, it was observed that beyond this threshold, incremental increases in the incident pump power resulted in a progressive degradation of the PML output power, which indicates that the phenomenon of thermal effect is generated in the gain medium [29]. As depicted in Figure 4b, the power stability curve was obtained by calculating the root mean square (RMS) deviation of the power recorded each second relative to the average output power of 620 mW (T = 5%). The measured RMS value of 0.69% indicates that the PML Tm:YAP laser, when utilizing Mo2TiAlC2 as the SA for modulation, exhibits exceptional operational stability over a two-hour period. Using the M2MS-BP209IP2 beam quality analysis system from Thorlabs (Newton, NJ, USA), a detailed evaluation was carried out. This assessment focused on analyzing the beam quality at an average output power of 620 mW, using a convex lens with a focal length of 200 mm. Along the x-axis and y-axis, the beam quality factors (M2) were determined to be 1.12 and 1.18, respectively. These values corresponded to initial divergence angles of 0.684° and 0.761°, as detailed in Figure 4c. Furthermore, the spatial beam profile analysis, as illustrated in the inset of Figure 4c, clearly confirms the fundamental TEM00 mode operation through both 2D and three-dimensional (3D) intensity distribution representations. As shown in Figure 4d, spectral analysis reveals emission at central output wavelengths of 1941 nm, 1942 nm and 1935 nm, 1937 nm for CW and PML Tm:YAP lasers at different transmittance, respectively, corresponding to absorbed pump powers of 3.65 W and 2.88 W. At varying transmittance, the output wavelength exhibits a negligible change. This is attributed to the fact that the output wavelength is primarily dictated by the crystal’s gain and the longitudinal mode selection within the resonator. The transmittance of the OC does not modify the intrinsic energy level structure of the gain medium [40]. The blue shift observed in the PML regime is fundamentally put down to the altered population dynamics within the gain medium. Specifically, during PML operation, the enhanced excited-state population induced a corresponding shift of the peak gain cross-section towards shorter wavelengths, as corroborated by a prior theoretical study [41]. Moreover, the minor yet third-order nonlinear absorption induced by the intracavity SA served a dual purpose: it effectively suppressed low-gain laser mode oscillations while simultaneously enhancing the population inversion rate in the three-level laser system. This combined effect manifests spectrally as a distinct blue shift in the emission wavelength, accompanied by a reduction in spectral linewidth due to the modified gain dynamics [42,43].
Under the optimized operating parameters (an average power emission of approximately 620 mW and an OC transmission of T = 5%), a systematic investigation was carried out on the time-domain dynamics of the PML Tm:YAP laser. An InGaAs photodetector (ET-5000 model, EOT, Ann Arbor, MI, USA) was used in conjunction with an 8 GHz digital oscilloscope (MSO64B, Tektronix, Beaverton, OR, USA) in this research. It is evident that by modulating the absorbed pump power, PML pulses with a PRF of approximately 106.3 MHz were generated. Interestingly, a decrease in pulse width was observed as the incident pump power increased. The theoretical evaluation of this PRF originates from the equation f = c/2L [44], where f represents the center frequency of the laser resonator, c denotes the constant speed of light, and L corresponds to the physical length of the system. The nonlinear effect of an SA was used to compress pulses, thereby achieving PML. When pulses propagate through the SA, the nonlinear absorption effect suppresses lower-energy pulses, while high-energy pulses pass through with minimal loss. After multiple round trips within the cavity, the pulses become progressively compressed, and their phases become locked. Repeated cycles in the cavity result in the leading and trailing edges gradually attenuating, ultimately achieving a stable laser output [45,46]. The narrowest pulse width, measuring 989.5 ps, was experimentally achieved at an absorbed pump power of 2.88 W. The pulse trains acquired under distinct temporal resolutions (4 μs/div, 200 ns/div, 100 ns/div, and 20 ns/div) are comprehensively presented in Figure 5a–d. Figure 5a depicts the standard PML pulse envelope on a large period, and Figure 5b–d depict the pulse trains on different periods. Time-domain analysis revealed the generation of ultrashort pulses with the shortest pulse width of 989.5 ps, corresponding to a fundamental PRF of 103.1 MHz. The experimental value exhibited excellent agreement with the theoretically predicted PRF of 106.3 MHz, with the observed deviation falling well within the acceptable range of experimental errors. These findings confirm the reliability of the theoretical framework and experimental methodology, demonstrating that the Tm:YAP laser modulated by Mo2TiAlC2-based SA can operate effectively in the PML mode.
