Mode-locked Tm Research Articles

Mo0.5W0.5S2 as saturable absorber for passively mode-locked Tm:YAP laser

In recent years, 2 μm pulsed lasers have received extensive attention from researchers due to their wide applications in materials processing and medical fields. In this work, we reported preparing Mo0.5W0.5S2 saturable absorber (SA) via liquid phase exfoliation and successfully using this SA in Tm:YAP lasers to generate passively mode-locked (PML) pulses. An average output power of 0.87 W was achieved with the injected pump power of 20.38 W in the PML Tm:YAP laser, corresponding to a slope efficiency of 4.8%. Moreover, a pulse width of 686.4 ps at 85.9 MHz was acquired with a central output wavelength of 1935 nm from the laser, and the beam quality of M2 was measured to be 1.10 and 1.12 in the X and Y directions. The potential of Mo0.5W0.5S2 material in the transition metal dichalcogenides family for saturable absorption property in the 2 μm region was demonstrated by this work.

1.4 W Passively Q-Switched Mode-Locked Tm:CALGO Laser with a MoS2 Saturable Absorber

The passively Q-switched mode-locked (QML) operation of a Tm:CaGdAlO4 (Tm:CALGO) bulk laser pumped by a wavelength-tunable Ti:sapphire oscillator using molybdenum disulfide (MoS2) as a saturable absorber was demonstrated. By using an output coupler with 3% transmittance, Q-switched mode-locked operation can be achieved with 3.56 W absorbed pump power. At a pump power of 6.77 W, laser pulses with the maximum average power of 1.44 W were obtained, corresponding to a slope efficiency of 21.3%. The laser delivered pulses centered at 1927 nm with a repetition frequency of 131.6 MHz. The experimental results confirm the promising application of the MoS2 in high-power Q-switched mode-locked solid-state lasers at 2 µm.

Dispersion-managed mode-locked Tm:ZBLAN fiber lasers.

We demonstrated a dispersion-managed 2 µm ultrafast laser based on Tm:ZBLAN fiber. By controlling intracavity net dispersion using passive fibers, we observed soliton, stretched-pulse, and dissipative-soliton mode-locked operations. In particular, the broadest output spectrum with a bandwidth at 30 dB below the peak of 320 nm and a pulse duration of 61 fs were obtained at a net dispersion of -0.010 ps2. These results revealed the relationship between net dispersion and spectral bandwidth in Tm:ZBLAN mode-locked lasers. To accurately estimate the net dispersion of the cavity, the dispersion of each fiber in the cavity was experimentally determined using a cross-correlation method with a Mach-Zehnder interferometer.

Passive harmonic mode-locking in Tm–Ho doped fiber laser with MoS2–ZnO saturable absorber deposited on the arc-shaped fiber

This work reports a harmonic mode-locked Tm–Ho doped fiber laser (THDFL) using newly fabricated MoS2–ZnO as a saturable absorber (SA). It generates harmonic mode-locking (HML) operation with a center wavelength of 1911.4 nm and a 3-dB bandwidth of 3.02 nm. The fundamental repetition rate and pulse width were 14.1 MHz and 2.05 ps, respectively. Based on the radio frequency (RF) spectrum, the observed signal-to-noise (SNR) of the fundamental HML pulse was 67.22 dB. Increasing the pump power with fine-tuning of the polarisation controller (PC), higher order HML pulses were also observed using the MoS2–ZnO SA. The highest stable HML frequency was 300 MHz, observed at the 21st HML. The central wavelength and 3-dB bandwidth of the HML pulse were 1915.2 nm and 2.29 nm, respectively. The 21st HML pulses demonstrated a SNR of 40.09 dB. No supermode noise was observed in the RF spectrum, indicating that the 21st HML pulses were relatively stable. With industry demand, this high repetition rate HML with MoS2–ZnO SA opens new avenues for comprehension and manipulation of electronic phenomena, paving the way for future innovations in ultrafast lasers.

