Absorbed Pump Power Research Articles

High-performance 320-nm continuous-wave solid-state laser

For the first time, to our knowledge, we realized a high-performance 320-nm continuous-wave (CW) laser with a fiber-coupled blue laser diode as the pump source. A V-shaped folded cavity is constituted by three mirrors, with a Pr3+:LiYF4 (Pr:YLF) as the laser crystal and a LiB3O5 (LBO) as the frequency doubling crystal, respectively. Under an absorbed pump power of 19.5 W, the maximum 320-nm output power reaches 4.26 W, corresponding to an optical conversion efficiency of 21.8% and a root-mean-square (RMS) power fluctuation of 0.61%, which give the best results of a 320-nm CW laser up to now. The excellent performance will make this ultraviolet laser source very suitable for practical applications, including semiconductor detection, spectral analysis, microscopic imaging, and biotechnology.

Growth, spectroscopy properties, and laser operation of single crystal fiber: Nd3+-doped CNGG

Nd3+-doped calcium niobium gallium garnet single crystal fibers (Nd:CNGG SCFs) with varying Nd3+ concentrations were successfully grown using the laser-heated pedestal growth (LHPG) method. The study thoroughly examines the fundamental physical structure, optical properties, and laser characteristics of the as-grown Nd:CNGG SCFs. Results indicate that the Nd:CNGG SCF exhibits broader absorption and emission full width at half maximum (FWHM) compared to bulk single crystals. Moreover, pumped by a commercial 808 nm laser diode, continuous-wave laser operation at 1061 nm with a half-height width of 1.86 nm was achieved. The laser output power reached 1.04 W at an absorbed power of 7.46 W, with a slope efficiency of 25.4% relative to the absorbed pump power. These findings suggest that Nd:CNGG SCF holds promise as a practical and potent candidate for laser gain medium, offering significant research potential in the field of lasers.

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.

Modeling of rare-earth-doped double-clad fiber laser based on rate equations with spatially averaged parameters

A mathematical model of a rare-earth doped double-clad fiber laser based on rate equations with spatially averaged parameters laser has been developed. Analytical expressions for the threshold absorbed pump power, slope efficiency and laser output power have been obtained for the CW regime. It has been shown that the results of output power calculations using the analytical model for CW double-clad ytterbium and neodymium doped lasers are in a good agreement with the results obtained using numerical models described in literature. A quantitative criterion for the applicability of the presented analytical model for calculating the parameters of double-clad fiber lasers has been proposed. The applicability of the proposed model to describe the transient stage of the operation of a fiber laser under continuous pumping has been demonstrated.

Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser. The slope efficiency reached 25.30% for the absorbed pump power. The optical signal-to-noise ratio (OSNR) of the laser was ∼69.78 dB, and the laser linewidth was ∼84.5 kHz. Additionally, the measured relative intensity noise (RIN) remained at -130 dB/Hz at frequencies above 9 MHz. The experimental results indicate that the TCDSF is a promising gain medium for single-frequency lasers at 1.7 µm.

High power widely tunable frequency-doubled 490 nm blue semiconductor disk laser

This paper presents a high power widely tunable frequency-doubled semiconductor disk laser emitting at 490 nm wavelength. The laser utilizes a specially designed gain chip with widened gain spectrum at the center wavelength of 980 nm, along with an anti-resonant microcavity, to extend the tuning range of the wavelength. A type-I phase-matched 5 mm length LBO crystal is used as the nonlinear crystal, and a fused quartz birefringent filter (BRF) is introduced to polarize the fundamental emission and narrow the linewidth of the laser. When the thickness of the used BRF is 1 mm, 50.7 nm tuning range of the 980 nm infrared laser is performed. A maximum output power of 5.36 W of the frequency-doubled 490 nm blue laser is achieved, and the optical-to-optical conversion efficiency from absorbed pump power to the blue light is about 15.3%. Meanwhile, a record tuning range of 21.5 nm of the blue laser is realized. The measured M2 factors of the blue laser are 1.00 in the x-direction and 1.04 in the y-direction, respectively.

