Simultaneous Dual-wavelength Laser Research Articles

Simultaneous Dual-Wavelength Laser Irradiation against Implant-Adherent Biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans for Improved Antimicrobial Photodynamic Therapy.

The efficiency of antimicrobial photodynamic therapy (PDT) might be improved by using multiple wavelengths. This study investigates the sensitivity of implant-adherent biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans to indocyanine green (ICG)-808 nm diode laser, toluidine blue O (TBO)-635 nm diode laser, and hydrogen peroxide (HP)-980 nm diode laser and their combination when irradiated with dual-wavelength laser irradiation (simultaneously 980-635 nm or 980-808 nm). After an incubation period of 72 h, the infected implants were randomly divided into seven different treatment modalities: Control, HP, HP-PDT, TBO-PDT, HP-TBO-PDT, ICG-PDT, and HP-ICG-PDT. After the treatments, the colony-forming units (CFUs)/mL and reactive oxygen species (ROS) generation were determined. All evaluated disinfection methods were significantly effective against the three investigated bacteria compared to the control. The combined treatment of HP-ICG-PDT or HP-TBO-PDT had the greatest antibacterial effect compared to each treatment alone. There were statistical differences between HP-ICG-PDT and ICG-PDT or HP-TBO-PDT and TBO-PDT for all three bacteria studied. PDT with simultaneous dual-wavelength laser irradiation is an efficient strategy to improve the therapeutic effect of PDT.

A 2 μm Dual-Wavelength Laser at Cryogenic Temperature with Balanced Simultaneous Emission

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature dependence of the laser spectra. The optimal temperature for balanced output evidently diminishes as the pump power density increases, thereby manifesting a rate of change quantified at 1.19 K/W. At the optimal temperature of 43.1 K, the optical-to-optical conversion efficiency of the Tm,Ho:YAP simultaneous dual-wavelength laser (SDWL) with a pump power of 11.8 W is 12.7%, corresponding to a slope efficiency of 15.8%.

Effective linewidth compression of a single-longitudinal-mode fiber laser with randomly distributed high scattering centers in the fiber induced by femtosecond laser pulses.

Femtosecond lasers can be used to create many functional devices in silica optical fibers with high designability. In this work, a femtosecond laser-induced high scattering fiber (HSF) with randomly distributed high scattering centers is used to effectively compress the linewidth of a fiber laser for the first time. A dual-wavelength, single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) is constructed for the demonstration, which is capable of switching among two single-wavelength operations and one dual-wavelength operation. We find that the delayed self-heterodyne beating linewidth of the laser can be reduced from >1 kHz to <150 Hz when the length of the HSF in the laser cavity increases from 0 m to 20 m. We also find that the intrinsic Lorentzian linewidth of the laser can be compressed to several Hz using the HSF. The efficiency and effectiveness of linewidth reduction are also validated for the case that the laser operates in simultaneous dual-wavelength lasing mode. In addition to the linewidth compression, the EDFL shows outstanding overall performance after the HSF is incorporated. In particular, the optical spectrum and SLM lasing state are stable over long periods of time. The relative intensity noise is as low as <-150 dB/Hz@>3 MHz, which is very close to the shot noise limit. The optical signal-to-noise ratios of >85 dB for single-wavelength operation and >83 dB for dual-wavelength operation are unprecedented over numerous SLM fiber lasers reported previously. This novel method for laser linewidth reduction is applicable across gain-medium-type fiber lasers, which enables low-cost, high-performance, ultra-narrow linewidth fiber laser sources for many applications.

Tunable continuous-wave dual-wavelength laser operation of Pr3+:LiYF4 around 900 nm

We present here the first tunable continuous-wave (CW) simultaneous dual-wavelength laser operation of a Pr3+:LiYF4 crystal in the 900 nm spectral range using a single birefringent filter (BF) under excitation with a frequency doubled optically pumped semiconductor laser. By adjusting the rotation angle of the BF, the CW simultaneous dual-wavelength lasers operating at 869 and 915 nm, 894 and 915 nm, 915 and 923 nm, were obtained respectively.

