Optical-optical Efficiency Research Articles

Efficient 1645 nm continuous-wave and Q‑switched Er:YAG laser pumped by 1532 nm narrow-band laser diode

Energy transfer upconversion induced thermal effects are mainly responsible for the low efficiency of laser diode pumped Er:YAG lasers. The current work adopts Er:YAG rods with 0.25% Er(3+) doping concentration, instead of the commonly used rods with 0.5% Er(3+) doping concentration. Results show that the thermal effect is greatly alleviated. A continuous-wave output of 10.2 W is obtained using 31 W incident pump power. Optical-optical efficiency is approximately 33%. Slope efficiency, with respect to the absorbed pump power, is as high as 83%, which is close to the quantum efficiency. In a Q-switched operation, 7 mJ pulses with a pulse width of ~65 ns are obtained at 100 Hz PRF.

Compact diode-directly-pumped passively mode-locked TEM00 Nd:GdVO4 laser at 1341 nm using a semiconductor saturable absorber mirror

We report on a compact 880-nm diode-directly-pumped passively mode-locked TEM00 Nd:GdVO4 laser at 1341 nm with a semiconductor saturable absorber mirror (SESAM) for the first time. Under the absorbed pump power of 14.6 W, the maximum output power of 1.27 W was obtained at the repetition rate of 85.3 MHz with the pulse width of 45.3 ps, corresponding to an optical-optical efficiency of 8.8% and the slope efficiency of 33.3%, respectively. The beam quality factor was measured to be M 2 = 1.18, indicating a TEM00 mode.

Analytical study of vertical external-cavity surface-emitting organic lasers

In this paper we report a detailed study of emission dynamics of an organic solid-state laser structure so-called VECSOL standing for Vertical External-Cavity Surface-emitting Organic Laser recently developed in our group. An optical-optical efficiency of 43% and 6.3% was reported for a 4-mm-long cavity incorporating 18- μ m-thick film of Poly(methyl methacrylate) (PMMA) doped with 1 wt.% of Rhodamine 640 when pumped with 7-ns-long and 0.5-ns-long pulses respectively. In order to understand the difference seen in lasing efficiency as a function of different parameters such as cavity length or pump pulse duration, Tang-Statz-deMars cavity rate equations are used to model the emission behavior in a pulsed regime. Based on this model, conversion efficiency could be optimized practically to values as high as 57%. Furthermore, some characteristics of this laser architecture such as lasing lifetime (up to 140 000 pulses at two times above lasing threshold), wavelength tuning (over 40 nm) and the system power scalability with potential operation up to mJ level are investigated.

LD end-pumped passively mode-locked Nd:YVO4 laser with single-walled carbon nanotubes

We demonstrate a LD end-pumped passively mode-locked Nd:YVO4 laser using a single-walled carbon nanotubes saturable absorber (SWCNT-SA). The SWCNT wafer was fabricated by electric arc discharge method on quartz substrate with absorption wavelength of 1064 nm. At the absorbed pump of 15.8 W, an output power of 750 mW CW (continuous wave) mode-locked laser pulse was achieved with the repetition of 79.7 MHz, corresponding to optical-optical efficiency of 4.75%.

Nanosecond vortex laser pulses with millijoule pulse energies from a Yb-doped double-clad fiber power amplifier

Nanosecond vortex pulses were generated using a stressed, large-mode-area, Yb-doped, fiber amplifier with an off-axis coupling technique for the first time. A pulse energy of 0.83 mJ (corresponding to a peak power of 59 kW) was achieved at a pump power of 25.7 W. The optical-optical efficiency was measured to be 31%. The millijoule nanosecond vortex pulses will be potentially applied to novel material processing, such as metal microneedle fabrication.

Kerr-Lens Self-Mode-Locked Laser Characteristics of Yb:Lu2SiO5 Crystal

A diode-pumped Kerr-lens self-mode-locked laser is achieved by using Yb: Lu2SiO5(Yb:LSO) crystal without additional components. Under the incident pump power of 14.44 W, a self-mode-locked output power of 2.98 W is obtained in the five-mirror cavity, corresponding to an optical-optical efficiency of 20.6%. Pulses as short as 8.2 ps are realized at 1059 nm, with the corresponding pulse energy and peak power of 28.9 nJ and 3.5 kW, respectively. A pair of SF10 prisms are inserted into the laser cavity to compensate for the group velocity dispersion. The pulse width is compressed to 2.2 ps with an average output power of 1.25 W.

