Passive Q-switching Operation Research Articles

Co/MoS2 nanocomposite for passive Q-switched pulse operation in erbium-doped fiber lasers

Co/MoS₂ nanocomposite for passive Q-switched pulse operation in erbium-doped fiber lasers

SESAM Q-switched Dy-doped fluoride fiber laser at 3.1 µm

We report on a passive Q-switching laser operation of an in-band pumped Dy-doped zirconium fluoride fiber using a commercially available semiconductor saturable absorber mirror (SESAM). Stable Q-switching pulse trains with minimum pulse duration of 460 ns, highest repetition frequency of 206 kHz, and pulse energy up to 1.7 µJ are demonstrated.

Passive Q-Switched Operation of Tm:YAP Laser with Graphene/WS2 Heterostructure Saturable Absorber

Passive Q-Switched Operation of Tm:YAP Laser with Graphene/WS2 Heterostructure Saturable Absorber

Highly nonlinear optic nucleic acid thin-solid film to generate short pulse laser

Using aqueous precursors, we report successfully fabricating thin-solid films of two nucleic acids, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). We investigated the potential of these films deposited on a fiber optic platform as all-fiber integrated saturable absorbers (SAs) for ultrafast nonlinear optics. RNA-SA performances were comparable to those of DNA-SA in terms of its nonlinear transmission, modulation depth, and saturation intensity. Upon insertion of these devices into an Erbium-doped fiber ring-laser cavity, both RNA and DNA SAs enabled efficient passive Q-switching operation. RNA-SA application further facilitated robust mode-locking and generated a transform-limited soliton pulse, exhibiting a pulse duration of 633 femtoseconds. A detailed analysis of these pulsed laser characteristics compared RNA and DNA fiber optic SAs with other nonlinear optic materials. The findings of this research establish the feasibility of utilizing RNA as a saturable absorber in ultrafast laser systems with an equal or higher potential as DNA, which presents novel possibilities for the nonlinear photonic applications of nucleic acid thin solid films.

Conversion from Q-switched to bright-dark soliton pair mode-locked operation in an InSb based erbium-doped fiber laser

In this experiment, stable Q-switched pulses and bright-dark soliton pairs were realized in an InSb based erbium-doped fiber laser. Firstly, when the pump power was between 70 and 115 mW, a stable passive Q-switched operation with a central wavelength of 1565.38 nm was achieved, and the signal-to-noise ratio (SNR) was about 37 dB. As the pump power increased, the repetition frequency of the Q-switched pulse can be increased from 4.0145 to 10.623 kHz. When the pump power was increased to the range of 185 to 450 mW, stable bright-dark soliton pairs mode-locked operation was realized, and the two peaks of the spectrum were located at 1568.67 and 1569.34 nm, respectively. The pulse repetition rate was 3.419 MHz, and the SNR was about 59 dB. This research will broaden the application of InSb in ultrafast optics and nonlinear optics.

Operation of a passively Q‐switched Tm:YAP laser with Ta2NiS5 as a saturable absorber

AbstractIn this study, the operation of compact diode‐pumped continuous wave and passively Q‐switched (PQS) Tm:YAlO3 (Tm:YAP) solid‐state lasers (SSLs) on the 3F4–3H6 transition is demonstrated. The first PQS operation of a mid‐infrared (mid‐IR) Tm:YAP laser at 1986.64 nm is realized with a Ta2NiS5‐based saturable absorber (SA). Under PQS mode, the Tm:YAP laser generated a maximum output power of 1.278/1.393 W with an optical‐to‐optical conversion efficiency of 8.81%/9.61%, corresponding to a narrowest pulse duration of 787/914 ns and a high repetition frequency of 187.932/151.115 kHz for 1.5%/2.5% transmittance of output coupler. The experimental results show that Ta2NiS5‐based SA is an excellent optical switch for diode‐pumped PQS mid‐IR SSL emitting around 2.0 μm.