Performance enhancement of diode-end-pumped quasi-three-level continuous-wave and passively Q-switched Nd:Gd3Ga5O12 lasers

Abstract We present the results on diode-end-pumped quasi-three-level lasers in continuous-wave and passively Q-switched regimes using a weakly Nd3+ doped Gd3Ga5O12 (GGG) crystal as active medium. In continuous-wave case, a maximum output power of 8.06 W at 937 nm is achieved with a slope efficiency of 47.3%. In passively Q-switched case, a simultaneous dual-wavelength laser at 937 nm and 933 nm is obtained with a maximum output power up to 1.72 W. The corresponding shortest pulse width is 21.1 ns at a repetition rate of 32.8 kHz, which leads to maximum pulse energy and peak power of 52.4 μJ and 2.48 kW, respectively. We believe that the present results represent the best that have ever achieved at this emission band in diode-end-pumped Nd:GGG lasers. Thus, for quasi-three-level laser, a weakly doped laser active medium could be an effective way for power scaling owing to thermal alleviation and reduction of reabsorption loss.

Experimental and clinical study of simultaneous dual-wavelength laser action in energetic cataract surgery

A new technique of energy cataract surgery with the simultaneous use of two wavelength of laser emission acting as high-intensity laser—endodissector (Nd:YAG, wavelength λ = 1.44 µm) and a low-intensity laser—endobiostimulator (He–Ne, wavelength λ = 0.632 μm) is represented. The surgical technique is bimanual. The radiation of high-intensity laser ensures the destruction of cataract lens of any density level without additional assistance of ultrasound and without manual fragmentation. The laser tip, which contacts the eye tissues, does not heat up. In the process of high-intensity laser action splitting and spalling of the eye lens core occurs. Laser energy does not go beyond the lens capsule as it is almost completely absorbed by the liquid of the anterior chamber (water) at less than 1 mm from the distal end of the laser tip. Simultaneous exposure to radiation of high-intensity and low-intensity lasers delivered to the eye lens via one laser tip provide to prevent the progression of posttraumatic inflammatory process in the eye at the initial stage of the start of pathophysiological intracellular changes. This ensures high efficiency and safety of simultaneous dual-wavelength laser cataract extraction (DW LCE).

High power simultaneous dual-wavelength CW and passively-Q-switched laser operation of LD pumped Tm:YLF at 1.9 and 2.3 µm.

Simultaneous dual-wavelength laser oscillation of Tm:YLF at 1.9 and 2.3 µm were successfully realized. The three-mirror cavity was exploited to study dual-wavelength laser performance, which is formed by a shared input mirror and two independent output couplers for the two laser wavelengths. Under an absorbed pump power of 15.2 W, the maximum CW output powers of 5.49 W around 1908nm and 1.12 W around 2305 nm were simultaneously obtained, corresponding to a total optical-to-optical conversion efficiency of 43.5%. A Cr2+:ZnSe was further used to passively Q-switch the dual-wavelength laser, generating pulses with pulse widths of 554 ns at 1.9 µm and 4 µs at 2.3 µm. To the best of our knowledge, this is the first report on the dual-wavelength laser operation of Tm3+-single-doped solid-state laser at 1.9 and 2.3 µm. The higher optical conversion efficiency, smaller wavelength competition effect and simultaneous dual-wavelength output make this Tm-doped solid-state laser have potential application in medical surgery.

Frequency expansion of efficient passively Q-switched orthogonally-polarized dual-wavelength laser

We report on the frequency expansion of efficient passively Q-switched (PQS) orthogonally-polarized dual-wavelength laser for the first time, to our knowledge. The dynamic of pulse synchronization for the PQS dual-wavelength laser was analyzed theoretically. With two Nd:YLF crystals, the simultaneous PQS orthogonally-polarized dual-wavelength laser at 1047 and 1053 nm was obtained with the maximum output powers of 4.5 and 4.2 W, respectively, resulting in a total optical-to-optical conversion efficiency of 18.7%. The timing jitter between the 1047 nm main pulse and 1053 nm main pulse was 26.6 ns. Furthermore, substituting one of the Nd:YLF crystals for a Nd:YAG crystal, two sets of simultaneous orthogonally-polarized dual-wavelength lasers at 1047, 1064 nm and 1053, 1064 nm were generated with near 6 W of output power.