V2O5/Ti3C2 MXene-Based Solid-State Passively Mode-Locked Tm:YAP laser at 2 μm

In the present work, V2O5/Ti3C2 MXene hybrid nanomaterials were successfully synthesized. The morphology and structure of the prepared V2O5/Ti3C2 MXene were investigated, and the results showed excellent bonding and strong interaction between Ti3C2 MXene and V2O5 nanoparticles. The nonlinear absorption properties of V2O5/Ti3C2 MXene nanocomposites at 2 μm have been investigated using power transfer techniques, and the large modulation depth of the material gives it potential for applications in nonlinear optics. As a result, a 2 μm solid-state mode-locked pulsed laser with V2O5/Ti3C2 MXene as a saturable absorber has been realized for the first time, generating a pulsed laser output as short as 657 ps, which corresponds to an average output power of 0.67 W. The results show that the synthesized V2O5/Ti3C2 MXene hybrid nanomaterials, which have a large optical nonlinearity, can be applied to generating an ultrashort 2 μm pulsed laser.

In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser

We report on a Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser with in-band pumping of the Tm ions by a spatially single-mode 1678 nm Raman fiber laser. The structurally disordered CaGdAlO4 host crystal is also codoped also with the passive Lu ion for additional inhomogeneous line broadening. The Tm,Ho,Lu:CaGdAlO4 laser generates soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm via soft-aperture Kerr-lens mode-locking. The corresponding average output power amounts to 91 mW at a pulse repetition rate of ∼86 MHz. The average output power can be scaled to 842 mW at the expense of slightly longer pulses of 155 fs at 2045.9 nm, which corresponds to a peak power of ∼58 kW. To the best of our knowledge, this represents the first demonstration of an in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at ∼2 µm.

Diode-pumped 88 fs SESAM mode-locked Tm,Ho:CLNGG laser at 2090 nm

We report on a passively mode-locked Tm,Ho:CLNGG laser operating at 2090 nm, pumped by a multimode fiber-coupled 793 nm laser diode, representing the first demonstration of a diode-pumped sub-100-fs mode-locked laser at 2.1 μm wavelength. Due to the disordered nature of the gain material that exhibits a broad and smooth gain profile, pulses as short as 88 fs were achieved with an average output power of 120 mW at a repetition rate of 70.3 MHz. Stable self-starting mode-locked operation was obtained using a semiconductor saturable absorber mirror based on the GaSb material system.

All-solid-state ultrafast 2µm laser with 1.83 W output power.

In this paper, a high-power all-solid-state ultrafast 2µm mode-locked laser is investigated. The particularity of this laser is the simultaneous utilization of two Tm:YAP crystals in the same resonant cavity, independently pumped by two laser diodes. Using a 20% output coupler, pulses with output power as high as 1.83W are achieved at a wavelength of 1938nm with a pulse duration of 1.97ps and a pulse repetition frequency of 100MHz. To our knowledge, this mode-locked laser achieves the highest output power of any mode-locked Tm:YAP ultrafast laser reported to date. In addition, this paper provides a new approach to solve the problem of low output power due to multi-mode low-brightness laser diode pumping.

Low-noise mode-locking in a GHz repetition rate Tm3+-doped fiber laser.

We demonstrate a GHz repetition rate mode-locked Tm3+-doped fiber laser with low noise. Based on a home-made Tm3+-doped barium gallo-germanate fiber with reduced dispersion, a broad optical spectrum of mode-locking is achieved, and its amplified spontaneous emission quantum-limited timing jitter is largely suppressed. Besides, we carefully investigate the influence of the intracavity pump strength on the noise performance of the mode-locked pulses and find that manipulating the intracavity pump power can be an effective method for optimizing the timing jitter and relative intensity noise (RIN). Particularly, RIN, which originated from the relaxation oscillation, can be effectively suppressed by 33 dB at offset frequencies of >1 MHz. The integrated timing jitter and RIN are only 7.9 fs (10 kHz-10 MHz) and 0.05% (10 Hz-10 MHz), respectively.

Kerr-lens mode-locked 49-fs Tm3+:YScO3 single-crystal laser at 2.1 µm.

We report on a continuous wave (CW) and Kerr-lens mode-locked (KLM) Tm3+:YScO3 single-crystal laser centered at 2.1 µm. Efficient CW laser operation with a maximum slope efficiency of 51% was achieved under in-band pumping by an Er:Yb fiber master oscillator power amplifier (MOPA). In KLM operation, pulses as short as 49 fs corresponding to seven optical cycles were achieved at a repetition rate of 96.7 MHz with an average output power of 126 mW. Such short pulse durations are enabled by the inhomogeneously broadened emission spectrum of Tm3+:YScO3 extending to above 2200 nm.