Passively Q-switched 3 μm erbium-doped solid state lasers using gold nanorods as broadband saturable absorber

The gold nanorods with an average aspect ratio of 30 were grown by the three-step seed-mediated wet chemistry growth method, resulting in a broadband spectral response in 3 μm region. Passive Q-switching operation of LD pumped 2.8 μm Er:YSGG and 2.9 μm Er:YAP laser was successfully realized by using the gold nanorods as saturable absorber. With regard to the Er:YSGG laser, the passively Q-switched pulses at 2796 nm with a maximum average output power of 234 mW, a minimum pulse width of 270.8 ns and a pulse repetition rate of 280.4 kHz were achieved. For the combination of Er:YAP and gold nanorods saturable absorber, a maximum average output power of 415 mW was obtained at 2919 nm. The minimum pulse width and pulse repetition rate were 313.2 ns and 196.8 kHz, respectively. The experimental results show that large-aspect-ratio gold nanorods can be used as a promising broadband saturable absorber to generate 3 μm short pulses.

Passively Q‐switched operation of a Tm:YAP laser with two WS2‐based saturable absorbers

AbstractIn this paper, a doubly passively Q‐switched (PQS) Tm:YAP laser was experimentally realized by using two WS2‐based saturable absorbers (SAs) for the first time. Under the doubly PQS operation, the pulse width of 0.93 µs at 1989.3 nm was obtained with an average output power (AOP) of 391 mW and peak power of 4.04 W. While for PQS Tm:YAP laser with single WS2‐based SA, a pulse width of 1.63 µs and an AOP of 676 mW was achieved with a peak power of 3.4 W. The experiment results indicate a conclusion that the doubly PQS technology is an efficient method to further compress the pulse width, enhance the stability of the pulses train, and improve the AOP for the Tm:YAP laser.

Active and passive Q-switching operation of 1 μm Yb:YSP laser with an optical chopper/AOM and MoWS2 nanosheets

In this paper, the laser diode (LD)-pumped all-solid-state Yb:YSr3 (PO4)3 (Yb:YSP) lasers with active and passive Q-switching operation were demonstrated for the first time. At the pump power of 5.5 W, the average output power was 369 mW and the single pulse energy was 184.5 μJ at 2 kHz in the active Q-switching operation with an optical chopper. For the acousto-optic modulator Q-switched laser, a 118 ns pulse duration and 2881 W pulse peak power at 0.5 kHz were obtained. Furthermore, MoWS2 nanosheets were implemented to the passively Q-switched Yb:YSP laser, generating stable pulses with duration of 1.45 μs at the repetition frequency of 55 kHz and verifying the optical response potential of MoWS2. The good laser beam quality of = 1.14 and = 1.12 were achieved as well.

PECVD-derived graphene saturable absorber mirror for 2.8 μm pulsed Er:ZBLAN fiber laser

Graphene has been emerging as an ideal mid-infrared saturable absorber (SA) due to its broadband absorption, ultrafast nonlinear optical response, high stability and thermal tolerance. However, the current routes (e.g. chemical vapor deposition and spin coating) for constructing graphene SAs are suffering from the limited flexibility in substrate choice and the introduction of impurities during the transfer process, resulting in poor film quality and unstable laser modulation. Here, we demonstrate a high-quality graphene SA mirror (GSAM) grown directly on calcium fluoride (CaF2) substrate by a low-temperature plasma enhanced chemical vapor deposition (PECVD) method for mid-infrared pulse modulation. The controllable growth of high-quality graphene film on the nickel-modified CaF2 substrate is realized by adjusting the growth time and hydrocarbon ratio during PECVD process. Consequently, the GSAM shows excellent nonlinear optical absorption with the modulation depth of 11.2%. By inserting the GSAM into the Er:ZBLAN fiber laser, a stable passive Q-switched (QS) operation can be achieved with an average output power of 142 mW and a pulse width of 300.2 ns. The slope efficiency of QS laser is up to 17.4% and the peak power is 7.76 W. Our strategy paves the way for developing high quality and modulation stability GSAM towards industrial applications of pulsed mid-infrared lasers.

Watt-level high-stability all-solid-state passively Q-switched laser based on germanene nanosheets

Excellent Q-switching operations modulated by new two-dimensional (2D) saturable absorber (SA) materials with stable performance is a hot topic in all-solid-state pulsed laser research. In this work, the watt-level high-stability passive Q-switching operation in a solid-state Nd:YVO4 laser utilizing the 2D germanene nanosheets as SA was first realized. The nonlinear optical properties of the germanene nanosheets (Ge-Ns) were characterized by experimental means. The stable Q-switched pulse sequence was acquired with a 60.6 ns narrowest pulse width and a 528.6 kHz maximal repetition rate. The average output power of 0.965 W and the corresponding pulse peak power of 30.12 W are obtained under the pump power of 7 W. The findings of the experiments demonstrate that germanene material has remarkable nonlinear optical properties and can be used as an excellent saturable absorber in the field of optical pulse modulation.