High-efficiency diode-pumped continuous-wave and passively Q-switched c-cut Nd:LaMgAl11O19 (Nd:LMA) lasers

We report on diode-pumped continuous-wave and passively Q-switched c-cut Nd:LMA lasers. For continuous-wave operation, the maximum output power reaches 3.10 W with slope efficiency of about 48.9% at 1055 nm and 2.63 W with slope efficiency of 43.1% at 1082 nm. For passively Q switched operation, using a Cr:YAG as saturable absorber, the achieved maximum average output power is 1.49 W at 1055 nm with pulse width of 18.4 ns. Moreover, we have also realized simultaneous dual-wavelength laser operation at 1055 and 1082 nm with a maximum average output power of 1.22 W and a pulse width of 19.4 ns. Furthermore, inserting an etalon for suppressing the 1055 nm line, we have operated single wavelength laser at 1082 nm with output power of 0.31 W and pulse width of 20.8 ns. This work has verified the potential of Nd:LMA crystal as a laser gain medium.

Dual-signal-resonant optical parametric oscillator intracavity driven by a coaxially end-pumped laser with compound gain media.

A flexible method of generating stable dual-wavelength laser pulses with tunable power ratio and pulse interval is proposed, through integrating a coaxially end-pumped laser with compound gain media and an intracavity pumped optical parametric oscillator (IOPO). A theoretical model was built by a set of time-domain coupling wave equations containing both the generation of two fundamental waves from a shared pump source and the conversion to signal waves through the parametric process. Simulations showed that by simply varying the pump focal position or pump wavelength, the gains in two laser crystals could be changed, leading to simultaneous change in average power ratio and time interval between two wavelengths. Experimental verifications were performed with combined laser crystals (Nd:YAG and a-cut Nd:YLF) and a nonlinear crystal (KTA), which enabled dual-wavelength signal output in the 1.5-1.6 μm eye-safe region and demonstrated coincident conclusions with theoretical results. As there was no gain competition between two fundamental waves, stable signal output was obtained. Moreover, various wavelength pairs in any wavelength ranges are possible by using different laser crystals and nonlinear crystals. It is believed that this is a promising method for generating simultaneous dual-wavelength laser pulses for applications in lidar, remote sensing, nonlinear frequency conversion, etc.

Investigations on continuous-wave and passively Q-switched Nd:LuAG ceramic lasers at eye-safe wavelengths

We report comparative studies on diode-pumped eye-safe Nd:LuAG ceramic lasers at 1.4 μm spectral region in continuous-wave regime. Six differently doped samples have been used to experimentally determine the optimized laser results. A maximum output power of 1.78 W is achieved with simultaneous dual-wavelength laser emission at 1418 and 1442 nm, which is believed the highest output power of Nd:LuAG ceramic at this specific wavelength. Using a V3+:YAG as saturable absorber, passively Q-switched Nd:LuAG ceramic laser is also realized, for the first time to our knowledge, with maximum average output power of 0.58 W and pulse width of about 34 ns at pulse repetition rate of 11.91 kHz, which lead to pulse energy of 49.3 μJ and pulse peak power of 1.43 kW.

Eye-safe Nd:LuAG ceramic lasers

Diode-pumped continuous-wave Nd:LuAG ceramic lasers at the 1.4-μm eye-safe spectral region are reported. A simultaneous dual-wavelength laser at 1418 nm and 1442 nm is achieved with a maximum output power of 1.37 W and a slope efficiency of 13.5% using a plane-concave cavity configuration. Laser generation at another emission line of 1432 nm is also realized with a maximum output power of 0.82 W with the help of an intracavity etalon. To improve the laser beam quality, a parallel plane laser cavity operating still at 1418 nm and 1442 nm is adopted in free-running mode.