Quasi-three-level continuous wave Nd:Na2La4(WO4)7 lasers at 0.9 μm

A diode-pumped continuous wave (CW) Nd:Na2La4(WO4)7 (Nd:NLW) laser operating at 0.9 μm on 4F3/2 → 4I9/2 transition was demonstrated. Four single- wavelengths (the 889 nm and 912 nm in σ-polarization, the 890 nm and 905 nm in π-polarization) were obtained by rotating an intracavity birefringent filter (BF).At an absorbed pump power of 17.4 W at 808 nm, the highest output power of single-wavelength at 912 nm was 3.4 W. Furthermore, the dual-wavelength at 889 and 912 nm in σ-polarization and the dual-wavelength at 890 and 905 nm in π-polarization were also achieved, respectively. At an absorbed pump power of 17.4 W, the maximum total output powers of the dual-wavelengths at 889 and 912 nm was 2.12 W. To the best of our knowledge, this is the first quasi-three-level Nd:NLW laser operating at 0.9 μm.

Tunable continuous wave Yb:CaWO4 laser operating in NIR spectral region

A tunable continuous wave (CW) Yb:CaWO4 laser operating in near infrared (NIR) spectral region is demonstrated by pumping with a diode laser. Continuously broadband tunable wavelengths are obtained in two polarizations by rotating the Lyot filter. The tuning widths of the output wavelengths in the π- and σ-polarizations are 42 nm (from 1005.2 nm to 1047.2 nm) and 41.8 nm (from 1005.1 nm to 1046.9 nm), respectively. At an absorbed pump power of 15.6 W at 976 nm, the maximum output powers in the π- and σ-polarizations are 5.2 W at 1026.2 nm and 4.7 W at 1028.1 nm, respectively. To the best of our knowledge, this is the first tunable laser operation by using Yb:CaWO4 crystal.

All-solid-state continuous-wave mode-locked Er:Lu2O3 laser at 3 µm

In this paper, we demonstrated stable continuous-wave passively mode-locked operation of an Er:Lu2O3 laser at 3 µm, utilizing a semiconductor saturable absorber mirror (SESAM). By operating the laser in a dry nitrogen environment and utilizing a thermoelectric cooler (TEC) temperature control device to mitigate the thermal effects of Er:Lu2O3 and enhance laser stability, we further compensated for group delay dispersion within the laser cavity through chirped mirrors, an shortest pulse duration of 12.0 ps at a average output power of 150 mW was achieved, which occurred at a center wavelength of 2844 nm, and a pulse repetition rate of 83.5 MHz. Additionally, we achieved a maximum continuous-wave mode-locked output power of 213 mW at an absorbed pump power of 8.3 W, equivalent to a pulse energy of 1.3 nJ. The RF spectrum analysis of the pulse train indicated a high SNR of nearly 70 dB, signifying excellent stability. To the best of our knowledge, This is the first report on the realization of an ultrashort pulse width mode-locked Er:Lu2O3 laser in the mid-infrared band.

Continuous-wave π-polarized 1084 nm laser based on Nd:MgO:LiNbO3 under 888 nm double-end pumping with low quantum defect

A continuous-wave π-polarized 1084 nm laser based on Nd:MgO:LiNbO3 crystal is reported under 888 nm double-end pumping with low quantum defect. When the absorbed pump power is 28 W, the π-polarized 1084 nm laser achieves a maximum output power of 8.73 W and a conversion efficiency of 31.1% under double-end thermally boosted pumping. The beam quality factor M2 is 1.61 and 1.68 in the x and y directions, respectively. Compared with the single-end pumping, the output power of the double-end pumping is increased by 3.33W, and the conversion efficiency is increased by 5.4%. The experimental results show that double-end thermally boosted pumping can handle higher injection power, resulting in a higher output power of π-polarized 1084 nm laser.

Orthogonally polarized dual-wavelength Pr:LiYF4 lasers in 1.3 μm region

We report a continuous-wave (CW) orthogonally polarized dual-wavelength Pr:LiYF4 laser in 1.3 μm region pumped by a Yb-doped fiber laser. The gain and loss of the wavelengths in the orthogonally polarized directions were balanced by an inclined etalon inserted into the cavity. At an absorbed pump power of 9.2 W, a dual-wavelength laser operating at 1310 nm in π-polarization and 1326 nm in σ-polarization with 2.26 W of total output power was achieved. Moreover, by continuing to adjust the tilt angle of the etalon, the three other pairs of dual-wavelengths (1289 and 1306 nm, 1289 and 1306 nm, and 1306 and 1310 nm) were also obtained. The output power ratio of each pair of dual wavelengths was nearly 1:1. To the best of our knowledge, this is the first work realizing the Pr:LiYF4 laser operating in 1.3 μm region.