CW and Q-switched operations of a Tm3+:YAP laser at 1892–1994 nm In-band fiber-laser pumped at 1670 nm

Tm3+:YAP lasers in-band fiber-laser pumped at 1670 nm with a linear or L-shaped cavity were studied in CW, actively and passively Q-switched regimes. High-efficiency CW and repetitively-pulsed operations were registered at three spectral regions: 1987–1994 nm, 1935–1941 nm and 1892–1897 nm. The transition between these three spectral regions was achieved by controlling the pump power and the output mirror in a laser cavity. The highest CW output power that was achieved without degrading the beam quality was 12.2 W at the 52% slope efficiency with respect to the incident pump. Acousto-optically Q-switched operation with the average power of 9.8 W at the 20 kHz pulse repetition rate (PRR) and 6 W at 3 kHz PRR was achieved, the pulse energy was scaled up to 2.7 mJ at 0.5 kHz PRR. The passive Q-switch operation at 1935–1938 nm was obtained using a Cr2+:ZnSe saturable absorber; the pulse energy reached 150 µJ at the 20 kHz PRR

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.

VOx/NaVO3 nanocomposite as a novel saturable absorber for passive Q-switching operation

We report VOx/NaVO3 nanocomposite as a novel saturable absorber for the first time, to the best of our knowledge. The efficient nonlinear absorption coefficient and the modulation depth are determined by the Z-scan technology. As a saturable absorber, a passively Q-switched Nd-doped bulk laser at 1.34 µm is demonstrated, producing the shortest pulse duration of 129 ns at a repetition rate of 274 kHz. In the passively Q-switched Tm:YLF laser with the prepared saturable absorber, the shortest pulse duration was 292 ns with a repetition rate of 155 kHz. Our work confirmed the saturable absorption in VOx/NaVO3 for possible optical modulation in the near-infrared region.

Highly efficient mode-locked and Q-switched Er3+-doped fiber lasers using a gold nanorod saturable absorber

Mode-locked and Q-switched pulsed fiber laser sources with wavelengths of 1.55 μm are widely used in various fields. Gold nanorods (GNRs) have been applied in biomedicine and optics owing to their biocompatibility, easy fabrication, and unique optical properties. This paper presents the analysis of a saturable absorber based on a colloidal gold nanorod (GNR) thin film for dual-function passively mode-locked and Q-switched 1.55-μm fiber lasers. The colloidal GNR thin film possesses superior properties such as a wide operating wavelength range, large nonlinear absorption coefficient, and a picosecond-order recovery time. Its modulation depth and saturation intensity at 1.55 μm are 7.8% and 6.55 MW/cm2, respectively. Passive mode-locked or Q-switched laser operation is achieved by changing the number of GNR thin-film layers. The advantages of these high-quality GNRs in mode-locked and Q-switched fiber lasers with record-high slope efficiency are verified by conducting comprehensive material and laser dynamic analyses. The self-starting mode-locked fiber laser with an efficiency as high as 24.91% and passively Q-switched fiber laser with the maximum energy of 0.403 μJ are successfully demonstrated. This paper presents the novel demonstration of reconfigurable mode-locked and Q-switched all-fiber lasers by incorporating colloidal GNR thin films.

Passively Q - Switched Linear Cavity IR Fibre Laser via Nonlinear Polarization Rotation

Abstract: Setup for self-starting passive Q-switch operation of IR fibre laser via nonlinear polarization rotation (NPR) was demonstrated for the first time for linear cavity. A Q-switched pulse duration of ~ 600 ns, a maximum peak power of ~16 W and an average power of 408 mW have been obtained at 223 kHz repetition rate for 5.1 W pump power from 1319 nm CW Nd: YAG laser launched to ~ 2.78 m unidirectional single-clad Tm-doped silica fibre linear cavity using only flat polarizer and feedback mirror to induce NPR. The dependence of the fibre laser output characteristics on the polarization angle of the polarizer is also reported. However, self induced passive Q-switching in linear fibre laser cavities is only observed in fibres with angled cleaved ends and with lengths that are around the optimum length for CW operation. Keywords: IR fibre laser, Passive Q-switching, Nonlinear polarization rotation, Linear cavity, Ring cavity. PACS: Fiber lasers, 42.55.Wd, Q-switching, 42.60.Gd.