New continuous-wave and Q-switched eye-safe Nd:YAG lasers at 1.4 μm spectral region

We report new results concerning 1.4 μm eye-safe laser sources based on a conventional Nd:YAG crystal. In free-running laser mode, we obtain the highest output power of 4.64 W at 1413 nm with slope efficiency of about 23.1%. With the aid of an etalon, we achieve a simultaneous dual-wavelength laser at 1413 and 1443 nm with maximum output power of 3.18 W and slope efficiency of about 16.7%. In addition, a single wavelength laser at 1431 nm is also yielded with maximum output power of 1.96 W and slope efficiency of about 11.8%. The dual-wavelength laser and single-wavelength laser (1431 nm) are believed to be the first demonstrations from diode-pumped Nd:YAG crystal. Using a single-wall carbon nanotube as the saturable absorber, we achieve dual-wavelength Q-switched laser operation at 1413 and 1443 nm with the narrowest pulse width of about 0.49 μs, for the first time to our knowledge.

Compact and Flexible Dual-Wavelength Laser Generation in Coaxial Diode-End-Pumped Configuration

A novel coaxial diode-end-pumping configuration with combined two laser crystals was proposed for simultaneous, compact, and flexible dual-wavelength laser generation. Theoretical simulations showed that by balancing the gain in both laser crystals by varying the pump focusing depth or pump wavelength, the power ratio for each wavelength could be tuned for either continuous wave or Q-switched operation, and the time interval between two pulses at different wavelengths in Q-switched mode was also tunable. Experimental verifications were performed, demonstrating coincident conclusions. As there was no gain competition between two wavelengths, the output characteristics were much more stable than dual-wavelength generation in a single-laser crystal. It is believed that this is a feasible and promising method for generating dual-wavelength laser for applications of spectroscopy, precision measurement, nonlinear optical frequency conversion to terahertz wave, and so on.

Full investigation into continuous-wave Nd:LuAG lasers on ^4F_3/2→^4I_13/2 transition around 13 and 14 μm

We report a full investigation of continuous-wave diode-pumped Nd:LuAG single crystal lasers on 4F3/2→4I13/2 transition around 1.3 and 1.4 μm. In free-running mode, a maximum output power of 4.18 W is achieved for a simultaneous dual-wavelength laser operation at 1321 and 1338 nm, which represents the highest output power for Nd:LuAG laser material at a 1.3 μm emission band. Three single wavelength lasers at 1340, 1332 and 1322 nm, as well as a dual-wavelength laser at 1334 and 1338 nm, are also generated with maximum output powers of 2.39, 2.63, 2.24 and 1.23 W, respectively, with the aid of a glass etalon. Moreover, a single wavelength laser at 1353 nm is also obtained with a maximum output power of 1.53 W. Furthermore, in free-running mode, simultaneous tri-wavelength eye-safe lasers at 1419, 1432 and 1442 nm are attained with a maximum output power of 1.83 W, and a 1.08 W single wavelength laser at 1419 nm is also yielded. Most of the 1.3 μm lasers and all of the 1.4 μm lasers are demonstrated for the first time to our knowledge. Thus, this work indicates that Nd:LuAG crystal is a very promising laser gain medium for high-power continuous-wave infrared laser generation.

High-power and high-efficiency diode-pumped Nd:LuYAG mixed crystal lasers operating at 939 and 946 nm.

We report on high-performance infrared lasers at 0.94μm based on quasi-three-level transition of F3/24→I9/24 in Nd:LuYAG mixed crystal, for the first time to our knowledge. The maximum output power was achieved to 5.64W with slope efficiency of approximately 52.5% at 946nm. The simultaneous dual-wavelength laser at 939 and 946nm is also obtained with maximum output power of 3.61W and slope efficiency of 34.8% by introducing a glass etalon into the cavity. Moreover, a 2.0-W single-wavelength laser at 939nm can be further attained by suitably tilting the etalon. Using a Cr:YAG saturable absorber, Q-switched laser operation is realized with maximum average output power of 0.68W and the narrowest pulse width of 8.4ns, which results in the maximum single pulse energy of approximately 55.3μJ and the maximum pulse peak power of approximately 6.15kW. Finally, thermal focal length of the laser crystal is estimated by using a flat-flat laser cavity.