Figure 6 demonstrates the radio-frequency (RF) spectrum of the PML Tm:YAP laser, with the test equipment identical to that in the preceding figure. This spectrum exhibits distinct and interference-free spectral peaks, providing robust evidence for the successful establishment of a stable mode-locked laser. Quantitative analysis indicates that within the 120 MHz spectral window, the signal-to-noise ratio (SNR) is discerned as roughly 61.3 dBm, achieved with a resolution bandwidth (RBW) of 480 KHz. Furthermore, the RF spectrum measured over a broader 500 MHz range at the same RBW, as shown in the subsidiary figure accompanying Figure 6 on the right, ascertains the formation of a stable and distortion-free PML pulsed laser, characterized by the absence of additional spurious peaks and exceptional spectral purity. The high spectral purity of the RF spectrum further corroborates the efficacy of the mode-locking mechanism, thus validating the system’s performance at the fundamental physical level. It was observed that the apparent harmonic intensity decreased significantly. This could potentially be attributed to the saturation effect of the photodetector induced by the input power or the attenuation effect of the coaxial cable connecting the photodetector and the RF analyzer, which might considerably reduce the measurement bandwidth [47].
Table 1 provides a detailed elucidation of the output characteristics for a range of pulsed solid-state lasers, each employing different 2D materials as SAs. In the PML Tm:YAP laser, the SA based on Mo2TiAlC2 achieves highly competitive pulse width performance. Furthermore, in addition to Mo2TiAlC2, other MAX phase materials also exhibit substantial competitive advantages. The extensive application of MAX phase materials in nonlinear optics highlights their significant potential as effective SAs. Notably, the achieved pulse width reaches the picosecond level, offering considerable benefits for practical applications. Furthermore, discernible from experimental outcomes is the fact that superior performance levels are exhibited by repetition frequency alongside both single-pulse energy and peak power.

5. Conclusions

In this study, we employed a self-developed I-scan system to systematically investigate the nonlinear optical absorption characteristics of an SA manifesting from Mo2TiAlC2 MAX phase material. The measured modulation depth reached 3.5%. By incorporating the Mo2TiAlC2-based SA into a PML laser cavity, we achieved an in-depth characterization of its performance in the ultrafast 2 μm laser region. Upon examining the experimental results, it is evident that when the absorbed pump power reaches 2.88 W, the system generates stable mode-locked pulses. This is accompanied by an average output power of 620 mW, with a central emission wavelength located at approximately 1937 nm, corresponding to a slope efficiency of 7.8%. Temporal analysis of the PML operation yielded a pulse duration of approximately 989.5 ps at a PRF of 103.1 MHz. Spatial beam quality assessment confirmed near-diffraction-limited performance with an M2 factor of ~1.15. These findings collectively underscore the significant potential of Mo2TiAlC2 MAX phase materials as high-performance nonlinear optical components for ultrafast laser systems operating in the 2 μm spectral region, offering promising prospects for applications in mid-infrared photonics and advanced laser technology.