Sulfur-doped graphitic carbon nitride for Tm:YAIO3 laser operation at 2.3 µm.

We report on the first, to the best of our knowledge, passive Q-switching operation at 2.3 µm passively based on Tm:YAIO3 (Tm:YAP) 3H4→3H5 transition with sulfur-doped graphitic carbon nitride (g-gC3N4) as the saturable absorber. Sulfur-doping engineering in g-C3N4 was manifested to enhance its mid-infrared nonlinear saturable absorption characteristics, which was confirmed by the conventional open-aperture Z-scan experiment with the excitation at 2.3 µm. The large effective nonlinear absorption coefficient of S-gC3N4 was determined to be -0.68cm/GW, indicating the remarkable MIR optical response. Initiated by S-gC3N4, a passively Q-switched laser operating at 2274.6 nm was configured with a-cut 3.0 at.% Tm:YAP as the gain medium. Stable Q-switching pulses were generated with the shortest pulse width of 140 ns, corresponding to the maximum peak power of 21.8 W. The experimental results reveal the effectiveness of sulfur doping to improve the performance of g-C3N4 in the MIR pulse generation.

Molybdenum Carbide Buried in D-Shaped Fibers as a Novel Saturable Absorber Device for Ultrafast Photonics Applications.

Study of nonlinear laser-matter interactions in 2D materials has promoted development of photonics applications. As a typical MXene material, molybdenum carbide (Mo2C) has attracted much attention because of its graphene-like structure. Here, a type of D-shaped fiber (DF)-buried Mo2C saturable absorber (SA) fabricated by magnetron-sputtering deposition (MSD) and sol-gel technique is reported. The Mo2C material was buried between the bottom DF and the upper amorphous silica fabricated by sol-gel technology. Therefore, the DF-based SA effectively solves the problem of material shedding and aging, thus improving the stability and damage threshold of the fiber laser. Application of the SA in erbium-doped fiber laser and stable passive Q-switched operation with a maximum pulse energy of 430.47 nJ is realized. By adjusting the polarization state and pump power, high-power mode-locked pulses are generated with a pulse duration and output power of 199 fs and 54.13 mW, respectively. Further, bound-state soliton pulses are obtained with a pulse width of 312 fs and soliton interval of 1.26 ps for the first time based on MXene materials. Moreover, by application of the SA in ytterbium-doped fiber lasers, a stable dissipative soliton mode-locked pulse is obtained with a pulse width of 23 ps. These results indicate that the DF-based buried Mo2C as a novel SA provides a reliable method for all-fiber and multifunctional high-power ultrafast laser.

Lawsone dye material as potential saturable absorber for Q-switched erbium doped fiber laser

In this paper, lawsone (2-hydroxy-1,4-naphthoquinone), a natural dye material is proposed and demonstrated as a saturable absorber (SA) for passive Q-switching operation in Erbium-doped fiber laser (EDFL) cavity. The lawsone-based SA was fabricated using a liquid-phase exfoliation technique. A tiny piece of the lawsone film was then cut and slot-in between two fiber ferrules so that it can easily be incorporated into a laser cavity as a Q-switcher. A stable Q-switched pulse train operation was observed with the repetition rate of 80 kHz and pulse width as narrow as 1.7 µs at 1564 nm wavelength. The maximum pulse energy and average power were obtained to be 53 nJ and 4.3 mW, respectively. The results indicate that the lawsone material can be a suitable SA for Q-switched pulse laser operating at the 1.5-µm region. To the best of our knowledge, this is the first time lawsone material is utilized as a SA device for generating Q-switched pulse.

Quasi-2D perovskites for high-power passive Q-switching in a 1.9 μm solid-state laser

For the first time, using the saturable absorption property of a quasi-2D perovskite film, a low-threshold and high-power passive Q-switched operation for a solid-state laser was realized at 1.9 μm. It indicated a promising commercial application.