Few-mode fiber based saturable absorber for ultra-fast fiber laser at 2 μm

The saturable absorption of the single mode-few-mode-single mode fiber (SMF-FMF-SMF) structure with respect to its passive mode-locking performance is still largely unexploited, although it is more conducive to the design and performance of the saturable absorber (SA) based on the nonlinear multimode interference effect. A series of FMF-based saturable absorbers with different FMF lengths are employed in passively mode-locked Tm fiber lasers for ultrafast pulse generations at 2 μm. The mode-locking performances using different FMF-based saturable absorbers were demonstrated. By comparing the saturable absorption characteristics and the respective mode-locking performances, we can conclude that it is easier to obtain the stable mode-locking output using saturable absorbers with the FMF lengths of 15.12 cm and 30.2 cm. The FMF saturable absorber with a 15.12 cm FMF has a large modulation depth of 40% and a saturation fluence of 108.23 μJ /cm2 which delivers ultrafast pulses with pulse width of 1.96 ps at 1878 nm. In addition, the harmonic mode-locking with stable and well-organized pulse trains could also be instantaneously achieved by increasing the pump power within the same cavity. Our results indicate that the SMF-FMF-SMF structure could operate as a SA while tuning its saturable absorption properties by changing the FMF length making it advantageous for mode locking fiber lasers.

Direct Kerr-lens mode-locked Tm: LuYO3 ceramics laser

Abstract A direct Kerr-lens mode-locked Tm: LuYO3 ceramics laser without the aid of any mode-locked starting element is reported for the first time. The pulse duration as short as 259 fs and maximum average output power of 326 mW are obtained at a repetition rate of 97.1 MHz. The corresponding optical spectrum centered at 2053 nm exhibits a bandwidth of 19.8 nm, which indicates the presence of nearly Fourier transform-limited pulses. Such a Kerr-lens mode-locked Tm: LuYO3 ceramics laser is a promising ultrashort pulse source, with both the excellent laser characteristics of Tm: LuYO3 and the high-power 790 nm LD pumping scheme.

Nb2AlC as saturable absorber for a passively mode-locked operation of Tm:YLF laser

The Nb2AlC material has attracted more and more attention in optoelectronics due to its excellent optical properties. Herein, the Nb2AlC-based saturated absorber (SA) was fabricated by ultrasonic thermal dissolution method and spin coating means, and a passively mode-locked (PML) Tm:YLF laser was perfectly demonstrated with the SA. With an incident pump power of 21.63W, a 0.379-W average output power and a 200-ps pulse width were achieved at 1872.1nm, corresponding to a per pulse energy of 3.15nJ and a peak power of 15.75W. In addition, the beam quality factors were measured to be 1.04 and 1.05 in the horizontal direction and vertical direction.

44-fs pulse generation at 2.05 µm from a SESAM mode-locked Tm:GdScO3 laser.

Pulses as short as 44 fs (6 optical cycles) with a spectral width of 120 nm are generated from a mode-locked solid-state laser near 2 µm employing an orthorhombic Tm:GdScO3 perovskite crystal. The average power amounts to 188 mW at a repetition rate of ∼77.6 MHz. The strong inhomogeneous line broadening in GdScO3 suggests optimum conditions for few-optical-cycle pulse generation of rare-earth ion doped GdScO3 bulk lasers.

Pb(Zrx,Ti1-x)O3 perovskite material for passively ultrafast pulse generation in a Tm:YAP laser

Ultrafast pulsed lasers (UPL) have critical applications in many fields, where a saturable absorber (SA) is an essential part. Perovskites have attracted much attention in SAs due to their unique structural features, which have not been mentioned in ultrafast pulsed lasers yet. In this paper, Pb(Zrx,Ti1-x)O3 (PZT) perovskite material is used as the SA equipment in an M-type passively mode-locked solid Tm:YAP UPL. Benefiting from the unique structure, the UPL possesses a ∼ 2 μm laser output and a repetition frequency of 102.04 MHz, as equipped in a 1466 mm length cavity. In addition, the output power of the laser is 0.721 and 0.297 W in continuous wave and passive mode-locked operation, respectively. Meanwhile, the laser gets the narrowest pulse width of 820.73 ps along with a peak power of 3.55 W, and it expresses quality factors of Mx2 = 1.09 and My2 = 1.12. at the highest average output power. These advantages indicating that the PZT can be an ideal SA material in a solid UPL.

Diode-pumped SESAM mode-locked Tm:Sc2SiO5 laser.