Author Contributions

Conceptualization, C.W. and X.Y.; methodology, C.W. and X.Y.; validation, C.W., T.C., and Z.M.; formal analysis, C.W. and T.C.; investigation, C.W.; resources, X.Y.; data curation, C.W., T.C., and Z.M.; writing—original draft preparation, C.W.; writing—review and editing, X.Y.; visualization, C.W.; supervision, S.N. and Z.L.; project administration and funding acquisition, X.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research received funding from various sources, including the Natural Science Foundation of Xinjiang Uygur Autonomous Region (2022D01A221), the Doctoral Research Startup Foundation of Xinjiang Normal University (XJNUZBS2406), the Postdoctoral Science Foundation of China (2021MD703833), the Ministry of Education’s Industry-University Cooperation and Collaborative Education Program (23110409093007), the Postdoctoral Foundation of Heilongjiang Province (LBHZ21206), and the “Tianchi Talents” Introduction Program under the Talent Development Fund of the Xinjiang Uygur Autonomous Region.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Gao, L.; Ding, Y.; Zhai, X.; Min, H.; Liu, G.; Lan, R.; Shen, Y. Passively Q-switched 2 μm laser based on graphene/BN heterostructure as saturable absorber. Opt. Laser Technol. 2024, 168, 109852. [Google Scholar] [CrossRef]
  2. Pierpoint, K.A.; Doroshenko, M.E.; Alimov, O.K.; Papashvili, A.G.; Konyushkin, V.A.; Nakladov, A.N.; Nekhoroshikh, A.V. Spectroscopic properties of Ho3+ optical centers in CaF2 crystals at the two-micron laser transition. J. Lumin. 2020, 228, 117584. [Google Scholar] [CrossRef]
  3. Li, Y.; He, X.; Wen, Z.; Wu, M.; Tang, G.; Song, X.; Qian, Q. Research Progress on 2 μm Germanate Glass Fibers and their laser applications. Ceram. Int. 2024, 51, 16584–16592. [Google Scholar] [CrossRef]
  4. Tao, W.; Sun, J.; Deng, Y.; Lian, Y.; Chen, Z.; Jiang, L. Au-Doped Black Silicon Photodetector Fabricated by a Femtosecond Laser with Excellent Near-Infrared Response. ACS Appl. Mater. Interfaces 2024, 16, 65710–65724. [Google Scholar] [CrossRef]
  5. Qiao, S.; He, Y.; Sun, H.; Patimisco, P.; Sampaolo, A.; Spagnolo, V.; Ma, Y. Ultra-highly sensitive dual gases detection based on photoacoustic spectroscopy by exploiting a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser. Light Sci. Appl. 2024, 13, 100. [Google Scholar] [CrossRef] [PubMed]
  6. Xu, C.; Hu, B.; Zhang, K.; Zhang, X.; Chen, Y.; Yao, H.; Zhao, G. High-SNR, high-repetition-rate, compact, picosecond, mid-infrared optical parametric oscillator pumped synchronously by a harmonic mode-locked fiber laser. Opt. Lett. 2025, 50, 1228–1231. [Google Scholar] [CrossRef]
  7. Guo, L.; Yang, Y.; Zhao, S.; Li, T.; Qiao, W.; Ma, B.; He, J. Room temperature watt-level 3.87 µm MgO: PPLN optical parametric oscillator under pumping with a Tm: YAP laser. Opt. Express 2020, 28, 32916–32924. [Google Scholar] [CrossRef]
  8. Yun, L.; Ding, C.; Ding, Y.; Han, D.; Zhang, J.; Cui, H.; Yu, K. High-power mode-locked fiber laser using lead sulfide quantum dots saturable absorber. J. Light. Technol. 2022, 40, 7901–7906. [Google Scholar] [CrossRef]