Watt-level cladding-pumped bismuth-doped fiber laser operating near 1.31 [formula omitted]m

We report, to the best of our knowledge, the first CW bismuth-doped fiber laser operating at around 1.31 μm with an output power of >1 W utilizing a cladding-pumping configuration with multimode semiconductor laser diodes emitting at a wavelength of 793 nm. The Bi-doped fiber (BDF) serving as an active medium of the laser was based on a pedestal-index design, where P2O5−SiO2 glass core surrounded by P-doped cladding. The BDF construction offers advanced gain characteristics and an increased mode size (∼13 μm). The fiber preform was fabricated by the conventional modified chemical vapor deposition (MCVD) method combined with all gas-phase doping technique. The BDF with low-index polymer coating provided sufficient cladding peak absorption at 750 nm belonging to bismuth active centers associated with phosphorus atoms (BACs-P) that allowed to develop a continuous-wave laser with a linear cavity configuration and enable a maximum slope efficiency of ∼ 4% with respect to the absorbed pump power. In addition, near-field spatial intensity distribution of optical beam has good quality (M2<1.13) and close to Gaussian mode profile in x and y directions. The perspectives for optimization of BDF design and laser system configurations based on such fibers for further power scaling are discussed.

Diode-end-pumped self-Q-switched Tm:YAlO3 laser at 2362 nm

A diode-end-pumped self-Q-switched Tm:YAlO3 laser at 2362 nm based on 3H4→3H5 transition is proposed for the first time according to the references. The max mean output power of 0.41 W with a slope efficiency of 14.1% was obtained under the absorbed pump power of 6.7 W, corresponding pulse width and pulse repetition frequency were 7.82 μs and 45.09 kHz respectively. By analyzing the laser beam spatial distribution, the self-Q-switched Tm:YAlO3 laser at 2362 nm was originated from the time-dependent lens mechanism. The present research provides an approach for generating Q-switched lasers in the 2.3 μm spectral region.

High average power (105 W) Fe:ZnSe laser pumped by radiation of laser diode side-pumped Er:YAG lasers.

A high average power re-frequency operation Fe:ZnSe laser using laser diode side-pumped free-running Er:YAG lasers as activating sources is presented. Two pieces of subsurface layer doped Fe:ZnSe polycrystal are adoptive in a reflective resonator configuration and face-cooled by liquid nitrogen. A maximal Fe:ZnSe laser power of 105 W at a wavelength of 4.1 μm is achieved upon pumping by ten home-made Er:YAG lasers with fiber coupled output working at a frequency of 250 Hz and a pulse duration of ∼420 μs. Corresponding to the maximum Fe:ZnSe laser power, the optical-optical efficiency and slope efficiency with respect to the absorbed pump power are 43% and 44% respectively. The beam quality factor M2 is measured to be 3.4. To the best of our knowledge, it is the highest output average power of an Fe:ZnSe laser reported.

Mid-infrared dual-wavelength operation of a diode-pumped Tm:YScO3 laser

A simultaneous continuous-wave (CW) dual-wavelength Tm:YScO3 laser using a single birefringent filter (BF) was experimentally demonstrated. We calculated the wavelength-dependent loss property of the BF. By adjusting the BF plate, the spectral intensity ratio of the generated wavelengths can be maintained to be 1:1. A simultaneous CW dual-wavelength Tm:YScO3 laser at 1948 and 2098 nm is experimentally realized. For a pump power of 15.2 W, mid-infrared dual-wavelength laser radiation at 1948 and 2098 nm and 5.9 W of output power using a 5% output coupler could be generated. A slope efficiency of 42.2% with respect to the absorbed pump power and optical-to-optical efficiency of 38.8% for the highest-incident pump power were obtained. To our knowledge, this is the first study that has realized the dual-wavelength in a Tm:YScO3 laser.