We report a diode-pumped passively mode-locked Tm:Sc2SiO5 (Tm:SSO) laser for the first time, to the best of our knowledge. The stable continuous-wave (CW) mode-locking is achieved with a semiconductor saturable absorber mirror (SESAM). Operating at the eye-safe wavelength of 1967.7 nm, the pulsed laser delivers a pulse duration of 16.5 ps with an average output power of 207 mW. At a fundamental repetition frequency of 81 MHz, the signal-to-noise ratio is as high as 70 dB. These results demonstrate the great potential of Tm:SSO crystal for ultrashort pulse generation.

2 μm soliton lasers in a bidirectional nonlinear polarization evolution Tm3+-doped fiber oscillator

We experimentally demonstrate a novel 2 μm soliton laser using a bidirectional nonlinear polarization evolution mode-locked Tm3+-doped fiber oscillator. The mode-locking operations between the laser signals propagating in clockwise and counterclockwise directions can be achieved through the intracavity polarization state adjustments independently, and the maximum achieved output powers are 332.5 and 367.8 mW with transfer efficiencies of 17.2 % and 18.3 %, respectively. Hysteresis in the output powers and spectra transformation between the two laser signals propagating in counter directions are observed and investigations are conducted in detail. Benefiting from the robust birefringence filtering effect, the central wavelength of this soliton laser can be continuously tuned from 1951.51 to 2015.89 nm. Stable high-order harmonic mode-locking (HML) operations are observed, and up to 633.02 MHz repetition rate with a central wavelength of 1992.55 nm is achieved. The monitored intensity spectra stability and average output power fluctuations exhibit excellent performance of this proposed 2 μm soliton fiber laser. The phase noise levels in two counter directions propagating light signals are characterized at different average output powers. Our experiment provides a potential technique for the generation of 2 μm solitons fiber laser that can be widely applied in ultrafast time-resolved measurements, mid-infrared frequency metrology, molecular spectroscopy, etc.

Efficient diode-pumped all-solid-state ultrafast 2.3 µm thulium-doped yttrium lithium fluoride laser

A diode-pumped passively mode-locked Tm3+-doped yttrium lithium fluoride (YLF) bulk laser at ∼2.3 µm is successfully achieved by using a kind of GaAs-based semiconductor saturable absorber mirror (SESAM). When working in the continuous mode-locking regime, stable ultrashort pulses with a duration of 52.5 ps and a repetition rate of 67 MHz are generated, with a corresponding maximum dual-output power of 284 mW. The radio-frequency spectrum of the output pulses demonstrates a high signal-to-noise ratio of 60 dB. To the best of our knowledge, this is the first report of a diode-pumped all-solid-state passively mode-locked thulium-doped laser at ∼2.3 µm.

SESAM mode-locked Tm:Y2O3 ceramic laser.

We demonstrate a widely tunable and passively mode-locked Tm:Y2O3 ceramic laser in-band pumped by a 1627-nm Raman fiber laser. A tuning range of 318 nm, from 1833 to 2151 nm, is obtained in the continuous-wave regime. The SESAM mode-locked laser produces Fourier-transform-limited pulses as short as 75 fs at ∼ 2.06 µm with an average output power of 0.26 W at 86.3 MHz. For longer pulse durations of 178 fs, an average power of 0.59 W is achieved with a laser efficiency of 29%. This is, to the best of our knowledge, the first mode-locked Tm:Y2O3 laser in the femtosecond regime. The spectroscopic properties and laser performance confirm that Tm:Y2O3 transparent ceramics are a promising gain material for ultrafast lasers at 2 µm.

Watt-level femtosecond Tm-doped "mixed" sesquioxide ceramic laser in-band pumped by a Raman fiber laser at 1627 nm.

We report on a semiconductor saturable absorber mirror mode-locked Tm:(Lu,Sc)2O3 ceramic laser in-band pumped by a Raman fiber laser at 1627 nm. The nonlinear refractive index (n2) of the Tm:(Lu,Sc)2O3 ceramic has been measured to be 4.66 × 10-20 m2/W at 2000 nm. An average output power up to 1.02 W at 2060 nm is achieved for transform-limited 280-fs pulses at a repetition rate of 86.5 MHz, giving an optical efficiency with respect to the absorbed pump power of 36.4%. Pulses as short as 66 fs at 2076 nm are produced at the expense of output power (0.3 W), corresponding to a spectral bandwidth of 69 nm. The present work reveals the potential of Tm3+-doped sesquioxide transparent ceramics for power scaling of femtosecond mode-locked bulk lasers emitting in the 2-µm spectral range.