  9. Fan, W.; Han, Y.; Chen, S.; Sun, S.; Zhao, X.; Bai, C.; Zhang, H. Nanosized indium selenide saturable absorber for multiple solitons operation in Er3+-doped fiber laser. Opt. Express 2023, 31, 10176–10190. [Google Scholar] [CrossRef]
  10. Li, L.; Cheng, J.; Zhao, Q.; Zhang, J.; Yang, H.; Zhang, Y.; Liu, W. Chromium oxide film for Q-switched and mode-locked pulse generation. Opt. Express 2023, 31, 16872–16881. [Google Scholar] [CrossRef]
  11. Yap, Y.; Chong, W.; Razgaleh, S.A.; Huang, N.; Ong, C.; Ahmad, H. Performance of Q-switched fiber laser using optically deposited reduced graphene oxide as saturable absorber. Fiber Integr. Opt. 2022, 41, 26–40. [Google Scholar] [CrossRef]
  12. Ooi, S.I.; Ahmad, H. Thermal release tape assisted mechanical exfoliation of pristine TMD and the performance of the exfoliated TMD saturable absorbers for Q-switched laser generation. Optic. Mater. 2022, 128, 112363. [Google Scholar] [CrossRef]
  13. Alghamdi, T.A.; Harun, S.W. Black phosphorus film as Q-switcher in neodymium-doped fiber laser. Heliyon 2024, 10, e37776. [Google Scholar] [CrossRef] [PubMed]
  14. Mohamad Rashid, N.N.; Ahmad, H.; Ismail, M.F.; Lokman, M.Q.; Zuikafly, S.N.F.; Yahaya, H.; Ahmad, F. Nanotubes in Chitin Mode Locker for Passive Mode−Locked Fibre Laser in 2.0 µm Region. Photonics 2023, 3, 257. [Google Scholar] [CrossRef]
  15. Liu, J.; Yang, F.; Lu, J.; Ye, S.; Guo, H.; Nie, H.; Ni, Z. High output mode-locked laser empowered by defect regulation in 2D Bi2O2Se saturable absorber. Nat. Commun. 2022, 13, 3855. [Google Scholar] [CrossRef]
  16. Mu, H.; Liu, Y.; Bongu, S.R.; Bao, X.; Li, L.; Xiao, S.; Bao, Q. Germanium nanosheets with dirac characteristics as a saturable absorber for ultrafast pulse generation. Adv. Mater. 2021, 33, 2101042. [Google Scholar] [CrossRef]
  17. Yu, J.; Kuang, X.; Li, J.; Zhong, J.; Zeng, C.; Cao, L.; Liu, Y. Giant nonlinear optical activity in two-dimensional palladium diselenide. Nat. Commun. 2021, 12, 1083. [Google Scholar] [CrossRef] [PubMed]
  18. Yang, S.; Smith, C.R.; Petersen, C.R. All-Fiber 2 µm Mamyshev Oscillator: Mapping of Different Operating Regimes. Laser Photonics Rev. 2025, 2500074. [Google Scholar] [CrossRef]
  19. Shi, Z.; Sun, S.; Wang, Q. Ultrafast soliton dynamics from an all-fiber self-starting thulium-doped Mamyshev oscillator. Opt. Lett. 2025, 50, 1025–1028. [Google Scholar] [CrossRef]
  20. Sarycheva, A.; Gogotsi, Y. Raman Spectroscopy Analysis of the Structure and Surface Chemistry of Ti3C2Tx MXene; Jenny Stanford Publishing: Singapore, 2023; pp. 333–355. [Google Scholar] [CrossRef]
  21. Alhabeb, M.; Maleski, K.; Mathis, T.S.; Sarycheva, A.; Hatter, C.B.; Uzun, S.; Gogotsi, Y. Selective Etching of Silicon from Ti3SiC2 (MAX) to Obtain 2D Titanium Carbide (MXene); Jenny Stanford Publishing: Singapore, 2023; pp. 451–462. [Google Scholar] [CrossRef]
  22. Nemani, S.K.; Zhang, B.; Wyatt, B.C.; Hood, Z.D.; Manna, S.; Khaledialidusti, R.; Anasori, B. High-entropy 2D carbide mxenes: TiVNbMoC3 and TiVCrMoC3. ACS Nano 2021, 15, 12815–12825. [Google Scholar] [CrossRef]
  23. Lin, X.; Zhang, G.; Zhang, W.; Li, Y.; Li, B.; Wang, B. Microstructure and mechanical properties of Mo-12Si-8.5 B alloy reinforced by layered Mo2TiAlC2 MAX phase. Int. J. Refract. Met. Hard Mater. 2022, 109, 105967. [Google Scholar] [CrossRef]