1.1-kW Ytterbium Monolithic Fiber Laser With Assembled End-Pump Scheme to Couple High Brightness Single Emitters

We demonstrate a continuous-wave all-fiber laser with master oscillator and two-stage power amplifier configuration. Diode pumping with single-emitter technology is used with the advantage of low cost and outstanding heat management. An assembled end-pumped scheme is employed to couple high brightness pump power into a gain fiber. The laser system generates 1.1-kW output power at 1085 nm, with the total optical-optical efficiency of about 66.5%, corresponding to 1655 W of applied pump power. The variable absorption of gain fiber is analyzed considering the launching spectra characteristics of single emitters, which is significant for the construction of the pump system.

High-power 880-nm diode-directly-pumped passively mode-locked Nd:YVO_4 laser at 1342 nm with a semiconductor saturable absorber mirror

A high-power 880-nm diode-directly-pumped passively mode-locked 1342 nm Nd:YVO₄ laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The laser mode radii in the laser crystal and on the SESAM were optimized carefully using the ABCD matrix formalism. An average output power of 2.3 W was obtained with a repetition rate of 76 MHz and a pulse width of 29.2 ps under an absorbed pump power of 12.1 W, corresponding to an optical-optical efficiency of 19.0% and a slope efficiency of 23.9%, respectively.

High-efficiency 17 W, 80 MHz repetition rate, passively mode-locked TEM00 Nd:YAG oscillator pumped at 885 nm

We report on a passively mode-locked TEM00 Nd:YAG oscillator with the beam quality at M2 = 1.1 by a semiconductor saturable absorber mirror under 885 nm laser diode direct pumping for the first time. A maximum average output power of 17 W at a repetition rate of 80 MHz with 39 ps pulse width was obtained under the absorbed pump power of 38 W, corresponding to an optical-optical efficiency of 44% and the slope efficiency of 69%, respectively.

High-power diode-directly-pumped tenth-order harmonic mode-locked TEM00 Nd:YVO4 laser with 1 GHz repetition rate

A high-efficiency high-power diode-directly-pumped tenth-order harmonic mode-locked TEM00 Nd:YVO4 laser with 1 GHz repetition rate was first demonstrated. The maximum output power was 10.4 W with optical-optical efficiency of 41.8% and slope efficiency of 78.1%, respectively, the pulse width was about 30 ps at the output power of 9.6 W. Based on the large third-order nonlinearity of Nd:YVO4, the tenth-order harmonic mode-locked pulses were induced by the intensity-dependent Kerr effect and the cooperative action of counter-propagating pulses colliding in the laser crystal for a colliding-pulse-modelocking-like cavity. The pulses were further modulated by a semiconductor saturable absorber mirror.

Watt-level ∼2μm laser output in Tm^3+-doped tungsten tellurite glass double-cladding fiber

We report, for the first time to the best of our knowledge, a watt level cw fiber laser at ~2 μm from a piece of 40-cm-long newly developed highly thulium-doped (3.76 × 10(20) ions/cm(3)) tungsten tellurite glass double cladding fiber pumped by a commercial 800 nm laser diode. The maximum output power of the fiber laser reaches 1.12 W. The slope efficiency and the optical-optical efficiency with respect to the absorbed pump are 20% and 16%, respectively. The lasing threshold is 1.46 W, and the lasing wavelength is centered at 1937 nm.

High power composite Nd:YAG/YAG zigzag dual-slab laser oscillator

We report a high power zigzag slab laser oscillator employing two composite Nd:YAG/YAG slab in the cavity. The CW laser output with the power of 401 W was achieved from the oscillator with the optical-optical efficiency of 32.6%. The beam quality is estimated as M x 2 ≈ 10, M y 2 ∼ 50 in the slab width and thickness direction, respectively.

Symmetric TEM_00 output from Q-switched quasi-concentric laser resonator with line-shaped end-pumping profile

We report a 12.2 W pulsed TEM(00) output from Q-switched quasi-concentric laser resonator with line-shaped end-pumping profile, with the repetition rate of 30 kHz and optical-optical efficiency of 27.1%. The laser output mode is symmetrized in two directions in terms of beam quality, waist radius, and waist position.

Pulse-series 1.57 μm optical parametric oscillator pumped by a Q-switched Nd:YAG laser with a variable reflectivity mirror

A method of generating 1.57 μm pulse-series eye-safe laser based on optical parametric oscillator (OPO) was developed. The 1.57 μm pulse-series OPO was pumped by a Q-switched Nd:YAG laser with a variable reflectivity unstable resonator. Every pulse-series includes three micro-pulses, and the pulse repetition rates, pulse numbers and pulse intervals were adjustable. The maximum output energy of the 3-micro-pulse-series was 274 mJ. The optical-optical efficiency of the OPO was about 40%.