CH3NH3PbBr3 as a saturable absorber for infrared passively Q-switched solid-state laser

Perovskite materials are used in the field of lasers and can achieved good results. In this paper, we prepared an organic–inorganic hybridized CH3NH3PbBr3 saturable absorber (SA). Continuous wave (CW) Tm:YAP solid-state lasers with CH3NH3PbBr3-SA successfully obtained pulsed lasing at 1987.5 nm after continuous tuning. In CW mode, the maximum absorbed pump power by the laser was 19.42 W, which corresponds to 0.68 W output power. The central output wavelength of the continuous wave laser was 1989.9 nm. In PQS mode, the output power of laser was 203 mW. Under the condition of maximum repetition frequency of 45 kHz, the narrowest pulse width of the PQS laser were 1.16 μs. Meanwhile, the laser produced a maximum single-pulse energy (4.5 μJ) and a maximum peak power (3.9 W). The beam quality factors (the horizontal/vertical directions) were M2 x = 1.1 and M2 y = 1.39. The CH3NH3PbBr3 was an excellent SA for infrared PQS solid-state lasers, which had a large potential for development applications in the field of lasers.

Demonstration of a 0.8 W continuous wave bulk laser around 2 μm in a Tm3+:Ga-rich BGG glass

Efficient lasing of Ga-rich BGG bulk glasses doped with Tm3+ is demonstrated. Two BGG bulk samples with Tm3+ ion concentrations of 1.27×1020 cm−3 and 2.54×1020 cm−3 were tested for their laser performance. In-band pumping was realized using a continuous-wave (CW) homemade Er-doped fiber laser at 1600 nm. A maximum slope efficiency of 27.7% was demonstrated with respect to the absorbed pump power. The emission cross-section was retrieved from the laser efficiency data for three different lasing wavelengths and compared with the theoretical calculations. The power scaling potential of the Tm3+:BGG glass was investigated and a maximum output power of 0.8 W was achieved.

Orthogonally polarized dual-wavelength Pr:LiGdF4 lasers in the green range

We demonstrate a diode-pumped continuous-wave tunable orthogonally polarized dual-wavelength Pr:LiGdF4 laser in the green range. The excellent mode matching between the pump and green lasers is achieved under the consideration of thermally induced effects. We analyze the condition of gain-to-loss balance via an uncoated glass etalon to achieve the dual-wavelength operation. At an absorbed pump power of 17.9 W, a dual-wavelength laser operating at 546 nm in π-polarization and 538 nm in σ-polarization with 1.72 W of average output power was obtained. Orthogonally polarized dual-wavelength laser operation at shorter- or longer-wavelength pairs with lower average output power could also be realized for other output-coupling transmissions. To the best of our knowledge, this is the first work realizing orthogonally polarized dual-wavelength operation in Pr:LiGdF4 lasers.

Spectroscopy and efficient dual-wavelength laser performances of a Nd:GYSAG crystal.

We reported on the spectral properties and dual-wavelength laser performances of a novel, to the best of our knowledge, Nd:Gd1.8Y1.2ScAl4O12 (Nd:GYSAG) crystal for the first time. The absorption spectra, emission spectra, and fluorescence lifetime were systematically investigated. Further, a continuous-wavelength (CW) laser output power up to 5.02 W was obtained under an absorbed pump power of 9.45 W with slope and optical-to-optical efficiencies of 59.4% and 53.1%, respectively, at 1061.2 and 1063.2 nm. A stable passively Q-switched (PQS) laser employing Cr:YAG as a saturable absorber (SA) was realized. The maximum average output power of 0.756 W with a slope of near 34.4% was obtained with the pulse width, pulse energy, and peak power of 14.0 ns, 128.1 µJ, and 9.15 kW, respectively. The results indicate that the Nd:GYSAG crystal is an excellent laser medium for generating a high-efficiency dual-wavelength laser and has potential in terahertz (THz) laser generation.

High beam quality continuous-wave 320 nm UV laser from a walk-off compensated intracavity frequency-doubled Pr:YLF laser

We report a high beam quality continuous-wave (CW) 320 nm ultra-violet (UV) laser. An end-pumped praseodymium-doped yttrium lithium fluoride (Pr:YLF) laser is constructed in a typical V-shaped cavity structure, while the UV output is obtained through intracavity frequency doubling using LiB3O5 (LBO). We investigate the dependence of the UV output power, as well as the spot profile on the LBO length, and find that the “walk-off” within LBO severely affects both the frequency-doubling efficiency and the beam quality of the UV output. Rotated twin LBO crystals are then applied to substitute for single long LBO crystal to compensate the walk-off effect, resulting in high-power 320 nm output up to 410 mW under the absorbed pump power of 4.0 W at 444 nm, with a high beam quality of M x 2=1.02 and M y 2=1.04.