  24. Ouadha, I.; Rached, H.; Azzouz-Rached, A.; Reggad, A.; Rached, D. Study of the structural, mechanical and thermodynamic properties of the new MAX phase compounds (Zr1-xTix)3AlC2. Comput. Condens. Matter. 2020, 23, e00468. [Google Scholar] [CrossRef]
  25. Hui, X.; Ge, X.; Zhao, R.; Li, Z.; Yin, L. Interface chemistry on MXene-based materials for enhanced energy storage and conversion performance. Adv. Funct. Mater. 2020, 30, 2005190. [Google Scholar] [CrossRef]
  26. Sokol, M.; ElMeligy, T.A.; Plummer, G.; Tucker, G.J.; Barsoum, M.W. Tensile creep of textured Ti2AlC in the 1000–1150° C temperature range. Acta Mater. 2023, 261, 119350. [Google Scholar] [CrossRef]
  27. Ahmad, H.; Makhfuz, M.J.M.; Yusoff, N.; Sadafi, N.; Samion, M.Z.; Yasin, M. Mode-locked operation in thulium-holmium doped fiber laser based on Cr2AlC MAX phase SA coated arc-shaped fiber. Opt. Quantum Electron. 2023, 55, 228. [Google Scholar] [CrossRef]
  28. Ahmad, H.; Kahar, N.A.; Ramli, R.; Yusoff, N.; Reduan, S.A.; Ismail, M.F.; Yasin, M. The performance of Ti2C MXene and Ti2AlC MAX Phase as saturable absorbers for passively mode-locked fiber laser. Opt. Fiber Technol. 2021, 67, 102683. [Google Scholar] [CrossRef]
  29. Sun, Y.J.; Lee, C.K.; Xu, J.L.; Zhu, Z.J.; Wang, Y.Q.; Gao, S.F.; Tu, C.Y. Passively Q-switched tri-wavelength Yb3+: GdAl3(BO3)4 solid-state laser with topological insulator Bi2Te3 as saturable absorber. Photonics Res. 2015, 3, A97–A101. [Google Scholar] [CrossRef]
  30. Zaini, M.A.Z.; Rahman, M.F.A.; Latiff, A.A.; Rusdi, M.F.M.; Roslan, I.A.Z.; Harun, S.W. Passive Q-switched pulse fibre laser with molybdenum titanium aluminum carbide (Mo2TiAlC2) saturable absorber. J. Mod. Opt. 2023, 70, 661–672. [Google Scholar] [CrossRef]
  31. Najm, M.M.; Al-Hiti, A.S.; Nizamani, B.; Abdullah, M.N.; Rosol, A.H.A.; Zhang, P.; Harun, S.W. Effect of MAX phase chromium aluminum carbide thin film thickness on Q-switched Erbium-doped fiber lasers. Opt. Fiber Technol. 2022, 70, 102853. [Google Scholar] [CrossRef]
  32. Qi, T.; Wu, H.; Li, M.; Hou, X.; Shen, Y.; Duan, X.; Yang, Y. Operation of a passively mode-locked Tm: YAG laser with tantalum aluminum carbide as a saturable absorber. Microw. Opt. Technol. Lett. 2024, 66, e33776. [Google Scholar] [CrossRef]
  33. Safuan, N.Z.M.; Rosol, A.H.A.; Zulkipli, N.; Yasin, M.; Harun, S.W. Generation of Picosecond Pulses in Erbium-Doped Fiber Lasers Via Mode Locking Using V4AlC3 Thin Film. J. Russ. Laser Res. 2023, 44, 384–391. [Google Scholar] [CrossRef]
  34. Yang, J.; Zou, H.; Chen, J.; Wen, Y.; Fan, Y.; Liu, Y.; Li, X. Reactive synthesis of porous Mo2Ti2AlC3 ceramic and its basic application properties. Ceram. Int. 2022, 48, 9205–9217. [Google Scholar] [CrossRef]
  35. Wang, C.; Chen, T.; Meng, Z.; Niu, S.; Li, Z.; Yang, X. Mo2TiAlC2 as a Saturable Absorber for a Passively Q-Switched Tm: YAlO3 Laser. Nanomaterials 2024, 14, 1823. [Google Scholar] [CrossRef]
  36. Zhang, K.; Feng, M.; Xie, J.; Sang, X.; Sun, G.; Tian, Y.; Huang, W. High-energy Q switched Yb-doped fiber laser based on a ternary layered structured Ti2AlC saturable absorber. Opt. Lett. 2022, 47, 5525–5528. [Google Scholar] [CrossRef]