Heat-fraction-limited CW Yb:YAG cryogenic solid-state laser with 100% photon slope efficiency

We report the demonstration of a heat-fraction-limited CW Yb:YAG laser operating near 77 K with output at 1029 nm, pumped with a diffraction-limited room-temperature CW Nd:YAG laser operating at 946 nm. With a 50% reflectivity outcoupler, the average threshold absorbed pump power was 18.8 mW and the average slope efficiency 91.9%, close to the heat-fraction limited value of 91.5%. Average optical to optical and photon slope efficiencies are 84% and 100% respectively. To the best of our knowledge this solid-state laser is the first to operate at the heat-fraction-limit and demonstrates record slope, photon slope and optical-optical efficiencies for optically-pumped solid-state lasers.

High Efficiency Multi-kW Diode-Side-Pumped Nd:YAG Laser with Reduced Thermal Effect

We demonstrate a high efficiency multi-kW diode-side-pumped Nd:YAG laser. High cooling efficiency of the diode-side-pumped module in the laser is achieved. The middle portion of the Nd:YAG rod in the module is cooled by a coolant jet with screwed side surface, and the end-caps of the rod without screwed side surface are cooled by Au coated on the surface. The thermal effect of the laser rod is reduced, which leads to high output power with high optical-optical conversion efficiency. By using three identical Nd:YAG laser modules, an output power of 4.2kWand beam quality of 58mm·mrad with an optical-optical efficiency of 35% at 1064nm is obtained in a laser oscillator. By using four identical Nd:YAG laser modules, an output power of 3.1 kW and beam quality of 17 mm·mrad with an optical-optical efficiency of 25.8% is demonstrated in a master oscillator power-amplifier system.

Stable single-longitudinal-mode fiber laser using PM FBG F-P etalon and PM fiber saturable absorber

we present a stable and high efficiency single-longitudinal-mode (SLM) fiber ring laser by using polarization-maintaining fiber Bragg grating Fabry-Perot (PM FBG F-P) etalon combining PM fiber saturable absorber. The PM FBG F-P etalon, which is directly fabricated in hydrogen-loaded PM fiber, is used as reflector and mode-selecting component to reduce the longitudinal-mode density greatly. Meanwhile, a segment un-pumped PM Er3+-doped fiber (EDF) serves as saturable absorber to suppress mode hopping and ensure the stable SLM operation. Stable SLM laser output at 1550.4 nm with linewidth of 2.0 kHz is observed. Laser output power is 43.7 mW for a pump power of 148 mW, optical-optical efficiency is 29.5% and signal-to-noise ratio (SNR) is larger than 55 dB.

High repetition rate dual-rod acousto-optics Q-switched composite Nd:YVO4 laser

We demonstrate the high-repetition rate acousto-optic Q-switching of a dual-rod Nd:YVO4 laser. Two thermally bonded composite YVO4-Nd:YVO4-YVO4 rod crystals were used as the gain medium to reduce the serious thermal effect. The pump mode and its influence on the laser mode were analyzed, and the effective pump radius was controlled by tuning the spectrum of laser diodes with adjustment on the temperature of laser diodes. Three different configurations of cavity optics were designed and the output performance using these cavities was investigated. In Q-switching operation, 73.2 W TEM00 mode average power at 650 kHz was obtained. The stable Q-switching range was from 80 kHz to 650 kHz with the pulse duration increasing from 17.5 ns to 80 ns. In CW operation, 78 W TEM00 mode and 93 W multi-mode output power was achieved with different cavity designs, corresponding to the optical-optical efficiency of 46.5% and 52.2% respectively.

LD bar corner-pumped TEM_00 CW composite Nd:YAG laser

Ray-tracing algorithm was used to simulate the pump absorption efficiency and pump absorption distribution of LD corner-pumped laser with different parameters of Nd:YAG composite slab crystal. Resonator experiment was performed to suppress the oscillation of higher-order modes and realize TEM(00) operation. Experiment results showed that the output power was 11.94 W with an optical-optical efficiency of over 26%, and the M2 factors of beam quality at width and thickness directions were 1.18 and 1.34, respectively. It has been proven that the corner-pumped configuration could obtain laser output with good beam quality as a result of high pump efficiency and good pump uniformity.

High-Efficiency High-Power Nd: YAG Laser under 885 nm Laser Diode Pumping

A high-efficiency high-power Nd:YAG laser under 885nm laser diode (LD) pumping is demonstrated. The laser crystal is carefully designed, and the overlapping between the pump modes and the laser modes is optimized. The maximum output power at 1064 nm is 87W under the absorbed pump power 127.7W, corresponding to a slope efficiency of 72.4% and an optical-optical efficiency of 68.1%. The optical-optical efficiency is 58.4% for the pump power emitted directly from the LD. To our best knowledge, this is the maximal optical-optical conversion efficiency obtained for the LD end-pumped Nd:YAG lasers so far.