Efficient diode-pumped nd:LuYAG lasers on 4F3/2 → 4I11/2 transition using a YAG etalon

We report diode-pumped Nd:LuYAG mixed crystal lasers around 1.06 μm. In free running mode, single wavelength laser at 1063.88nm is obtained with maximum output power of 8.71W and slope efficiency of 60.4%. The laser result represents the best laser performance of Nd:LuYAG laser so far. Using an undoped YAG thin plate to act as intracavity etalon, four simultaneous dual-wavelength lasers can be yielded, i.e. 1064.12 and 1060.95nm with maximum output power of 4.32W and slope efficiency of about 31.6%, 1064.37 and 1072.89nm with maximum output power of 2.06W and slope efficiency of about 15.0%, 1063.88 and 1052.41nm with maximum output power of 1.82W and slope efficiency of about 14.4%, as well as 1063.88 and 1068.26nm with maximum output power of 1.51W and slope efficiency of about 13.1%. These dual-wavelength lasers are all generated for the first time to our knowledge in Nd:LuYAG crystal. The multiple peak structure of the Nd:LuYAG mixed crystal like Nd:YAG single crystal could be a potential laser source for THz wave generation.

Single- and dual-wavelength lasers of diode-pumped Nd:LuYAG mixed crystal on various 4F3/2 → 4I13/2 Stark-level transitions

A diode-end-pumped Nd:LuYAG mixed crystal laser in the 1.3 μm spectral domain using a simple and compact two-mirror laser cavity is reported for the first time to our knowledge. In the free-running laser operation, we obtain a simultaneous dual-wavelength laser at about 1319 and 1338 nm with a maximum output power of 2.92 W and a slope efficiency of about 26.7%. By inserting an undoped YAG etalon into the laser cavity, the two 1319 and 1338 nm lasers can be operated singly with the maximum output powers of 1.36 and 1.73 W. Moreover, three simultaneous dual-wavelength lasers at 1334.67 and 1340.93 nm, 1319.15 and 1354.57 nm, and 1335.54 and 1354.94 nm can also be yielded with maximum output powers of 1.02, 0.66, and 0.47 W as well as slope efficiencies of 12.3%, 8.9%, and 6.9%, respectively. These dual-wavelength laser sources provide potential THz wave generation by beat frequency.

Orthogonally polarized dual-wavelength Yb:KGW laser induced by thermal lensing

Simultaneous dual-wavelength laser oscillation with orthogonal polarizations has been observed and analyzed in a continuous wave N g-cut Yb:KGW oscillator. Without inserting any optical elements for polarization control, the N m- and N p-polarized modes, each of which possessed a distinct wavelength, coexisted and switched twice in two power regimes as the pump power was varied. The two wavelengths and their separation slightly depended on output coupling level. The wavelength switching and coexistence was studied and explained by considering the thermal and spectral anisotropy of the Yb:KGW crystals, which led to polarization-dependent reabsorption loss in the unpumped regions of the crystal. The maximum average output power obtained in the dual-wavelength regime was 4.6 W.

Power scaling and wavelength tuning of diode-pumped Nd:LSO laser at 1.35 μm

We report a power scaled laser operation of diode-pumped Nd:LSO lasers at 1.35 μm. With single-end-pumping scheme, maximum output power reaches 0.77 W at 1358.99 nm in free-running mode. By inserting an etalon, wavelength tuning can be realized with tuning range of at least 6.5 nm from 1356.95 nm to 1363.39 nm. Simultaneous dual-wavelength laser at 1331.63 and 1357.43 nm can also be generated with total output power of 0.19 W, for the first time to our knowledge. Further power scaling to 1.03 W of the 1358.99 nm laser is finally achieved by recycling the remaining pump power, which represents the highest output power so far for 1.3 μm silicate lasers.