  37. Zhang, Q.; Jiang, X.; Zhang, M.; Jin, X.; Zhang, H.; Zheng, Z. Wideband saturable absorption in metal-organic frameworks (MOFs) for mode-locking Er-and Tm-doped fiber lasers. Nanoscale 2020, 12, 4586–4590. [Google Scholar] [CrossRef] [PubMed]
  38. Ma, Z.; Hao, Q.; Wang, H.; Gao, Q.; Mi, S.; Li, D.; Xu, B. Passively mode-locked Tm: YAP laser with a V2AlC saturable absorber. Microw. Opt. Technol. Lett. 2024, 66, e70007. [Google Scholar] [CrossRef]
  39. Shen, Y.; Han, X.; Li, L.; Duan, X.; Zhou, L.; Xie, W.; Yang, Y. Continuous-wave mode-locked Tm: YAG laser with GaAs-based SESAM. Infrared Phys. Technl. 2020, 111, 103539. [Google Scholar] [CrossRef]
  40. Li, L.; Yang, X.; Zhou, L. High beam quality passively Q-switched operation of a slab Tm: YLF laser with a MoS2 saturable absorber mirror. Opt. Laser Technol. 2019, 112, 39–42. [Google Scholar] [CrossRef]
  41. Li, L.; Yang, X.; Zhou, L. BN as a saturable absorber for a passively mode-locked 2 µm solid-state laser. Phys. Status Solidi RRL 2019, 13, 1800482. [Google Scholar] [CrossRef]
  42. Gao, Q.; Yang, X.; Li, S.; Wageh, S.; Al-Hartomy, O.A.; Al-Sehemi, A.G.; Zhang, H. Pb (Zrx,Ti1-x)O3 perovskite material for passively ultrafast pulse generation in a Tm: YAP laser. Opt. Laser Technol. 2023, 157, 108707. [Google Scholar] [CrossRef]
  43. Yan, B.; Zhang, B.; He, J.; Nie, H.; Li, G.; Liu, J.; Yang, K. Ternary chalcogenide Ta2NiS5 as a saturable absorber for a 1.9 μm passively Q-switched bulk laser. Opt. Lett. 2019, 44, 451–454. [Google Scholar] [CrossRef] [PubMed]
  44. Liu, B.; Yang, W.; Yang, X.; Li, L. Passively mode-locked Tm: YAP laser with a Ti3AlC2-based saturable absorber. Opt. Commun. 2025, 578, 131498. [Google Scholar] [CrossRef]
  45. Wu, Q.; Peng, L.; Huang, Z. Advancements in ultrafast photonics: Confluence of nonlinear optics and intelligent strategies. Light Sci. Appl. 2025, 14, 97. [Google Scholar] [CrossRef]
  46. Radnatarov, D.; Khripunov, S.; Kobtsev, S. Automatic electronic-controlled mode locking self-start in fibre lasers with non-linear polarisation evolution. Opt. Express 2013, 21, 20626–20631. [Google Scholar] [CrossRef] [PubMed]
  47. Feng, T.; Yang, K.; Zhao, J. 1.21 W passively mode-locked Tm: LuAG laser. Opt. Express 2015, 23, 11819–11825. [Google Scholar] [CrossRef] [PubMed]
  48. Zhang, Y.; Ling, W.; Qiao, D.; Sun, R.; Chen, C. Passively Q-switched mode-locked Tm,Ho: CaYAlO4 laser based on double-walled carbon nanotube saturable absorber. Front. Phys. 2020, 8, 86. [Google Scholar] [CrossRef]
  49. Chen, C.; Ling, W.; Sun, R.; Xu, Q.; Zhang, Y. Watt-level dual-wavelength Q-switched mode-locked all-solid-state Tm: CYA laser. Front. Phys. 2020, 7, 252. [Google Scholar] [CrossRef]
  50. Wang, Z.; Zhang, B.; He, J.; Yang, K.; Han, K.; Ning, J.; Lou, F. Passively Q-switched mode-locking of Tm: YAP laser based on Cr: ZnS saturable absorber. Appl. Opt. 2015, 54, 4333–4336. [Google Scholar] [CrossRef]
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Figure 1. Nonlinear optical absorption performance of the Mo2TiAlC2-based SA.
Figure 1. Nonlinear optical absorption performance of the Mo2TiAlC2-based SA.
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Figure 2. Spot radius within the cavity of the PML Tm:YAP laser.
Figure 2. Spot radius within the cavity of the PML Tm:YAP laser.
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Figure 3. Experimental setup of the PML Tm:YAP laser with the Mo2TiAlC2-based SA.
Figure 3. Experimental setup of the PML Tm:YAP laser with the Mo2TiAlC2-based SA.
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Figure 4. (a) Correlation between resulting output power and absorbed pump power for CW and PML modes at T = 2% and T = 5%; (b) stability of output power in PML mode at T = 5%; (c) beam quality of PML mode at T = 5%; (d) output spectrum for CW and PML modes at T = 2% and T = 5%.
Figure 4. (a) Correlation between resulting output power and absorbed pump power for CW and PML modes at T = 2% and T = 5%; (b) stability of output power in PML mode at T = 5%; (c) beam quality of PML mode at T = 5%; (d) output spectrum for CW and PML modes at T = 2% and T = 5%.
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Figure 5. Pulse trains generated by the PML Tm:YAP laser across various temporal dimensions. (a) 4 μs/div; (b) 200 ns/div; (c) 100 ns/div; (d) 20 ns/div.
Figure 5. Pulse trains generated by the PML Tm:YAP laser across various temporal dimensions. (a) 4 μs/div; (b) 200 ns/div; (c) 100 ns/div; (d) 20 ns/div.
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Figure 6. The PML Tm:YAP laser’s RF spectrum. Inset presents an expansive spectral region of 0.5 GHz.
Figure 6. The PML Tm:YAP laser’s RF spectrum. Inset presents an expansive spectral region of 0.5 GHz.
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Table 1. A detailed comparison of the output characteristics of PML all solid-state lasers incorporating various SAs.
Table 1. A detailed comparison of the output characteristics of PML all solid-state lasers incorporating various SAs.
SAsCrystalsWavelength
(nm)		Pulse Width
(ps)		Repetition Frequency (MHz)Pulse Energy
(nJ)		Output Power
(mW)		Peak Power
(W)		Ref.
V2AlCTm:YAP1939107782.4925.72.1223.8[36]
DWCNTTm,Ho:CaYAlO4208579998.040.650.0640.82[48]
MoS2Tm:CYA1877994103.711.11.1511.08[49]
Cr:ZnSTm:YAP19769803502.60.9402.74[50]
Pb(Zrx,Ti1−x)O3Tm:YAP1936.1820.7102.042.90.2973.55[41]
Mo2TiAlC2Tm:YAP1937989.5103.16.010.6206.08This work
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MDPI and ACS Style

Wang, C.; Chen, T.; Meng, Z.; Niu, S.; Li, Z.; Yang, X. Passively Mode-Locked Tm:YAP Laser Utilizing a Mo2TiAlC2 MAX Phase Saturable Absorber for Modulation. Photonics 2025, 12, 610. https://doi.org/10.3390/photonics12060610

AMA Style

Wang C, Chen T, Meng Z, Niu S, Li Z, Yang X. Passively Mode-Locked Tm:YAP Laser Utilizing a Mo2TiAlC2 MAX Phase Saturable Absorber for Modulation. Photonics. 2025; 12(6):610. https://doi.org/10.3390/photonics12060610

Chicago/Turabian Style

Wang, Chen, Tianjie Chen, Zhe Meng, Sujian Niu, Zhaoxue Li, and Xining Yang. 2025. "Passively Mode-Locked Tm:YAP Laser Utilizing a Mo2TiAlC2 MAX Phase Saturable Absorber for Modulation" Photonics 12, no. 6: 610. https://doi.org/10.3390/photonics12060610

APA Style

Wang, C., Chen, T., Meng, Z., Niu, S., Li, Z., & Yang, X. (2025). Passively Mode-Locked Tm:YAP Laser Utilizing a Mo2TiAlC2 MAX Phase Saturable Absorber for Modulation. Photonics, 12(6), 610. https://doi.org/10.3390/photonics12060610

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